Boundary conditions for diffusion in the pack-aluminizing of nickel.

NASA Technical Reports Server (NTRS)

Sivakumar, R.; Seigle, L. L.; Menon, N. B.

1973-01-01

The surface compositions of nickel specimens coated for various lengths of time in aluminizing packs at 2000 F were studied, in order to obtain information about the kinetics of the pack-cementation process in the formation of aluminide coatings. The results obtained indicate that the surface compositions of the coated nickel specimens are independent of time, at least for time between 0.5 and 20 hrs. Another important observation is that the specimens gained weight during the coating process.

The effect of cobalt content in U-700 type alloys on degradation of aluminide coatings

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.

1985-01-01

The influence of cobalt content in U-700 type alloys on the behavior of aluminide coatings is studied in burner rig cyclic oxidation tests at 1100C. It is determined that aluminide coatings on alloys with higher cobalt offer better oxidation protection than the same coatings on alloys containing less cobalt.

Corrosion-resistant fuel cladding allow for liquid metal fast breeder reactors

DOEpatents

Brehm, Jr., William F.; Colburn, Richard P.

1982-01-01

An aluminide coating for a fuel cladding tube for LMFBRs (liquid metal fast breeder reactors) such as those using liquid sodium as a heat transfer agent. The coating comprises a mixture of nickel-aluminum intermetallic phases and presents good corrosion resistance to liquid sodium at temperatures up to 700.degree. C. while additionally presenting a barrier to outward diffusion of .sup.54 Mn.

Aluminide coatings for nickel base alloys

NASA Technical Reports Server (NTRS)

Fiedler, H. C.; Sieraski, R. J.

1971-01-01

The metalliding process was used to aluminide IN-100 and TD NiCr. Aluminum was deposited over a broad range of deposition rates, with two types of coating structures resulting. Chromium, silicon, titanium and yttrium were also individually deposited simutaneously with aluminum on IN-100. None of these had a marked effect on the oxidation resistance of the aluminide coating. Porosity-free aluminide coatings with good oxidation resistance were formed on TD NiCr providing the aluminum concentration did not exceed 8 percent, the limit of solubility in the gamma phase.

Structure and Properties of the Aluminide Coatings on the Inconel 625 Superalloy

NASA Astrophysics Data System (ADS)

Adamiak, Stanisław; Bochnowski, Wojciech; Dziedzic, Andrzej; Filip, Ryszard; Szeregij, Eugeniusz

2016-01-01

The research samples used in this study were based on the Inconel 625 alloy; the examined samples were coated with aluminide films deposited in a low-activity chemical vapor deposition (CVD) process. The samples' microstructure was investigated with optical and electron microscopy and energy dispersive X-ray spectroscopy analysis. Hardness measurements were performed using Vickers and Berkovich test methods. The adhesion of the aluminide coating was determined by fractography. It was shown that the fracture mechanism was different for the respective zones of the aluminide coating and the substrate material. The outer zone of the aluminide coating is characterized by an intercrystalline fracture, with a small contribution of transcrystalline fracture within individual grains (large crystallites in the bottom of the zone, composed of smaller crystallites, also show an intercrystalline fracture). The substrate material exhibited a ductile intercrystalline fracture. Based on this investigation, an increase of the microhardness of the material occurring at loads below 0.2 N was observed. When determining microhardness of aluminide coating it is necessary to take into account the optimal choice of the indentation tip.

High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C

NASA Technical Reports Server (NTRS)

Deadmore, D. L.

1974-01-01

Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

Development of improved high temperature coatings for IN-792 + HF

NASA Technical Reports Server (NTRS)

Profant, D. D.; Naik, S. K.

1981-01-01

The development for t-55 l712 engine of high temperature for integral turbine nozzles with improved thermal fatigue resistance without sacrificing oxidation/corrosion protection is discussed. The program evaluated to coating systems which comprised one baseline plasma spray coating (12% Al-NiCoCrALY), three aluminide coatings including the baseline aluminide (701), two CoNiCrAly (6% Al) + aluminide systems and four NiCoCrY + aluminide coating were evaluated. The two-step coating processes were investigated since it offered the advantage of tailoring the composition as well as properly coating surfaces of an integral or segmented nozzle. Cyclic burner rig thermal fatigue and oxidation/corrosion tests were used to evaluate the candidate coating systems. The plasma sprayed 12% Al-NiCoCrAlY was rated the best coating in thermal fatigue resistance and outperformed all coatings by a factor between 1.4 to 2.5 in cycles to crack initiation. However, this coatings is not applicable to integral or segmented nozzles due to the line of sight limitation of the plasma spray process. The 6% Al-CoNiCrAlY + Mod. 701 aluminide (32 w/o Al) was rated the best coating in oxidation/corrosion resistance and was rated the second best in thermal fatigue resistance.

Oxidation of Slurry Aluminide Coatings on Cast Stainless Steel Alloy CF8C-Plus at 800oC in Water Vapor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haynes, James A; Armstrong, Beth L; Dryepondt, Sebastien N

A new, cast austenitic stainless steel, CF8C-Plus, has been developed for a wide range of high temperature applications, including diesel exhaust components, turbine casings and turbocharger housings. CF8C-Plus offers significant improvements in creep rupture life and creep rupture strength over standard CF8C steel. However, at higher temperatures and in more aggressive environments, such as those containing significant water vapor, an oxidation-resistant protective coating will be necessary. The oxidation behavior of alloys CF8C and CF8C-Plus with various aluminide coatings were compared at 800oC in air plus 10 vol% water vapor. Due to their affordability, slurry aluminides were the primary coating systemmore » of interest, although chemical vapor deposition (CVD) and pack cementation coatings were also compared. Additionally, a preliminary study of the low cycle fatigue behavior of aluminized CF8C-Plus was conducted at 800oC. Each type of coating provided substantial improvements in oxidation behavior, with simple slurry aluminides showing very good oxidation resistance after 4,000 h testing in water vapor. Preliminary low cycle fatigue results indicated that thicker aluminide coatings degraded high temperature fatigue properties of CF8C-Plus, whereas thinner coatings did not. Results suggest that appropriately designed slurry aluminide coatings are a viable option for economical, long-term oxidation protection of austenitic stainless steels in water vapor.« less

An experimental, low-cost, silicon slurry/aluminide high-temperature coating for superalloys

NASA Technical Reports Server (NTRS)

Young, S. G.; Deadmore, D. L.

1979-01-01

A duplex silicon-slurry/aluminide coating has been developed and cyclically tested in Mach 1 combustion gases for oxidation and thermal fatigue resistance at 1093 C and in Mach 0.3 gases for hot-corrosion resistance at 900 C. The base-metal superalloys were VIA and B-1900. The coated B-1900 specimens performed much better in oxidation than similar specimens coated with aluminides and almost as well as the more-expensive Pt-Al and MCrAlY (where M is Ni and/or Co) coatings deposited by the physical vapor deposition process. The coating also provided good hot-corrosion protection. Metallographic, X-ray, and electron microprobe studies were made to characterize the coating, determine failure mechanisms, and study some of the changes due to exposure.

Iridium Aluminide Coats For Protection Against Ox idation

NASA Technical Reports Server (NTRS)

Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Jang, Qin

1996-01-01

Iridium aluminide coats investigated for use in protecting some metallic substrates against oxidation at high temperatures. Investigation prompted by need for cost-effective anti-oxidation coats for walls of combustion chambers in rocket engines. Also useful in special terrestrial applications like laboratory combustion chambers and some chemical-processing chambers.

Silicon-slurry/aluminide coating. [protecting gas turbine engine vanes and blades

NASA Technical Reports Server (NTRS)

Deadmore, D. L.; Young, S. G. (Inventor)

1983-01-01

A low cost coating protects metallic base system substrates from high temperatures, high gas velocity ovidation, thermal fatigue and hot corrosion and is particularly useful fo protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrates from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue and increased the resistance of certain superalloys to hot corrosion.

Mechanical properties of coated titanium Beta-21S after exposure to air at 700 and 800 C

NASA Technical Reports Server (NTRS)

Wiedemann, Karl E.; Bird, R. Keith; Wallace, Terryl A.; Clark, Ronald K.

1992-01-01

Mechanical properties of Beta-21S (Ti-15Mo-3Al-2.7Nb-0.2Si, wt percent) with glass, aluminide, and glass-on-aluminide coatings less than 3-micron thick were studied. Coatings were deposited by sol-gel processing or electron-beam evaporation onto 4.5-mil (113-micron) thick Beta-21S sheet from which, after oxidizing in air at 700 or 800 C, tensile test specimens were machined. Plastic elongation was the most severely degraded of the tensile properties; the glass-on-aluminide coatings were the most effective in preventing degradation. It was found that oxygen trapping by forming oxides in the coating, and reactions between the coatings and the Beta-21S alloy played significant roles.

Method of protecting a surface with a silicon-slurry/aluminide coating. [coatings for gas turbine engine blades and vanes

NASA Technical Reports Server (NTRS)

Deadmore, D. L.; Young, S. G. (Inventor)

1982-01-01

A low cost coating for protecting metallic base system substrates from high temperatures, high gas velocity oxidation, thermal fatigue and hot corrosion is described. The coating is particularly useful for protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrate from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue. Also, the Si-Al coating increased the resistance of certain superalloys to hot corrosion.

Internally coated air-cooled gas turbine blading

NASA Technical Reports Server (NTRS)

Hsu, L.; Stevens, W. G.; Stetson, A. R.

1979-01-01

Ten candidate modified nickel-aluminide coatings were developed using the slip pack process. These coatings contain additives such as silicon, chromium and columbium in a nickel-aluminum coating matrix with directionally solidified MAR-M200 + Hf as the substrate alloy. Following a series of screening tests which included strain tolerance, dynamic oxidation and hot corrosion testing, the Ni-19A1-1Cb (nominal composition) coating was selected for application to the internal passages of four first-stage turbine blades. Process development results indicate that a dry pack process is suitable for internal coating application resulting in 18 percent or less reduction in air flow. Coating uniformity, based on coated air-cooled blades, was within + or - 20 percent. Test results show that the presence of additives (silicon, chromium or columbium) appeared to improve significantly the ductility of the NiA1 matrix. However, the environmental resistance of these modified nickel-aluminides were generally inferior to the simple aluminides.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

Life prediction and constitutive models for engine hot section anisotropic materials

NASA Technical Reports Server (NTRS)

Swanson, G. A.

1984-01-01

The development of directionally solidified and single crystal alloys is perhaps the most important recent advancement in hot section materials technology. The objective is to develop knowledge that enables the designer to improve anisotropic gas turbine parts to their full potential. Two single crystal alloys selected were PWA 1480 and Alloy 185. The coatings selected were an overlay coating, PWA 286, and an aluminide diffusion coating, PWA 273. The constitutive specimens were solid and cylindrical; the fatigue specimens were hollow and cylindrical. Two thicknesses of substrate are utilized. Specimens of both thickness (0.4 and 1.5 mm) will be coated and then tested for tensile, creep, and fatigue properties.

Method of protecting the surface of a substrate. [by applying aluminide coating

NASA Technical Reports Server (NTRS)

Gedwill, M. A. (Inventor); Grisaffe, S. J.

1974-01-01

The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

Formation of Aluminide Coatings on Fe-Based Alloys by Chemical Vapor Deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ying; Pint, Bruce A; Cooley, Kevin M

2008-01-01

Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr-Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electronmore » probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr-Al pellets were replaced with Fe-Al metals in some aluminizing process runs and similar coatings were achieved.« less

Interdiffusion behaviors of iron aluminide coatings on China low activation martensitic steel

NASA Astrophysics Data System (ADS)

Zhu, X. X.; Yang, H. G.; Yuan, X. M.; Zhao, W. W.; Zhan, Q.

2014-12-01

The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe2Al5 layer was formed on CLAM substrate by pack cementation process with Fe2Al5 donor powder and NH4Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe2Al5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe2Al5 as a function of processing parameters. The Wagner's equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al.

Welding and Joining of Titanium Aluminides

PubMed Central

Cao, Jian; Qi, Junlei; Song, Xiaoguo; Feng, Jicai

2014-01-01

Welding and joining of titanium aluminides is the key to making them more attractive in industrial fields. The purpose of this review is to provide a comprehensive overview of recent progress in welding and joining of titanium aluminides, as well as to introduce current research and application. The possible methods available for titanium aluminides involve brazing, diffusion bonding, fusion welding, friction welding and reactive joining. Of the numerous methods, solid-state diffusion bonding and vacuum brazing have been most heavily investigated for producing reliable joints. The current state of understanding and development of every welding and joining method for titanium aluminides is addressed respectively. The focus is on the fundamental understanding of microstructure characteristics and processing–microstructure–property relationships in the welding and joining of titanium aluminides to themselves and to other materials. PMID:28788113

An Oxidation-Resistant Coating Alloy for Gamma Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P.; Smialek, James L.; Brindley, William J.

1997-01-01

Titanium aluminides based on the g-phase (TiAl) offer the potential for component weight savings of up to 50 percent over conventional superalloys in 600 to 850 C aerospace applications. Extensive development efforts over the past 10 years have led to the identification of "engineering" gamma-alloys, which offer a balance of room-temperature mechanical properties and high-temperature strength retention. The gamma class of titanium aluminides also offers oxidation and interstitial (oxygen and nitrogen) embrittlement resistance superior to that of the alpha(sub 2) (Ti3Al) and orthorhombic (Ti2AlNb) classes of titanium aluminides. However, environmental durability is still a concern, especially at temperatures above 750 to 800 C. Recent work at the NASA Lewis Research Center led to the development of an oxidation-resistant coating alloy that shows great promise for the protection of gamma titanium aluminides.

Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

1998-01-01

A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

Hot corrosion behavior of platinum-modified nickel- and cobalt-based alloys and coatings

NASA Astrophysics Data System (ADS)

Deodeshmukh, Vinay Prakash

High temperature degradation by hot corrosion (650-1000°C) and/or oxidation (>1000°C) can severely reduce the longevity of advanced gas turbine engine components. The protection of high-temperature components against hot corrosion or oxidation is typically conferred by the application of either a diffusion or overlay metallic coating that is able to form a continuous, adherent, and slow-growing oxide scale. There are currently no coatings that provide adequate protection to both hot corrosion and oxidation. Indeed, there is a particular need for such protective coatings because many advanced aero, marine, and industrial gas-turbines operate in both hot corrosion and oxidation regimes in their duty cycle. Recent work at Iowa State University (ISU) has showed that a wide range Pt+Hf-modified gamma'-Ni3Al + gamma-Ni alloy compositions form a very adherent and slow-growing Al 2O3 scale. In fact, the results reported suggest that Pt+Hf-modified gamma' + gamma coatings offer a viable superior alternative to beta-NiAl(Pt)-based coatings. The main thrust of this study was to assess and establish optimum target gamma' + gamma coating compositions for extending the service life of high-temperature gas turbine components exposed to hot corrosion and oxidation conditions. Both high temperature hot-corrosion (HTHC-900°C) and low temperature hot-corrosion (LTHC-705°C) behaviors of the Pt+Hf-modified gamma' + gamma alloys were assessed. The salt used to bring about hot corrosion was Na 2SO4. Quite interestingly, it was found that the HTHC resistance of gamma' + gamma alloys improved with up to about 10 at.% Pt addition, but then decreased significantly with increasing Pt content up to 30 at.% (the maximum level studied); however, under LTHC conditions the resistance of gamma' + gamma alloys improved with increasing Pt content up to 30 at.%. To further improve hot corrosion resistance of Pt+Hf-modified gamma' + gamma alloys, the effects of systematic additions of Cr, Si, and Cr+Si were assessed. The effects pre-oxidation treatments were also studied to further improve the hot corrosion resistance. In addition, high-temperature oxidation behavior of various modified of gamma' + gamma alloys was studied in air at 1150°C under both isothermal and cyclic oxidation conditions. Certain modified versions of gamma' + gamma coating composition(s) exhibited excellent resistance to both hot corrosion and oxidation. Finally, the HTHC and LTHC resistance of novel Pt+Hf-modified gamma' + gamma-based diffusion coatings using a pack cementation process developed at ISU were studied and compared with state-of-the-art commercial coatings. It was found that the Pt+Hf-modified gamma' + gamma coating exhibited superior resistance to both types of hot corrosion with the preoxidation treatment; while, only Pt-modified beta exhibited excellent LTHC resistance with no pre-oxidation treatment. This study also involved evaluating the hot corrosion resistance of various commercially available Pt-modified beta-NiAl diffusion aluminides and CoCrAlY-based overlay coatings for marine gas turbine engine components under both HTHC and LTHC conditions. The Al-Pt-rich beta aluminide exhibited improved resistance to both types of hot corrosion compared to the various Ni-rich beta aluminide and CoCrAlY coatings.

Thin coatings for protecting titanium aluminides in high-temperature oxidizing environments

NASA Technical Reports Server (NTRS)

Wiedemann, K. E.; Taylor, P. J.; Clark, R. K.; Wallace, T. A.

1991-01-01

Titanium aluminides have high specific strengths at high temperatures but are susceptible to environmental attack. Their use in many aerospace applications would require that they be protected with coatings that, for structural efficiency, must be thin. It is conceivable that acceptable coatings might be found in several oxide systems, and consequently, oxide coatings of many compositions were prepared from sol-gels for study. Response-surface methodology was used to refine coating compositions and factorial experiments were used to develop coating strategies. Oxygen permeability diagrams of two-layer coatings for several oxide systems, an analysis of multiple-layer coatings on rough and polished surfaces, and modeling of the oxidation weight gain are presented.

Enriched aluminide coatings for dispersion strengthened nickel materials

NASA Technical Reports Server (NTRS)

Levinstein, M. A.

1973-01-01

Improved aluminide/barrier coating combinations for dispersion strengthened nickel materials were investigated. The barrier materials involved alloys with refractory metal content to limit interdiffusion between the coating and the substrate, thereby minimizing void formation. Improved aluminide coatings involved the dispersion of aluminum-rich compounds. Coatings were tested in argon at 1533 K (2300 F) for 100 hours and in cyclic oxidation at 1422 K (2100 F). Two coatings on TDNiCr completed 300 hours of oxidation testing, none on TDNi. Selected coating combinations were evaluated in Mach 1 burner rig testing using JP-4 fuel and air at 1422 K (2100 F) and 1477 K (2200 F) for 350 and 100 hours, respectively. Static oxidation in 1-hour cycles was conducted at 1533 K (2300 F) for 100 hours. For comparison purposes a physical vapor deposition (PVD) NiCrAlY coating was tested concurrently. Only the NiCrA1Y coating survived the 1477 K (2200 F)/100-hour burner rig test and 275 hours of the 350-hour 1422 K (2100 F) test. Elevated temperature exposure reduced room temperature tensile properties but had little effect on elevated temperature properties.

The Oxidation and Protection of Gamma Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P.; Brindley, William J.; Smialek, James L.; Locci, Ivan E.

1996-01-01

The excellent density-specific properties of the gamma class of titanium aluminides make them attractive for intermediate-temperature (600-850 C) aerospace applications. The oxidation and embrittlement resistance of these alloys is superior to that of the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, since gamma alloys form an intermixed Al2O3/TiO2 scale in air rather than the desired continuous Al2O3 scale, oxidation resistance is inadequate at the high end of this temperature range (i.e., greater than 750-800 C). For applications at such temperatures, an oxidation-resistant coating will be needed; however, a major drawback of the oxidation-resistant coatings currently available is severe degradation in fatigue life by the coating. A new class of oxidation-resistant coatings based in the Ti-Al-Cr system offers the potential for improved fatigue life.

Oxidation and hot corrosion of coated and bare oxide dispersion strengthened superalloy MA-755E

NASA Technical Reports Server (NTRS)

Glasgow, T. K.; Santoro, G. J.

1981-01-01

Cyclic hot corrosion and oxidation of an experimental oxide dispersion strengthened (ODS) superalloy MA-755E were conducted in a hot gas stream at Mach 0.3. The response of the ODS alloy, bare or with protective coatings, was similar to that of a conventional cast alloy, IN-792, in hot corrosion at 900 C. However, during oxidation at 1100 and 1150 C the ODS alloy differed from the cast alloy by developing a greater amount of subsurface porosity. Compared with a diffused aluminide coating, an electron beam vapor deposited NiCrAlY coating offered superior oxidation protection and decreased porosity formation. In additional testing, the tendency to form porosity was associated with the large grains of recrystallized powder metallurgy alloys but was independent of the presence of an oxide dispersion.

Effects of silicon additions on oxidation and mechanical behavior of the nickel-base superalloy B-1900

NASA Technical Reports Server (NTRS)

Miner, R. V., Jr.; Lowell, C. E.

1975-01-01

Test specimens with nominal additions of Si were tested in oxidation, thermal fatigue, sulfidation, tension, and stress rupture, and were also extensively studied metallographically. Alloy B-1900 modified with 0.6- or 1.2-wt% Si exhibited oxidation resistance equivalent to that of aluminide-coated B-1900 during cyclic, high-gas-velocity oxidation tests. Resistances to thermal fatigue and sulfidation were improved by the Si additions, but were not superior to aluminide-coated B-1900. Stress-rupture tests at 1000 C of specimens given the standard heat treatment to simulate an aluminide coating cycle showed Si to be detrimental. However, application of another heat treatment increased the rupture life of the alloy with 0.6-wt% Si to that of the unmodified B-1900 given the standard heat treatment.

The effect of environment on thermal barrier coating lifetime

DOE PAGES

Pint, Bruce A.; Unocic, Kinga A.; Haynes, James Allen

2016-03-15

While the water vapor content of the combustion gas in natural gas-fired land-based turbines is ~10%, it can be 20–85% with coal-derived (syngas or H 2) fuels or innovative turbine concepts for more efficient carbon capture. Additional concepts envisage working fluids with high CO 2 contents to facilitate carbon capture and sequestration. To investigate the effects of changes in the gas composition on thermal barrier coating (TBC) lifetime, furnace cycling tests (1-h and 100-h cycles) were performed in air with 10, 50, and 90 vol. % water vapor and CO 2-10% H 2O and compared to prior results in drymore » air or O 2. Two types of TBCs were investigated: (1) diffusion bond coatings (Pt-diffusion or Pt-modified aluminide) with commercial electron-beam physical vapor-deposited yttria-stabilized zirconia (YSZ) top coatings on second-generation superalloy N5 and N515 substrates and (2) high-velocity oxygen fuel (HVOF) sprayed MCrAlYHfSi bond coatings with air plasma-sprayed YSZ top coatings on superalloys X4, 1483, or 247 substrates. For both types of coatings exposed in 1-h cycles, the addition of water vapor resulted in a decrease in coating lifetime, except for Pt-diffusion coatings which were unaffected by the environment. In 100-h cycles, environment was less critical, perhaps because coating failure was chemical (i.e., due to interdiffusion) rather than mechanical. As a result, in both 1-h and 100-h cycles, CO 2 did not appear to have any negative effect on coating lifetime.« less

Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces

NASA Technical Reports Server (NTRS)

Dussinger, Peter M.; Lindemuth, James E.

1997-01-01

The principal objective of this Phase 2 SBIR program was to develop and demonstrate a practically insoluble coating for nickel-based superalloys for Stirling engine heat pipe applications. Specific technical objectives of the program were: (1) Determine the solubility corrosion rates for Nickel 200, Inconel 718, and Udimet 72OLI in a simulated Stirling engine heat pipe environment, (2) Develop coating processes and techniques for capillary groove and screen wick structures, (3) Evaluate the durability and solubility corrosion rates for capillary groove and screen wick structures coated with an insoluble coating in cylindrical heat pipes operating under Stirling engine conditions, and (4) Design and fabricate a coated full-scale, partial segment of the current Stirling engine heat pipe for the Stirling Space Power Convertor program. The work effort successfully demonstrated a two-step nickel aluminide coating process for groove wick structures and interior wall surfaces in contact with liquid metals; demonstrated a one-step nickel aluminide coating process for nickel screen wick structures; and developed and demonstrated a two-step aluminum-to-nickel aluminide coating process for nickel screen wick structures. In addition, the full-scale, partial segment was fabricated and the interior surfaces and wick structures were coated. The heat pipe was charged with sodium, processed, and scheduled to be life tested for up to ten years as a Phase 3 effort.

Environmental protection to 922K (1200 F) for titanium alloys

NASA Technical Reports Server (NTRS)

Groves, M. T.

1973-01-01

Evaluations are presented of potential coating systems for protection of titanium alloys from hot-salt stress-corrosion up to temperatures of 755 K (900 F) and from oxidation embrittlement up to temperature of 922 K (1200 F). Diffusion type coatings containing Si, Al, Cr, Ni or Fe as single coating elements or in various combinations were evaluated for oxidation protection, hot-salt stress-corrosion (HSSC) resistance, effects on tensile properties, fatigue properties, erosion resistance and ballistic impact resistance on an alpha and beta phase titanium alloy (Ti-6Al-2Sn-4Zr-2Mo). All of the coatings investigated demonstrated excellent oxidation protectiveness, but none of the coatings provided protection from hot-salt stress-corrosion. Experimental results indicated that both the aluminide and silicide types of coatings actually decreased the HSSC resistance of the substrate alloy. The types of coatings which have typically been used for oxidation protection of refractory metals and nickel base superalloys are not suitable for titanium alloys because they increase the susceptibility to hot-salt stress-corrosion, and that entirely new coating concepts must be developed for titanium alloy protection in advanced turbine engines.

Successful Surface Treatments for Reducing Instabilities in Advanced Nickel-base Superalloys for Turbine Blades

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; MacKay, Rebecca A.; Garg, Anita; Ritzert, Frank J.

2004-01-01

An optimized carburization treatment has been developed to mitigate instabilities that form in the microstructures of advanced turbine airfoil materials. Current turbine airfoils consist of a single crystal superalloy base that provides the mechanical performance of the airfoil, a thermal barrier coating (TBC) that reduces the temperature of the base superalloy, and a bondcoat between the superalloy and the TBC, that improves the oxidation and corrosion resistance of the base superalloy and the spallation resistance of the TBC. Advanced nickel-base superalloys containing high levels of refractory metals have been observed to develop an instability called secondary reaction zone (SRZ), which can form beneath diffusion aluminide bondcoats. This instability between the superalloy and the bondcoat has the potential of reducing the mechanical properties of thin-wall turbine airfoils. Controlled gas carburization treatments combined with a prior stress relief heat treatment and adequate surface preparation have been utilized effectively to minimize the formation of SRZ. These additional processing steps are employed before the aluminide bondcoat is deposited and are believed to change the local chemistry and local stresses of the surface of the superalloy. This paper presents the detailed processing steps used to reduce SRZ between platinum aluminide bondcoats and advanced single crystal superalloys.

Low cost high temperature, duplex coating for superalloys

NASA Technical Reports Server (NTRS)

Young, S. G.; Deadmore, D. L.

1981-01-01

Duplex silicon-slurry/aluminide coating substantially improves high temperature resistance to oxidation and corrosion of nickel base alloys. Coating used in critical sections of power systems like turbojet engines extends their operating capabilities.

Plasma Spray and Pack Cementation Process Optimization and Oxidation Behaviour of Novel Multilayered Coatings

NASA Astrophysics Data System (ADS)

Gao, Feng

The hot section components in gas turbines are subjected to a harsh environment with the temperature being increased continuously. The higher temperature has directly resulted in severe oxidation of these components. Monolithic coatings such as MCrAIY and aluminide have been traditionally used to protect the components from oxidation; however, increased operating temperature quickly deteriorates the coatings due to accelerated diffusion of aluminum in the coatings. To improve the oxidation resistance a group of multilayered coatings are developed in this study. The multilayered coatings consist of a Cr-Si co-deposited layer as the diffusion barrier, a plasma sprayed NiCrA1Y coating as the middle layer and an aluminized top layer. The Cr-Si and aluminized layers are fabricated using pack cementation processes and the NiCrA1Y coatings are produced using the Mettech Axial III(TM) System. All of the coating processes are optimized using the methodology of Design of Experiments (DOE) and the results are analyzed using statistical method. The optimal processes are adopted to fabricate the multilayered coatings for oxidation tests. The coatings are exposed in air at 1050°C and 1150°C for 1000 hr. The results indicate that a Cr layer and a silicon-rich barrier layer have formed on the interface between the Cr-Si coating and the NiCrA1Y coating. This barrier layer not only prevents aluminum and chromium from diffusing into the substrate, but also impedes the diffusion of other elements from the substrate into the coating. The results also reveal that, for optimal oxidation resistance at 1050°C, the top layer in a multilayered coating should have at least Al/Ni ratio of one; whereas the multilayered coating with the All Ni ratio of two in the top layer exhibits the best oxidation resistance at 1150°C. The DOE methodology provides an excellent means for process optimization and the selection of oxidation test matrix, and also offers a more thorough understanding of the effects of process parameters on the coating microstructure, and the effects of layers and their interactions on the oxidation behavior of the multilayered coatings.

Oxidation, Creep And Fatigue Properties of Bare and Coated 31V alloy

DOE PAGES

Dryepondt, Sebastien N.; Jones, Samuel J.; Zhang, Ying; ...

2014-12-06

Increasing the efficiency of natural gas reciprocating engines will require materials with better mechanical and corrosion resistance at high temperatures. One solution to increase the lifetime of exhaust valves is to apply an aluminide coating to prevent corrosion assisted fatigue cracking, but the impact of the coating on the valve material mechanical properties needs to be assessed. Creep and high cycle fatigue (HCF) testing were conducted at 816°C on bare and slurry or pack-coated 31V alloy. After annealing according to the 31V standard heat treatment, the coated and bare creep specimens exhibited very similar creep rupture lives. The HCF behaviormore » of the pack-coated alloy was close to the behavior of the bar alloy, but fatigue lifetimes of slurry-coated 31V specimens had higher variability. Aluminide coatings have the potential to improve the valve performance at high temperature, but the coating deposition process needs to be tailored for the substrate standard heat treatment.« less

Diffusion coefficient of hydrogen in a cast gamma titanium aluminide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sundaram, P.A.; Wessel, E.; Ennis, P.J.

1999-06-04

Gamma titanium aluminides have the potential for high temperature applications because of their high specific strength and specific modulus. Their oxidation resistance is good, especially at intermediate temperatures and with suitable alloying additions, good oxidation resistance can be obtained up to 800 C. One critical area of application is in combustion engines in aero-space vehicles such as hypersonic airplanes and high speed civil transport airplanes. This entails the use of hydrogen as a fuel component and hence the effect of hydrogen on the mechanical properties of gamma titanium aluminides is of significant scientific and technological utility. The purpose of thismore » short investigation is to use an electrochemical method under galvanostatic conditions to determine the diffusion coefficient of hydrogen in a cast gamma titanium aluminide, a typical technical alloy with potential application in gas turbines under creep conditions. This result will be then compared with that obtained by microhardness profiling of electrolytically hydrogen precharged material.« less

Life prediction and constitutive models for engine hot section anisotropic materials program

NASA Technical Reports Server (NTRS)

Swanson, G. A.; Linask, I.; Nissley, D. M.; Norris, P. P.; Meyer, T. G.; Walker, K. P.

1986-01-01

This report presents the results of the first year of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and/or fatigue data, tests were conducted on coated and uncoated PWA 1480 specimens tensilely loaded in the 100 , 110 , 111 , and 123 directions. A literature survey of constitutive models was completed for both single crystal alloys and metallic coating materials; candidate models were selected. One constitutive model under consideration for single crystal alloys applies Walker's micromechanical viscoplastic formulation to all slip systems participating in the single crystal deformation. The constitutive models for the overlay coating correlate the viscoplastic data well. For the aluminide coating, a unique test method is under development. LCF and TMF tests are underway. The two coatings caused a significant drop in fatigue life, and each produced a much different failure mechanism.

Iron aluminide alloy coatings and joints, and methods of forming

DOEpatents

Wright, Richard N.; Wright, Julie K.; Moore, Glenn A.

1994-01-01

A method of joining two bodies together, at least one of the bodies being predominantly composed of metal, the two bodies each having a respective joint surface for joining with the joint surface of the other body, the two bodies having a respective melting point, includes the following steps: a) providing aluminum metal and iron metal on at least one of the joint surfaces of the two bodies; b) after providing the aluminum metal and iron metal on the one joint surface, positioning the joint surfaces of the two bodies in juxtaposition against one another with the aluminum and iron positioned therebetween; c) heating the aluminum and iron on the juxtaposed bodies to a temperature from greater than or equal to 600.degree. C. to less than the melting point of the lower melting point body; d) applying pressure on the juxtaposed surfaces; and e) maintaining the pressure and the temperature for a time period effective to form the aluminum and iron into an iron aluminide alloy joint which bonds the juxtaposed surfaces and correspondingly the two bodies together. The method can also effectively be used to coat a body with an iron aluminide coating.

Iron aluminide alloy coatings and joints, and methods of forming

DOEpatents

Wright, R.N.; Wright, J.K.; Moore, G.A.

1994-09-27

Disclosed is a method of joining two bodies together, at least one of the bodies being predominantly composed of metal, the two bodies each having a respective joint surface for joining with the joint surface of the other body, the two bodies having a respective melting point, includes the following steps: (a) providing aluminum metal and iron metal on at least one of the joint surfaces of the two bodies; (b) after providing the aluminum metal and iron metal on the one joint surface, positioning the joint surfaces of the two bodies in juxtaposition against one another with the aluminum and iron positioned therebetween; (c) heating the aluminum and iron on the juxtaposed bodies to a temperature from greater than or equal to 600 C to less than the melting point of the lower melting point body; (d) applying pressure on the juxtaposed surfaces; and (e) maintaining the pressure and the temperature for a time period effective to form the aluminum and iron into an iron aluminide alloy joint which bonds the juxtaposed surfaces and correspondingly the two bodies together. The method can also effectively be used to coat a body with an iron aluminide coating.

Duplex aluminized coatings

NASA Technical Reports Server (NTRS)

Gedwill, M. A.; Grisaffe, S. J. (Inventor)

1975-01-01

The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

The effect of Cr, Co, Al, Mo and Ta on a series of cast Ni-base superalloys on the stability of an aluminide coating during cyclic oxidation in Mach 0.3 burner rig

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.; Barrett, C. A.

1986-01-01

The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-based gamma/gamma'superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on a full 2(sup 5)-fractional statistical design supplemented by 10 star point alloys and a center point alloy. This full central composite design of 43 alloys plus two additional alloys with extreme Al levels allowed a complete second degree estimating equation to be derived from the 5-compositional variables. The weight change/time data for the coated samples fitted well to the paralinear oxidation model and enabled a modified oxidation attack parameter, K'(sub a) to be derived to rank the alloys and log K' (sub a ) to be used as the dependent variable in the estimating equation to determine the oxidation resistance of the coating as a function of the underlying alloy content. The most protective aluminide coatings are associated with the highest possible base ally contents of CR and Al and at a 4 percent Ta level. The Mo and Co effects interact but at fixed levels of 0, 5, or 10% Co. A 4% Mo level is optimum.

Magnetohydrodynamic electrode

DOEpatents

Marchant, David D.; Killpatrick, Don H.

1978-01-01

An electrode capable of withstanding high temperatures and suitable for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator consists of a sintered powdered metal base portion, the upper surface of the base being coated with a first layer of nickel aluminide, an intermediate layer of a mixture of nickel aluminide - refractory ceramic on the first layer and a third or outer layer of a refractory ceramic material on the intermediate layer. The sintered powdered metal base resists spalling by the ceramic coatings and permits greater electrode compliance to thermal shock. The density of the powdered metal base can be varied to allow optimization of the thermal conductivity of the electrode and prevent excess heat loss from the channel.

Plasma electrolytic oxidation of Titanium Aluminides

NASA Astrophysics Data System (ADS)

Morgenstern, R.; Sieber, M.; Grund, T.; Lampke, T.; Wielage, B.

2016-03-01

Due to their outstanding specific mechanical and high-temperature properties, titanium aluminides exhibit a high potential for lightweight components exposed to high temperatures. However, their application is limited through their low wear resistance and the increasing high-temperature oxidation starting from about 750 °C. By the use of oxide ceramic coatings, these constraints can be set aside and the possible applications of titanium aluminides can be extended. The plasma electrolytic oxidation (PEO) represents a process for the generation of oxide ceramic conversion coatings with high thickness. The current work aims at the clarification of different electrolyte components’ influences on the oxide layer evolution on alloy TNM-B1 (Ti43.5Al4Nb1Mo0.1B) and the creation of compact and wear resistant coatings. Model experiments were applied using a ramp-wise increase of the anodic potential in order to show the influence of electrolyte components on the discharge initiation and the early stage of the oxide layer growth. The production of PEO layers with technically relevant thicknesses close to 100 μm was conducted in alkaline electrolytes with varying amounts of Na2SiO3·5H2O and K4P2O7 under symmetrically pulsed current conditions. Coating properties were evaluated with regard to morphology, chemical composition, hardness and wear resistance. The addition of phosphates and silicates leads to an increasing substrate passivation and the growth of compact oxide layers with higher thicknesses. Optimal electrolyte compositions for maximum coating hardness and thickness were identified by statistical analysis. Under these conditions, a homogeneous inner layer with low porosity can be achieved. The frictional wear behavior of the compact coating layer is superior to a hard anodized layer on aluminum.

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5, Section 4: Processing: Matrices and Composites. Part 1

DTIC Science & Technology

1989-10-15

aluminides such as those in Ni, Fe, Nb and Ti systems have received considerable attention. In the development and evaluation of mechanical properties ...The first section in Book 1 is concerned with the properties and structure of bimaterial interfaces and the related problem of coating decohesion and...accomplished in a few hours. CONSOLIDATION - HIP consolidation of titanium aluminide powders produced by Rapid Solidification Rate (RSR) and Rotating

Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel

NASA Astrophysics Data System (ADS)

Huilgol, Prashant; Rajendra Udupa, K.; Udaya Bhat, K.

2018-02-01

Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.

Insoluble coatings for Stirling engine heat pipe condenser surfaces

NASA Astrophysics Data System (ADS)

Dussinger, Peter M.

1993-09-01

The work done by Thermacore, Inc., Lancaster, Pennsylvania, for the Phase 1, 1992 SBIR National Aeronautics and Space Administration Contract, 'Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces' is described. The work was performed between January 1992 and July 1992. Stirling heat engines are being developed for electrical power generation use on manned and unmanned earth orbital and planetary missions. Dish Stirling solar systems and nuclear reactor Stirling systems are two of the most promising applications of the Stirling engine electrical power generation technology. The sources of thermal energy used to drive the Stirling engine typically are non-uniform in temperature and heat flux. Liquid metal heat pipe receivers are used as thermal transformers and isothermalizers to deliver the thermal energy at a uniform high temperature to the heat input section of the Stirling engine. The use of a heat pipe receiver greatly enhances system efficiency and potential life span. One issue that is raised during the design phase of heat pipe receivers is the potential solubility corrosion of the Stirling engine heat input section by the liquid metal working fluid. This Phase 1 effort initiated a program to evaluate and demonstrate coatings, applied to nickel based Stirling engine heater head materials, that are practically 'insoluble' in sodium, potassium, and NaK. This program initiated a study of nickel aluminide as a coating and developed and demonstrated a heat pipe test vehicle that can be used to test candidate materials and coatings. Nickel 200 and nickel aluminide coated Nickel 200 were tested for 1000 hours at 800 C at a condensation heat flux of 25 W/sq cm. Subsequent analyses of the samples showed no visible sign of solubility corrosion of either coated or uncoated samples. The analysis technique, photomicrographs at 200X, has a resolution of better than 2.5 microns (.0001 in). The results indicate that the heat pipe environment is not directly comparable to liquid metal pumped loop data, that nickel aluminide is still a leading candidate for solubility corrosion protection, and that longer duration tests are required to reach a definitive conclusion whether coatings are required at all. Should further testing be required, the test vehicle and analytical tools were developed.

Insoluble coatings for Stirling engine heat pipe condenser surfaces

NASA Technical Reports Server (NTRS)

Dussinger, Peter M.

1993-01-01

The work done by Thermacore, Inc., Lancaster, Pennsylvania, for the Phase 1, 1992 SBIR National Aeronautics and Space Administration Contract, 'Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces' is described. The work was performed between January 1992 and July 1992. Stirling heat engines are being developed for electrical power generation use on manned and unmanned earth orbital and planetary missions. Dish Stirling solar systems and nuclear reactor Stirling systems are two of the most promising applications of the Stirling engine electrical power generation technology. The sources of thermal energy used to drive the Stirling engine typically are non-uniform in temperature and heat flux. Liquid metal heat pipe receivers are used as thermal transformers and isothermalizers to deliver the thermal energy at a uniform high temperature to the heat input section of the Stirling engine. The use of a heat pipe receiver greatly enhances system efficiency and potential life span. One issue that is raised during the design phase of heat pipe receivers is the potential solubility corrosion of the Stirling engine heat input section by the liquid metal working fluid. This Phase 1 effort initiated a program to evaluate and demonstrate coatings, applied to nickel based Stirling engine heater head materials, that are practically 'insoluble' in sodium, potassium, and NaK. This program initiated a study of nickel aluminide as a coating and developed and demonstrated a heat pipe test vehicle that can be used to test candidate materials and coatings. Nickel 200 and nickel aluminide coated Nickel 200 were tested for 1000 hours at 800 C at a condensation heat flux of 25 W/sq cm. Subsequent analyses of the samples showed no visible sign of solubility corrosion of either coated or uncoated samples. The analysis technique, photomicrographs at 200X, has a resolution of better than 2.5 microns (.0001 in). The results indicate that the heat pipe environment is not directly comparable to liquid metal pumped loop data, that nickel aluminide is still a leading candidate for solubility corrosion protection, and that longer duration tests are required to reach a definitive conclusion whether coatings are required at all. Should further testing be required, the test vehicle and analytical tools were developed.

Effects of silver and group II fluoride solid lubricant additions to plasma-sprayed chromium carbide coatings for foil gas bearings to 650 C

NASA Technical Reports Server (NTRS)

Wagner, R. C.; Sliney, Harold E.

1986-01-01

A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start-stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 748. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The additional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-Psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rPm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

MANTECH Project Book, 1992

DTIC Science & Technology

1992-01-01

RUGATE FILTER PROCESS AND PRODUCTION ................ 111 MANUFACTURING SCIENCE FOR TITANIUM ALUMINIDE COMPOSITE ENGINE STRU CTURES...rejection and mission filters , anti-reflection coatings, and dichroic layers which can have demanding optical requirements. Rugate m coatings can be used to...SCIENCE RUGATE FILTER PROCESS AND PRODUCTION CONTRACT NUMBER: F33615-86-C-5059STATEMENT OF NEED Achieving the optical performance specifications for

Creep fatigue life prediction for engine hot section materials (isotropic)

NASA Technical Reports Server (NTRS)

Nelson, R. S.; Levan, G. W.; Schoendorf, J. F.

1992-01-01

A series of high temperature strain controlled fatigue tests have been completed to study the effects of thermomechanical fatigue, multiaxial loading, reactive environments, and imposed mean stresses. The baseline alloy used in these tests was cast B1900+Hf (with and without coatings); a small number of tests of wrought INCO 718 are also included. A strong path dependence was demonstrated during the thermomechanical fatigue testing, using in-phase, out-phase, and non-proportional (elliptical and 'dogleg') strain-temperature cycles. The multiaxial tests also demonstrated cycle path to be a significant variable, using both proportional and non-proportional tension-torsion loading. Environmental screening tests were conducted in moderate pressure oxygen and purified argon; the oxygen reduced the specimen lives by two, while the argon testing produced ambiguous data. Both NiCoCrAlY overlay and diffusion aluminide coatings were evaluated under isothermal and TMF conditions; in general, the lives of the coated specimens were higher that those of uncoated specimens. Controlled mean stress TMF tests showed that small mean stress changes could change initiation lives by orders of magnitude; these results are not conservatively predicted using traditional linear damage summation rules. Microstructures were evaluated using optical, SEM and TEM methods.

Progress in Protective Coatings for Aircraft Gas Turbines: A Review of NASA Sponsored Research

NASA Technical Reports Server (NTRS)

Merutka, J. P.

1981-01-01

Problems associated with protective coatings for advanced aircraft gas turbines are reviewed. Metallic coatings for preventing titanium fires in compressors are identified. Coatings for turbine section are also considered, Ductile aluminide coatings for protecting internal turbine-blade cooling passage surface are also identified. Composite modified external overlay MCrAlY coatings deposited by low-pressure plasma spraying are found to be better in surface protection capability than vapor deposited MCrAlY coatings. Thermal barrier coating (TBC), studies are presented. The design of a turbine airfoil is integrated with a TBC, and computer-aided manufacturing technology is applied.

Aluminide slurry coatings for protection of ferritic steel in molten nitrate corrosion for concentrated solar power technology

NASA Astrophysics Data System (ADS)

Audigié, Pauline; Bizien, Nicolas; Baráibar, Ignacio; Rodríguez, Sergio; Pastor, Ana; Hernández, Marta; Agüero, Alina

2017-06-01

Molten nitrates can be employed as heat storage fluids in solar concentration power plants. However molten nitrates are corrosive and if operating temperatures are raised to increase efficiencies, the corrosion rates will also increase. High temperature corrosion resistant coatings based on Al have demonstrated excellent results in other sectors such as gas turbines. Aluminide slurry coated and uncoated P92 steel specimens were exposed to the so called Solar Salt (industrial grade), a binary eutectic mixture of 60 % NaNO3 - 40 % KNO3, in air for 2000 hours at 550°C and 580°C in order to analyze their behavior as candidates to be used in future solar concentration power plants employing molten nitrates as heat transfer fluids. Coated ferritic steels constitute a lower cost technology than Ni based alloy. Two different coating morphologies resulting from two heat treatment performed at 700 and 1050°C after slurry application were tested. The coated systems exhibited excellent corrosion resistance at both temperatures, whereas uncoated P92 showed significant mass loss from the beginning of the test. The coatings showed very slow reaction with the molten Solar Salt. In contrast, uncoated P92 developed a stratified, unprotected Fe, Cr oxide with low adherence which shows oscillating Cr content as a function of coating depth. NaFeO2 was also found at the oxide surface as well as within the Fe, Cr oxide.

Effects of silver and group 2 fluorides addition to plasma sprayed chromium carbide high temperature solid lubricant for foil gas bearing to 650 deg C

NASA Technical Reports Server (NTRS)

Wagner, R. C.; Sliney, H. E.

1984-01-01

A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start/stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 718. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The addtitional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rpm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

Thermal coatings for titanium-aluminum alloys

NASA Technical Reports Server (NTRS)

Cunnington, George R.; Clark, Ronald K.; Robinson, John C.

1993-01-01

Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer.

High temperature surface protection. [10 gas turbines

NASA Technical Reports Server (NTRS)

Levine, S. R.

1978-01-01

Alloys of the MCrAlX type are the basis for high temperature surface protection systems in gas turbines. M can be one or more of Ni, Co, or Fe and X denotes a reactive metal added to enhance oxide scale adherence. The selection and formation as well as the oxidation, hot corrosion and thermal fatigue performance of MCrAlX coatings are discussed. Coatings covered range from simple aluminides formed by pack cementation to the more advanced physical vapor deposition overlay coatings and developmental plasma spray deposited thermal barrier coatings.

Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

NASA Astrophysics Data System (ADS)

Banu, Alexandra; Marcu, Maria; Petrescu, Simona; Ionescu, Nicolae; Paraschiv, Alexandru

2016-12-01

This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resistance behavior of two titanium aluminides of α2 + γ(Ti3Al + TiAl) and orthorhombic Ti2NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti2NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.

Examination of the influence of coatings on thin superalloy sections. Volume 2: Detailed procedures and data. [corrosion resistance

NASA Technical Reports Server (NTRS)

Kaufman, M.

1974-01-01

The effects of an aluminide coating, Codep B-1, and of section thickness were investigated on two cast nickel base superalloys, Rene 80 and Rene 120. Cast section thicknesses ranged from 0.038 cm to 0.15 cm. Simulated engine exposures for 1000 hours at 899C or 982C in a jet fuel burner rig with cyclic air cooling were studied, as were the effects of surface machining before coating and re-machining and re-coating after exposures. The properties evaluated included tensile at room temperature., 871C and 982C, stress rupture at 760C, 871C, 982C and 1093C, high cycle mechanical fatigue at room temperature., and thermal fatigue with a 1093C peak temperature. Thin sections had tensile strengths similar to standard size bars up to 871C and lower strengths at 982C and above, with equivalent elongation, and stress rupture life was lower for thin sections at all test conditions. The aluminide coating lowered tensile and rupture strengths up to 871C, with greater effects on thinner specimens. Elevated temperature exposure lowered tensile and rupture strengths of thinner specimens at the lower test temperatures. Surface machining had little effect on properties, but re-machining after exposure reduced thickness and increased metallurgical changes enough to lower properties at most test conditions.

Use of ion beams to simulate reaction of reactor fuels with their cladding

NASA Astrophysics Data System (ADS)

Birtcher, R. C.; Baldo, P.

2006-01-01

Processes occurring within reactor cores are not amenable to direct experimental observation. Among major concerns are damage, fission gas accumulation and reaction between the fuel and its cladding all of which lead to swelling. These questions can be investigated through simulation with ion beams. As an example, we discuss the irradiation driven interaction of uranium-molybdenum alloys, intended for use as low-enrichment reactor fuels, with aluminum, which is used as fuel cladding. Uranium-molybdenum coated with a 100 nm thin film of aluminum was irradiated with 3 MeV Kr ions to simulate fission fragment damage. Mixing and diffusion of aluminum was followed as a function of irradiation with RBS and nuclear reaction analysis using the 27Al(p,γ)28Si reaction which occurs at a proton energy of 991.9 keV. During irradiation at 150 °C, aluminum diffused into the uranium alloy at a irradiation driven diffusion rate of 30 nm2/dpa. At a dose of 90 dpa, uranium diffusion into the aluminum layer resulted in formation of an aluminide phase at the initial interface. The thickness of this phase grew until it consumed the aluminum layer. The rapid diffusion of Al into these reactor fuels may offer explanation of the observation that porosity is not observed in the fuel particles but on their periphery.

Coating-Substrate Systems for Thermomechanically Durable Turbine Airfoils

DTIC Science & Technology

2015-06-30

vapor phase NiA ! aluminide and NiAI(Cr.Zr) coated Rene N5 samples cycled at 1093°C with Ae, = 0.35%. PtAI VPA NiAI(Cr,Zr) EQ Y-Y’ 10000.0... 505 (2001). 2. T.M. Pollock and S. Tin, AIAA J. Propulsion and Power, 22, 2, (2006), pp. 361 - 374. 3. A.G. Evans, D.R. Clarke and C.G. Lev

Surface modifications of steels to improve corrosion resistance in sulfidizing-oxidizing environments

NASA Astrophysics Data System (ADS)

Behrani, Vikas

Industrial and power generation processes employ units like boilers and gasifiers to burn sulfur containing fuels to produce steam and syn gas (H 2 and CO), which can generate electricity using turbines and fuel cells. These units often operate under environments containing gases such as H 2S, SO2, O2 etc, which can attack the metallic structure and impose serious problems of corrosion. Corrosion control in high temperature sulfur bearing environments is a challenging problem requiring information on local gaseous species at the surface of alloy and mechanisms of degradation in these environments. Coatings have proved to be a better alternative for improving corrosion resistance without compromising the bulk mechanical properties. Changes in process conditions may result in thermal and/or environment cycling between oxidizing and sulfidizing environments at the alloy surface, which can damage the protective scale formed on the alloy surface, leading to increase in corrosion rates. Objective of this study was to understand the effect of fluctuating environments on corrosion kinetics of carbon steels and develop diffusion based coatings to mitigate the high temperatures corrosion under these conditions. More specifically, the focus was: (1) to characterize the local gaseous environments at the surface of alloys in boilers; (2) optimizing diffusion coatings parameters for carbon steel; (3) understand the underlying failure mechanisms in cyclic environments; (4) to improve aluminide coating behavior by co-deposition of reactive elements such as Yttrium and Hafnium; (5) to formulate a plausible mechanism of coating growth and effects of alloying elements on corrosion; and (6) to understand the spallation behavior of scale by measuring stresses in the scales. The understanding of coating mechanism and effects of fluctuating gaseous environments provides information for designing materials with more reliable performance. The study also investigates the mechanism behind the effect of REs on scale adhesion and sulfidation behavior. Thus, the present work will have a broad impact on the field of materials and coatings selection for high temperature industrial environments such as boilers and gasifiers, and provides information on RE-modified aluminized coatings on carbon steel as an alternative for the use of bulk superalloys under high temperature sulfur bearing environments.

Development of Oxidation Protection Coatings for Gamma Titanium Aluminide Alloys

NASA Technical Reports Server (NTRS)

Wallace, T. A.; Bird, R. K.; Sankaran, S. N.

2003-01-01

Metallic material systems play a key role in meeting the stringent weight and durability requirements for reusable launch vehicle (RLV) airframe hot structures. Gamma titanium aluminides (gamma-TiAl) have been identified as high-payoff materials for high-temperature applications. The low density and good elevated temperature mechanical properties of gamma-TiAl alloys make them attractive candidates for durable lightweight hot structure and thermal protection systems at temperatures as high as 871 C. However, oxidation significantly degrades gamma-TiAl alloys under the high-temperature service conditions associated with the RLV operating environment. This paper discusses ongoing efforts at NASA Langley Research Center to develop durable ultrathin coatings for protecting gamma-TiAl alloys from high-temperature oxidation environments. In addition to offering oxidation protection, these multifunctional coatings are being engineered to provide thermal control features to help minimize heat input into the hot structures. This paper describes the coating development effort and discusses the effects of long-term high-temperature exposures on the microstructure of coated and uncoated gamma-TiAl alloys. The alloy of primary consideration was the Plansee alloy gamma-Met, but limited studies of the newer alloy gamma-Met-PX were also included. The oxidation behavior of the uncoated materials was evaluated over the temperature range of 704 C to 871 C. Sol-gel-based coatings were applied to the gamma-TiAl samples by dipping and spraying, and the performance evaluated at 871 C. Results showed that the coatings improve the oxidation resistance, but that further development is necessary.

Ultrahigh vacuum, high temperature, low cycle fatigue of coated and uncoated Rene 80

NASA Technical Reports Server (NTRS)

Kortovich, C. S.

1976-01-01

A study was conducted on the ultrahigh vacuum strain controlled by low cycle fatigue behavior of uncoated and CODEP B-1 aluminide coated Rene' 80 nickel-base superalloy at 1000 C (1832 F) and 871 C (1600 F). The results indicated little effect of coating or temperature on the fatigue properties. There was, however, a significant effect on fatigue life when creep was introduced into the strain cycles. The effect of this creep component was analyzed in terms of the method of strainrange partitioning.

K-Rb Laser Pump Lamp

DTIC Science & Technology

1975-11-01

for K-Rb Lamps With Xenon and Argon Figure 25 Specimen for Protective Coating Evaluation 65 Figure 26 Specimen Coated With Fused Tin- Aluminide After...through hot titanium and copper purifiers to maia.in low levels (a few ppm) of oxygen, nitrogen and water vapor. The box also contains an integral...case with titanium , zirconium, thorium, and other common reactive metals. 15 - -’-- .--󈨑CP>4 -_ A thin strip of uranium is inserted into the fill

Environmentally Resistant Mo-Si-B-Based Coatings

NASA Astrophysics Data System (ADS)

Perepezko, J. H.; Sossaman, T. A.; Taylor, M.

2017-06-01

High-temperature applications have demonstrated aluminide-coated nickel-base superalloys to be remarkably effective, but are reaching their service limit. Alternate materials such as refractory (e.g., W, Mo) silicide alloys and SiC composites are being considered to extend high temperature capability, but the silica surfaces on these materials require coatings for enhanced environmental resistance. This can be accomplished with a Mo-Si-B-based coating that is deposited by a spray deposition of Mo followed by a chemical vapor deposition of Si and B by pack cementation to develop an aluminoborosilica surface. Oxidation of the as-deposited (Si + B)-pack coatings proceeds with partial consumption of the initial MoSi2 forming amorphous silica. This Si depletion leads to formation of a B-saturated Mo5Si3 (T1) phase. Reactions between the Mo and the B rich phases develop an underlying Mo5SiB2 (T2) layer. The T1 phase saturated with B has robust oxidation resistance, and the Si depletion is prevented by the underlying diffusion barrier (T2). Further, due to the natural phase transformation characteristics of the Mo-Si-B system, cracks or scratches to the outer silica and T1 layers can be repaired from the Si and B reservoirs of T2 + MoB layer to yield a self-healing characteristic. Mo-Si-B-based coatings demonstrate robust performance up to at least 1700 °C not only to the rigors of elevated temperature oxidation, but also to CMAS attack, hot corrosion attack, water vapor and thermal cycling.

Department of Defense Program Solicitation 94; Small Business Technology Transfer (STTR) Program; Fiscal Year 1994.

DTIC Science & Technology

1994-01-01

advanced diesel engine components; high-temperature titanium aluminide and Al-Fe alloys for aircraft and missile engines; environmentally compliant...gun-chamber liners and KE penetrator stabilizer fins, tips, and leading edges; low cost, ceramic thermal barrier coatings for gas turbine blades and

AFWAL FY80 Technical Accomplishments Report.

DTIC Science & Technology

1981-12-01

through cooperative effort of the Materials and Certain compositions in the titanium aluminide Propulsion Laboratories. In addition to an extensive system...Bonded Structures Technology Transitioned .................................................. 43 Superplastically Formed and Diffusion Bonded Titanium ...Technology ................................................................................................. 75 First RSR Radial Wafer Blade Engine Test

Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets

NASA Technical Reports Server (NTRS)

Hoffmann, E. K.; Bird, R. K.; Bales, T. T.

1989-01-01

A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

The Corrosion Control of Fastening Systems for Aircraft Carrier Steam Catapults

DTIC Science & Technology

1976-03-31

mixture AT Aluminum powder and titanium powder 1:1 mixture MP Multiphase MP35N (powder) NA Nickel Aluminide base coat and aluminum top coat T Titanium ...Subsequent lifting or peeling was also accomplished by the use of a knife blade on areas not in contact with the "Fette Head". The densification process "s...75 of big bolt. White Titanium corrosion products elsewhere. After 552 hr. 57 salt spray AT .002 Aluminum/ Red rust in recess bottom around Titanium

An Investigation of the Oxide Adhesion and Growth Characteristics on Platinum Modified Aluminide Coatings.

DTIC Science & Technology

1986-09-01

OfI STANDARITD N0 A S In 0 Lfl NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS 49 o AN INVESTIGATION OF THE OXIDE ADHESION AND GROWTH...CHARACTERISTICS ON PLATINUM MODIFIED ALUMIINIDE COATINGS by Margaret Shannon Farrell September 1986 Thesis Advisor: P. H. Boone Approved for public release...COVERED 14 DATE OF REPORT (Year, Month. Day) 15 PAGE COLNT Mlaster’s Thesis FROM TO__ 1986 September 61 𔄀 5i-PALEV ENTARY NOTATION - COSATI CODES 18

Evaluation of iron aluminide weld overlays for erosion - corrosion resistant boiler tube coatings in low NO{sub x} boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

DuPont, J.N.; Banovic, S.W.; Marder, A.R.

1996-08-01

Low NOx burners are being installed in many fossil fired power plants in order to comply with new Clean Air Regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion is often enhanced and premature tube failures can occur. Failures due to oxidation and solid particle erosion are also a concern. A program was initiated in early 1996 to evaluate the use of iron aluminide weld overlays for erosion/corrosion protection of boiler tubes in Low NOx boilers. Composite iron/aluminum wires will be used with the Gas Metal Arc Welding (GMAW) process to prepare overlays on boiler tubesmore » steels with aluminum contents from 8 to 16wt%. The weldability of the composite wires will be evaluated as a function of chemical composition and welding parameters. The effect of overlay composition on corrosion (oxidation and sulfidation) and solid particle erosion will also be evaluated. The laboratory studies will be complemented by field exposures of both iron aluminide weld overlays and co-extruded tubing under actual boiler conditions.« less

9th Annual Science and Engineering Technology Conference

DTIC Science & Technology

2008-04-17

Disks Composite Technology Titanium Aluminides Processing Microstructure Properties Curve Generator Go-Forward: Integrated Materials & Process Models...Initiatives Current DPA/T3s: Atomic Layer Deposition Hermetic Coatings: ...domestic ALD for electronic components; transition to fabrication process ...Production windows estim • Process capability fully established >Production specifications in place >Supply chain established •All necessary property

Reactive multilayer synthesis of hard ceramic foils and films

DOEpatents

Makowiecki, Daniel M.; Holt, Joseph B.

1996-01-01

A method for synthesizing hard ceramic materials such as carbides, borides nd aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coild as a tape for later use.

Preparation of low-sulfur platinum and platinum aluminide layers in thermal barrier coatings

NASA Technical Reports Server (NTRS)

Spitsberg, Irene T. (Inventor); Walston, William S. (Inventor); Schaeffer, Jon C. (Inventor)

2003-01-01

A method for preparing a coated nickel-base superalloy article reduces the sulfur content of the surface region of the metallic coating layers to low levels, thereby improving the adhesion of the coating layers to the article. The method includes depositing a first layer of platinum overlying the surface of a substrate, depositing a second layer of aluminum over the platinum, and final desulfurizing the article by heating the article to elevated temperature, preferably in hydrogen, and removing a small amount of material from the surface that was exposed during the step of heating. A ceramic layer may be deposited over the desulfurized article. The article may also be similarly desulfurized at other points in the fabrication procedure.

Hot corrosion evaluation of aluminide coated superalloys in support of an ASTM Round Robin program

NASA Technical Reports Server (NTRS)

Santoro, G.

1975-01-01

Commercial aluminized coatings on substrates were hot corroded at 900 C in a 0.3 Mach burner rig with 5 ppm synthetic sea salt and at two cycling frequencies. Extensive post-exposure examinations were conducted on the corroded specimens such as metallography, X-ray diffraction, scanning electron microscopy, microprobe raster scans, and spectrographic analyses. Thermodynamic calculations were made of the equilibrium burner flame composition and the calculations were compared to the experimental findings. It was found that localized spalling of the coatings preceded coating failure. It is suggested that the spalling of the coatings is due to the formation of localized stresses caused by the depletion of chromium and aluminum in the coating or the enrichment of the coating with sulfur. For the materials and test conditions investigated, it was found that coating life is dependent only upon the initial coating thickness and not on the type of aluminized coating, the substrate, or the cycle frequency.

Ranking protective coatings: Laboratory vs. field experience

NASA Astrophysics Data System (ADS)

Conner, Jeffrey A.; Connor, William B.

1994-12-01

Environmentally protective coatings are used on a wide range of gas turbine components for survival in the harsh operating conditions of engines. A host of coatings are commercially available to protect hot-section components, ranging from simple aluminides to designer metallic overlays and ceramic thermal barrier coatings. A variety of coating-application processes are available, and they range from simple pack cementation processing to complex physical vapor deposition, which requires multimillion dollar facilities. Detailed databases are available for most coatings and coating/process combinations for a range of laboratory tests. Still, the analysis of components actually used in engines often yields surprises when compared against predicted coating behavior from laboratory testing. This paper highlights recent work to develop new laboratory tests that better simulate engine environments. Comparison of in-flight coating performance as well as industrial and factory engine testing on a range of hardware is presented along with laboratory predictions from standard testing and from recently developed cyclic burner-rig testing.

Static and dynamic oxidation of Ti-14Al-21Nb and coatings

NASA Technical Reports Server (NTRS)

Wiedemann, K. E.; Sankaran, S. N.; Clark, R. K.; Wallace, T. A.

1989-01-01

The oxidation of Ti-14Al-21Nb (wt pct) was studied under static conditions at 649 to 1093 C for as long as 120 hr, and under simulated hypersonic flight (dynamic oxidation) conditions at 982 C for as many as 16 half-hour cycles. Under simulated hypersonic flight conditions heavy oxidation and spalling of the oxide was observed. It was concluded that titanium aluminides used in hypersonic applications must have oxidation-protective coatings. In this preliminary study coatings about 1 micron thick were applied by sputter deposition, from solutions, and from sol-gels. It was found that, because of cracks and porosity, the sputter-deposited coatings did not have sufficient film integrity to shield the alloy. Some of the coatings applied from sol-gels demonstrated film integrity in 1 hr exposures at 982 C.

Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsipas, Sophia A., E-mail: stsipas@ing.uc3m.es; Go

Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgymore » (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition conditions •External TiN and internal a Mo-rich layer on all alloy substrates •Titanium aluminides and Ti-Al mixed nitrides are formed on Ti-6Al-4V •The presence of Al and V alloying elements modifies the diffusion of Mo.« less

Reactive multilayer synthesis of hard ceramic foils and films

DOEpatents

Makowiecki, D.M.; Holt, J.B.

1996-02-13

A method is disclosed for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.

Moisture-Induced TBC Spallation on Turbine Blade Samples

NASA Technical Reports Server (NTRS)

Smialek, James

2011-01-01

Delayed failure of TBCs is a widely observed laboratory phenomenon, although many of the early observations went unreported. The weekend effect or DeskTop Spallation (DTS) is characterized by initial survival of a TBC after accelerated laboratory thermal cycling, then failure by exposure to ambient humidity or water. Once initiated, failure can occur quite dramatically in less than a second. To this end, the water drop test and digital video recordings have become useful techniques in studies at NASA (Smialek, Zhu, Cuy), DECHMA (Rudolphi, Renusch, Schuetze), and CNRS Toulouse/SNECMA (Deneux, Cadoret, Hervier, Monceau). In the present study the results for a commercial turbine blade, with a standard EB-PVD 7YSZ TBC top coat and Pt-aluminide diffusion bond coat are reported. Cut sections were intermittently oxidized at 1100, 1150, and 1200 C and monitored by weight change and visual appearance. Failures were distributed widely over a 5-100 hr time range, depending on temperature. At some opportune times, failure was captured by video recording, documenting the appearance and speed of the moisture-induced spallation process. Failure interfaces exhibited alumina scale grains, decorated with Ta-rich oxide particles, and alumina inclusions as islands and streamers. The phenomenon is thus rooted in moisture-induced delayed spallation (MIDS) of the alumina scale formed on the bond coat. In that regard, many studies show the susceptibility of alumina scales to moisture, as long as high strain energy and a partially exposed interface exist. The latter conditions result from severe cyclic oxidation conditions, which produce a highly stressed and partially damaged scale. In one model, it has been proposed that moisture reacts with aluminum in the bond coat to release hydrogen atoms that embrittle the interface. A negative synergistic effect with interfacial sulfur is also invoked.

CVD Fiber Coatings for Al2O3/NiAl Composites

NASA Technical Reports Server (NTRS)

Boss, Daniel E.

1995-01-01

While sapphire-fiber-reinforced nickel aluminide (Al2O3/NiAl) composites are an attractive candidate for high-temperature structures, the significant difference in the coefficient of thermal expansion between the NiAl matrix and the sapphire fiber creates substantial residual stresses in the composite. This study seeks to produce two fiber-coating systems with the potential to reduce the residual stresses in the sapphire/NiAl composite system. Chemical vapor deposition (CVD) was used to produce both the compensating and compliant-fiber coatings for use in sapphire/NiAl composites. A special reactor was designed and built to produce the FGM and to handle the toxic nickel precursors. This process was successfully used to produce 500-foot lengths of fiber with coating thicknesses of approximately 3 microns, 5 microns, and 10 microns.

Corrosion Behavior of Candidate Materials Used for Urea Hydrolysis Equipment in Coal-Fired Selective Catalytic Reduction Units

NASA Astrophysics Data System (ADS)

Lu, Jintao; Yang, Zhen; Zhang, Bo; Huang, Jinyang; Xu, Hongjie

2018-05-01

Corrosion tests were performed in the laboratory in order to assess the corrosion resistance of candidate materials used in urea hydrolysis equipment. The materials to be evaluated were exposed at 145 °C for 1000 h. Alloys 316L, 316L Mod., HR3C, Inconel 718, and TC4 were evaluated. Additionally, aluminide and chromate coatings applied to a 316L substrate were examined. After exposure, the mass changes in the test samples were measured by a discontinuous weighing method, and the morphologies, compositions, and phases of the corrosion products were analyzed using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Results indicated that continuous pitting and dissolution corrosion were the main failure modes for 316L stainless steel. 316L Mod. and HR3C alloy showed better corrosion resistance than 316L due to their relatively high Cr contents, but HR3C exhibited a strong tendency toward intergranular corrosion. Inconel 718, TC4, and aluminide and chromate coating samples showed similar corrosion processes: only depositions formed by hydrothermal reactions were observed. Based on these results, a possible corrosion process in the urea hydrolysis environment was discussed for these candidate materials and questions to be clarified were proposed.

Initial Assessment of Environmental Barrier Coatings for the Prometheus Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. Frederick

2005-12-15

Depending upon final design and materials selections, a variety of engineering solutions may need to be considered to avoid chemical degradation of components in a notional space nuclear power plant (SNPP). Coatings are one engineered approach that was considered. A comprehensive review of protective coating technology for various space-reactor structural materials is presented, including refractory metal alloys [molybdenum (Mo), tungsten (W), rhenium (Re), tantalum (Ta), and niobium (Nb)], nickel (Ni)-base superalloys, and silicon carbide (Sic). A summary description of some common deposition techniques is included. A literature survey identified coatings based on silicides or iridium/rhenium as the primary methods formore » environmental protection of refractory metal alloys. Modified aluminide coatings have been identified for superalloys and multilayer ceramic coatings for protection of Sic. All reviewed research focused on protecting structural materials from extreme temperatures in highly oxidizing conditions. Thermodynamic analyses indicate that some of these coatings may not be protective in the high-temperature, impure-He environment expected in a Prometheus reactor system. Further research is proposed to determine extensibility of these coating materials to less-oxidizing or neutral environments.« less

Structural Property Effects for Platinum Modified Aluminide Coatings.

DTIC Science & Technology

1986-09-01

change from a low energy fracture to a high energy one occurs is called the DBTT. Transition temperatures are exhibited by body centered cubic and...tdapcrature as a result of residual ~:n~~.’ estresses unless the sample had been plastically deformed. Use ofpl~stic ..... .:,.as jilwed exam-ination of a...34 Fracture Properties of Superalloys," Superalloys Source Book, American Society for Metals, 1984. 11. American Society for Metals, Metals Handbook, Desk

Evaluation of thermal barrier coating systems on novel substrates

NASA Astrophysics Data System (ADS)

Pint, B. A.; Wright, I. G.; Brindley, W. J.

2000-06-01

Testing was conducted on both plasma-sprayed (PS) and electron beam-physical vapor deposited (EB-PVD) Y2O3-stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs) applied directly to oxidation-resistant substrates such as β-NiAl, oxide-dispersed FeCrAl, and NiCr. On an alloy that forms a very adherent alumina scale, β-NiAl+Zr, the coating lifetime of YSZ in furnace cyclic tests was 6 or more times longer than on state-of-the-art, YSZ coatings on single-crystal Ni-base superalloys with MCrAlY or Pt aluminide bond coats. Coatings on FeCrAl alloys appear to be a viable option for applications such as the external skin of the X-33, single stage to orbit, reusable launch vehicle. Model chromia-forming bond coat compositions also show promise for power generation applications at temperatures where hot corrosion may be a major problem. In general, while this work examined unique materials systems, many of the same fundamental failure mechanisms observed in conventional TBCs were observed.

Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

DOEpatents

Liu, Chain T.

1988-03-15

Nickel aluminides and nickel-iron aluminides treated with hafnium or zirconium, boron and cerium to which have been added chromium to significantly improve high temperature ductility, creep resistance and oxidation properties in oxidizing environments.

Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

NASA Technical Reports Server (NTRS)

Mehrotra, Gopal M.

1992-01-01

Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

Life prediction and constitutive models for engine hot section anisotropic materials

NASA Technical Reports Server (NTRS)

Swanson, G. A.; Linask, I.; Nissley, D. M.; Norris, P. P.; Meyer, T. G.; Walker, K. P.

1987-01-01

The results are presented of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and fatigue data, tests were conducted on uncoated and coated specimens loaded in the CH76 100 CH110 , CH76 110 CH110 , CH76 111 CH110 and CH76 123 CH110 crystallographic directions. Two constitutive models are being developed and evaluated for the single crystal materials: a micromechanic model based on crystallographic slip systems, and a macroscopic model which employs anisotropic tensors to model inelastic deformation anisotropy. Based on tests conducted on the overlay coating material, constitutive models for coatings also appear feasible and two initial models were selected. A life prediction approach was proposed for coated single crystal materials, including crack initiation either in the coating or in the substrate. The coating initiated failures dominated in the tests at load levels typical of gas turbine operation. Coating life was related to coating stress/strain history which was determined from specimen data using the constitutive models.

Manufacturing Techniques for Titanium Aluminide Based Alloys and Metal Matrix Composites

DTIC Science & Technology

2010-01-01

aluminides are being used in the low pressure turbine (LPT) blades . In addition, titanium aluminides were also investigated for use in High Speed Civil... Titanium aluminides are also being used in General Electric’s GEnex gas turbine engine for the 6th and the 7th stage of the low pressure turbine blades ...ABSTRACT Title of Dissertation: MANUFACTURING TECHNIQUES FOR TITANIUM ALUMINIDE BASED ALLOYS AND METAL MATRIX COMPOSITES

Moisture-Induced TBC Spallation on Turbine Blade Samples

NASA Technical Reports Server (NTRS)

Smialek, James L.

2011-01-01

Delayed failure of TBCs is a widely observed laboratory phenomenon, although many of the early observations went unreported. "The weekend effect" or "DeskTop Spallation" (DTS) is characterized by initial survival of a TBC after accelerated laboratory thermal cycling, then failure by exposure to ambient humidity or water. Once initiated, failure can occur quite dramatically in less than a second. To this end, the water drop test and digital video recordings have become useful techniques in studies at NASA (Smialek, Zhu, Cuy), DECHMA (Rudolphi, Renusch, Schuetze), and CNRS Toulouse/SNECMA (Deneux, Cadoret, Hervier, Monceau). In the present study the results for a commercial turbine blade, with a standard EB-PVD 7YSZ TBC top coat and Pt-aluminide diffusion bond monitored by weight change and visual appearance. Failures were distributed widely over a 5-100 hr time range, depending on temperature. At some opportune times, failure was captured by video recording, documenting the appearance and speed of the moisture-induced spallation process. Failure interfaces exhibited alumina scale grains, decorated with Ta-rich oxide particles, and alumina inclusions as islands and streamers. The phenomenon is thus rooted in moisture-induced delayed spallation (MIDS) of the alumina scale formed on the bond coat. In that regard, many studies show the susceptibility of alumina scales to moisture, as long as high strain energy and a partially exposed interface exist. The latter conditions result from severe cyclic oxidation conditions, which produce a highly stressed and partially damaged scale. In one model, it has been proposed that moisture reacts with aluminum in the bond coat to release hydrogen atoms that 'embrittle' the interface. A negative synergistic effect with interfacial sulfur is also invoked.

High Temperature Oxidation of Superalloys and Intermetallic Compounds

DTIC Science & Technology

2010-02-28

such as nickel aluminides (NisAI and NiAl), iron aluminides (FeAl, and Fe3AI) and titanium aluminides (TiAl and Ti3AI) are a class of advanced...80um by YAI2 phase segregation at grain boundaries preventing grain growth [6,8], other work has suggested that oxidation of titanium aluminides ...strengthened Titanium aluminides of similar composition. In this work, a study of the oxidation behavior of ingot-metallurgy processes titanium

Internal coating of air-cooled gas turbine blades

NASA Technical Reports Server (NTRS)

Hsu, L. L.; Stetson, A. R.

1980-01-01

Four modified aluminide coatings were developed for IN-792 + Hf alloy using a powder pack method applicable to internal surfaces of air-cooled blades. The coating compositions are Ni-19Al-1Cb, Ni-19Al-3Cb, Ni-17Al-20Cr, and Ni-12Al-20Cr. Cyclic burner rig hot corrosion (900 C) and oxidation (1050 C) tests indicated that Ni-Al-Cb coatings provided better overall resistance than Ni-Al-Cr coatings. Tensile properties of Ni-19Al-1Cb and Ni-12Al-20Cr coated test bars were fully retained at room temperature and 649 C. Stress rupture results exhibited wide scatter around uncoated IN-792 baseline, especially at high stress levels. High cycle fatigue lives of Ni-19Al-1Cb and Ni-12Al-20Cr coated bars (as well as RT-22B coated IN-792) suffered approximately 30 percent decrease at 649 C. Since all test bars were fully heat treated after coating, the effects of coating/processing on IN-792 alloy were not recoverable. Internally coated Ni-19Al-1Cb, Ni-19Al-3Cb, and Ni-12Al-20Cr blades were included in 500-hour endurance engine test and the results were similar to those obtained in burner rig oxidation testing.

Thermal barrier coating life prediction model

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Pilsner, B. H.

1985-01-01

This is the first report of the first phase of a 3-year program. Its objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, then to develop and verify life prediction models accounting for these degradation modes. The first task (Task I) is to determine the major failure mechanisms. Presently, bond coat oxidation and bond coat creep are being evaluated as potential TBC failure mechanisms. The baseline TBC system consists of an air plasma sprayed ZrO2-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene'80 substrate. Pre-exposures in air and argon combined with thermal cycle tests in air and argon are being utilized to evaluate bond coat oxidation as a failure mechanism. Unexpectedly, the specimens pre-exposed in argon failed before the specimens pre-exposed in air in subsequent thermal cycles testing in air. Four bond coats with different creep strengths are being utilized to evaluate the effect of bond coat creep on TBC degradation. These bond coats received an aluminide overcoat prior to application of the top coat to reduce the differences in bond coat oxidation behavior. Thermal cycle testing has been initiated. Methods have been selected for measuring tensile strength, Poisson's ratio, dynamic modulus and coefficient of thermal expansion both of the bond coat and top coat layers.

Development of high toughness, high strength aluminide-bonded carbide ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becher, P.F.; Plucknett, K.P.; Tiegs, T.N.

1997-04-01

Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that aremore » retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.« less

Oxidation of high-temperature intermetallics; Proceedings of the Workshop, Cleveland, OH, Sept. 22, 23, 1988

NASA Technical Reports Server (NTRS)

Grobstein, Toni (Editor); Doychak, Joseph (Editor)

1989-01-01

The present conference on the high-temperature oxidation behavior of aerospace structures-applicable intermetallic compounds discusses the influence of reactive-element additions on the oxidation of Ni3Al base alloys, the effect of Ni3Al oxidation below 850 C on fracture behavior, the oxidation of FeAl + Hf, Zr, and B, the synergistic effect of Al and Si on the oxidation resistance of Fe alloys, and pack cementation coatings of Cr-Al on Fe, Ni, and Co alloys. Also discussed are the formation of alumina on Nb- and Ti-base alloys, the oxidation behavior of titanium aluminide alloys, silicide coatings for refractory metals, the oxidation of chromium disilicide, and the oxidation behavior of nickel beryllides.

Effects of surface chemistry on hot corrosion life

NASA Technical Reports Server (NTRS)

Fryxell, R. E.

1984-01-01

Baseline burner rig hot corrosion with Udimet 700, Rene' 80; uncoated and with RT21, Codep, or NiCoCrAlY coatings were tested. Test conditions are: 900C, hourly thermal cycling, 0.5 ppm sodium as NaCl in the gas stream, velocity 0.3 Mach. The uncoated alloys exhibited substantial typical sulfidation in the range of 140 to 170 hours. The aluminide coatings show initial visual evidence of hot corrosion at about 400 hours, however, there is no such visual evidence for the NiCoCrAlY coatings. The turbine components show sulfidation. The extent of this distress appeared to be inversely related to the average length of mission which may, reflect greater percentage of operating time near ground level or greater percentage of operation time at takeoff conditions (higher temperatures). In some cases, however, the location of maximum distress did not exhibit the structural features of hot corrosion.

Manufacturing techniques for titanium aluminide based alloys and metal matrix composites

NASA Astrophysics Data System (ADS)

Kothari, Kunal B.

Dual phase titanium aluminides composed vastly of gamma phase (TiAl) with moderate amount of alpha2 phase (Ti3Al) have been considered for several high temperature aerospace and automobile applications. High specific strength coupled with good high temperature performance in the areas of creep and oxidation resistance makes titanium aluminides "materials of choice" for next generation propulsion systems. Titanium alumnides are primarily being considered as potential replacements for Ni-based superalloys in gas turbine engine components with aim of developing more efficient and leaner engines exhibiting high thrust-to-weight ratio. Thermo-mechanical treatments have shown to enhance the mechanical performance of titanium aluminides. Additionally, small additions of interstitial elements have shown further and significant improvement in the mechanical performance of titanium alumnide alloys. However, titanium aluminides lack considerably in room temperature ductility and as a result manufacturing processes of these aluminides have greatly suffered. Traditional ingot metallurgy and investment casting based methods to produce titanium aluminide parts in addition to being expensive, have also been unsuccessful in producing titanium aluminides with the desired mechanical properties. Hence, the manufacturing costs associated with these methods have completely outweighed the benefits offered by titanium aluminides. Over the last two decades, several powder metallurgy based manufacturing techniques have been studied to produce titanium aluminide parts. These techniques have been successful in producing titanium aluminide parts with a homogeneous and refined microstructure. These powder metallurgy techniques also hold the potential of significant cost reduction depending on the wide market acceptance of titanium aluminides. In the present study, a powder metallurgy based rapid consolidation technique has been used to produce near-net shape parts of titanium aluminides. Micron-sized titanium aluminide powders were rapidly consolidated to form near-net shape titanium aluminide parts in form of small discs and tiles. The rapidly consolidated titanium aluminide parts were found to be fully dense. The microstructure morphology was found to vary with consolidation conditions. The mechanical properties were found to be significantly dependent on microstructure morphology and grain size. Due to rapid consolidation, grain growth during consolidation was limited, which in turn led to enhanced mechanical properties. The high temperature mechanical properties for the consolidated titanium aluminide samples were characterized and were found to retain good mechanical performance up to 700°C. Micron-sized titanium aluminide powders with slightly less Aluminum and small Nb, and Cr additions were rapidly consolidated into near-net shape parts. The consolidated parts were found to exhibit enhanced mechanical performance in terms of ductility and yield strength. The negative effect of Oxygen on the flexural strength at high temperatures was found to be reduced with the addition of Nb. In an effort to further reduce the grain size of the consolidated titanium aluminide samples, the as-received titanium aluminide powders were milled in an attrition mill. The average powder particle size of the powders was reduced by 60% after milling. The milled powders were then rapidly consolidated. The grain size of the consolidated parts was found to be in the sub-micrometer range. The mechanical properties were found to be significantly enhanced due to reduction of grain size in the sub-micrometer range. In order to develop a metal matrix composite based on titanium aluminide matrix reinforced with titanium boride, an experiment to study the effect of rapid consolidation on titanium diboride powders was conducted. Micron-sized titanium diboride powders were consolidated and were found to be 93% dense and exhibited minimal grain growth. The low density of the consolidated part was attributed to low consolidation temperature. Titanium aluminide and titanium diboride powders were blended together in an attrition mill and rapidly consolidated. A metal matrix composite with titanium aluminide matrix reinforced with titanium monoboride plates was formed. The titanium diboride in the powder form was found to be transformed to titanium monoboroide plates during consolidation due to the thermodynamic equilibrium between titanium and titanium monoboride. The metal matrix composite was found to be 90% dense. The low density was due to particle size mismatch between the matrix and reinforcement powders and low consolidation temperature. An increase in the volume of titanium monoboride plates in the metal matrix composite was accompanied by an increase in the elastic modulus of the metal matrix composite.

Evaluation of coatings for cobalt- and nickel-base superalloys, volume 2

NASA Technical Reports Server (NTRS)

Moore, V. S.; Brentnall, W. D.; Stetson, A. R.

1970-01-01

The final results of an oxidation-reduction rig evaluation of aluminide coatings are presented, as applied to 1N-100 and B1900 nickel-base and X-10 and WI-52 cobalt-base alloys. Burner rigs were used which operated on JP-5 fuel and air, producing a gas velocity of 0.85 (2000 to 2500 ft/sec) at the specimen's leading edge. One-hour heating cycles were used with three minutes of air blast cooling. Results of testing at temperatures ranging from T sub max of 1850 to 2050 F indicate that coated B1900 has the longest oxidation life at all temperatures, followed by IN-100X-40WI-52, based on a weight change criterion. Coatings on nickel-base alloys provided more than twice the life of coating on cobalt-base alloys at comparable temperatures. The coatings with higher aluminum content and comparable thickness had longer lives. Silicon appeared to be a beneficial additive in the nickel-base alloy coatings for long term, low temperature life, but not for short term, high temperature performance. Chromium was identified in all coatings. Extrapolating the life results obtained to 1600 F, all the selected coatings on the four alloys would be protective for at least 10,000 hours.

Method for applying a diffusion barrier interlayer for high temperature components

DOEpatents

Wei, Ronghua; Cheruvu, Narayana S.

2016-03-08

A coated substrate and a method of forming a diffusion barrier coating system between a substrate and a MCrAl coating, including a diffusion barrier coating deposited onto at least a portion of a substrate surface, wherein the diffusion barrier coating comprises a nitride, oxide or carbide of one or more transition metals and/or metalloids and a MCrAl coating, wherein M includes a transition metal or a metalloid, deposited on at least a portion of the diffusion barrier coating, wherein the diffusion barrier coating restricts the inward diffusion of aluminum of the MCrAl coating into the substrate.

Detection of thermally grown oxides in thermal barrier coatings by nondestructive evaluation

NASA Astrophysics Data System (ADS)

Fahr, A.; Rogé, B.; Thornton, J.

2006-03-01

The thermal-barrier coatings (TBC) sprayed on hot-section components of aircraft turbine engines commonly consist of a partially stabilized zirconia top-coat and an intermediate bond-coat applied on the metallic substrate. The bond-coat is made of an aluminide alloy that at high engine temperatures forms thermally grown oxides (TGO). Although formation of a thin layer of aluminum oxide at the interface between the ceramic top-coat and the bond-coat has the beneficial effect of protecting the metallic substrate from hot gases, oxide formation at splat boundaries or pores within the bond-coat is a source of weakness. In this study, plasma-sprayed TBC specimens are manufactured from two types of bond-coat powders and exposed to elevated temperatures to form oxides at the ceramic-bond-coat boundary and within the bond-coat. The specimens are then tested using nondestructive evaluation (NDE) and destructive metallography and compared with the as-manufactured samples. The objective is to determine if NDE can identify the oxidation within the bond-coat and give indication of its severity. While ultrasonic testing can provide some indication of the degree of bond-coat oxidation, the eddy current (EC) technique clearly identifies severe oxide formation within the bond-coat. Imaging of the EC signals as the function of probe location provides information on the spatial variations in the degree of oxidation, and thereby identifies which components or areas are prone to premature damage.

Joining of Gamma Titanium Aluminides

DTIC Science & Technology

2002-09-01

AFRL-ML-WP-TR-2003-4036 JOINING OF GAMMA TITANIUM ALUMINIDES LTC William A. Baeslack, III Metals Branch (AFRL/MLLM) Metals, Ceramics, and...GAMMA TITANIUM ALUMINIDES 5c. PROGRAM ELEMENT NUMBER 62102F 5d. PROJECT NUMBER MO2R 5e. TASK NUMBER 10 6. AUTHOR(S) LTC William A...comparatively discusses the results of research and development performed on the joining of gamma titanium aluminides during the past two decades. Although

An Investigation of the Hot Corrosion Protectivity Behavior of Platinum Modified Aluminide Coatings on Nickel-Based Superalloys

DTIC Science & Technology

1987-03-01

is unlimited. WCRT LAIISIPIcaiIo IP THIS P431 IEPORT DOCUMENTATION PAGE* is REIPOT SECURilY CLASSIFICATION 1b RISTRtC7IVI MARKINGS la FURITY... grow until it forms a continuous surface layer. At this point, there is a parabolic decrease in the rate of oxidation and the surface stabilizes. If...surface as PtA1 2 and Pt 2 A13. Consequently, the platinum concentration gradient that develops is highest at the surface, but, rapidly diminishes as the

Cost benefit study of advanced materials technology for aircraft turbine engines

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Johnston, R. P.

1977-01-01

The cost/benefits of eight advanced materials technologies were evaluated for two aircraft missions. The overall study was based on a time frame of commercial engine use of the advanced material technologies by 1985. The material technologies evaluated were eutectic turbine blades, titanium aluminide components, ceramic vanes, shrouds and combustor liners, tungsten composite FeCrAly blades, gamma prime oxide dispersion strengthened (ODS) alloy blades, and no coat ODS alloy combustor liners. They were evaluated in two conventional takeoff and landing missions, one transcontinental and one intercontinental.

Cyclic Deformation, Damage, and Effects of Environment in the Ni3Al Ordered Alloy at Elevated Temperature

DTIC Science & Technology

1991-03-29

restricts atomic mobility leading to slower diffusion and perhaps better creep resistance. Ordered intermetallics such as aluminides and silicides are...evaluation of the mechanical properties of these materials (specifically creep , oxidation and fatigue) must be evaluated before implementation in...rate by an order of magnitude (frcm 0.001/s to 0.01/s) doubled the fatigue life at a given plastic strain range. When tested in vacuum environments

Thermal-Mechanical Fatigue Testing of a Titanium-Aluminide Alloy.

DTIC Science & Technology

1987-12-01

DIMSTRIBUTION STA Approved for pubi robing e% dQ *- AFIT/GAB/AA/87D-18 THERMAL-MECHANICAL FATIGUE TESTING OF A TITANIUM - ALUMINIDE ALLOY THESIS John J...THERMAL-MECHANICAL FATIGUE TESTING OF A TITANIUM - ALUMINIDE ALLOY THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute...develop a Thermal-Mechanical Fatigue (TMF) testing system for titanium - aluminide compact tension specimens. I could not have accomplished this without the

Applicability and Performance Benefits of XD (Tradename) Titanium Aluminides to Expendable Gas Turbine Engines

DTIC Science & Technology

1993-08-01

analysis A dynamic analysis was conducted on the blades and splitters. The existing design for the compressor was used and XD® titanium aluminide property...AD-A272 998 ARMY RESEARCH LABORATORY Applicability and Performance Benefits of XD® Titanium Aluminides to Expendable Gas Turbine Engines Pamela...Benefits of XD® Contract # Titanium Aluminides to Expendable Gas Turbine DAAL04-91-C-0034 Fnginpq 6. AUTHOR(S) Pamela Sadler, K. Sharvan Kumar, John A. S

Thermo-Mechanical Fatigue of a Fiber Reinforced Titanium Aluminide Composite

DTIC Science & Technology

1991-03-01

Puiitr]on Air Foic. Base, Oiio 91 10 25 038 DTIC 4E L L E C :i<. THERMO- MECHAN I CAL FAT I GUE OF A FIBER REINFORCED TITANIUM ALUMINIDE COMPOSITE Thesis...reinforced titanium aluminide composite was investigated. Three test specimens were subjected to in-phase thermo- mechanical cycling and four to out-of...Unclassified UL ............................... AFIT/GAE/ENY/91S-1 THERMO- MECHANICAL FATIGUE OF A FIBER REINFORCED TITANIUM ALUMINIDE COMPOSITE THESIS

Diffusion Barriers to Increase the Oxidative Life of Overlay Coatings

NASA Technical Reports Server (NTRS)

Nesbitt, James A.; Lei, Jih-Fen

1999-01-01

Currently, most blades and vanes in the hottest section of aero gas turbine engines require some type of coating for oxidation protection. Newly developed single crystal superalloys have the mechanical potential to operate at increasingly higher component temperatures. However, at these elevated temperatures, coating/substrate interdiffusion can shorten the protective life of the coating. Diffusion barriers between overlay coatings and substrates are being examined to extend the protective life of the coating. A previously- developed finite-difference diffusion model has been modified to predict the oxidative life enhancement due to use of a diffusion barrier. The original diffusion model, designated COSIM, simulates Al diffusion in the coating to the growing oxide scale as well as Al diffusion into the substrate. The COSIM model incorporates an oxide growth and spalling model to provide the rate of Al consumption during cyclic oxidation. Coating failure is predicted when the Al concentration at the coating surface drops to a defined critical level. The modified COSIM model predicts the oxidative life of an overlay coating when a diffusion barrier is present eliminating diffusion of Al from the coating into the substrate. Both the original and the modified diffusion models have been used to predict the effectiveness of a diffusion barrier in extending the protective life of a NiCrAl overlay coating undergoing cyclic oxidation at 1100 C.

Utilization of gas-atomized titanium and titanium-aluminide powder

NASA Astrophysics Data System (ADS)

Moll, John H.

2000-05-01

A gas-atomization process has been developed producing clean, high-quality, prealloyed spherical titanium and titanium-aluminide powder. The powder is being used to manufacture hot-isostatically pressed consolidated shapes for aerospace and nonaerospace allocations. These include gamma titanium-aluminide sheet and orthorhombic titanium-aluminide wire as well as niche markets, such as x-ray drift standards and sputtering targets. The powder is also being used in specialized processes, including metal-matrix composites, laser forming, and metal-injection molding.

Identification of thermodynamically stable ceramic reinforcement materials for iron aluminide matrices

NASA Technical Reports Server (NTRS)

Misra, Ajay K.

1990-01-01

Aluminide-base intermetallic matrix composites are currently being considered as potential high-temperature materials. One of the key factors in the selection of a reinforcement material is its chemical stability in the matrix. In this study, chemical interactions between iron aluminides and several potential reinforcement materials, which include carbides, oxides, borides, and nitrides, are analyzed from thermodynamic considerations. Several chemically compatible reinforcement materials are identified for the iron aluminides with Al concentrations ranging from 40 to 50 at. pct.

Corrosion behavior of an HVOF-sprayed Fe3Al coating in a high-temperature oxidizing/sulfidizing environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.

An iron aluminide (Fe3Al) intermetallic coating was deposited onto a F22 (2.25Cr-1Mo) steel substrate using a JP-5000 high velocity oxy-fuel (HVOF) thermal spray system. The as-sprayed coating was examined by electron microscopy and X-ray diffraction and was characterized in terms of oxidation and adhesion. Fe3Al-coated steel specimens were exposed to a mixed oxidizing/sulfidizing environment at 500, 600, 700, and 800DGC for approximately seven days. The gaseous environment consisted of N2-10%CO-5%CO2-2%H2O-0.12%H2S (by volume). All specimens gained mass after exposure to the environment and the mass gains were found to be inversely proportional to temperature increases. Representative specimens exposed at each temperaturemore » were cross-sectioned and subjected to examination under a scanning electron microscope (SEM) and X-ray mapping. Results are presented in terms of corrosion weight gain and corrosion product formation. The purpose of the research presented here was to evaluate the effectiveness of an HVOF-sprayed Fe3Al coating in protecting a steel substrate exposed to a fossil energy environment.« less

Effect of grain orientation and coating on thermal fatigue resistance of a directionally solidified superalloy (MAR-M 247)

NASA Technical Reports Server (NTRS)

Bizon, P. T.; Dreshfield, R. L.; Calfo, F. D.

1979-01-01

The effect of off-axis directionally solidified (DS) grain growth on thermal fatigue life of Mar-M 247 alloy was evaluated. Uncoated conventionally cast as well as DS wedge bars were cycled in a burner rig between 1070 C and room temperature. The longitudinal axis and leading edge of the specimen coincided. As the angle between the specimen longitudinal axis and growth axis increased, the thermal fatigue life decreased for both the uncoated and aluminide-coated bars. Life increases of about 50 cycles for the DS conditions were attributed to coating. The decrease in thermal fatigue life with increasing angle is primarily attributed to the increase in modulus of elasticity with increasing angle and not to the intersection of DS grain boundaries with the specimen leading edge. The thermal fatigue cracks were observed to be transgranular in the DS material. Limited tensile and stress-rupture properties of conventionally cast and off-axis DS Mar-M 247 alloy are also presented.

On Some Mechanical Properties and Wear Behavior of Sintered Bronze Based Composites Reinforced with Some Aluminides Microadditives

NASA Astrophysics Data System (ADS)

Feldshtein, E.; Kiełek, P.; Kiełek, T.; Dyachkova, L.; Letsko, A.

2017-05-01

In the paper, the changes in some mechanical properties and wear behavior of CuSn10 sintered bronze and MMCs based on this bronze reinforced with composite ultrafine aluminide powders FeAl/15 % Al2O3, NiAl/15 % Al2O3 and Ti-46Al-8Cr are described. It was observed that the presence of aluminides in the MMCs leads to an increase in the hardness, but the flexural strength may increase or decrease depending on the type of aluminide. The presence of aluminides in the MMC reduces the wear rate considerably. It is decreased in the direction of FeAl/15 % Al2O3 → NiAl/15 % Al2O3 → Ti-46Al-8Cr aluminides and for the best MMC composition the advantage is about 20 times. In the MMCs wear process, micro-craters are formed on the contact surface and it is the principal reason of a decrease in the wear rate.

R&D on Composition and Processing of Titanium Aluminide Alloys for Turbine Engines

DTIC Science & Technology

1982-07-01

45433. AUTHORITY AFWAL ltr, 6 Feb 1987 THIS PAGE IS UNCLASSIFIED AFWAL-TR-82-4086 R&D ON COMPOSITION AND PROCESSING4 OF TITANIUM ALUMINIDE ALLOYS FOR...TR-82-4086- 4. TITLE (and Subitfle) S TYPE OF REPORT I PERIOO COVEREO R&D ON COMPOSITION AND PROCESSING OF Interim Technical Report TITANIUM ALUMINIDE ...ILLUSTRATIONS FICURE PACE 1 As-received titanium aluminide ingots supplied 9 by RMI. (a) S/N 20007; (b) left to right, S/N 20008, S/N 20009, S/N 20010

Investigation of reaction kinetics and interfacial phase formation in Ti3Al + Nb composites

NASA Technical Reports Server (NTRS)

Wawner, F. E.; Gundel, D. B.

1992-01-01

Titanium aluminide metal matrix composites are prominent materials systems being considered for high temperature aerospace applications. One of the major problems with this material is the reactivity between existing reinforcements and the matrix after prolonged thermal exposure. This paper presents results from an investigation of reaction kinetics between Ti-14Al-21Nb (wt pct) and SCS-6 fibers and SiC fibers with surface coatings of TiB2, TiC, TiN, W, and Si. Microstructural evaluation of the reaction layers as well as matrix regions around the fibers is presented.

Pseudo-icosahedral Cr55Al232 -δ as a high-temperature protective material

NASA Astrophysics Data System (ADS)

Rosa, R.; Bhattacharya, S.; Pabla, J.; He, H.; Misuraca, J.; Nakajima, Y.; Bender, A. D.; Antonacci, A. K.; Adrip, W.; McNally, D. E.; Zebro, A.; Kamenov, P.; Geschwind, G.; Ghose, S.; Dooryhee, E.; Ibrahim, A.; Tritt, T. M.; Aronson, M. C.; Simonson, J. W.

2018-03-01

We report here a course of basic research into the potential suitability of a pseudo-icosahedral Cr aluminide as a material for high-temperature protective coatings. Cr55Al232 -δ [ δ =2.70 (6 ) ] exhibits high hardness at room temperature as well as low thermal conductivity and excellent oxidation resistance at 973 K, with an oxidation rate comparable to those of softer, denser benchmark materials. The origin of these promising properties can be traced to competing long-range and short-range symmetries within the pseudo-icosahedral crystal structure, suggesting new criteria for future materials research.

An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

NASA Technical Reports Server (NTRS)

Shanabarger, Mickey R.

1994-01-01

The goal of this program has been to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. During the present program, the interaction of hydrogen with the surfaces of alpha-2 (Ti3Al) titanium aluminide, gamma (TiAl) titanium aluminide, and beryllium were studied. The interaction of low pressure hydrogen with gamma titanium aluminide and beryllium was found to be relatively weak. Weak in the sense that adsorption leads to a low surface concentration of dissociated hydrogen, i.e., the chemisorption process is reversible at room temperature (300 K) for gamma titanium aluminide and the sticking coefficient for chemisorption is extremely small for beryllium. Hydrogen was found to interact readily with alpha-2 titanium aluminide to form a stable surface hydride at 300 K. These results correlate well with other recent studies which show that the mechanical properties for alpha-2 titanium aluminide are readily degraded in hydrogen while gamma titanium aluminide exhibits less degradation and beryllium essentially no degradation. The interaction of oxygen with the surface of several of these materials was studied. More recently, preliminary hydrogen permeation studies were completed for three high temperature alloys, Incoloy 909, Mo-47.5Re (wt. %), and this past year, Haynes 188.

Modeling of Micromechanisms of Fatigue and Fracture in Hybrid Materials

DTIC Science & Technology

1990-06-15

titanium aluminides . Unclassified SECURITY CLASSIFICATION OF THIS PAGE Report No. UCB/R/90/A1065 Final Report to U.S. Air Force Office of Scientific...PARTICULATE-REINFORCED Ti-6AI-4V COMPOSITES ............... 52 5. TITANIUM ALUMINIDE INTERMETALLICS ............................................ 59 6...preliminary examination of the microstructure of titanium aluminides . V 1. INTRODUCTION In recent years, the need for lighter materials with high

Iron aluminides and nickel aluminides as materials for chemical air separation

DOEpatents

Kang, Doohee

1991-01-01

The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

International Workshop on Gamma Aluminide Alloy Technology. Section Three

DTIC Science & Technology

1997-04-18

Structure / Property Relationships General Mechanical Behavior Tensile Fracture Toughness Creep Fatigue; FCG, Inverse Ductility/FT Relationship...Workshop on Gamma Titanium Aluminide Alloy Technology. 1 May 1996-3 May 1996 The Topics covered include: Fundamental research issues for...understanding the emerging class of Gamma Titanium Aluminide Alloy Technologies 14. SUBJECT TERMS 15. NUMBER OF PAGES 16. PRICE CODE N/A 17. SECURITY

Iron aluminides and nickel aluminides as materials for chemical air separation

DOEpatents

Kang, D.

1991-01-29

The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

Spark plasma sintering of titanium aluminide intermetallics and its composites

NASA Astrophysics Data System (ADS)

Aldoshan, Abdelhakim Ahmed

Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

Al-Mn CVD-FBR coating on P92 steel as protection against steam oxidation at 650 °C: TGA-MS study

NASA Astrophysics Data System (ADS)

Castañeda, S. I.; Pérez, F. J.

2018-02-01

The initial stages oxidation of the P92 ferritic/martensitic steel with and without Al-Mn coating at 650 °C in Ar+40%H2O for 240 h were investigated by mass spectrometry (MS) and thermogravimetric analysis (TGA). TGA-MS measurements were conducted in a closed steam loop. An Al-Mn coating was deposited on P92 steel at 580 °C for 2 h by chemical vapour deposition in a fluidized bed reactor (CVD-FBR). The coating as-deposited was treated in the same reactor at 700 °C in Ar for 2h, in order to produce aluminide phases that form the protective alumina layer (Al2O3) during oxidation. MS measurements at 650 °C of the Al-Mn/P92 sample for 200 h indicated the presence of (Al-Mn-Cr-Fe-O) volatile species of small intensity. Uncoated P92 steel oxidized under the same steam oxidation conditions emitted greater intensities of volatile species of Cr, Fe and Mo in comparison with intensities from coated steel. TGA measurements verified that the mass gained by the coated sample was up to 300 times lower than for uncoated P92 steel. The morphology, composition and structure of samples by Scanning Electron Microscopy SEM, Backscattered Electron (BSE) detection, X-ray Energy Dispersive Spectrometry (EDAX) and X-ray Diffraction (XRD) are described.

United States Air Force Research Initiation Program for 1987. Volume 3

DTIC Science & Technology

1989-04-01

Influence of Microstructural Variations Dr. Ravinder Diwan on the Thermomechanical Processing in Dynamic Material Modeling of Titanium Aluminides , 760,7MG...7MG-077 INFLUENCE OF MICROSTRUCTURAL VARIATIONS ON THE THERMOMECHANICAL PROCESSING IN DYNAMIC MATERIAL MODELING OF TITANIUM ALUMINIDES MARCH 15, 1989...provided on this project. Final Report Submitted: March 15, 1989. 75-1 ABSTRACT Titanium aluminides with strong thermodynamically stable intermetallic phases

Anti-diffusion metal coated O-rings

DOEpatents

Biallas, George Herman; Boyce, James Reid

2016-03-22

A method for inhibiting diffusion of gases and/or transmission of photons through elastomeric seals and a diffusion inhibiting elastomeric seal wherein at least a portion of the surface of a diffusion inhibiting elastomeric seal is coated with a compatibly-deformable, malleable metal coating.

The effect of interface properties on nickel base alloy composites

NASA Technical Reports Server (NTRS)

Groves, M.; Grossman, T.; Senemeier, M.; Wright, K.

1995-01-01

This program was performed to assess the extent to which mechanical behavior models can predict the properties of sapphire fiber/nickel aluminide matrix composites and help guide their development by defining improved combinations of matrix and interface coating. The program consisted of four tasks: 1) selection of the matrices and interface coating constituents using a modeling-based approach; 2) fabrication of the selected materials; 3) testing and evaluation of the materials; and 4) evaluation of the behavior models to develop recommendations. Ni-50Al and Ni-20AI-30Fe (a/o) matrices were selected which gave brittle and ductile behavior, respectively, and an interface coating of PVD YSZ was selected which provided strong bonding to the sapphire fiber. Significant fiber damage and strength loss was observed in the composites which made straightforward comparison of properties with models difficult. Nevertheless, the models selected generally provided property predictions which agreed well with results when fiber degradation was incorporated. The presence of a strong interface bond was felt to be detrimental in the NiAI MMC system where low toughness and low strength were observed.

High temperature behavior of B2-based ruthenium aluminide systems

NASA Astrophysics Data System (ADS)

Cao, Fang

Ru-modified NiAl-based bond coats have the potential to improve the durability of Superalloy-Thermal Barrier Coating systems (TBCs) for advanced gas turbine engines. A fundamental understanding of the high temperature mechanical behavior across the Ni-Al-Ru B2 phase field can provide direction for the development of these new bond coats for TBCs. The purpose of this study has been to describe the fundamental processes of creep deformation in single phase B2 Ru-Al-Ni ternary alloys which would form the basis for the bond coats. To accomplish this, five ternary alloys with compositions located within the B2 field across the NiAl-RuAl phase region were fabricated and investigated. Special emphasis was placed on characterizing creep deformation and describing the operative creep mechanisms in these alloys. At room temperature, brittle failure was observed in the Ni-rich alloys in compression, while improved strength and ductility were displayed in two Ru-rich ternary alloys at temperatures up to 700°C. Exceptional creep strength was observed in these alloys, as compared to other high melting temperature B2 intermetallics. A continuous increase of the melting temperature and creep resistance with the increasing of the Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Ni-rich alloys, while uniformly distributed jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. A transition of the creep mechanism from viscous glide controlled to jogged screw motion in these Ru-Al-Ni ternary B2 alloys with increasing Ru/Ni ratio is demonstrated by the characteristics of the creep deformation process, stress change creep tests, post-creep dislocation analyses, and numerical modeling. Additionally, the knowledge of the cyclic oxidation behavior of ruthenium aluminide-based alloy is essential, as many high-temperature applications for which this intermetallic might be utilized undergo repeated severe thermal cycling. Thus the second portion of this thesis focuses on the characterization of the cyclic oxidation properties of RuAl-based alloys. The cyclic oxidation behavior of six RuAl-based alloys was studied in air over the temperature range of 1000°C to 1300°C. Oxidation kinetics have been shown to be influenced by microstructure as well as the addition of platinum.

Effect of grain size on the high temperature properties of B2 aluminides

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel

1987-01-01

Measurements of the slow plastic flow behavior of cobalt, iron and nickel B2 crystal structure aluminides were conducted on materials fabricated by metallurical techniques. Due to this processing, the aluminides invariably had small equiaxed grains, ranging in size from about 3 to 60 microns in diameter. Grain size was dependent on the extrusion temperature used for powder consolidation, and it proved to be remarkably stable at elevated temperatures. Mechanical properties of all three aluminides were determined via constant velocity compression testing in air between 1000 and 1400 K at strain rates ranging from approx. 10 to the minus 3 power to 10 to the minus 7 power s (-1).

Pseudo-icosahedral Cr 55 Al 232 - δ as a high-temperature protective material

DOE PAGES

Rosa, R.; Bhattacharya, S.; Pabla, J.; ...

2018-03-19

In this paper, we report here a course of basic research into the potential suitability of a pseudo-icosahedral Cr aluminide as a material for high temperature protective coatings. Cr 55Al 232-δ [δ = 2.70(6)] exhibits high hardness at room temperature as well as low thermal conductivity and excellent oxidation resistance at 973 K, with an oxidation rate comparable to those of softer, denser benchmark materials. Lastly, the origin of these promising properties can be traced to competing long-range and short-range symmetries within the pseudo-icosahedral crystal structure, suggesting new criteria for future materials research.

Pseudo-icosahedral Cr 55 Al 232 - δ as a high-temperature protective material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosa, R.; Bhattacharya, S.; Pabla, J.

In this paper, we report here a course of basic research into the potential suitability of a pseudo-icosahedral Cr aluminide as a material for high temperature protective coatings. Cr 55Al 232-δ [δ = 2.70(6)] exhibits high hardness at room temperature as well as low thermal conductivity and excellent oxidation resistance at 973 K, with an oxidation rate comparable to those of softer, denser benchmark materials. Lastly, the origin of these promising properties can be traced to competing long-range and short-range symmetries within the pseudo-icosahedral crystal structure, suggesting new criteria for future materials research.

Sintered Intermetallic Reinforced 434L Ferritic Stainless Steel Composites

NASA Astrophysics Data System (ADS)

Upadhyaya, A.; Balaji, S.

2009-03-01

The present study examines the effect of aluminide (Ni3Al, Fe3Al) additions on the sintering behavior of ferritic 434L stainless steels during solid-state sintering (SSS) and supersolidus liquid-phase sintering (SLPS). 434L stainless steel matrix composites containing 5 and 10 wt pct of each aluminide were consolidated at 1200 °C (SSS) and 1400 °C (SLPS). The effects of sintering and aluminide additions on the densification, microstructural evolution, mechanical, tribological, and corrosion behavior of sintered ferritic (434L) stainless steels were investigated. The performances of the 434L-aluminide composites were compared with the straight 434L stainless steels processed at similar conditions. Supersolidus sintering resulted in significant improvement in densification, mechanical, wear, and corrosion resistance in both straight 434L and 434L-aluminide composites. Fe3Al additions to 434L stainless steels result in improved wear resistance without significant degradation of corrosion resistance in 3.56 wt pct NaCl solution.

FY97 Materials & Processes Technology Area Plan

DTIC Science & Technology

1996-09-01

Offices ess has Center Technology Coun- ings, the first use ever of gamma (SPOs). In addition, we provide cil (CTCs) technology needs Titanium Aluminide ...300,000 in form- structive evaluation (NDE). Four Agreements (CRDAs) with 7 ing of Titanium Aluminide with Data EAchange Agreements more in negotiation and...Systems Aircraft Range with r 50% Decrease in Fuel Propulsion Syste s =Consumption Titanium Aluminides Cast Titanium 25000F Ceramic Matrix Transition

An Investigation of the Interatomic Bonding Characteristics of a Ti - 51at.% Al Alloy by X-Ray Diffraction

DTIC Science & Technology

1991-06-01

GROUP SUBGROUP X-ray Diffraction, XRD, TiAI, titanium , aluminum, bonding characteristics, titanium aluminides , Debye-Waller temperature factor...XRD Powder Particles (575X) .............. 47 viii I. INTRODUCTION Titanium aluminides are recognized for their high specific strength, particularly at...bonding characteristics of binary titanium aluminides . Upon the introduction of a third element to the system, a rearrangement of the valence

Research to Conduct an Exploratory Experimental and Analytical Investigation of Alloys

DTIC Science & Technology

1980-11-01

Properties of Forged and Heat 31 Treated Alpha-Two Titanium Aluminide Alloys 10 Effect of Interstitial Elements on Room 33 Temperature Notched (Kt-3.9...percent (three to five percent of engine weight) would be achieved with widespread application of the titanium aluminides in rotating hardwarei...vanadium substitution effect was also undertaken. One of the inconsistencies in the previous titanium aluminide investigations has been the poorer

Microstructure of Dense Thin Sheets of gamma-TiAl Fabricated by Hot Isostatic Pressing of Tape-Cast Monotapes (Preprint)

DTIC Science & Technology

2007-02-01

fabrication of dense thin sheets of gamma titanium aluminide . Polarized light microscopy revealed a fine-grained microstructure but a few isolated...HIPed (near-gamma) microstructure occurred. 15. SUBJECT TERMS gamma titanium aluminide , thin sheet, tape casting, hot isostatic pressing 16...sheets (250–300 μm thick) of gamma titanium aluminide (γ-TiAl). Polarized light microscopy revealed a fine-grained microstructure (average grain

Innovative Processing of Composites for Ultra-High Temperature Applications. Book 2

DTIC Science & Technology

1993-11-01

with dispersed aluminum and nickel particles [6). Successful toughening has also been observed in titanium aluminide [7] and molybdenum disilicide [g,9...2) Nb-based aluminides with the major focus on NbAl3. I Research Summary To achieve the goal of this program, the present investigation has been...toughening to produce hybrid composites. I Niobium aluminid Matrix Composites Reactive hot compaction (RHC) has been successfully utilized to produce

Anisotropic Thermal Diffusivities of Plasma-Sprayed Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Takahashi, Satoru

2017-09-01

Thermal barrier coatings (TBCs) are used to shield the blades of gas turbines from heat and wear. There is a pressing need to evaluate the thermal conductivity of TBCs in the thermal design of advanced gas turbines with high energy efficiency. These TBCs consist of a ceramic-based top coat and a bond coat on a superalloy substrate. Usually, the focus is on the thermal conductivity in the thickness direction of the TBC because heat tends to diffuse from the surface of the top coat to the substrate. However, the in-plane thermal conductivity is also important in the thermal design of gas turbines because the temperature distribution within the turbine cannot be ignored. Accordingly, a method is developed in this study for measuring the in-plane thermal diffusivity of the top coat. Yttria-stabilized zirconia top coats are prepared by thermal spraying under different conditions. The in-plane and cross-plane thermal diffusivities of the top coats are measured by the flash method to investigate the anisotropy of thermal conduction in a TBC. It is found that the in-plane thermal diffusivity is higher than the cross-plane one for each top coat and that the top coats have significantly anisotropic thermal diffusivity. The cross-sectional and in-plane microstructures of the top coats are observed, from which their porosities are evaluated. The thermal diffusivity and its anisotropy are discussed in detail in relation to microstructure and porosity.

Melt Spinning of Intermetallic Alloys: Heat Transfer and Microstructure

DTIC Science & Technology

1992-04-21

newly emerging mdLerials such as titanium aluminides and other intermetallic alloys[4,5]. These materials must possess good mechanical and corrosion...alloys such as titanium aluminides with the surrounding atmosphere, it utilizes a tilting water-cooled copper hearth and the apparatus is in a 5 psi Argon... titanium aluminide in the form of filament or ribbon break olf into short segments. The solidified ribbons have lengths of 5 - 15 mm, widths of 0.5

United States Air Force Summer Research Program 1991. Summer Faculty Research Program (SFRP) Reports. Volume 5B. Wright Laboratory

DTIC Science & Technology

1992-01-09

interfaces of intermetallic-matrix composites (for example, with Ti-Il wt.% Al-14 wt.% Nb and other titanium aluminides combined with various fibers... titanium aluminide intermetallics should be processed, tested and characterized by TEM. These intermetallic-matrix composites (IMC) are important for...these titanium aluminides have a greater CTE mismatch and have been modelled to undergo significant plastic deformation as a result of thermal processing

The effect of solidification rate on the formability of nickel aluminide containing iron and boron

NASA Technical Reports Server (NTRS)

Carro, G.; Flanagan, W. F.

1987-01-01

Following reports that rapid solidification improves the ductility of some nickel aluminides, an investigation has been conducted of the possibility of additional improvement in a nickel aluminide containing both Fe and B. Free fall-solidified and free fall/splat-quenched samples similar to those producible under microgravity conditions in space were prepared, and their microstructure was characterized. Attention is given to the preliminary results of tests quantitatively measuring mechanical properties.

The effective boundary conditions and their lifespan of the logistic diffusion equation on a coated body

NASA Astrophysics Data System (ADS)

Li, Huicong; Wang, Xuefeng; Wu, Yanxia

2014-11-01

We consider the logistic diffusion equation on a bounded domain, which has two components with a thin coating surrounding a body. The diffusion tensor is isotropic on the body, and anisotropic on the coating. The size of the diffusion tensor on these components may be very different; within the coating, the diffusion rates in the normal and tangent directions may be in different scales. We find effective boundary conditions (EBCs) that are approximately satisfied by the solution of the diffusion equation on the boundary of the body. We also prove that the lifespan of each EBC, which measures how long the EBC remains effective, is infinite. The EBCs enable us to see clearly the effect of the coating and ease the difficult task of solving the PDE in a thin region with a small diffusion tensor. The motivation of the mathematics includes a nature reserve surrounded by a buffer zone.

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, M.L.; Sikka, V.K.

1996-06-11

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined. 4 figs.

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

1996-01-01

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

Research to Conduct an Exploratory Experimental and Analytical Investigation of Alloys

DTIC Science & Technology

1978-03-01

d« (f n«r««a«rv on« 149*111* hv *l«c* f*u0«««> Titanium Aluminides , Alloy Development, Mechemical Properties, Powder Metallurgy, Forging, Joining...Ccmpcsition of Titanium 79 Aluminida Alloy 9 Nuclear Metals Reported REP Titanium 80 Aluminide Powder Size Distribution 10 Phase I, Task I...137 141 24 Chemical Composition of Titanium Aluminide Alloy TMCA Heat 75301 Ti-13.5Al-21.4Nb 25 Isothermal Forging Results 26 Tensile Results

Advances in the Systems and Processes for the Production of Gamma Titanium Aluminide Bars and Powder

NASA Astrophysics Data System (ADS)

Haun, Robert E.

2017-12-01

A historical look at the melt processing of gamma titanium aluminides is presented first, followed by recent advances in melting equipment design by Retech to produce 50-mm and 100-mm-diameter ingots up to 1000 mm long. Equipment design for the economical production of gamma titanium aluminide powder is then discussed. The focus in industry has shifted away from basic research to cost-effective production of these titanium alloys for aerospace and automotive engine applications.

Microstructural Effects on the Deformation and Fracture of the Alloy Ti- 25Al-10Nb-3B-1Mo

DTIC Science & Technology

1992-12-01

Materials Development Branch whose stimulating discussions on titanium aluminide physical and mechanical metallurgy helped immensely. This thesis may not... properties and fracture is somewhat different in the a 2 +0/B2 titanium aluminides from conventional a+13 titanium alloys. When trying to explain the...effects of microstructure and temperature on tensile and fracture behavior were explored for the titanium aluminide alloy Ti-25AI-l0Nb-3V-lMo (atomic

Thermal Diffusivity Measurement for Thermal Spray Coating Attached to Substrate Using Laser Flash Method

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Tanaka, Takashi; Endo, Satoshi; Baba, Tetsuya; Harada, Yoshio; Kojima, Yoshitaka; Kawasaki, Akira; Ono, Fumio

2011-11-01

Ceramic-based thermal barrier coatings are used as heat and wear shields of gas turbine blades. There is a strong need to evaluate the thermal conductivity of coating for thermal design and use. The thermal conductivity of a bulk material is obtained as the product of thermal diffusivity, specific heat capacity, and density above room temperature in many cases. Thermal diffusivity and thermal conductivity are unique for a given material because they are sensitive to the structure of the material. Therefore, it is important to measure them in each sample. However it is difficult to measure the thermal diffusivity and thermal conductivity of coatings because coatings are attached to substrates. In order to evaluate the thermal diffusivity of a coating attached to the substrate, we have examined the laser flash method with the multilayer model on the basis of the response function method. We carried out laser flash measurements in layered samples composed of a CoNiCrAlY bond coating and a 8YSZ top coating by thermal spraying on a Ni-based superalloy substrate. It was found that the procedure using laser flash method with the multilayer model is useful for the thermal diffusivity evaluation of a coating attached to a substrate.

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells

PubMed Central

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n+ emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion. PMID:25520602

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

PubMed

Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

Investigation of Pb Li compatibility issues for the dual coolant blanket concept

NASA Astrophysics Data System (ADS)

Pint, B. A.; Moser, J. L.; Tortorelli, P. F.

2007-08-01

One proposed blanket concept uses advanced ferritic alloys and a SiC/SiC composite flow channel insert with both Pb-17 at.%Li and He coolants. As the first step in determining the long-term compatibility of SiC/SiC in Pb-Li, specimens of high-purity, chemical vapor deposited (CVD) SiC were exposed in capsules for up to 5000 h at 800 °C and 1000 h at 1200 °C. Dissolved Si was detected in the Pb-Li after the highest temperature exposures suggesting that SiC may be limited to <1100 °C in Pb-Li. Aluminide coatings are being considered for corrosion resistant coatings for the tubing between the first wall and the heat exchanger. Initial results indicate that, in Pb-Li at 700 °C, FeCrAl, Fe 3Al and NiAl form a protective alumina layer which reduces dissolution compared to type 316 stainless steel.

Method of applying a cerium diffusion coating to a metallic alloy

DOEpatents

Jablonski, Paul D [Salem, OR; Alman, David E [Benton, OR

2009-06-30

A method of applying a cerium diffusion coating to a preferred nickel base alloy substrate has been discovered. A cerium oxide paste containing a halide activator is applied to the polished substrate and then dried. The workpiece is heated in a non-oxidizing atmosphere to diffuse cerium into the substrate. After cooling, any remaining cerium oxide is removed. The resulting cerium diffusion coating on the nickel base substrate demonstrates improved resistance to oxidation. Cerium coated alloys are particularly useful as components in a solid oxide fuel cell (SOFC).

Corrosion resistant coatings suitable for elevated temperature application

DOEpatents

Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

2012-07-31

The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

NASA Astrophysics Data System (ADS)

Lo, Wei-Yang; Yang, Yong

2014-08-01

Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

Chromium modified nickel-iron aluminide useful in sulfur bearing environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cathcart, J.V.; Liu, C.T.

1989-06-13

This patent describes an improved nickel-iron aluminide containing chromium and molybdenum additions to improve resistance to sulfur attack. The corrosive effects of sulfur are discussed and the chemical composition of corrosion resistant alloys is illustrated.

Large Scale Evaluation fo Nickel Aluminide Rolls

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2005-09-01

This completed project was a joint effort between Oak Ridge National Laboratory and Bethlehem Steel (now Mittal Steel) to demonstrate the effectiveness of using nickel aluminide intermetallic alloy rolls as part of an updated, energy-efficient, commercial annealing furnace system.

Evolution of the Structure of Local Regions of Fused Metal in Explosion-Welded Nickel-Aluminum Composites Under Heat Treatment

NASA Astrophysics Data System (ADS)

Shmorgun, V. G.; Bogdanov, A. I.; Gurevich, L. M.

2016-03-01

The methods of electron, optical, and atomic force microscopy are used to study the structure, morphology and phase composition of local regions of fused metal in an explosion-welded nickel-aluminum composite. It is shown that the diffusion zone formed due to the heat treatment repeats the contour of the fuse in the first stage and then "absorbs" it upon duration of the hold thus leveling the phase composition. ANi2Al3 Aluminide layer forms on the side of nickel and a NiAl3 layer forms on the side of aluminum.

A Compendium of Scale Surface Microstructures: Ni(pt)al Coatings Oxidized at 1150 C for 2000 1-h Cycles

NASA Technical Reports Server (NTRS)

Smialek, James L.; Garg, Anita

2010-01-01

The surface structure of scales formed on Ni(Pt)Al coatings was characterized by SEM/EDS/BSE in plan view. Two nominally identical {100} samples of aluminide coated CMSX4 single crystal were oxidized at 1150 C for 2000 1-h cycles and were found to produce somewhat disparate behavior. One sample, with less propensity for coating grain boundary ridge deformation, presented primarily alpha-Al2O3 scale structures, with minimal weight loss and spallation. The original scale structure, still retained over most of the sample, consisted of the classic theta-alpha transformation-induced ridge network structure, with approx. 25 nm crystallographic steps and terraces indicative of surface rearrangement to low energy alumina planes. The scale grain boundary ridges were often decorated with a fine, uniform distribution of (Hf,Ti)O2 particles. Another sample, producing steady state weight losses, exhibited much interfacial spallation and a complex assortment of different structures. Broad areas of interfacial spalling, crystallographically-faceted (Ni,Co)(Al,Cr)2O4 spinel, with an alpha-Al2O3 base scale, were the dominant features. Other regions exhibited nodular spinel grains, with fine or (Ta,Ti)-rich (rutile) particles decorating or interspersed with the spinel. While these features were consistent with a coating that presented more deformation at extruded grain boundaries, the root cause of the different behavior between the duplicate samples could not be conclusively identified.

Kinetic Monte Carlo Simulations of Oxygen Diffusion in Environmental Barrier Coating Materials

NASA Technical Reports Server (NTRS)

Good, Brian S.

2017-01-01

Ceramic Matrix Composite (CMC) materials are of interest for use in next-generation turbine engine components, offering a number of significant advantages, including reduced weight and high operating temperatures. However, in the hot environment in which such components operate, the presence of water vapor can lead to corrosion and recession, limiting the useful life of the components. Such degradation can be reduced through the use of Environmental Barrier Coatings (EBCs) that limit the amount of oxygen and water vapor reaching the component. Candidate EBC materials include Yttrium and Ytterbium silicates. In this work we present results of kinetic Monte Carlo (kMC) simulations of oxygen diffusion, via the vacancy mechanism, in Yttrium and Ytterbium disilicates, along with a brief discussion of interstitial diffusion. An EBC system typically includes a bond coat located between the EBC and the component surface. Bond coat materials are generally chosen for properties other than low oxygen diffusivity, but low oxygen diffusivity is nevertheless a desirable characteristic, as the bond coat could provide some additional component protection, particularly in the case where cracks in the coating system provide a direct path from the environment to the bond coat interface. We have therefore performed similar kMC simulations of oxygen diffusion in this material.

Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

DOEpatents

Sikka, Vinod K.

1992-01-01

A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, Joachim H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1450.degree. C. for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOEpatents

Schneibel, J.H.

1997-06-10

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, J.H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Investigation to develop a method to apply diffusion barrier to high strength fibers

NASA Technical Reports Server (NTRS)

Veltri, R. D.; Paradis, R. D.; Douglas, F. C.

1975-01-01

A radio frequency powered ion plating process was used to apply the diffusion barriers of aluminum oxide, yttrium oxide, hafnium oxide and titanium carbide to a substrate tungsten fiber. Each of the coatings was examined as to its effect on both room temperature strength and tensile strength of the base tungsten fiber. The coated fibers were then overcoated with a nickel alloy to become single cell diffusion couples. These diffusion couples were exposed to 1093 C for 24 hours, cycled between room temperature and 1093 C, and given a thermal anneal for 100 hours at 1200 C. Tensile testing and metallographic examinations determined that the hafnium oxide coating produced the best high temperature diffusion barrier for tungsten of the four coatings.

Environmental protection of titanium alloys at high temperatures

NASA Technical Reports Server (NTRS)

Wright, I. G.; Wood, R. A.; Seltzer, M. S.

1974-01-01

Various concepts were evaluated for protecting titanium alloys from oxygen contamination at 922 K (1200 F) and from hot-salt stress-corrosion at 755 K (900 F). It is indicated that oxygen-contamination resistance can be provided by a number of systems, but for hot-salt stress-corrosion resistance, factors such as coating integrity become very important. Titanium aluminides resist oxygen ingress at 922 K through the formation of alumina (on TiAl3) or modified TiO2 (on Ti3Al, TiAl) scales. TiAl has some resistance to attack by hot salt, but has limited ductility. Ductile Ti-Ni and Ti-Nb-Cr-Al alloys provide limited resistance to oxygen ingress, but are not greatly susceptible to hot-salt stress-corrosion cracking.

Hot corrosion of the B2 nickel aluminides

NASA Technical Reports Server (NTRS)

Ellis, David L.

1993-01-01

The hot corrosion behavior of the B2 nickel aluminides was studied to determine the inherent hot corrosion resistance of the beta nickel aluminides and to develop a mechanism for the hot corrosion of the beta nickel aluminides. The effects of the prior processing of the material, small additions of zirconium, stoichiometry of the materials, and preoxidation of the samples were also examined. Additions of 2, 5, and 15 w/o chromium were used to determine the effect of chromium on the hot corrosion of the beta nickel aluminides and the minimum amount of chromium necessary for good hot corrosion resistance. The results indicate that the beta nickel aluminides have inferior inherent hot corrosion resistance despite their excellent oxidation resistance. Prior processing and zirconium additions had no discernible effect on the hot corrosion resistance of the alloys. Preoxidation extended the incubation period of the alloys only a few hours and was not considered to be an effective means of stopping hot corrosion. Stoichiometry was a major factor in determining the hot corrosion resistance of the alloys with the higher aluminum alloys having a definitely superior hot corrosion resistance. The addition of chromium to the alloys stopped the hot corrosion attack in the alloys tested. From a variety of experimental results, a complex hot corrosion mechanism was proposed. During the early stages of the hot corrosion of these alloys the corrosion is dominated by a local sulphidation/oxidation form of attack. During the intermediate stages of the hot corrosion, the aluminum depletion at the surface leads to a change in the oxidation mechanism from a protective external alumina layer to a mixed nickel-aluminum spinel and nickel oxide that can occur both externally and internally. The material undergoes extensive cracking during the later portions of the hot corrosion.

Kinetic Monte Carlo Simulations of Diffusion in Environmental Barrier Coating Materials

NASA Technical Reports Server (NTRS)

Good, Brian

2017-01-01

Ceramic Matrix Components (CMC) components for use in turbine engines offer a number of advantages compared with current practice. However, such components are subject to degradation through a variety of mechanisms. In particular, in the hot environment inside a turbine in operation a considerable amount of water vapor is present, and this can lead to corrosion and recession. Environmental Barrier Coating (EBC) systems that limit the amount of oxygen and water reaching the component are required to reduce this degradation and extend component life. A number of silicate-based materials are under consideration for use in such coating systems, including Yttterbium and Yttrium di- and monosilicates. In this work, we present results of kinetic Monte Carlo computer simulations of oxygen diffusion in Yttrium disilicate, and compare with previous work on Yttterbium disilicate. Coatings may also exhibit cracking, and the cracks can provide a direct path for oxygen to reach the component. There is typically a bond coat between the coating and component surface, but the bond coat material is generally chosen for properties other than low oxygen diffusivity. Nevertheless, the degree to which the bond coat can inhibit oxygen diffusion is of interest, as it may form the final defense against oxygen impingement on the component. We have therefore performed similar simulations of oxygen diffusion through HfSiO4, a proposed bond coat material.

Hydrogenated amorphous carbon coatings on implants drastically reduce biofilm formation and water permeation

NASA Astrophysics Data System (ADS)

Bernsmann, Falk; Laube, Norbert; Baldsiefen, Gerhard; Castellucci, Mattia

2014-11-01

Inflammations and crystalline bacterial biofilms (encrustations) remain a major complication in long-term artificial urinary tract drainage. To solve this problem we present urological implants with coatings made of amorphous hydrogenated carbon (a-C:H) that show excellent protection from encrustation in-vitro as well as in-vivo. Part of the success of a-C:H coatings is attributed to their ability to act as a diffusion barrier between an implant and the body, which prevents leaching of solvents from polymeric implants. To further enhance their barrier properties a-C:H coatings are combined with parylene coatings to develop diffusion-barrier multilayer coatings with a total thickness between 0.2 μm and 0.8 μm. The combination of the two types of coatings leads to a reduction of water diffusion by a factor of up to ten with respect to uncoated 25 μm thick polyimide sub-strates. The diffusion of water vapour from a controlled atmospheric pressure chamber through coated foils to a vacuum chamber is measured in a custom-built device.

Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection

NASA Astrophysics Data System (ADS)

Bläckberg, L.; Fay, A.; Jõgi, I.; Biegalski, S.; Boman, M.; Elmgren, K.; Fritioff, T.; Johansson, A.; Mårtensson, L.; Nielsen, F.; Ringbom, A.; Rooth, M.; Sjöstrand, H.; Klintenberg, M.

2011-11-01

In this work Al2O3 and SiO2 coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al2O3 coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.

Oxidation resistant filler metals for direct brazing of structural ceramics

DOEpatents

Moorhead, Arthur J.

1986-01-01

A method of joining ceramics and metals to themselves and to one another is described using essentially pure trinickel aluminide and trinickel aluminide containing small amounts of carbon. This method produces strong joints that can withstand high service temperatures and oxidizing environments.

Method for producing titanium aluminide weld rod

DOEpatents

Hansen, Jeffrey S.; Turner, Paul C.; Argetsinger, Edward R.

1995-01-01

A process for producing titanium aluminide weld rod comprising: attaching one end of a metal tube to a vacuum line; placing a means between said vacuum line and a junction of the metal tube to prevent powder from entering the vacuum line; inducing a vacuum within the tube; placing a mixture of titanium and aluminum powder in the tube and employing means to impact the powder in the tube to a filled tube; heating the tube in the vacuum at a temperature sufficient to initiate a high-temperature synthesis (SHS) reaction between the titanium and aluminum; and lowering the temperature to ambient temperature to obtain a intermetallic titanium aluminide alloy weld rod.

Evaluation of a Gamma Titanium Aluminide for Hypersonic Structural Applications

NASA Technical Reports Server (NTRS)

Johnson, W. Steven; Weeks, Carrell E.

2005-01-01

Titanium matrix composites (TMCs) have been extensively evaluated for their potential to replace conventional superalloys in high temperature structural applications, with significant weight-savings while maintaining comparable mechanical properties. New gamma titanium aluminide alloys and an appropriate fiber could offer an improved TMC for use in intermediate temperature applications (400-800 C). The purpose of this investigation is the evaluation of a gamma titanium aluminide alloy with nominal composition Ti-46.5Al-4(Cr,Nb,Ta,B)at.% as a structural material in future aerospace transportation systems, where very light-weight structures are necessary to meet the goals of advanced aerospace programs.

Castable nickel aluminide alloys for structural applications

DOEpatents

Liu, Chain T.

1992-01-01

The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition.

A new diffusion-inhibited oxidation-resistant coating for superalloys

NASA Technical Reports Server (NTRS)

Gedwill, M. A.; Glasgow, T. K.; Levine, S. R.

1981-01-01

A concept for enhanced protection of superalloys consists of adding an oxidation- and diffusion-resistant cermet layer between the superalloy and the outer oxidation-resistant metallic alloy coating. Such a duplex coating was compared with a physical-vapor-deposited (PVD) NiCrAlY coating in cyclic oxidation at 1150 C. The substrate alloy was MA 754 - an oxide-dispersion-strengthened superalloy that is difficult to coat. The duplex coating, applied by plasma spraying, outperformed the PVD coating on the basis of weight change and both macroscopic and metallographic observations.

Ion Diffusion-Directed Assembly Approach to Ultrafast Coating of Graphene Oxide Thick Multilayers.

PubMed

Zhao, Xiaoli; Gao, Weiwei; Yao, Weiquan; Jiang, Yanqiu; Xu, Zhen; Gao, Chao

2017-10-24

The layer-by-layer (LbL) assembly approach has been widely used to fabricate multilayer coatings on substrates with multiple cycles, whereas it is hard to access thick films efficiently. Here, we developed an ion diffusion-directed assembly (IDDA) strategy to rapidly make multilayer thick coatings in one step on arbitrary substrates. To achieve multifunctional coatings, graphene oxide (GO) and metallic ions were selected as the typical building blocks and diffusion director in IDDA, respectively. With diffusion of metallic ions from substrate to negatively charged GO dispersion spontaneously (i.e., from high-concentration region to low-concentration region), GO was assembled onto the substrate sheet-by-sheet via sol-gel transformation. Because metallic ions with size of subnanometers can diffuse directionally and freely in the aqueous dispersion, GO was coated on the substrate efficiently, giving rise to films with desired thickness up to 10 μm per cycle. The IDDA approach shows three main merits: (1) high efficiency with a μm-scale coating rate; (2) controllability over thickness and evenness; and (3) generality for substrates of plastics, metals and ceramics with any shapes and morphologies. With these merits, IDDA strategy was utilized in the efficient fabrication of functional graphene coatings that exhibit outstanding performance as supercapacitors, electromagnetic interference shielding textiles, and anticorrosion coatings. This IDDA approach can be extended to other building blocks including polymers and colloidal nanoparticles, promising for the scalable production and application of multifunctional coatings.

Alloyed coatings for dispersion strengthened alloys

NASA Technical Reports Server (NTRS)

Wermuth, F. R.; Stetson, A. R.

1971-01-01

Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.

Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia

NASA Technical Reports Server (NTRS)

Good, Brian

2011-01-01

Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

The effect of silicon on the oxidation behavior of NiAlHf coating system

NASA Astrophysics Data System (ADS)

Dai, Pengchao; Wu, Qiong; Ma, Yue; Li, Shusuo; Gong, Shengkai

2013-04-01

Two types of NiAlHf coatings doped with different content of Si (1 at.% and 2 at.%) were deposited on a Ni3Al based single crystal superalloy IC32 by electron beam physical vapor deposition (EB-PVD) method, respectively. For comparison, NiAlHf coating with 0 at.% Si was also prepared. The oxidation tests were carried out at 1423 K in air. At the initial stage of oxidation, large amount of flake-like θ-Al2O3 was found on NiAlHf coating surface. However, no θ-Al2O3 was observed in 2 at.% Si doped NiAlHf coating except α-Al2O3. It revealed that the Si additions could contribute to the transformation from θ-Al2O3 to α-Al2O3. When oxidation time prolonged to 100 h, it was found that the degradation of NiAlHf coating was very severe with no residual β-phase, which was due to the serious inter-diffusion between the coating and substrate. In contrast, the inter-diffusion in Si-doped coating was reduced with some residual β-phase and R-Ni(Mo, Re) precipitates. The presence of Si could retard the inter-diffusion of elements between coating and substrate, indicating a barrier diffusion effect. As a result, the oxidation resistance of NiAlHf coating was improved significantly.

Design, fabrication, and bench testing of a solar chemical receiver

NASA Technical Reports Server (NTRS)

Summers, W. A.; Pierre, J. F.

1981-01-01

Solar thermal energy can be effectively collected, transported, stored, and utilized by means of a chemical storage and transport system employing the reversible SO2 oxidation reaction. A solar chemical receiver for SO3 thermal decomposition to SO2 and oxygen was analyzed. Bench tests of a ten foot section of a receiver module were conducted with dissociated sulfuric acid (SO3 and H2O) in an electrical furnace. Measured percent conversion of SO3 was 85% of the equilibrium value. Methods were developed to fabricate and assemble a complete receiver module. These methods included applying an aluminide coating to certain exposed surfaces, assembling concentric tubes with a wire spacer, applying a platinum catalyst to the tubing wall, and coiling the entire assembly into the desired configuration.

Cyclic furnace oxidation of clad WI-52 systems at 1040 C and 1090 C

NASA Technical Reports Server (NTRS)

Gedwill, M. A.

1972-01-01

Cyclic furnace oxidation studies were conducted on the cobalt alloy WI-52 clad with Ni-30Cr, Fe-25Cr-4A1, and Ni-20Cr-4A1 foils (0.051 to 0.254 mm thick). Tests as long as 400 hours using 1- and 20-hour cycles showed that the Ni-Cr- and Fe-Cr-A1 claddings were about equally protective at both temperatures. The protective ability of these alloys was influenced by exposure temperature and cladding thickness. At both temperatures, they protected WI-52 about as well as, or better than, a widely used commercial aluminide coating. The Ni-Cr-Al claddings did not protect WI-52 nearly as well. Interdiffusion generally influenced the oxidation behavior of all clad WI-52 systems.

Determination of hydrogen permeability in uncoated and coated superalloys

NASA Technical Reports Server (NTRS)

Bhattacharyya, S.; Vesely, E. J., Jr.; Hill, V. L.

1981-01-01

Hydrogen permeability, diffusivity, and solubility data were obtained for eight wrought and cast high temperature alloys over the range 650 to 815 C. Data were obtained for both uncoated alloys and wrought alloys coated with four commercially available coatings. Activation energies for permeability, diffusivity and solubility were calculated.

Transmitting and reflecting diffuser. [for ultraviolet light

NASA Technical Reports Server (NTRS)

Keafer, L. S., Jr.; Burcher, E. E.; Kopia, L. P. (Inventor)

1973-01-01

A near-Lambertian diffuser is described which transmits and reflects ultraviolet light. An ultraviolet grade fused silica substrate is coated with vaporized fuse silica. The coating thickness is controlled, one thickness causing ultraviolet light to diffuse and another thickness causing ultraviolet light to reflect a near Lambertian pattern.

Protective coatings for sensitive materials

DOEpatents

Egert, Charles M.

1997-01-01

An enhanced protective coating to prevent interaction between constituents of the environment and devices that can be damaged by those constituents. This coating is provided by applying a synergistic combination of diffusion barrier and physical barrier materials. These materials can be, for example, in the form of a plurality of layers of a diffusion barrier and a physical barrier, with these barrier layers being alternated. Further protection in certain instances is provided by including at least one layer of a getter material to actually react with one or more of the deleterious constituents. The coating is illustrated by using alternating layers of an organic coating (such as Parylene-C.TM.) as the diffusion barrier, and a metal coating (such as aluminum) as the physical barrier. For best results there needs to be more than one of at least one of the constituent layers.

Improving the Corrosion Resistance of Biodegradable Magnesium Alloys by Diffusion Coating Process

NASA Astrophysics Data System (ADS)

Levy, Galit Katarivas; Aghion, Eli

Magnesium alloys suffer from accelerated corrosion in physiological environment and hence their use as a structural material for biodegradable implants is limited. The present study focuses on a diffusion coating treatment that amplifies the beneficial effect of Neodymium on the corrosion resistance of magnesium alloys. The diffusion coating layer was obtained by applying 1 µm Nd coating on EW10X04 magnesium alloy using Electron-gun evaporator and PVD process. The coated alloy was heat treated at 350°C for 3 hours in a protective atmosphere of N2+0.2%SF6. The micro structure characteristics were evaluated by SEM, XRD, and XPS; the corrosion resistance was examined by potentiodynamic polarization and EIS analysis. The corrosion resistance of the diffusion coated alloy was significantly improved compared to the uncoated material. This was related to: (i) formation of Nd2O3 in the outer scale, (ii) integration of Nd in the MgO oxide layer, and (iii) formation of secondary phase Mg41Nd5 along the grain boundaries of α-Mg.

Environmental Studies on Titanium Aluminide Alloys

NASA Technical Reports Server (NTRS)

Brindley, William J.; Bartolotta, Paul A.; Smialek, James L.; Brady, Michael P.

2005-01-01

Titanium aluminides are attractive alternatives to superalloys in moderate temperature applications (600 to 850 C) by virtue of their high strength-to-density ratio (high specific strength). These alloys are also more ductile than competing intermetallic systems. However, most Ti-based alloys tend to degrade through interstitial embrittlement and rapid oxidation during exposure to elevated temperatures. Therefore, their environmental behavior must be thoroughly investigated before they can be developed further. The goals of titanium aluminide environmental studies at the NASA Lewis Research Center are twofold: characterize the degradation mechanisms for advanced structural alloys and determine what means are available to minimize degradation. The studies to date have covered the alpha 2 (Ti3Al), orthorhombic (Ti2AlNb), and gamma (TiAl) classes of alloys.

Approximation of effective moisture-diffusion coefficient to characterize performance of a barrier coating

NASA Astrophysics Data System (ADS)

Nagai, Shingo

2013-11-01

We report estimation of the effective diffusion coefficient of moisture through a barrier coating to develop an encapsulation technology for the thin-film electronics industry. This investigation targeted a silicon oxide (SiOx) film that was deposited on a plastic substrate by a large-process-area web coater. Using the finite difference method based on diffusion theory, our estimation of the effective diffusion coefficient of a SiOx film corresponded to that of bulk glass that was previously reported. This result suggested that the low diffusivities of barrier films can be obtained on a mass-production level in the factory. In this investigation, experimental observations and mathematical confirmation revealed the limit of the water vapor transmission rate on the single barrier coating.

Reaction diffusion in the nickel-chromium-aluminum and cobalt-chromium-aluminum systems

NASA Technical Reports Server (NTRS)

Levine, S. R.

1977-01-01

The effects of MCrAl coating-substrate interdiffusion on oxidation life and the general mutliphase, multicomponent diffusion problem were examined. Semi-infinite diffusion couples that had sources representing coatings and sinks representing gas turbine alloys were annealed at 1,000, 1,095, 1,150, or 1,205 C for as long as 500 hours. The source and sink aluminum and chromium contents and the base metal (cobalt or nickel) determined the parabolic diffusion rate constants of the couples and predicted finite coating lives. The beta source strength concept provided a method (1) for correlating beta recession rate constants with composition; (2) for determining reliable average total, diffusion, and constitutional activation energies; and (3) for calculating interdiffusion coefficients.

Protective coatings for sensitive materials

DOEpatents

Egert, C.M.

1997-08-05

An enhanced protective coating is disclosed to prevent interaction between constituents of the environment and devices that can be damaged by those constituents. This coating is provided by applying a synergistic combination of diffusion barrier and physical barrier materials. These materials can be, for example, in the form of a plurality of layers of a diffusion barrier and a physical barrier, with these barrier layers being alternated. Further protection in certain instances is provided by including at least one layer of a getter material to actually react with one or more of the deleterious constituents. The coating is illustrated by using alternating layers of an organic coating (such as Parylene-C{trademark}) as the diffusion barrier, and a metal coating (such as aluminum) as the physical barrier. For best results there needs to be more than one of at least one of the constituent layers. 4 figs.

Preparation and Bond Properties of Thermal Barrier Coatings on Mg Alloy with Sprayed Al or Diffused Mg-Al Intermetallic Interlayer

NASA Astrophysics Data System (ADS)

Fan, Xizhi; Wang, Ying; Zou, Binglin; Gu, Lijian; Huang, Wenzhi; Cao, Xueqiang

2014-02-01

Sprayed Al or diffused Mg-Al layer was designed as interlayer between the thermal barrier coatings (TBCs) and Mg alloy substrate. The effects of the interlayer on the bond properties of the coats were investigated. Al layers were prepared by arc spraying and atmospheric plasma spraying (APS), respectively. Mg-Al diffused layer was obtained after the heat treatment of the sprayed sample (Mg alloy with APS Al coat) at 400 °C. The results show that sprayed Al interlayer does not improve the bond stability of TBCs. The failure of the TBCs on Mg alloy with Al interlayer occurs mainly due to the low strength of Al layer. Mg-Al diffused layer improves corrosion resistance of substrate and the bond interface. The TBCs on Mg alloy with Mg-Al diffused interlayer shows better bond stability than the sample of which the TBCs is directly sprayed on Mg alloy substrate by APS.

On the interdiffusion in multilayered silicide coatings for the vanadium-based alloy V-4Cr-4Ti

NASA Astrophysics Data System (ADS)

Chaia, N.; Portebois, L.; Mathieu, S.; David, N.; Vilasi, M.

2017-02-01

To provide protection against corrosion at high temperatures, silicide diffusion coatings were developed for the V-4Cr-4Ti alloy, which can be used as the fuel cladding in next-generation sodium-cooled fast breeder reactors. The multilayered coatings were prepared by halide-activated pack cementation using MgF2 as the transport agent and pure silicon (high activity) as the master alloy. Coated pure vanadium and coated V-4Cr-4Ti alloy were studied and compared as substrates. In both cases, the growth of the silicide layers (V3Si, V5Si3, V6Si5 and VSi2) was controlled exclusively by solid-state diffusion, and the growth kinetics followed a parabolic law. Wagner's analysis was adopted to calculate the integrated diffusion coefficients for all silicides. The estimated values of the integrated diffusion coefficients range from approximately 10-9 to 10-13 cm2 s-1. Then, a diffusion-based numerical approach was used to evaluate the growth and consumption of the layers when the coated substrates were exposed at critical temperatures. The estimated lifetimes of the upper VSi2 layer were 400 h and 280 h for pure vanadium and the V-4Cr-4Ti alloy, respectively. The result from the numeric simulation was in good agreement with the layer thicknesses measured after aging the coated samples at 1150 °C under vacuum.

Aluminum and Other Coatings for the Passivation of Tritium Storage Vessels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spencer, W.; Korinko, P.

Using a highly sensitive residual gas analyzer, the off-gassing of hydrogen, water, and hydrocarbons from surface-treated storage vessels containing deuterium was measured. The experimental storage vessels were compared to a low-off-gassing, electro-polished 304L canister. Alternative vessels were made out of aluminum, or were coatings on 304L steel. Coatings included powder pack aluminide, electro-plated aluminum, powder pack chromide, dense electro-plated chromium, copper plated, and copper plated with 25 and 50 percent nano-diamond. Vessels were loaded with low pressure deuterium to observe exchange with protium or hydrogen as observed with formation of HD and HDO. Off gas of D 2O or possiblemore » CD 4 was observed at mass 20. The main off-gas in all of the studies was H 2. The studies indicated that coatings required significant post-coating treatment to reduce off-gas and enhance the permeation barrier from gases likely added during the coating process. Dense packed aluminum coatings needed heating to drive off water. Electro-plated aluminum, chromium and copper coatings appeared to trap hydrogen from the plating process. Nano-diamond appeared to enhance the exchange rate with hydrogen off gas, and its coating process trapped significant amounts of hydrogen. Aluminum caused more protium exchange than chromium-treated surfaces. Aluminum coatings released more water, but pure aluminum vessels released small amounts of hydrogen, little water, and generally performed well. Chromium coating had residual hydrogen that was difficult to totally outgas but otherwise gave low residuals for water and hydrocarbons. Our studies indicated that simple coating of as received 304L metal will not adequately block hydrogen. The base vessel needs to be carefully out-gassed before applying a coating, and the coating process will likely add additional hydrogen that must be removed. Initial simple bake-out and leak checks up to 350° C for a few hours was found to be inadequate. All of the studies indicated that vessels needed several days of vacuum baking at 350-450° C to fully outgas the residual gases, which were mostly hydrogen. The current standard practice of out-gassing from ultra-clean, electro-polished 304L vessels with both vacuum bake-out and followed by an oxidative bake out to enhance the chromium surface performed the best in these studies.« less

Development of black scattering coatings for space application (etude de traitements noirs diffusants pour application spatiale)

NASA Astrophysics Data System (ADS)

Mestreau-Garreau, Agnes; Pezant, Christian; Cousin, Bernard; Etcheto, Pierre; Otrio, Georges

2017-11-01

In the context of Research and Technology (R&T), studies have been performed on the coatings of vane edge in the 0.4 to 1 μm spectral range. The main purposes of the study were to improve the diffusing black coatings available on the market and to look for other diffusing black coatings. At the same time, we have also improved the machining technologies of vane edges. The characterisation (thermal tests, radiometric measurements, adhesion tests) of the most promising technologies has been carried out. The results have pointed out the stainless steel vanes with the edge obtained by polishing or by advanced grinding.

Chromium Vaporization Reduction by Nickel Coatings For SOEC Interconnect Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael V. Glazoff; Sergey N. Rashkeev; J. Stephen Herring

2014-09-01

The vaporization of Cr-rich volatile species from interconnect materials is a major source of degradation that limits the lifetime of planar solid oxide devices systems with metallic interconnects, including Solid Oxide Electrolysis Cells, or SOECs. Some metallic coatings (Ni, Co, and Cu) significantly reduce the Cr release from interconnects and slow down the oxide scale growth on the steel substrate. To shed additional light upon the mechanisms of such protection and find a suitable coating material for ferritic stainless steel materials, we used a combination of first-principles calculations, thermodynamics, and diffusion modeling to investigate which factors determine the quality ofmore » the Ni metallic coating at stainless steel interconnector. We found that the Cr migration in Ni coating is determined by a delicate combination of the nickel oxidation, Cr diffusion, and phase transformation processes. Although the formation of Cr2O3 oxide is more exothermic than that of NiO, the kinetic rate of the chromia formation in the coating layer and its surface is significantly reduced by the low mobility of Cr in nickel oxide and in NiCr2O4 spinel. These results are in a good agreement with diffusion modeling for Cr diffusion through Ni coating layer on the ferritic 441 steel substrate.« less

COATED CARBON ELEMENT FOR USE IN NUCLEAR REACTORS AND THE PROCESS OF MAKING THE ELEMENT

DOEpatents

Pyle, R.J.; Allen, G.L.

1963-01-15

S>This patent relates to a carbide-nitride-carbide coating for carbon bodies that are to be subjected to a high temperature nuclear reactor atmosphere, and a method of applying the same. This coating is a highly efficient diffusion barrier and protects the C body from corrosion and erosion by the reactor atmosphere. Preferably, the innermost coating is Zr carbide, the middle coatlng is Zr nitride, and the outermost coating is a mixture of Zr and Nb carbide. The nitride coating acts as a diffusion barrier, while the innermost carbide bonds the nitride to the C body and prevents deleterious reaction between the nitride and C body. The outermost carbide coating protects the nitride coating from the reactor atmosphere. (AEC)

Titanium Aluminide Applications in the High Speed Civil Transport

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.; Krause, David L.

1999-01-01

It is projected that within the next two decades, overseas air travel will increase to over 600,000 passengers per day. The High Speed Civil Transport (HSCT) is a second-generation supersonic commercial aircraft proposed to meet this demand. The expected fleet of 500 to 1500 aircraft is required to meet EPA environmental goals; the HSCT propulsion system requires advanced technologies to reduce exhaust and noise pollution. A part of the resultant strategy for noise attenuation is the use of an extremely large exhaust nozzle. In the nozzle, several critical components are fabricated from titanium aluminide: the divergent nap uses wrought gamma; the nozzle sidewall is a hybrid fabrication of both wrought gamma face sheet and cast gamma substructure. This paper describes the HSCT program and the use of titanium aluminide for its components.

Iron aluminide alloy container for solid oxide fuel cells

DOEpatents

Judkins, Roddie Reagan; Singh, Prabhakar; Sikka, Vinod Kumar

2000-01-01

A container for fuel cells is made from an iron aluminide alloy. The container alloy preferably includes from about 13 to about 22 weight percent Al, from about 2 to about 8 weight percent Cr, from about 0.1 to about 4 weight percent M selected from Zr and Hf, from about 0.005 to about 0.5 weight percent B or from about 0.001 to about 1 weight percent C, and the balance Fe and incidental impurities. The iron aluminide container alloy is extremely resistant to corrosion and metal loss when exposed to dual reducing and oxidizing atmospheres at elevated temperatures. The alloy is particularly useful for containment vessels for solid oxide fuel cells, as a replacement for stainless steel alloys which are currently used.

Laser Cladding of γ-TiAl Intermetallic Alloy on Titanium Alloy Substrates

NASA Astrophysics Data System (ADS)

Maliutina, Iuliia Nikolaevna; Si-Mohand, Hocine; Piolet, Romain; Missemer, Florent; Popelyukh, Albert Igorevich; Belousova, Natalya Sergeevna; Bertrand, Philippe

2016-01-01

The enhancement of titanium and titanium alloy's tribological properties is of major interest in many applications such as the aerospace and automotive industry. Therefore, the current research paper investigates the laser cladding of Ti48Al2Cr2Nb powder onto Ti6242 titanium alloy substrates. The work was carried out in two steps. First, the optimal deposition parameters were defined using the so-called "combined parameters," i.e., the specific energy E specific and powder density G. Thus, the results show that those combined parameters have a significant influence on the geometry, microstructure, and microhardness of titanium aluminide-formed tracks. Then, the formation of dense, homogeneous, and defect-free coatings based on optimal parameters has been investigated. Optical and scanning electron microscopy techniques as well as energy-dispersive spectroscopy and X-ray diffraction analyses have shown that a duplex structure consisting of γ-TiAl and α 2-Ti3Al phases was obtained in the coatings during laser cladding. Moreover, it was shown that produced coatings exhibit higher values of microhardness (477 ± 9 Hv0.3) and wear resistance (average friction coefficient is 0.31 and volume of worn material is 5 mm3 after 400 m) compared to those obtained with bare titanium alloy substrates (353 Hv0.3, average friction coefficient is 0.57 and a volume of worn material after 400 m is 35 mm3).

Preparation and evaluation of metoprolol tartrate sustained-release pellets using hot melt extrusion combined with hot melt coating.

PubMed

Yang, Yan; Shen, Lian; Li, Juan; Shan, Wei-Guang

2017-06-01

The objective of this study was to prepare and evaluate metoprolol tartrate sustained-release pellets. Cores were prepared by hot melt extrusion and coated pellets were prepared by hot melt coating. Cores were found to exist in a single-phase state and drug in amorphous form. Plasticizers had a significant effect on torque and drug content, while release modifiers and coating level significantly affected the drug-release behavior. The mechanisms of drug release from cores and coated pellets were Fickian diffusion and diffusion-erosion. The coated pellets exhibited sustained-release properties in vitro and in vivo.

Innovative coating of nanostructured vanadium carbide on the F/M cladding tube inner surface for mitigating the fuel cladding chemical interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yong; Phillpot, Simon

Fuel cladding chemical interactions (FCCI) have been acknowledged as a critical issue in a metallic fuel/steel cladding system due to the formation of low melting intermetallic eutectic compounds between the fuel and cladding steel, resulting in reduction in cladding wall thickness as well as a formation of eutectic compounds that can initiate melting in the fuel at lower temperature. In order to mitigate FCCI, diffusion barrier coatings on the cladding inner surface have been considered. In order to generate the required coating techniques, pack cementation, electroplating, and electrophoretic deposition have been investigated. However, these methods require a high processing temperaturemore » of above 700 oC, resulting in decarburization and decomposition of the martensites in a ferritic/martensitic (F/M) cladding steel. Alternatively, organometallic chemical vapor deposition (OMCVD) can be a promising process due to its low processing temperature of below 600 oC. The aim of the project is to conduct applied and fundamental research towards the development of diffusion barrier coatings on the inner surface of F/M fuel cladding tubes. Advanced cladding steels such as T91, HT9 and NF616 have been developed and extensively studied as advanced cladding materials due to their excellent irradiation and corrosion resistance. However, the FCCI accelerated by the elevated temperature and high neutron exposure anticipated in fast reactors, can have severe detrimental effects on the cladding steels through the diffusion of Fe into fuel and lanthanides towards into the claddings. To test the functionality of developed coating layer, the diffusion couple experiments were focused on using T91 as cladding and Ce as a surrogate lanthanum fission product. By using the customized OMCVD coating equipment, thin and compact layers with a few micron between 1.5 µm and 8 µm thick and average grain size of 200 nm and 5 µm were successfully obtained at the specimen coated between 300oC and 500 oC, respectively. The coating layer contains both carbon and vanadium elements as quantified by WED, and the phases mainly consist of a mixture of V2C and VC, which was confirmed using X-ray diffraction patterns. In addition, the ratio between V and C varies with processing temperature, and it was observed that a higher temperature promotes the carbon adsorption and increases thickness of the coating. With optimized deposition conditions, we can apply the coating technique toward the actual T91 cladding materials, and provide the possibilities for the real application in sodium-cooled fast reactors (SFRs). Diffusion couple experiments were performed at both 550 oC and 690 oC, which corresponds to normal and aggressive operating temperatures, respectively. The results show that vanadium carbide coating with wider thickness (8 µm) and lower carbon concentration (27 at.%) reduced the width of the inter diffusion region, indicating that vanadium carbide coating can mitigate FCCI effectively. In specific, inter-diffusion between Fe and Ce was prohibited over most area, but Ce diffusion occurred toward the coating and the Fe substrate through thinner coating layer, which needs further optimization in terms of uniform coating thickness. Overall, it is concluded that this coating process can be successfully applied onto the inner surface of HT9 cladding tubes and the FCCI can be effectively mitigated if not totally eliminated.« less

Design for Oxidation Resistance

NASA Technical Reports Server (NTRS)

Smialek, James L.; Schaeffer, Jon C.; Barrett, Charles A.

1997-01-01

Alloys intended for use in high-temperature environment rely on the formation of a continuous, compact, slow-growing oxide layer for oxidation and hot corrosion resistance. To be protective, this oxide layer must be chemically, thermodynamically stable. Successful alloy design for oxidative environment is best achieved by developing alloys that are capable of forming adherent scales of either alumina (Al2O3), chromia (Cr2O3), or silica (SiO2). In this article, emphasis has been placed on the issue related to high-temperature oxidation of superalloys used in gas turbine engine application. Despite the complexity of these alloys, optimal performance has been associated with protective alumina scale formation. As will be described below, both compositional makeup and protective coatings play key role in providing oxidation protection. Other high-temperature materials described include nickel and titanium aluminide intermetallics, refractory metal, and ceramics.

Cermet materials

DOEpatents

Kong, Peter C [Idaho Falls, ID

2008-12-23

A self-cleaning porous cermet material, filter and system utilizing the same may be used in filtering particulate and gaseous pollutants from internal combustion engines having intermetallic and ceramic phases. The porous cermet filter may be made from a transition metal aluminide phase and an alumina phase. Filler materials may be added to increase the porosity or tailor the catalytic properties of the cermet material. Additionally, the cermet material may be reinforced with fibers or screens. The porous filter may also be electrically conductive so that a current may be passed therethrough to heat the filter during use. Further, a heating element may be incorporated into the porous cermet filter during manufacture. This heating element can be coated with a ceramic material to electrically insulate the heating element. An external heating element may also be provided to heat the cermet filter during use.

Breakthrough Air Force Capabilities Spawned By Basic Research

DTIC Science & Technology

2007-04-01

AboutAFOSR/about_history.htm>. 15 Ibid. 16 Ibid. 4 1990s • Titanium Aluminides . AFOSR-sponsored research looked at titanium aluminides , which are...the 1970s, AFOSR sponsored research on ways to increase the strength and fatigue resistance of titanium , aluminum, and nickel alloys used for...High-Efficiency Swept Shock Compressor Blades . AFOSR-sponsored research looked at making rotor blades in axial flow compressors more efficient

Bibliography on Hot Isostatic Pressing (HIP) Technology

DTIC Science & Technology

1992-11-01

alloys are used mainly as compressor discs and fan blades . Today titanium alloys are more important as structural materials for modern warplanes and...2.5Fc, microstructure. fatigue life crack initiation, tensile properties 2. P/M Processing of Titanium Aluminides Moll, John H., Yolton, C. F...toughness, hardness, titanium additions niobium additions 2. Consolidation of Nickel Aluminide Powders Using Hot Isostatic Pressing Wright, R. N., Knibloe

Repair welding of gamma titanium aluminide castings

NASA Astrophysics Data System (ADS)

Kelly, T. J.

This paper examines the GTA repair welding of cast Ti-48Al-2Cr-2Nb gamma titanium aluminide. Pre-weld heat treatment, preheat and welding parameters are evaluated and discussed. A wide range of GTAW parameters is demonstrated for use with this alloy and the resulting weld structure is examined. The effects of postweld heat treatment on the structure of the weld deposit is also determined.

Barrier mechanism of multilayers graphene coated copper against atomic oxygen irradiation

NASA Astrophysics Data System (ADS)

Zhang, Haijing; Ren, Siming; Pu, Jibin; Xue, Qunji

2018-06-01

Graphene has been demonstrated as a protective coating for Cu under ambient condition because of its high impermeability and light-weight oxidation barrier. However, it lacks the research of graphene as a protective coating in space environment. Here, we experimentally and theoretically study the oxidation behavior of graphene-coated Cu in vacuum atomic oxygen (AO) condition. After AO irradiation, the experimental results show multilayer graphene has better anti-oxidation than monolayer graphene. Meanwhile, the calculation results show the oxidation appeared on the graphene's grain boundaries or the film's vacancy defects for the monolayer graphene coated Cu foil. Moreover, the calculation results show the oxidation process proceeds slowly in multilayers because of the matched defects overlaps each other to form a steric hindrance to suppress the O atom diffusion in the vertical direction, and the mismatched defects generates potential energy barriers for interlayer to suppress the O atom diffusion in the horizontal direction. Hence, multilayer graphene films could serve as protection coatings to prevent diffusion of O atom.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

NASA Astrophysics Data System (ADS)

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; Haynes, J. Allen; Porter, Wallace D.; England, Roger D.; Hays, Michael; Dwivedi, Gopal; Sampath, Sanjay

2018-02-01

Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.

Complex fine-scale diffusion coating formed at low temperature on high-speed steel substrate

NASA Astrophysics Data System (ADS)

Chaus, A. S.; Pokorný, P.; Čaplovič, Ľ.; Sitkevich, M. V.; Peterka, J.

2018-04-01

A complex B-C-N diffusion coating was produced at 580 °C for 1 h on AISI M35 steel substrate and compared with a reference coating formed at 880 °C for 2.5 h. The surface and the cross-sections of the samples were subjected to detailed characterisation. The surface roughness, hardness, residual stresses and adhesion of the coatings were also evaluated together with cutting tests using drills on coated and uncoated samples while monitoring cutting force and torque. The surface of the steel treated at 580 °C revealed Fe2B, boron nitride and boron iron carbide, but FeB was noted to be absent. The 580 °C coating had the fine-scale microstructure, which resulted in the excellent adhesion and enhanced wear resistance, relative to reference samples that contained coarse borides. The results established that a complex fine-scale diffusion coating enhanced the wear resistance and reduces the cutting force and torque during drilling, thereby increasing the drill life by a factor of 2.2.

Welding of gamma titanium aluminide alloys

NASA Technical Reports Server (NTRS)

Smashey, Russell W. (Inventor); Snyder, John H. (Inventor); Kelly, Thomas J. (Inventor); Sheranko, Ronald L. (Inventor)

1998-01-01

An article made of a gamma titanium aluminide alloy is welded, as for example in the weld repair of surface cracks, by removing foreign matter from the area to be welded, first stress relieving the article, cooling the entire article to a welding temperature of from about 1000.degree. F. to about 1400.degree. F., welding a preselected region in an inert atmosphere at the welding temperature, and second stress relieving the article. Welding is preferably accomplished by striking an arc in the preselected region so as to locally melt the alloy in the preselected region, providing a filler metal having the same composition as the gamma titanium aluminide alloy of the article, and feeding the filler metal into the arc so that the filler metal is melted and fused with the article to form a weldment upon solidification.

A review of rapid solidification studies of intermetallic compounds

NASA Technical Reports Server (NTRS)

Koch, C. C.

1985-01-01

A review of rapid solidification studies of high-temperature ordered intermetallic compounds is presented. Emphasis is on the nickel - and iron- aluminides which are of potential interest as structural materials. The nickel-base aluminides which have been rapidly solidified exhibit changes in grain size, compositional segregation, and degree of long range order (as reflected in APB size and distribution) which markedly affect mechanical properties. Some experiments indicate the formation of a metastable L1(2) phase in rapidly solidified Fe-(Ni,Mn)-Al-C alloys, while other work observes only a metastable fcc phase in the same composition range. The metastable phases and/or microstructures in both nickel and iron aluminides are destroyed by annealing at temperatures above 750 K, with subsequent degradation of mechanical properties. Rapid solidification studies of several other intermetallic compounds are briefly noted.

Formation of Cr2O3 Diffusion Barrier Between Cr-Contained Stainless Steel and Cold-Sprayed Ni Coatings at High Temperature

NASA Astrophysics Data System (ADS)

Xu, Ya-Xin; Luo, Xiao-Tao; Li, Cheng-Xin; Yang, Guan-Jun; Li, Chang-Jiu

2016-02-01

A novel approach to prepare a coating system containing an in situ grown Cr2O3 diffusion barrier between a nickel top layer and 310SS was reported. Cold spraying was employed to deposit Ni(O) interlayer and top nickel coating on the Cr-contained stainless steel substrate. Ni(O) feedstock was prepared by mechanical alloying of pure nickel powders in ambient atmosphere, acting as an oxygen provider. The post-spray annealing was adopted to grow in situ Cr2O3 layer between the substrate and nickel coating. The results revealed that the diffusible oxygen can be introduced into nickel powders by mechanical alloying. The oxygen content increases to 3.25 wt.% with the increase of the ball milling duration to 8 h, while Ni(O) powders maintain a single phase of Ni. By annealing the sample in Ar atmosphere at 900 °C, a continuous Cr2O3 layer of 1-2 μm thick at the interface between 310SS and cold-sprayed Ni coating is formed. The diffusion barrier effect evaluation by thermal exposure at 750 °C shows that the Cr2O3 oxide layer effectively suppresses the outward diffusion of Fe and Cr in the substrate effectively.

The Thermal Diffusivity Measurement of the Two-layer Ceramics Using the Laser Flash Methodn

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Ogwa, Mitsue; Baba, Tetsuya; Mizuno, Mineo

Ceramics-based thermal barrier coatings are used as heat and wear shields of gas turbines. There are strong needs to evaluate thermophysical properties of coating, such as thermal conductivity, thermal diffusivity and heat capacity of them. Since the coatings are attached on substrates, it is no easy to measure these properties separately. The laser flash method is one of the most popular thermal diffusivity measurement methods above room temperature for solid materials. The surface of the plate shape specimen is heated by the pulsed laser-beam, then the time variation of the temperature of the rear surface is observed by the infrared radiometer. The laser flash method is non-contact and short time measurement. In general, the thermal diffusivity of solids that are dense, homogeneous and stable, are measured by this method. It is easy to measure thermal diffusivity of a specimen which shows heat diffusion time about 1 ms to 1 s consistent with the specimen thickness of about 1 mm to 5 mm. On the other hand, this method can be applied to measure the specific heat capacity of the solids. And it is also used to estimate the thermal diffusivity of an unknown layer in the layered materials. In order to evaluate the thermal diffusivity of the coating attached on substrate, we have developed a measurement procedure using the laser flash method. The multi-layer model based on the response function method was applied to calculate the thermal diffusivity of the coating attached on substrate from the temperature history curve observed for the two-layer sample. We have verified applicability of the laser flash measurement with the multi-layer model using the measured results and the simulation. It was found that the laser flash measurement for the layered sample using the multi-layer model was effective to estimate the thermal diffusivity of an unknown layer in the sample. We have also developed the two-layer ceramics samples as the reference materials for this procedure.

Advanced Tomographic Imaging Methods for the Analysis of Materials

DTIC Science & Technology

1991-08-01

used in composite manufacture: aluminum, silicon carbide, and titanium aluminide . Also depicted in Fig. 2 are the energy intervals which can...SiC-fiber (SCS6) in a titanium - aluminide matrix. The contrast between SiC and AtIis only 10% over a broad eiaergy range. Therefore, distinguishing the...borehole logging, orrodent detection on turbine blades , kerogen analysis of shale, and contents of coals (sulfur, minerals, and btu). APSTNG

High-temperature fabricable nickel-iron aluminides

DOEpatents

Liu, Chain T.

1988-02-02

Nickel-iron aluminides are described that are based on Ni.sub.3 Al, and have significant iron content, to which additions of hafnium, boron, carbon and cerium are made resulting in Ni.sub.3 Al base alloys that can be fabricated at higher temperatures than similar alloys previously developed. Further addition of molybdenum improves oxidation and cracking resistance. These alloys possess the advantages of ductility, hot fabricability, strength, and oxidation resistance.

Anisotropic Damage Mechanics Modeling in Metal Matrix Composites

DTIC Science & Technology

1993-05-15

conducted on a titanium aluminide SiC-reinforced metal matrix composite. Center-cracked plates with laminate layups of (0/90) and (±45). were tested... interfacial damage mechanisms as debonding or delamination. Equations (2.14) and (2.15) represent the damage transformation equations for the stress... titanium aluminide SiC 46 continuous reinforced metal matrix composite. As a means of enforcing quality assurance, all manufacturing and cutting of the

Method of manufacturing iron aluminide by thermomechanical processing of elemental powders

DOEpatents

Deevi, Seetharama C.; Lilly, Jr., A. Clifton; Sikka, Vinod K.; Hajaligol, Mohammed R.

2000-01-01

A powder metallurgical process of preparing iron aluminide useful as electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 20 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1 % rare earth metal, .ltoreq.1% oxygen, and/or .ltoreq.3% Cu. The process includes forming a mixture of aluminum powder and iron powder, shaping the mixture into an article such as by cold rolling the mixture into a sheet, and sintering the article at a temperature sufficient to react the iron and aluminum powders and form iron aluminide. The sintering can be followed by hot or cold rolling to reduce porosity created during the sintering step and optional annealing steps in a vacuum or inert atmosphere.

Effects of In Situ Intermetallics on the Microstructural Array and Saline Corrosion Performance of Cast Al/WCp Composites

NASA Astrophysics Data System (ADS)

Lekatou, A. G.; Gkikas, N.; Gousia, V.; Lentzaris, K.; Karantzalis, A. E.

2018-06-01

Al-matrix composites, ex situ reinforced with WC nanoparticles and in situ reinforced with Al3(Ti,W), Al12W, Al5W and Al4W, have been fabricated by casting assisted by K2TiF6 wetting agent addition and mechanical stirring. A satisfactory particle incorporation and distribution accompanied by a high reactivity have been attained. The presence, topography, chemical composition of all included phases and their occurrence as clusters or single particles are clarified and justified. Al12W is the predominant aluminide phase at WC ≤ 1.5 vol.%. Al4W (primarily) and Al5W (secondarily) are the predominant aluminide phases at WC ≥ 2.0 vol.%. WC nanoparticles have acted as heterogeneous nucleation sites to Al3Ti particles. Reverse polarization tests in 3.5 wt.% NaCl show that the governing form of corrosion is intergranular corrosion of Al around Al3FeSi2 eutectic, fine plates. The corrosion steps/mechanisms are identified. Clusters of aluminides and carbide nanoparticles, as well as intergranular WC nano-dispersoids and their Al-matrix have remained corrosion-free. The role of the aluminides combined with WC remaining nano-cores as inhibitors of the eutectic Al3FeSi2 cathodic activity is highlighted.

Diffusion mechanisms in chemical vapor-deposited iridium coated on chemical vapor-deposited rhenium

NASA Technical Reports Server (NTRS)

Hamilton, J. C.; Yang, N. Y. C.; Clift, W. M.; Boehme, D. R.; Mccarty, K. F.; Franklin, J. E.

1992-01-01

Radiation-cooled rocket thruster chambers have been developed which use CVD Re coated with CVD Ir on the interior surface that is exposed to hot combustion gases. The Ir serves as an oxidation barrier which protects the structural integrity-maintaining Re at elevated temperatures. The diffusion kinetics of CVD materials at elevated temperatures is presently studied with a view to the prediction and extension of these thrusters' performance limits. Line scans for Ir and Re were fit on the basis of a diffusion model, in order to extract relevant diffusion constants; the fastest diffusion process is grain-boundary diffusion, where Re diffuses down grain boundaries in the Ir overlayer.

Active bio-based food-packaging: Diffusion and release of active substances through and from cellulose nanofiber coating toward food-packaging design.

PubMed

Lavoine, Nathalie; Guillard, Valérie; Desloges, Isabelle; Gontard, Nathalie; Bras, Julien

2016-09-20

Cellulose nanofibers (CNFs) were recently investigated for the elaboration of new functional food-packaging materials. Their nanoporous network was especially of interest for controlling the release of active species. Qualitative release studies were conducted, but quantification of the diffusion phenomenon observed when the active species are released from and through CNF coating has not yet been studied. Therefore, this work aims to model CNF-coated paper substrates as controlled release system for food-packaging using release data obtained for two model molecules, namely caffeine and chlorhexidine digluconate. The applied mathematical model - derived from Fickian diffusion - was validated for caffeine only. When the active species chemically interacts with the release device, another model is required as a non-predominantly diffusion-controlled release was observed. From caffeine modeling data, a theoretical active food-packaging material was designed. The use of CNFs as barrier coating was proved to be the ideal material configuration that best meets specifications. Copyright © 2016. Published by Elsevier Ltd.

Collaborative Research and Development Delivery. Order 0041: Models for the Prediction of Interfacial Properties

DTIC Science & Technology

2006-08-01

and analytical techniques. Materials with larger grains, such as gamma titanium aluminide , can be instrumented with strain gages on each grain...scale. Materials such as Ti-15-Al-33Nb(at.%) have a significantly smaller microstructure than gamma titanium aluminide , therefore strain gages can...contact fatigue problems that arise at the blade -disk interface in aircraft engines. The stress fields can be used to predict the performance of

United States Air Force Summer Faculty Research Program. 1989 Program Management Report

DTIC Science & Technology

1989-12-01

Thermomechanical Dr. James Sherwood Response of a Titanium Aluminide Metal Matrix Composite Using a Viscoplastic Constitutive Theory 123 Photoreflectance of AlGaAs...presence of microcracks from the surrounding microstructural features. 231 INVESTIGATION OF THE THERMOMECHANICAL RESPONSE OF A TITANIUM ALUMINIDE ...arranged in a periodic fashion exist in the internal cooling passage of a turbine blade or vane. To study the momentum transfer, it uses hot-wire anemometry

Enhanced Life Prediction Technology for Engine Rotor Life Extension (ERLE)

DTIC Science & Technology

2008-09-01

related a0 to dislocation pileups and mode II shear cracks, and found satisfactory agreement with small-crack data from titanium aluminides . Tanaka...Symp. Gamma Titanium Aluminides , TMS, 1999, pp. 517-525. [11] K. Tanaka, Y. Nakai, and M. Yamashita, “Fatigue Growth Threshold of Small Cracks...between his formulation and a variety of experimental data. While titanium was not included in the Tanaka comparisons, Brown and Taylor [12] have

Quantum Mechanical Approach to Understanding Structural, Electronic and Mechanical Properties of Intermetallics

DTIC Science & Technology

1989-01-26

Understanding Structural , Electronic and Mechanical Properties of Tntermetallics by A.J. Freeman, Principal Investigator ABSTRACT The primary goal of...like LI or Mg would lower EF into the minimum in the DOS and hence stabilize the L1 2 . A. Structural Phase Stability of Titanium Aluminides Most...34 Structural Stability Calculations in the Titanium -Aluminium System", Conf. on Titanium Aluminides , Wright-Patterson Air Force Base, Nov. 1986

High temperature properties of non-critical Fe-Al alloys doped by non critical or “slightly–critical” elements

NASA Astrophysics Data System (ADS)

Vodičková, Věra; Hanus, Pavel; Vlasák, Tomáš; Švec, Martin

2018-03-01

Iron aluminides were developed as an alternative to stainless steels after World War II. The main intended impact was to save strategic elements (chromium or nickel). The result of these investigations was development of registered alloys as Pyroferal (Czechoslovak Republic), Thugal (Soviet Union) or Thermagal (France). The investigation of these type alloys continued in the nineties thanks to technological progress. In this time iron aluminides seems to be promising material with very good corrosive and environment resistivity. The mechanical properties of binary iron aluminides (Fe-Al) are average at higher temperatures but strengthening effect of alloying elements is significant. The aim of the article is to show influence of non-critical additives (such as C, Ti, Zr) and also “slightly critical” elements as e.g. Ce, Nb on high temperature creep properties of alloys.

In-service testing of Ni{sub 3}Al coupons and trays in carburizing furnaces at Delphi Saginaw. CRADA final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Santella, M.L.; Viswanathan, S.

1998-08-01

This Cooperative Research and Development Agreement (CRADA) report deals with the development of nickel aluminide alloy for improved longer life heat-resistant fixture assemblies for batch and continuous pusher carburizing furnaces. The nickel aluminide development was compared in both coupon and component testing with the currently used Fe-Ni-Cr heat-resisting alloy known as HU. The specific goals of the CRADA were: (1) casting process development, (2) characterization and possible modification of the alloy composition to optimize its manufacturing ability and performance under typical furnace operating conditions, and (3) testing and evaluation of specimens and prototype fixtures. In support of the CRADA objectives,more » coupons of nickel aluminide and the HU alloy were installed in both batch and pusher furnaces. The coupons were taken from two silicon levels and contained welds made with two different filler compositions (IC-221LA and IC-221W). Both nickel-aluminide and HU coupons were removed from the batch and pusher carburizing furnace at time intervals ranging from one month to one year. The exposed coupons were cut and mounted for metallographic, hardness, and microprobe analysis. The results of the microstructural analysis have been transmitted to General Motors Corporation, Saginaw Division (Delphi Saginaw) through reports that were presented at periodic CRADA review meetings. Based on coupon testing and verification of the coupon results with the testing of trays, Delphi Saginaw moved forward with the use of six additional trays in a batch furnace and two assemblies in a pusher furnace. Fifty percent of the trays and fixtures are in the as-cast condition and the remaining trays and fixtures are in the preoxidized condition. The successful operating experience of two assemblies in the pusher furnace for nearly a year formed the basis for a production run of 63 more assemblies. The production run required melting of 94 heats weighing 500 lb. each. Twenty-six of the 94 heats were from virgin stock, and 68 were from the revert that used 50% virgin and 50% revert. Detailed chemical analysis of the 94 heats reflected that the nickel aluminide can be cast into heat-treat fixtures under production conditions. In addition to the chemical analysis, the castings showed excellent dimensional reproducibility. A total of six batch furnace trays and 65 pusher furnace assemblies of nickel aluminide alloy IC-221M are currently operating in production furnaces at Delphi Saginaw. Two of the pusher furnace assemblies have completed two years of service without any failure. The CRADA has accomplished the goal of demonstrating that the nickel aluminide can be produced under commercial production conditions and it has superior performance over the currently used HU alloy in both batch and pusher furnaces.« less

Streaming potential method for characterizing interaction of electrical double layers between rice roots and Fe/Al oxide-coated quartz in situ.

PubMed

Liu, Zhao-Dong; Wang, Hai-Cui; Li, Jiu-Yu; Xu, Ren-Kou

2017-10-01

The interaction between rice roots and Fe/Al oxide-coated quartz was investigated through zeta potential measurements and column leaching experiments in present study. The zeta potentials of rice roots, Fe/Al oxide-coated quartz, and the binary systems containing rice roots and Fe/Al oxide-coated quartz were measured by a specially constructed streaming potential apparatus. The interactions between rice roots and Fe/Al oxide-coated quartz particles were evaluated/deduced based on the differences of zeta potentials between the binary systems and the single system of rice roots. The zeta potentials of the binary systems moved in positive directions compared with that of rice roots, suggesting that there were overlapping of diffuse layers of electric double layers on positively charged Fe/Al oxide-coated quartz and negatively charged rice roots and neutralization of positive charge on Fe/Al oxide-coated quartz with negative charge on rice roots. The greater amount of positive charges on Al oxide led to the stronger interaction of Al oxide-coated quartz with rice roots and the more shift of zeta potential compared with Fe oxide. The overlapping of diffuse layers on Fe/Al oxide-coated quartz and rice roots was confirmed by column leaching experiments. The greater overlapping of diffuse layers on Al oxide and rice roots led to more simultaneous adsorptions of K + and NO 3 - and greater reduction in leachate electric conductivity when the column containing Al oxide-coated quartz and rice roots was leached with KNO 3 solution, compared with the columns containing rice roots and Fe oxide-coated quartz or quartz. When the KNO 3 solution was replaced with deionized water to flush the columns, more K + and NO 3 - were desorbed from the binary system containing Al oxide-coated quartz and rice roots than from other two binary systems, suggesting that the stronger electrostatic interaction between Al oxide and rice roots promoted the desorption of K + and NO 3 - from the binary system and enhanced overlapping of diffuse layers on these oppositely charged surfaces compared with other two binary systems. In conclusion, the overlapping of diffuse layers occurred between positively charged Fe/Al oxides and rice roots, which led to neutralization of opposite charge and affected adsorption and desorption of ions onto and from the charged surfaces of Fe/Al oxides and rice roots.

Oxidation behavior of Al/Cr coating on Ti2AlNb alloy at 900 °C

NASA Astrophysics Data System (ADS)

Yang, Zhengang; Liang, Wenping; Miao, Qiang; Chen, Bowen; Ding, Zheng; Roy, Nipon

2018-04-01

In this paper, the Al/Cr coating was fabricated on the surface of Ti2AlNb alloy via rf magnetron sputtering and double glow treatment to enhance oxidation resistance. The protective coating with an outer layer of Al and inner layer of Cr has great bonding strength due to the in-diffusion of Cr and the inter-diffusion between Al and Cr to form Al-Cr alloyed layer which has great hardness. Acoustic emission curve which was detected via WS-2005 scratch tester indicates the bonding strength between Al/Cr coating and substrate is great. Morphology of Ti2AlNb alloy with Al/Cr coating after scratch test shows that the scratch is smooth without disbanding, and the depth and breadth of scratch are changed uniformly. The mass change was reduced after oxidation test due to the Al/Cr protective coating. Isothermal oxidation test at 900 °C was researched. Results indicate that Al/Cr coating provided oxidation resistance of Ti2AlNb alloy with prolonged air exposure at 900 °C. Al2O3 was detected by XRD patterns and SEM images, and was formed on the surface of Ti2AlNb alloy to protect substrate during oxidation test. A certain content of Cr is beneficial for the formation of Al2O3. Besides, Cr2O3 was produced under Al2O3 by outward diffusion of Cr to protect substrate sequentially, no cracks were discovered on Al/Cr protective coating. The process of Ti outward diffusion into surface was suppressive due to integration of Cr-Ti and Al-Ti intermetallics. A steady, adherent and continuous coated layer of Al/Cr on Ti2AlNb alloy increases oxidation resistance.

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

NASA Technical Reports Server (NTRS)

Smialek, James L.

2008-01-01

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However, adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for thermal barrier coatings (TBCs), culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Continued development of abradable gas path seals. [for gas turbine engines

NASA Technical Reports Server (NTRS)

Shiembob, L. T.

1975-01-01

Major program objectives were the continued development of NiCrAlY feltmetal and honeycomb systems for knife edge seal applications in the 1144 to 1366 K temperature range, and to initiate abradable seal material evaluation for blade tip seal applications in the 1366 to 1589 K temperature range. Larger fiber size, higher density feltmetal showed greatly improved erosion resistance with a slight reduction in abradability compared to the baseline feltmetal. Pack aluminide coating of the honeycomb extended the oxidation resistance and slightly improved the abradability of this material. Evaluation through selected abradability, erosion and oxidation testing, and pertinent metallography led to selection of a plasma sprayed yttria stabilized zirconia (ZrO2)/CoCrAlY layered system as the system with the most potential to meet the 1589 K requirement for blade tip seals. This system demonstrated structural integrity, erosion resistance, and some degree of abradability.

Cermet materials, self-cleaning cermet filters, apparatus and systems employing same

DOEpatents

Kong, Peter C.

2005-07-19

A self-cleaning porous cermet material, filter and system utilizing the same may be used in filtering particulate and gaseous pollutants from internal combustion engines having intermetallic and ceramic phases. The porous cermet filter may be made from a transition metal aluminide phase and an alumina phase. Filler materials may be added to increase the porosity or tailor the catalytic properties of the cermet material. Additionally, the cermet material may be reinforced with fibers or screens. The porous filter may also be electrically conductive so that a current may be passed therethrough to heat the filter during use. Further, a heating element may be incorporated into the porous cermet filter during manufacture. This heating element can be coated with a ceramic material to electrically insulate the heating element. An external heating element may also be provided to heat the cermet filter during use.

Overlay coating degradation by simultaneous oxidation and coating/substrate interdiffusion. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.

1983-01-01

Degradation of NiCrAlZr overlay coatings on various NiCrAl substrates was examined after cyclic oxidation. Concentration/distance profiles were measured in the coating and substrate after various oxidation exposures at 1150 C. For each stubstrate, the Al content in the coating decreased rapidly. The concentration/distance profiles, and particularly that for Al, reflected the oxide spalling resistance of each coated substrate. A numerical model was developed to simulate diffusion associated with overlay-coating degradation by oxidation and coating/substrate interdiffusion. Input to the numerical model consisted of the Cr and Al content of the coating and substrate, ternary diffusivities, and various oxide spalling parameters. The model predicts the Cr and Al concentrations in the coating and substrate after any number of oxidation/thermal cycles. The numerical model also predicts coating failure based on the ability of the coating to supply sufficient Al to the oxide scale. The validity of the model was confirmed by comparison of the predicted and measured concentration/distance profiles. The model was subsequently used to identify the most critical system parameters affecting coating life.

Aqueous pathways dominate permeation of solutes across Pisum sativum seed coats and mediate solute transport via diffusion and bulk flow of water.

PubMed

Niemann, Sylvia; Burghardt, Markus; Popp, Christian; Riederer, Markus

2013-05-01

The permeability of seed coats to solutes either of biological or anthropogenic origin plays a major role in germination, seedling growth and seed treatment by pesticides. An experimental set-up was designed for investigating the mechanisms of seed coat permeation, which allows steady-state experiments with isolated seed coats of Pisum sativum. Permeances were measured for a set of organic model compounds with different physicochemical properties and sizes. The results show that narrow aqueous pathways dominate the diffusion of solutes across pea seed coats, as indicated by a correlation of permeances with the molecular sizes of the compounds instead of their lipophilicity. Further indicators for an aqueous pathway are small size selectivity and a small effect of temperature on permeation. The application of an osmotic water potential gradient across isolated seed coats leads to an increase in solute transfer, indicating that the aqueous pathways form a water-filled continuum across the seed coat allowing the bulk flow of water. Thus, the uptake of organic solutes across pea testae has two components: (1) by diffusion and (2) by bulk water inflow, which, however, is relevant only during imbibition. © 2012 Blackwell Publishing Ltd.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

DOE PAGES

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; ...

2018-01-04

In this paper, multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow.more » The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. Finally, the microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.« less

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.

In this paper, multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow.more » The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. Finally, the microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.« less

Diffusion mechanism in molten salt baths during the production of carbide coatings via thermal reactive diffusion

NASA Astrophysics Data System (ADS)

Ghadi, Aliakbar; Saghafian, Hassan; Soltanieh, Mansour; Yang, Zhi-gang

2017-12-01

The diffusion mechanism of carbide-forming elements from a molten salt bath to a substrate surface was studied in this research, with particular focus on the processes occurring in the molten bath at the time of coating. Metal, oxide, and metal-oxide baths were investigated, and the coating process was performed on H13 steel substrates. Scanning electron microscopy and electron-probe microanalysis were used to study the coated samples and the quenched salt bath. The thickness of the carbide coating layer was 6.5 ± 0.5, 5.2 ± 0.5, or 5.7 ± 0.5 μm depending on whether it was deposited in a metal, oxide, or metal-oxide bath, respectively. The phase distribution of vanadium-rich regions was 63%, 57%, and 74% of the total coating deposited in metal, oxide, and metal-oxide baths, respectively. The results obtained using the metal bath indicated that undissolved suspended metal particles deposited onto the substrate surface. Then, carbon subsequently diffused to the substrate surface and reacted with the metal particles to form the carbides. In the oxide bath, oxide powders dissolved in the bath with or without binding to the oxidative structure (Na2O) of borax; they were then reduced by aluminum and converted into metal particles. We concluded that, in the metal and oxide baths, the deposition of metal particles onto the sample surface is an important step in the formation of the coating.

Defense Small Business Innovation Research Program (SBIR). Volume 3. Air Force Abstracts of Phase 1 Awards 1987.

DTIC Science & Technology

1988-04-01

RESISTANCE, AS WELL AS GUIDELINES FROM APPROPRIATE AEROSPACE SPECIFICATIONS; MATERIALS WILL INCLUDE ALUMINUM AND TITANIUM ALLOYS, PLUS A FEW STEELS...VAPOR SYNTHESIS OF NIOBIUM ALUMINIDES TOPIC# 105 OFFICE: AFWAL/ML DIRECT SYNTHESIS OF NbA1 ALLOY FOILS BY CHEMICAL VAPOR DEPOSITION ONTO INERT SUBSTRATES...GROWT OF GAMMA PRIME NICKEL ALUMINIDE (Ni3AI) %% TOPICt 104 OFFICE: AFWAL/ML . SMALL BUSINESS INNOVATION RESEARCH (SBIR) PROGRAM - PHASE 1 PAGE 555

Corrosion resistant iron aluminides exhibiting improved mechanical properties and corrosion resistance

DOEpatents

Liu, C.T.; McKamey, C.G.; Tortorelli, P.F.; David, S.A.

1994-06-14

The specification discloses a corrosion-resistant intermetallic alloy comprising, in atomic percent, an FeAl iron aluminide containing from about 30 to about 40% aluminum alloyed with from about 0.01 to 0.4% zirconium and from 0.01 to about 0.8% boron. The alloy exhibits considerably improved room temperature ductility for enhanced usefulness in structural applications. The high temperature strength and fabricability is improved by alloying with molybdenum, carbon, chromium and vanadium. 9 figs.

Electron Beam Welding to Join Gamma Titanium Aluminide Articles

NASA Technical Reports Server (NTRS)

Kelly, Thomas Joseph (Inventor)

2008-01-01

A method is provided for welding two gamma titanium aluminide articles together. The method includes preheating the two articles to a welding temperature of from about 1700 F to about 2100 F, thereafter electron beam welding the two articles together at the welding temperature and in a welding vacuum to form a welded structure, and thereafter annealing the welded structure at an annealing temperature of from about 1800 F to about 2200 F, to form a joined structure.

Corrosion resistant iron aluminides exhibiting improved mechanical properties and corrosion resistance

DOEpatents

Liu, Chain T.; McKamey, Claudette G.; Tortorelli, Peter F.; David, Stan A.

1994-01-01

The specification discloses a corrosion-resistant intermetallic alloy comprising, in atomic percent, an FeAl iron aluminide containing from about 30 to about 40% aluminum alloyed with from about 0.01 to 0.4% zirconium and from 0.01 to about 0.8% boron. The alloy exhibits considerably improved room temperature ductility for enhanced usefulness in structural applications. The high temperature strength and fabricability is improved by alloying with molybdenum, carbon, chromium and vanadium.

Matrix diffusion coefficients in volcanic rocks at the Nevada test site: influence of matrix porosity, matrix permeability, and fracture coating minerals.

PubMed

Reimus, Paul W; Callahan, Timothy J; Ware, S Doug; Haga, Marc J; Counce, Dale A

2007-08-15

Diffusion cell experiments were conducted to measure nonsorbing solute matrix diffusion coefficients in forty-seven different volcanic rock matrix samples from eight different locations (with multiple depth intervals represented at several locations) at the Nevada Test Site. The solutes used in the experiments included bromide, iodide, pentafluorobenzoate (PFBA), and tritiated water ((3)HHO). The porosity and saturated permeability of most of the diffusion cell samples were measured to evaluate the correlation of these two variables with tracer matrix diffusion coefficients divided by the free-water diffusion coefficient (D(m)/D*). To investigate the influence of fracture coating minerals on matrix diffusion, ten of the diffusion cells represented paired samples from the same depth interval in which one sample contained a fracture surface with mineral coatings and the other sample consisted of only pure matrix. The log of (D(m)/D*) was found to be positively correlated with both the matrix porosity and the log of matrix permeability. A multiple linear regression analysis indicated that both parameters contributed significantly to the regression at the 95% confidence level. However, the log of the matrix diffusion coefficient was more highly-correlated with the log of matrix permeability than with matrix porosity, which suggests that matrix diffusion coefficients, like matrix permeabilities, have a greater dependence on the interconnectedness of matrix porosity than on the matrix porosity itself. The regression equation for the volcanic rocks was found to provide satisfactory predictions of log(D(m)/D*) for other types of rocks with similar ranges of matrix porosity and permeability as the volcanic rocks, but it did a poorer job predicting log(D(m)/D*) for rocks with lower porosities and/or permeabilities. The presence of mineral coatings on fracture walls did not appear to have a significant effect on matrix diffusion in the ten paired diffusion cell experiments.

Matrix diffusion coefficients in volcanic rocks at the Nevada test site: Influence of matrix porosity, matrix permeability, and fracture coating minerals

NASA Astrophysics Data System (ADS)

Reimus, Paul W.; Callahan, Timothy J.; Ware, S. Doug; Haga, Marc J.; Counce, Dale A.

2007-08-01

Diffusion cell experiments were conducted to measure nonsorbing solute matrix diffusion coefficients in forty-seven different volcanic rock matrix samples from eight different locations (with multiple depth intervals represented at several locations) at the Nevada Test Site. The solutes used in the experiments included bromide, iodide, pentafluorobenzoate (PFBA), and tritiated water ( 3HHO). The porosity and saturated permeability of most of the diffusion cell samples were measured to evaluate the correlation of these two variables with tracer matrix diffusion coefficients divided by the free-water diffusion coefficient ( Dm/ D*). To investigate the influence of fracture coating minerals on matrix diffusion, ten of the diffusion cells represented paired samples from the same depth interval in which one sample contained a fracture surface with mineral coatings and the other sample consisted of only pure matrix. The log of ( Dm/ D*) was found to be positively correlated with both the matrix porosity and the log of matrix permeability. A multiple linear regression analysis indicated that both parameters contributed significantly to the regression at the 95% confidence level. However, the log of the matrix diffusion coefficient was more highly-correlated with the log of matrix permeability than with matrix porosity, which suggests that matrix diffusion coefficients, like matrix permeabilities, have a greater dependence on the interconnectedness of matrix porosity than on the matrix porosity itself. The regression equation for the volcanic rocks was found to provide satisfactory predictions of log( Dm/ D*) for other types of rocks with similar ranges of matrix porosity and permeability as the volcanic rocks, but it did a poorer job predicting log( Dm/ D*) for rocks with lower porosities and/or permeabilities. The presence of mineral coatings on fracture walls did not appear to have a significant effect on matrix diffusion in the ten paired diffusion cell experiments.

Thermal-mechanical fatigue of high temperature structural materials

NASA Astrophysics Data System (ADS)

Renauld, Mark Leo

Experimental and analytical methods were developed to address the effect of thermal-mechanical strain cycling on high temperature structural materials under uniaxial and biaxial stress states. Two materials were used in the investigation, a nickel-base superalloy of low ductility, IN-738LC and a high ductility material, 316 stainless steel. A uniaxial life prediction model for the IN-738LC material was based on tensile hysteresis energy measured in stabilized, mid-life hysteresis loops. Hold-time effects and temperature cycling were incorporated in the hysteresis energy approach. Crack growth analysis was also included in the model to predict the number of TMF cycles to initiate and grow a fatigue crack through the coating. The nickel-base superalloy, IN-738LC, was primarily tested in out-of-phase (OP) TMF with a temperature range from 482-871sp°C (900-1600sp°F) under continuous and compressive hold-time cycling. IN-738LC fatigue specimens were coated either with an aluminide, NiCoCrAlHfSi overlay or CoNiCrAlY overlay coating on the outer surface of the specimen. Metallurgical failure analysis via optical and scanning electron microscopy, was used to characterize failure behavior of both substrate and coating materials. Type 316 SS was subjected to continuous biaxial strain cycling with an in-phase (IP) TMF loading and a temperature range from 399-621sp°C (750-1150sp°F). As a result, a biaxial TMF life prediction model was proposed on the basis of an extended isothermal fatigue model. The model incorporates a frequency effect and phase factors to assess the different damage mechanisms observed during TMF loading. The model was also applied to biaxial TMF data generated on uncoated IN-738LC.

Progress on Fabrication of Planar Diffusion Couples with Representative TRISO PyC/SiC Microstructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunn, John D.; Jolly, Brian C.; Gerczak, Tyler J.

Release of fission products from tristructural-isotropic (TRISO) coated particle fuel limits the fuel’s operational lifetime and creates potential safety and maintenance concerns. A need for diffusion analysis in representative TRISO layers exists to provide fuel performance models with high fidelity data to improve fuel performance and efficiency. An effort has been initiated to better understand fission product transport in, and release from, quality TRISO fuel by investigating diffusion couples with representative pyrocarbon (PyC) and silicon carbide (SiC). Here planar PyC/SiC diffusion couples are being developed with representative PyC/SiC layers using a fluidized bed chemical vapor deposition (FBCVD) system identical tomore » those used to produce laboratory-scale TRISO fuel for the Advanced Gas Reactor Fuel Qualification and Development Program’s (AGR) first fuel irradiation. The diffusivity of silver, the silver and palladium system, europium, and strontium in the PyC/SiC will be studied at elevated temperatures and under high temperature neutron irradiation. The study also includes a comparative study of PyC/SiC diffusion couples with varying TRISO layer properties to understand the influence of SiC microstructure (grain size) and the PyC/SiC interface on fission product transport. The first step in accomplishing these goals is the development of the planar diffusion couples. The diffusion couple construction consists of multiple steps which includes fabrication of the primary PyC/SiC structures with targeted layer properties, introduction of fission product species and seal coating to create an isolated system. Coating development has shown planar PyC/SiC diffusion couples with similar properties to AGR TRISO fuel can be produced. A summary of the coating development process, characterization methods, and status are presented.« less

Method of making gas diffusion layers for electrochemical cells

DOEpatents

Frisk, Joseph William; Boand, Wayne Meredith; Larson, James Michael

2002-01-01

A method is provided for making a gas diffusion layer for an electrochemical cell comprising the steps of: a) combining carbon particles and one or more surfactants in a typically aqueous vehicle to make a preliminary composition, typically by high shear mixing; b) adding one or more highly fluorinated polymers to said preliminary composition by low shear mixing to make a coating composition; and c) applying the coating composition to an electrically conductive porous substrate, typically by a low shear coating method.

Process for diffusing metallic coatings into ceramics to improve their voltage withstanding capabilities

DOEpatents

Miller, H. Craig; Zuhr, Herbert F.

1978-01-01

The disclosure relates to a method for diffusing a coating of manganese powder and titanium powder into a ceramic to improve its voltage hold off withstanding capability. The powder coated ceramic is fired for from about 30 to about 90 minutes within about one atmosphere of wet hydrogen at a temperature within the range of from about 1450.degree. to about 1520.degree. C to cause the mixture to penetrate into the ceramic to a depth on the order of a millimeter.

Practical field repair of fused slurry silicide coating for space shuttle t.p.s.

NASA Technical Reports Server (NTRS)

Reznik, B. D.

1971-01-01

Study of short-time high-temperature diffusion treatments as part of a program of development of methods of reapplying fused slurry silicide coating in the field. The metallographic structure and oxidation behavior of R512E applied to Cb-752 coated under simulated field repair conditions was determined. Oxidation testing in reduced pressure environment has shown that performance equivalent to furnace-processed specimens can be obtained in a two-minute diffusion at 2700 F.

Materials for Advanced Turbine Engines (MATE). Project 4: Erosion resistant compressor airfoil coating

NASA Technical Reports Server (NTRS)

Rashid, J. M.; Freling, M.; Friedrich, L. A.

1987-01-01

The ability of coatings to provide at least a 2X improvement in particulate erosion resistance for steel, nickel and titanium compressor airfoils was identified and demonstrated. Coating materials evaluated included plasma sprayed cobalt tungsten carbide, nickel carbide and diffusion applied chromium plus boron. Several processing parameters for plasma spray processing and diffusion coating were evaluated to identify coating systems having the most potential for providing airfoil erosion resistance. Based on laboratory results and analytical evaluations, selected coating systems were applied to gas turbine blades and evaluated for surface finish, burner rig erosion resistance and effect on high cycle fatigue strength. Based on these tests, the following coatings were recommended for engine testing: Gator-Gard plasma spray 88WC-12Co on titanium alloy airfoils, plasma spray 83WC-17Co on steel and nickel alloy airfoils, and Cr+B on nickel alloy airfoils.

Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

NASA Technical Reports Server (NTRS)

Douglas, F. C.; Paradis, E. L.; Veltri, R. D.

1973-01-01

A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed.

International Conference on Mechanical Fatigue of Advanced Materials Held in Santa Barbara, California on 13-18 January 1991

DTIC Science & Technology

1991-02-15

been published on the basic microstructure of the monolithic alloys, particularly in the case of nickel and titanium aluminides , and several composite...34Initiation and Growth in Iniermetallic Compounds- N.S. Stoloff (invited) "Fatigue of Titanium Aluminides at Ambient and Elevated Ternperaiures" ). Bowen...applications such as life estimation for gas-turbine blades , the relevance of "small-crack" data is not fully appreciated. 3 Metal-Matrix Composites

Experimental and Computational Study of Interphase Properties and Mechanics in Titanium Metal Matrix Composites at Elevated Temperatures

DTIC Science & Technology

2005-03-01

size of the interphase [22-24]. Yang and Jeng [45], in a study of the titanium aluminides Ti-24-11 and Ti-25-10, and a metastable beta titanium Ti-15-3... Titanium Aluminide Matrix Composites," Workshop proceedings on Titanium Matrix Components, P.R. Smith and W.C. Revelos, eds., Wright-Patterson AFB...Experimental and Computational Study of Interphase Properties and Mechanics in Titanium Metal Matrix Composites at Elevated Temperatures Final Report

Nickel aluminide alloy for high temperature structural use

DOEpatents

Liu, Chain T.; Sikka, Vinod K.

1991-01-01

The specification discloses nickel aluminide alloys including nickel, aluminum, chromium, zirconium and boron wherein the concentration of zirconium is maintained in the range of from about 0.05 to about 0.35 atomic percent to improve the ductility, strength and fabricability of the alloys at 1200.degree. C. Titanium may be added in an amount equal to about 0.2 to about 0.5 atomic percent to improve the mechanical properties of the alloys and the addition of a small amount of carbon further improves hot fabricability.

Effect of hydrogen on cathodic corrosion of titanium aluminide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, K.W.; Jin, J.W.; Qiao, L.J.

1996-01-01

Cathodic corrosion of titanium aluminide (TiAl) during hydrogen charging in various acidic aqueous solutions and in molten salt at 160 C was studied. At constant potential, the rate of cathodic corrosion (V) was much higher than during anodic dissolution, and V increased linearly with increasing current. V was 10 times higher in the acid solution than in the salt solution under the same current. Disruption of the surface film by local hydride formation during cathodic polarization was shown to be the key step.

Deterioration of reflecting coatings by intermetallic diffusion.

PubMed

Hunter, W R; Mikes, T L; Hass, G

1972-07-01

Gold diffraction gratings overcoated with Al + MgF(2) to increase their efficiency in the vacuum ultraviolet suffered a severe loss in efficiency within six months to a year after coating; for example, from 50% to 2% at lambda1216 A. The cause of this loss was assumed to be interdiffusion of Au and Al; therefore, a more complete study of Au-Al film combinations was performed. The coatings were aged at room and elevated temperatures. Reflectance measurements were made in the visible and vacuum ultraviolet spectral regions. For wavelengths longer than lambda900 A, the measurements show very little change until the diffusion boundary reaches the penetration depth of the radiation. If Al is the first surface layer, however, reflectance measurements at lambda584 A permit measuring the progress of the diffusion boundary toward the Al surface because of the low absorptance of Al at this wavelength. Interdiffusion can be effectively eliminated by the use of thin dielectric layers uch as SiO and the natural oxide of Al. Such protected coatings have been exposed for one week at a temperature of 170 degrees C with no visible sign of diffusion, whereas a similar coating without the barrier layer would become useless in less than 1 h. Some preliminary studies have been made with Pt-Al film combinations.

Kinetics of pack aluminization of nickel

NASA Technical Reports Server (NTRS)

Seigle, L. L.; Gupta, B. K.; Shankar, R.; Sarkhel, A. K.

1978-01-01

The kinetics of pack aluminization of unalloyed nickel in packs of varying aluminum activity with various halide activators were studied. Surface compositions of the coatings as functions of time, temperature, and pack composition were obtained in order to establish the boundary conditions for diffusion in the system. The structure of the packs was also examined in order to clarify the mechanism of aluminum transport. The results indicate that the kinetics of pack aluminization are controlled jointly by gas diffusion in the pack and solid diffusion in the coating. Levine and Caves' model for gas diffusion was combined with calculations of rates of diffusion in the solid to formulate a more complete theory for the kinetics of pack aluminization.

Multi-layer light-weight protective coating and method for application

NASA Technical Reports Server (NTRS)

Wiedemann, Karl E. (Inventor); Clark, Ronald K. (Inventor); Taylor, Patrick J. (Inventor)

1992-01-01

A thin, light-weight, multi-layer coating is provided for protecting metals and their alloys from environmental attack at high temperatures. A reaction barrier is applied to the metal substrate and a diffusion barrier is then applied to the reaction barrier. A sealant layer may also be applied to the diffusion barrier if desired. The reaction barrier is either non-reactive or passivating with respect to the metal substrate and the diffusion barrier. The diffusion barrier is either non-reactive or passivating with respect to the reaction barrier and the sealant layer. The sealant layer is immiscible with the diffusion barrier and has a softening point below the expected use temperature of the metal.

Nanowire membrane-based nanothermite: towards processable and tunable interfacial diffusion for solid state reactions.

PubMed

Yang, Yong; Wang, Peng-peng; Zhang, Zhi-cheng; Liu, Hui-ling; Zhang, Jingchao; Zhuang, Jing; Wang, Xun

2013-01-01

Interfacial diffusion is of great importance in determining the performance of solid-state reactions. For nanometer sized particles, some solid-state reactions can be triggered accidently by mechanical stress owing to their large surface-to-volume ratio compared with the bulk ones. Therefore, a great challenge is the control of interfacial diffusion for solid state reactions, especially for energetic materials. Here we demonstrate, through the example of nanowire-based thermite membrane, that the thermite solid-state reaction can be easily tuned via the introduction of low-surface-energy coating layer. Moreover, this silicon-coated thermite membrane exhibit controlled wetting behavior ranging from superhydrophilic to superhydrophobic and, simultaneously, to significantly reduce the friction sensitivity of thermite membrane. This effect enables to increase interfacial resistance by increasing the amount of coating material. Indeed, our results described here make it possible to tune the solid-state reactions through the manipulation of interfacial diffusion between the reactants.

Nanowire Membrane-based Nanothermite: towards Processable and Tunable Interfacial Diffusion for Solid State Reactions

NASA Astrophysics Data System (ADS)

Yang, Yong; Wang, Peng-Peng; Zhang, Zhi-Cheng; Liu, Hui-Ling; Zhang, Jingchao; Zhuang, Jing; Wang, Xun

2013-04-01

Interfacial diffusion is of great importance in determining the performance of solid-state reactions. For nanometer sized particles, some solid-state reactions can be triggered accidently by mechanical stress owing to their large surface-to-volume ratio compared with the bulk ones. Therefore, a great challenge is the control of interfacial diffusion for solid state reactions, especially for energetic materials. Here we demonstrate, through the example of nanowire-based thermite membrane, that the thermite solid-state reaction can be easily tuned via the introduction of low-surface-energy coating layer. Moreover, this silicon-coated thermite membrane exhibit controlled wetting behavior ranging from superhydrophilic to superhydrophobic and, simultaneously, to significantly reduce the friction sensitivity of thermite membrane. This effect enables to increase interfacial resistance by increasing the amount of coating material. Indeed, our results described here make it possible to tune the solid-state reactions through the manipulation of interfacial diffusion between the reactants.

Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 2: The Influence of Formulation Parameters on Drug Release.

PubMed

Dereymaker, Aswin; Pelgrims, Jirka; Engelen, Frederik; Adriaensens, Peter; Van den Mooter, Guy

2017-04-03

This study aimed to investigate the pharmaceutical performance of an indomethacin-polyvinylpyrrolidone (PVP) glass solution applied using fluid bed processing as a layer on inert sucrose spheres and subsequently top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) on the diffusion and release behavior were also considered. In addition, the role of a charge interaction between drug and controlled release polymer on the release was investigated. Diffusion experiments pointed to the influence of pore former concentration, rate controlling polymer type, and coating solvent on the permeability of the controlled release membranes. This can be translated to drug release tests, which show the potential of diffusion tests as a preliminary screening test and that diffusion is the main factor influencing release. Drug release tests also showed the effect of coating layer thickness. A charge interaction between INDO and ERL was demonstrated, but this had no negative effect on drug release. The higher diffusion and release observed in ERL-based rate controlling membranes was explained by a higher hydrophilicity, compared to EC.

Chromium boron surfaced nickel-iron base alloys

NASA Technical Reports Server (NTRS)

Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

1984-01-01

Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

Multi-objective optimization of hole characteristics during pulsed Nd:YAG laser microdrilling of gamma-titanium aluminide alloy sheet

NASA Astrophysics Data System (ADS)

Biswas, R.; Kuar, A. S.; Mitra, S.

2014-09-01

Nd:YAG laser microdrilled holes on gamma-titanium aluminide, a newly developed alloy having wide applications in turbine blades, engine valves, cases, metal cutting tools, missile components, nuclear fuel and biomedical engineering, are important from the dimensional accuracy and quality of hole point of view. Keeping this in mind, a central composite design (CCD) based on response surface methodology (RSM) is employed for multi-objective optimization of pulsed Nd:YAG laser microdrilling operation on gamma-titanium aluminide alloy sheet to achieve optimum hole characteristics within existing resources. The three characteristics such as hole diameter at entry, hole diameter at exit and hole taper have been considered for simultaneous optimization. The individual optimization of all three responses has also been carried out. The input parameters considered are lamp current, pulse frequency, assist air pressure and thickness of the job. The responses at predicted optimum parameter level are in good agreement with the results of confirmation experiments conducted for verification tests.

1000 to 1300 K slow plastic compression properties of Al-deficient NiAl

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Kumar, K. S.; Mannan, S. K.

1991-01-01

Nickel aluminides containing 37, 38.5 and 40 at. pct Al have been fabricated by XD synthesis and hot pressing. Such materials were compression tested in air under constant velocity conditions between 1000 and 1300 K. Examination of the microstructures of hot pressed and compression tested aluminides indicated that the structure consisted of two phases, gamma-prime and NiAl, for essentially all conditions, where gamma-prime was usually found on the NiAl grain boundaries. The stress-strain behavior of all three intermetallics was similar where flow at a nominally constant stress occurred after about two-percent plastic deformation. Furthermore, the 1000 to 1300 K flow stress-strain rate properties are nearly identical for these materials, and they are much lower than those for XD processed Ni-50Al. The overall deformation of the two phase nickel aluminides appears to be controlled by dislocation climb in NiAl rather than processes in gamma-prime.

Strengthening of Fe3Al Aluminides by One or Two Solute Elements

NASA Astrophysics Data System (ADS)

Kratochvíl, Petr; Daniš, Stanislav; Minárik, Peter; Pešička, Josef; Král, Robert

2017-09-01

The compressive yield stress of Fe-26Al with additives Ti (0.5 to 4 at. pct), Cr (0.5 to 8 at. pct), Mo (0.5 to 4 at. pct), and V (0.5 to 8 at. pct) at 1073 K (800 °C) has been determined. The effect of the concentration of diverse solutes on the yield stress at 1073 K (800 °C) was compared, and the additivity of the effects of solutes was tested. The effects in iron aluminides with two solutes (V and Ti, Ti and Cr, V and Cr) are compared with those of a single solute V, Ti, and Cr. It is found that the additivity of yield stress increments is valid only for lower solute concentrations. When the amount of the solute atoms increases, the yield stress increment is substantially higher than the sum of the yield stress increments of single solutes. This behavior is related to the high-temperature order in iron aluminides.

Influence of strain rate and temperature on the mechanical behavior of iron aluminide-based alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, G.T.

Iron aluminides are receiving increasing attention as potential high temperature structural materials due to their excellent oxidation and sulfidation resistance. Although the influence of strain rate on the microstructure/property relationships of pure iron and a variety of iron alloys and steels has been extensively studied, the effect of strain rate on the stress-strain and deformation response of iron aluminides remains poorly understood. In this paper the influence of strain rate, varied between 0.001 and 10{sup 4} s{sup {minus}1}, and temperature, between 77 & 1073{degree}K, on the mechanical behavior of Fe-40Al-0.1B and Fe-16.12Al-5.44Cr-0.11Zr-0.13C-1.07Mo-006Y, called FAP-Y, (both in at.%) is presented. Themore » rate sensitivity and work hardening of Fe-40Al and the disordered alloy based on Fe-16% Al are discussed as a function of strain rate and temperature.« less

Influence of microstructure on hardness of plasma sprayed Al2O3-TiO2-MgO coatings with interface diffusion by heat treatment

NASA Astrophysics Data System (ADS)

Chen, Kunlun; Song, Peng; Li, Chao; Lu, Jiansheng

2017-12-01

The effect of heat treatment on the microstructure and mechanical properties of Al2O3-TiO2 coatings doped with 5 wt% MgO was investigated in this paper. The composite coatings were prepared by atmospheric plasma spraying (APS) and heat treated at 1000 °C for 24 h in Ar. The coatings were analyzed using scanning electron microscopy with electron probe x-ray microanalysis and x-ray diffraction. The hardness was determined using a Vickers hardness test on the as-sprayed coatings and after heat treatment. The results showed that the interface diffusion between the Al-rich and Ti-rich layers resulted in mutual pinning within the coating during the heat treatment. The newly formed MgAl2O4 phase promoted cracking-healing behavior within the coating. We conclude that increase of the hardness of the coatings was mainly caused by the mutual pinning interface and crack healing.

Method For Improving The Oxidation Resistance Of Metal Substrates Coated With Thermal Barrier Coatings

DOEpatents

Thompson, Anthony Mark; Gray, Dennis Michael; Jackson, Melvin Robert

2003-05-13

A method for providing a protective coating on a metal-based substrate is disclosed. The method involves the application of an aluminum-rich mixture to the substrate to form a discontinuous layer of aluminum-rich particles, followed by the application of a second coating over the discontinuous layer of aluminum-rich particles. Aluminum diffuses from the aluminum-rich layer into the substrate, and into any bond coat layer which is subsequently applied. Related articles are also described. A method for providing a protective coating on a metal-based substrate is disclosed. The method involves the application of an aluminum-rich mixture to the substrate to form a discontinuous layer of aluminum-rich particles, followed by the application of a second coating over the discontinuous layer of aluminum-rich particles. Aluminum diffuses from the aluminum-rich layer into the substrate, and into any bond coat layer which is subsequently applied. Related articles are also described.

From Coating to Dopant: How the Transition Metal Composition Affects Alumina Coatings on Ni-Rich Cathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Binghong; Key, Baris; Lapidus, Saul H.

Surface alumina coatings have been shown to be an effective way to improve the stability and cyclability of cathode materials. However, a detailed understanding of the relationship between the surface coatings and the bulk layered oxides is needed to better define the critical cathode–electrolyte interface. In this work, we systematically studied the effect of the composition of Ni-rich LiNi xMn yCo 1–x–yO 2 (NMC) on the surface alumina coatings. Changing cathode composition from LiNi 0.5Mn 0.3Co 0.2O 2 (NMC532) to LiNi 0.6Mn 0.2Co 0.2O 2 (NMC622) and LiNi 0.8Mn 0.1Co 0.1O 2 (NMC811) was found to facilitate the diffusion ofmore » surface alumina into the bulk after high-temperature annealing. By use of a variety of spectroscopic techniques, Al was seen to have a high bulk compatibility with higher Ni/Co content, and low bulk compatibility was associated with Mn in the transition metal layer. It was also noted that the cathode composition affected the observed morphology and surface chemistry of the coated material, which has an effect on electrochemical cycling. The presence of a high surface Li concentration and strong alumina diffusion into the bulk led to a smoother surface coating on NMC811 with no excess alumina aggregated on the surface. Structural characterization of pristine NMC particles also suggests surface Co segregation, which may act to mediate the diffusion of the Al from the surface to the bulk. The diffusion of Al into the bulk was found to be detrimental to the protection function of surface coatings leading to poor overall cyclability, indicating the importance of compatibility between surface coatings and bulk oxides on the electrochemical performance of coated cathode materials.In conclusion, these results are important in developing a better coating method for synthesis of next-generation cathode materials for lithium-ion batteries.« less

From Coating to Dopant: How the Transition Metal Composition Affects Alumina Coatings on Ni-Rich Cathodes

DOE PAGES

Han, Binghong; Key, Baris; Lapidus, Saul H.; ...

2017-11-01

Surface alumina coatings have been shown to be an effective way to improve the stability and cyclability of cathode materials. However, a detailed understanding of the relationship between the surface coatings and the bulk layered oxides is needed to better define the critical cathode–electrolyte interface. In this work, we systematically studied the effect of the composition of Ni-rich LiNi xMn yCo 1–x–yO 2 (NMC) on the surface alumina coatings. Changing cathode composition from LiNi 0.5Mn 0.3Co 0.2O 2 (NMC532) to LiNi 0.6Mn 0.2Co 0.2O 2 (NMC622) and LiNi 0.8Mn 0.1Co 0.1O 2 (NMC811) was found to facilitate the diffusion ofmore » surface alumina into the bulk after high-temperature annealing. By use of a variety of spectroscopic techniques, Al was seen to have a high bulk compatibility with higher Ni/Co content, and low bulk compatibility was associated with Mn in the transition metal layer. It was also noted that the cathode composition affected the observed morphology and surface chemistry of the coated material, which has an effect on electrochemical cycling. The presence of a high surface Li concentration and strong alumina diffusion into the bulk led to a smoother surface coating on NMC811 with no excess alumina aggregated on the surface. Structural characterization of pristine NMC particles also suggests surface Co segregation, which may act to mediate the diffusion of the Al from the surface to the bulk. The diffusion of Al into the bulk was found to be detrimental to the protection function of surface coatings leading to poor overall cyclability, indicating the importance of compatibility between surface coatings and bulk oxides on the electrochemical performance of coated cathode materials.In conclusion, these results are important in developing a better coating method for synthesis of next-generation cathode materials for lithium-ion batteries.« less

Coercivity enhancement of Dy-coated Nd-Fe-B flakes by crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukunaga, H.; Sugimoto, Y.; Nakano, M.

2011-04-01

The coercivity of isotropic Dy-coated Nd-Fe-B flakes was enhanced by crystallization and simultaneous diffusion of Dy from their surfaces. Amorphous Dy-coated Nd-Fe-B flakes were crystallized by heating them to 923 K 2over a 2 min period followed by rapid cooling. During crystallization, the Dy on the surface diffused into the flakes. This low-temperature rapid annealing produced flakes with fine grains and the Dy diffusion enhanced their coercivity. The coercivity after crystallization increased with increasing Dy layer thickness, although the remanence decreased when the layer thickness exceeded 3 {mu}m. Thick coatings of over 6 {mu}m resulted in the formation of DyFe{submore » 2}, which degraded the magnetic properties of the crystallized flakes. Flakes with a 3-{mu}m-thick coating exhibited excellent magnetic properties after annealing: They had a coercivity of 1880 kA/m and a remanence of 78 emu/g. This coercivity is approximately 500 kA/m higher than that of uncoated flakes, whereas the remanence is comparable to that of uncoated flakes.« less

Very Hard Corrosion-Resistant Roll-Bonded Cr Coating on Mild Steel in Presence of Graphite

NASA Astrophysics Data System (ADS)

Kumar, Pankaj; Khara, S.; Shekhar, S.; Mondal, K.

2017-12-01

The present work discusses the development of very hard Cr and Cr-carbide coating by roll bonding of Cr powder on a mild steel followed by annealing at 800, 1000, 1100 and 1200 °C with and without the presence of graphite powder packing in argon environment. In addition, the effect of a roll skin pass of 5% prior to the application of coating was studied. The presence of graphite allows diffusion of both carbon and Cr in the mild steel substrate, leading to the formation of Cr-carbide on the outer surface, making the surface very hard (VHN 1800). Depending on the annealing temperature and processing condition, diffusion layer thickness of Cr is found to be in the range of 10-250 μm with Cr content of 12.5-15 wt.% across the diffusion layer. Excellent stable passivity of the coated surface is observed in 0.2 N H2SO4, which is comparable to a highly passivating 304 stainless steel, and very low corrosion rate of the coating is observed as compared to the substrate mild steel.

High reflected cubic cavity as long path absorption cell for infrared gas sensing

NASA Astrophysics Data System (ADS)

Yu, Jia; Gao, Qiang; Zhang, Zhiguo

2014-10-01

One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

Reducing bubbles in glass coatings improves electrical breakdown strength

NASA Technical Reports Server (NTRS)

Banks, B.

1968-01-01

Helium reduces bubbles in glass coatings of accelerator grids for ion thrustors. Fusing the coating in a helium atmosphere creates helium bubbles in the glass. In an argon atmosphere, entrapped helium diffuses out of the glass and the bubbles collapse. The resultant coating has a substantially enhanced electrical breakdown strength.

Chemical Vapor Synthesis of Titanium Aluminides by Reaction of Aluminum Subchloride and Titanium Tetrachloride

NASA Astrophysics Data System (ADS)

Zakirov, Roman A.; Parfenov, Oleg G.; Solovyov, Leonid A.

2018-02-01

A new process for developing titanium aluminides (TiAls) using chemical vapor synthesis was investigated in a laboratory experiment. Aluminum subchloride (AlCl) was used as the reducing agent in the reaction with TiCl4 and the source of aluminum for Ti-Al alloy. Two types of products, with large crystals and fine particles, were fabricated. The large crystals were determined to be TiAl, with small amounts of Ti and Ti3Al phases. The composition of fine particles, on the other hand, varied in wide range.

Microstructure and properties of cryomilled nickel aluminide extruded with chromium or molybdenum

NASA Technical Reports Server (NTRS)

Aikin, Beverly J. M.; Dickerson, Robert M.; Dickerson, Patricia O.

1995-01-01

Previous results from high energy, attrition milled NiAl in liquid nitrogen (cryomilled) indicate that this process can produce high temperature, creep resistant AlN particulate reinforced materials. However, the low temperature toughness of such materials is below that preferred for structural applications in aerospace engines. In order to improve the toughness of these materials, prealloyed nickel aluminide (Ni-53 atomic percent Al) powder was cryomilled and mixed with chromium or molybdenum powders. The resulting materials were hot extruded and tested for room temperature toughness and 1300 K compressive strength.

Thermodynamic analysis of chemical compatibility of several reinforcement materials with niobium aluminides

NASA Technical Reports Server (NTRS)

Misra, Ajay K.

1989-01-01

Chemical compatibility of several reinforcement materials with three niobium aluminides, Nb3Al, Nb2Al, and NbAl3, were examined from thermodynamic considerations. The reinforcement materials considered in this study include carbides, borides, nitrides, oxides, silicides, and Engel-Brewer compounds. Thermodynamics of the Nb-Al system were reviewed and activities of Nb and Al were derived at desired calculation temperatures. Criteria for chemical compatibility between the reinforcement material and Nb-Al compounds have been defined and several chemically compatible reinforcement materials have been identified.

Three-Dimensional Structure Analysis and Percolation Properties of a Barrier Marine Coating

PubMed Central

Chen, Bo; Guizar-Sicairos, Manuel; Xiong, Gang; Shemilt, Laura; Diaz, Ana; Nutter, John; Burdet, Nicolas; Huo, Suguo; Mancuso, Joel; Monteith, Alexander; Vergeer, Frank; Burgess, Andrew; Robinson, Ian

2013-01-01

Artificially structured coatings are widely employed to minimize materials deterioration and corrosion, the annual direct cost of which is over 3% of the gross domestic product (GDP) for industrial countries. Manufacturing higher performance anticorrosive coatings is one of the most efficient approaches to reduce this loss. However, three-dimensional (3D) structure of coatings, which determines their performance, has not been investigated in detail. Here we present a quantitative nano-scale analysis of the 3D spatial structure of an anticorrosive aluminium epoxy barrier marine coating obtained by serial block-face scanning electron microscopy (SBFSEM) and ptychographic X-ray computed tomography (PXCT). We then use finite element simulations to demonstrate how percolation through this actual 3D structure impedes ion diffusion in the composite materials. We found the aluminium flakes align within 15° of the coating surface in the material, causing the perpendicular diffusion resistance of the coating to be substantially higher than the pure epoxy. PMID:23378910

Enhancement and degradation of the R2* relaxation rate resulting from the encapsulation of magnetic particles with hydrophilic coatings.

PubMed

de Haan, Hendrick W; Paquet, Chantal

2011-12-01

The effects of including a hydrophilic coating around the particles are studied across a wide range of particle sizes by performing Monte Carlo simulations of protons diffusing through a system of magnetic particles. A physically realistic methodology of implementing the coating by cross boundary jump scaling and transition probabilities at the coating surface is developed. Using this formulation, the coating has three distinct impacts on the relaxation rate: an enhancement at small particle sizes, a degradation at intermediate particle sizes, and no effect at large particles sizes. These varied effects are reconciled with the underlying dephasing mechanisms by using the concept of a full dephasing zone to present a physical picture of the dephasing process with and without the coating for all sizes. The enhancement at small particle sizes is studied systemically to demonstrate the existence of an optimal ratio of diffusion coefficients inside/outside the coating to achieve maximal increase in the relaxation rate. Copyright © 2011 Wiley Periodicals, Inc.

High-temperature properties of joint interface of VPS-tungsten coated CFC

NASA Astrophysics Data System (ADS)

Tamura, S.; Liu, X.; Tokunaga, K.; Tsunekawa, Y.; Okumiya, M.; Noda, N.; Yoshida, N.

2004-08-01

Tungsten coated carbon fiber composite (CFC) is a candidate material for the high heat flux components in fusion reactors. In order to investigate the high-temperature properties at the joint interface of coating, heat load experiments by using electron beam were performed on VPS-tungsten coated CX-2002U samples. After the heat load test for 3.6 ks at 1400 °C, tungsten-rhenium multilayer (diffusion barrier for carbon) at the joint interface of coating was observed clearly. But, at the temperatures above 1600 °C, the multilayer was disappeared and a tungsten carbide layer was formed in the VPS-tungsten coating. At the temperatures below 1800 °C, the thickness of this layer logarithmically increased with increasing its loading time. At 2000 °C, the growth of the tungsten carbide layer was proportional to the square root of loading time. These results indicate that the diffusion barrier for carbon is not expected to suppress the carbide formation at the joint interface of the VPS-tungsten coating above 1600 °C.

Corrosion and Fatigue Behavior of High-Strength Steel Treated with a Zn-Alloy Thermo-diffusion Coating

NASA Astrophysics Data System (ADS)

Mulligan, C. P.; Vigilante, G. N.; Cannon, J. J.

2017-11-01

High and low cycle fatigue tests were conducted on high-strength steel using four-point bending. The materials tested were ASTM A723 steel in the as-machined condition, grit-blasted condition, MIL-DTL-16232 heavy manganese phosphate-coated condition, and ASTM A1059 Zn-alloy thermo-diffusion coated (Zn-TDC). The ASTM A723 steel base material exhibits a yield strength of 1000 MPa. The effects of the surface treatments versus uncoated steel were examined. The fatigue life of the Zn-TDC specimens was generally reduced on as-coated specimens versus uncoated or phosphate-coated specimens. Several mechanisms are examined including the role of compressive residual stress relief with the Zn-TDC process as well as fatigue crack initiation from the hardened Zn-Fe alloy surface layer produced in the gas-metal reaction. Additionally, the effects of corrosion pitting on the fatigue life of coated specimens are explored as the Zn-TDC specimens exhibit significantly improved corrosion resistance over phosphate-coated and oiled specimens.

High Speed, Low Cost Fabrication of Gas Diffusion Electrodes for Membrane Electrode Assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeCastro, Emory S.; Tsou, Yu-Min; Liu, Zhenyu

Fabrication of membrane electrode assemblies (MEAs) depends on creating inks or pastes of catalyst and binder, and applying this suspension to either the membrane (catalyst coated membrane) or gas diffusion media (gas diffusion electrode) and respectively laminating either gas diffusion media or gas diffusion electrodes (GDEs) to the membrane. One barrier to cost effective fabrication for either of these approaches is the development of stable and consistent suspensions. This program investigated the fundamental forces that destabilize the suspensions and developed innovative approaches to create new, highly stable formulations. These more concentrated formulations needed fewer application passes, could be coated overmore » longer and wider substrates, and resulted in significantly lower coating defects. In March of 2012 BASF Fuel Cell released a new high temperature product based on these advances, whereby our customers received higher performing, more uniform MEAs resulting in higher stack build yields. Furthermore, these new materials resulted in an “instant” increase in capacity due to higher product yields and material throughput. Although not part of the original scope of this program, these new formulations have also led us to materials that demonstrate equivalent performance with 30% less precious metal in the anode. This program has achieved two key milestones in DOE’s Manufacturing R&D program: demonstration of processes for direct coating of electrodes and continuous in-line measurement for component fabrication.« less

Effect of the Platinum Electroplated Layer Thickness on the Coatings' Microstructure

NASA Astrophysics Data System (ADS)

Zagula-Yavorska, Maryana; Gancarczyk, Kamil; Sieniawski, Jan

2017-03-01

CMSX 4 and Inconel 625 superalloys were coated by platinum layers (3 and 7 μm thick) in the electroplating process. The heat treatment of platinum layers (at 1,050 ˚C for 2 h) was performed to increase platinum adherence to the superalloys substrate. The diffusion zone obtained on CMSX 4 superalloy (3 and 7 μm platinum thick before heat treatment) consisted of two phases: γ-Ni(Al, Cr) and (Al0.25Pt0.75)Ni3. The diffusion zone obtained on Inconel 625 superalloy (3 μm platinum thick before heat treatment) consisted of the α-Pt(Ni, Cr, Al) phase. Moreover, γ-Ni(Cr, Al) phase was identified. The X-ray diffraction (XRD) results revealed the presence of platinum in the diffusion zone of the heat-treated coating (7 μm platinum thick) on Inconel 625 superalloy. The surface roughness parameter Ra of heat-treated coatings increased with the increase of platinum layers thickness. This was due to the unequal mass flow of platinum and nickel.

Kinetic Monte Carlo Simulation of Oxygen Diffusion in Ytterbium Disilicate

NASA Astrophysics Data System (ADS)

Good, Brian

2015-03-01

Ytterbium disilicate is of interest as a potential environmental barrier coating for aerospace applications, notably for use in next generation jet turbine engines. In such applications, the diffusion of oxygen and water vapor through these coatings is undesirable if high temperature corrosion is to be avoided. In an effort to understand the diffusion process in these materials, we have performed kinetic Monte Carlo simulations of vacancy-mediated oxygen diffusion in Ytterbium Disilicate. Oxygen vacancy site energies and diffusion barrier energies are computed using Density Functional Theory. We find that many potential diffusion paths involve large barrier energies, but some paths have barrier energies smaller than one electron volt. However, computed vacancy formation energies suggest that the intrinsic vacancy concentration is small in the pure material, with the result that the material is unlikely to exhibit significant oxygen permeability.

Sodium ion diffusion in Al2O3: a distinct perspective compared with lithium ion diffusion.

PubMed

Jung, Sung Chul; Kim, Hyung-Jin; Choi, Jang Wook; Han, Young-Kyu

2014-11-12

Surface coating of active materials has been one of the most effective strategies to mitigate undesirable side reactions and thereby improve the overall battery performance. In this direction, aluminum oxide (Al2O3) is one of the most widely adopted coating materials due to its easy synthesis and low material cost. Nevertheless, the effect of Al2O3 coating on carrier ion diffusion has been investigated mainly for Li ion batteries, and the corresponding understanding for emerging Na ion batteries is currently missing. Using ab initio molecular dynamics calculations, herein, we first find that, unlike lithiation, sodiation of Al2O3 is thermodynamically unfavorable. Nonetheless, there can still exist a threshold in the Na ion content in Al2O3 before further diffusion into the adjacent active material, delivering a new insight that both thermodynamics and kinetics should be taken into account to describe ionic diffusion in any material media. Furthermore, Na ion diffusivity in NaxAl2O3 turns out to be much higher than Li ion diffusivity in LixAl2O3, a result opposite to the conventional stereotype based on the atomic radius consideration. While hopping between the O-rich trapping sites via an Na-O bond breaking/making process is identified as the main Na ion diffusion mechanism, the weaker Na-O bond strength than the Li-O counterpart turns out to be the origin of the superior diffusivity of Na ions.

Background Paper on Aerospace & Missile Needs

DTIC Science & Technology

2006-05-01

Micro- welding based coatings Trivalent chromium plated coatings Nano-composite Ni-P and Co-P based plated coatings Thermal diffusion coatings Plasma...working in conjunction with Advanced Surfaces and Processes, Inc. to determine the applicability of another type of ESD process. Trivalent Chromium ...Plating: Trivalent chromium is considered to be much less toxic than hexavalent chromium . Consequently, trivalent chromium coatings are being

COATED ALLOYS

DOEpatents

Harman, C.G.; O'Bannon, L.S.

1958-07-15

A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

Defect structures in ordered intermetallics; grain boundaries and surfaces in FeAl, NiAl, CoAl and TiAl

NASA Astrophysics Data System (ADS)

Mutasa, Batsirai Manyara

Ordered intermetallics based on transition metal aluminides have been proposed as structural materials for advanced aerospace applications. The development of these materials, which have the advantages of low density and high operating temperatures, have been focused on the aluminides of titanium, nickel and iron. Though these materials exhibit attractive properties at elevated temperatures, their utilization is limited due to their propensity for low temperature fracture and susceptibility to decreased ductility due to environmental effects. A major embrittlement mechanism at ambient temperatures in these aluminides has been by the loss of cohesive strength at the interfaces (intergranular failure). This study focuses on this mechanism of failure, by undertaking a systematic study of the energies and structures of specific grain boundaries in some of these compounds. The relaxed atomistic grain boundary structures in B2 aluminides, FeAl, NiAl and CoAl and L10 gamma-TiAl were investigated using molecular statics and embedded atom potentials in order to explore general trends for a series of B2 compounds as well as TiAl. The potentials used correctly predict the proper mechanism of compositional disorder of these compounds. Using these potentials, point defects, free surface energies and various grain boundary structures of similar energies in three B2 compounds, FeAl, NiAl and CoAl were studied. These B2 alloys exhibited increasing anti-phase boundary energies respectively. The misorientations chosen for detailed study correspond to the Sigma5(310) and Sigma5(210) boundaries. These boundaries were investigated with consideration given to possible variations in the local chemical composition. The effects of both boundary stoichiometry and bulk stoichiometry on grain boundary energetics were also considered. Defect energies were calculated for boundaries contained in both stoichiometric and off-stoichiometric bulk. The surface energies for these aluminides were also calculated so that trends concerning the cohesive energy of the boundaries could be studied. The implications of stoichiometry, the multiplicity of the boundary structures and possible transformations between them for grain boundary brittleness are also discussed.

Optimization and design of pigments for heat-insulating coatings

NASA Astrophysics Data System (ADS)

Wang, Guang-Hai; Zhang, Yue

2010-12-01

This paper reports that heat insulating property of infrared reflective coatings is obtained through the use of pigments which diffuse near-infrared thermal radiation. Suitable structure and size distribution of pigments would attain maximum diffuse infrared radiation and reduce the pigment volume concentration required. The optimum structure and size range of pigments for reflective infrared coatings are studied by using Kubelka—Munk theory, Mie model and independent scattering approximation. Taking titania particle as the pigment embedded in an inorganic coating, the computational results show that core-shell particles present excellent scattering ability, more so than solid and hollow spherical particles. The optimum radius range of core-shell particles is around 0.3 ~ 1.6 μm. Furthermore, the influence of shell thickness on optical parameters of the coating is also obvious and the optimal thickness of shell is 100-300 nm.

Modelling of the mercury loss in fluorescent lamps under the influence of metal oxide coatings

NASA Astrophysics Data System (ADS)

Santos Abreu, A.; Mayer, J.; Lenk, D.; Horn, S.; Konrad, A.; Tidecks, R.

2016-11-01

The mercury transport and loss mechanisms in the metal oxide coatings of mercury low pressure discharge fluorescent lamps have been investigated. An existing model based on a ballistic process is discussed in the context of experimental mercury loss data. Two different approaches to the modeling of the mercury loss have been developed. The first one is based on mercury transition rates between the plasma, the coating, and the glass without specifying the underlying physical processes. The second one is based on a transport process driven by diffusion and a binding process of mercury reacting to mercury oxide inside the layers. Moreover, we extended the diffusion based model to handle multi-component coatings. All approaches are applied to describe mercury loss experiments under the influence of an Al 2 O 3 coating.

Nanowire Membrane-based Nanothermite: towards Processable and Tunable Interfacial Diffusion for Solid State Reactions

PubMed Central

Yang, Yong; Wang, Peng-peng; Zhang, Zhi-cheng; Liu, Hui-ling; Zhang, Jingchao; Zhuang, Jing; Wang, Xun

2013-01-01

Interfacial diffusion is of great importance in determining the performance of solid-state reactions. For nanometer sized particles, some solid-state reactions can be triggered accidently by mechanical stress owing to their large surface-to-volume ratio compared with the bulk ones. Therefore, a great challenge is the control of interfacial diffusion for solid state reactions, especially for energetic materials. Here we demonstrate, through the example of nanowire-based thermite membrane, that the thermite solid-state reaction can be easily tuned via the introduction of low-surface-energy coating layer. Moreover, this silicon-coated thermite membrane exhibit controlled wetting behavior ranging from superhydrophilic to superhydrophobic and, simultaneously, to significantly reduce the friction sensitivity of thermite membrane. This effect enables to increase interfacial resistance by increasing the amount of coating material. Indeed, our results described here make it possible to tune the solid-state reactions through the manipulation of interfacial diffusion between the reactants. PMID:23603809

Automated array assembly task, phase 1

NASA Technical Reports Server (NTRS)

Carbajal, B. G.

1977-01-01

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Very Long Term Oxidation of Ti-48Al-2Cr-2Nb at 704 C In Air

NASA Technical Reports Server (NTRS)

Locci, I. E.; Brady, M. P.; MacKay, R. A.; Smith, J. W.

1997-01-01

Introduction Titanium aluminides are of great interest for intermediate-temperature (600 C - 850 C) aerospace and power generation applications because of their high specific properties. Replacement of conventional superalloys by titanium aluminides offers the potential of significant weight savings. Extensive development efforts over the past IO years have led to the identification of y (TiAl) + alpha(sub 2) (Ti3Al) alloys, such as the G.E. alloy Ti48Al-2Cr-2Nb (all composition in at. %), which offer a balance of room temperature mechanical properties and high-temperature strength retention. The two phase gamma + alpha(sub 2) class of titanium aluminides also offers superior oxidation and embrittlement resistance compared to the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, environmental durability is still a major concern. Significant progress has recently been made in understanding the fundamental aspects of the oxidation behavior of binary gamma + alpha(sub 2) Ti-Al alloys. However, most of this work has concentrated on short term (less than 1000 hours), high temperature (900 C - 1000 C) exposures. Also little data are available in the literature regarding the oxidation behavior of the quaternary and higher order gamma + alpha(sub 2) engineering alloys. This is especially true for the very long-term, low temperature conditions likely to be experienced during engineering applications. The present work addresses this regime to fill this gap by characterizing the oxidation behavior of Ti48Al-2Cr-2Nb for periods up to 9000 h at 704 C in air.

Thermophysical Properties of Cold and Vacuum Plasma Sprayed Cu-Cr-X Alloys, NiAl and NiCrAlY Coatings. Part 1; Electrical and Thermal Conductivity, Thermal Diffusivity, and Total Hemispherical Emissivity

NASA Technical Reports Server (NTRS)

Raj, S. V.

2017-01-01

This two-part paper reports the thermophysical properties of several cold and vacuum plasma sprayed monolithic Cu and Ni-based alloy coatings. Part I presents the electrical and thermal conductivity, thermal diffusivity, and total hemispherical emissivity data while Part II reports the specific heat capacity data for these coatings. Metallic copper alloys, stoichiometric NiAl and NiCrAlY coatings were fabricated by either the cold sprayed or the vacuum plasma spray deposition processes for thermal property measurements between 77 and 1223 K. The temperature dependencies of the thermal conductivities, thermal diffusivities, electrical conductivities and total hemispherical emissivities of these cold and vacuum sprayed monolithic coatings are reported in this paper. The electrical and thermal conductivity data correlate reasonably well for Cu-8%Cr-1%Al, Cu-23%Cr-5%Al and NiAl in accordance with the Wiedemann-Franz (WF) law although a better fit is obtained using the Smith-Palmer relationship. The Lorentz numbers determined from the WF law are close to the theoretical value.

Thermophysical Properties of Cold- and Vacuum Plasma-Sprayed Cu-Cr-X Alloys, NiAl and NiCrAlY Coatings I: Electrical and Thermal Conductivity, Thermal Diffusivity, and Total Hemispherical Emissivity

NASA Astrophysics Data System (ADS)

Raj, S. V.

2017-11-01

This two-part paper reports the thermophysical properties of several cold- and vacuum plasma-sprayed monolithic Cu- and Ni-based alloy coatings. Part I presents the electrical and thermal conductivity, thermal diffusivity, and total hemispherical emissivity data, while Part II reports the specific heat capacity data for these coatings. Metallic copper alloys and stoichiometric NiAl and NiCrAlY coatings were fabricated by either the cold spray or the vacuum plasma spray deposition processes for thermal property measurements between 77 and 1223 K. The temperature dependencies of the thermal conductivities, thermal diffusivities, electrical conductivities, and total hemispherical emissivities of these cold- and vacuum-sprayed monolithic coatings are reported in this paper. The electrical and thermal conductivity data correlate reasonably well for Cu-8%Cr-1%Al, Cu-23%Cr-5%Al, and NiAl in accordance with the Wiedemann-Franz (WF) law although a better fit is obtained using the Smith-Palmer relationship. The Lorentz numbers determined from the WF law are close to the theoretical value.

Diffuse reflectance of TiO 2 pigmented paints: Spectral dependence of the average pathlength parameter and the forward scattering ratio

NASA Astrophysics Data System (ADS)

Vargas, William E.; Amador, Alvaro; Niklasson, Gunnar A.

2006-05-01

Diffuse reflectance spectra of paint coatings with different pigment concentrations, normally illuminated with unpolarized radiation, have been measured. A four-flux radiative transfer approach is used to model the diffuse reflectance of TiO2 (rutile) pigmented coatings through the solar spectral range. The spectral dependence of the average pathlength parameter and of the forward scattering ratio for diffuse radiation, are explicitly incorporated into this four-flux model from two novel approximations. The size distribution of the pigments has been taken into account to obtain the averages of the four-flux parameters: scattering and absorption cross sections, forward scattering ratios for collimated and isotropic diffuse radiation, and coefficients involved in the expansion of the single particle phase function in terms of Legendre polynomials.

Morphology and Optical Properties of Black-Carbon Particles Relevant to Engine Emissions

NASA Astrophysics Data System (ADS)

Michelsen, H. A.; Bambha, R.; Dansson, M. A.; Schrader, P. E.

2013-12-01

Black-carbon particles are believed to have a large influence on climate through direct radiative forcing, reduction of surface albedo of snow and ice in the cryosphere, and interaction with clouds. The optical properties and morphology of atmospheric particles containing black carbon are uncertain, and characterization of black carbon resulting from engines emissions is needed. Refractory black-carbon particles found in the atmosphere are often coated with unburned fuel, sulfuric acid, water, ash, and other combustion by-products and atmospheric constituents. Coatings can alter the optical and physical properties of the particles and therefore change their optical properties and cloud interactions. Details of particle morphology and coating state can also have important effects on the interpretation of optical diagnostics. A more complete understanding of how coatings affect extinction, absorption, and incandescence measurements is needed before these techniques can be applied reliably to a wide range of particles. We have investigated the effects of coatings on the optical and physical properties of combustion-generated black-carbon particles using a range of standard particle diagnostics, extinction, and time-resolved laser-induced incandescence (LII) measurements. Particles were generated in a co-flow diffusion flame, extracted, cooled, and coated with oleic acid. The diffusion flame produces highly dendritic soot aggregates with similar properties to those produced in diesel engines, diffusion flames, and most natural combustion processes. A thermodenuder was used to remove the coating. A scanning mobility particle sizer (SMPS) was used to monitor aggregate sizes; a centrifugal particle mass analyzer (CPMA) was used to measure coating mass fractions, and transmission electron microscopy (TEM) was used to characterize particle morphologies. The results demonstrate important differences in optical measurements between coated and uncoated particles.

Phase Evaluation in Al2O3 Fiber-Reinforced Ti2AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range

DTIC Science & Technology

2011-01-01

composition: 97% Al2O3 and 3% SiO2] fibers. In both cases, the fibers were chopped with a razor blade into 5 cm lengths. Mixing of the powder and...the presence of XRD amorphous Ti- aluminides (see below) or other phases cannot be ruled out at this juncture. When the XRD spectrum of the as-received...not shown). No peaks belonging to any Ti- aluminide were found suggesting them to be amorphous or at most nano-crystalline. A typical TEM micrograph of

International Workshop on Gamma Aluminide Alloy Technology. Section Four

DTIC Science & Technology

1997-04-18

a «—■ i— Q. O C (N i < 00 i H B £ 32 £ M U XI c o L. 4-» 5 Autogenous keyhole plasma weld in Ti-48Al-2Mn-2Nb casting, xlO...34: -, Sl Overview of joining gamma alloys P Threadgill J Lee, W A Baeslack and T J Kelly: Weld fusion zone phenomena in Ti (45-48)A1-Nb-Cr y...titanium aluminides, submitted to Welding Journal. a c 9 "" o « JL ° V GO I ■ CO ’ V ** K _ L

Filler metal alloy for welding cast nickel aluminide alloys

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

1998-01-01

A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.

Hydrogen partitioning and transport in titanium aluminides

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Lee, Weon S.

1993-01-01

This report gives the final summary of the research work perfomed from March 1, 1990 to August 28, 1993. Brief descriptions of the research findings are given on the surface variation of Ti-14Al-21Nb as a function of temperature under ultrahigh vacuum conditions; titanium aluminides: surface composition effects as a function of temperature; Auger electron intensity variation in oxygen-charged silver; and segregation of sulfur on a titanium surface studied by Auger electron spectroscopy. Each description details one or more of the attached corresponding figures. Published journal documents are provided as appendices to give further detail.

Ion-plasma protective coatings for gas-turbine engine blades

NASA Astrophysics Data System (ADS)

Kablov, E. N.; Muboyadzhyan, S. A.; Budinovskii, S. A.; Lutsenko, A. N.

2007-10-01

Evaporated, diffusion, and evaporation—diffusion protective and hardening multicomponent ionplasma coatings for turbine and compressor blades and other gas-turbine engine parts are considered. The processes of ion surface treatment (ion etching and ion saturation of a surface in the metallic plasma of a vacuum arc) and commercial equipment for the deposition of coatings and ion surface treatment are analyzed. The specific features of the ion-plasma coatings deposited from the metallic plasma of a vacuum arc are described, and the effect of the ion energy on the phase composition of the coatings and the processes occurring in the surface layer of an article to be treated are discussed. Some properties of ion-plasma coatings designed for various purposes are presented. The ion surface saturation of articles made from structural materials is shown to change the structural and phase states of their surfaces and, correspondingly, the related properties of these materials (i.e., their heat resistance, corrosion resistance, fatigue strength, and so on).

Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

NASA Astrophysics Data System (ADS)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2016-06-01

Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

Improving oxidation resistance and thermal insulation of thermal barrier coatings by intense pulsed electron beam irradiation

NASA Astrophysics Data System (ADS)

Mei, Xianxiu; Liu, Xiaofei; Wang, Cunxia; Wang, Younian; Dong, Chuang

2012-12-01

In this paper, intense pulsed electron beam was used for the irradiation treatment of 6-8% Y2O3-stablized ZrO2 thermal barrier coating prepared by electron beam-physical vapor deposition to achieve the "sealing" of columnar crystals, thus improving their thermal insulation properties and high temperature oxidation resistance. The electron beam parameters used were: pulse duration 200 μs, electron voltage 15 kV, energy density 3, 5, 8, 15, 20 J/cm2, and pulsed numbers 30. 1050 °C cyclic oxidation and static oxidation experiments were used for the research on oxidation resistance of the coatings. When the energy density of the electron beam was larger than 8 J/cm2, ZrO2 ceramic coating surface was fully re-melted and became smooth, dense and shiny. The coating changed into a smooth polycrystalline structure, thus achieving the "sealing" effect of the columnar crystals. After irradiations with the energy density of 8-15 J/cm2, the thermally grown oxide coating thickness decreased significantly in comparison with non-irradiated coatings, showing that the re-melted coating improved the oxidation resistance of the coatings. The results of thermal diffusivity test by laser flash method showed that the thermal diffusion rate of the irradiated coating was lower than that of the coating without irradiation treatment, and the thermal insulation performance of irradiated coating was improved.

Oral controlled release optimization of pellets prepared by extrusion-spheronization processing.

PubMed

Bianchini, R; Vecchio, C

1989-06-01

Controlled release high dosage forms of a typical drug such as Indobufen were prepared as multiple-unit doses by employing extrusion-spheronization processing and subsequently film coating operations. The effects of drug particle size, drug/binder ratio, extruder screen size and preparation reproducibility on the physical properties of the spherical granules were evaluated. Controlled release optimization was obtained on the same granules by coating with polymeric membranes of different thickness consisting of water-soluble and insoluble substances. Film coating was applied from an organic solution using pan coating technique. The drug diffusion is allowed by dissolution of part of the membrane leaving small channels of the polymer coat. Further preparations were conducted to evaluate coatings applied from aqueous dispersion (pseudolatex) using air suspension coating technique. In this system the drug diffusion is governed by the intrinsic pore network of the membrane. The most promising preparations having the desired in vitro release, were metered into hard capsules to obtain the drug unit dosage. Accelerated stability tests were carried out to assess the influence of time and the other storage parameters on the drug release profile.

Metallic Thin-Film Bonding and Alloy Generation

NASA Technical Reports Server (NTRS)

Peotter, Brian S. (Inventor); Fryer, Jack Merrill (Inventor); Campbell, Geoff (Inventor); Droppers, Lloyd (Inventor)

2016-01-01

Diffusion bonding a stack of aluminum thin films is particularly challenging due to a stable aluminum oxide coating that rapidly forms on the aluminum thin films when they are exposed to atmosphere and the relatively low meting temperature of aluminum. By plating the individual aluminum thin films with a metal that does not rapidly form a stable oxide coating, the individual aluminum thin films may be readily diffusion bonded together using heat and pressure. The resulting diffusion bonded structure can be an alloy of choice through the use of a carefully selected base and plating metals. The aluminum thin films may also be etched with distinct patterns that form a microfluidic fluid flow path through the stack of aluminum thin films when diffusion bonded together.

In-Field Diffuse Ultraviolet Spectroscopy and Imaging of the Stardust Sample Return Capsule

NASA Technical Reports Server (NTRS)

Pugel, D. Elizabeth; Stackpoole, Mairead; McNamara, Karen; Schwartz, C.; Warren, J.; Kontinos, Dean

2008-01-01

In-field diffuse Ultraviolet (UV) spectroscopy and imaging systems were developed for the purposes of evaluating the surface chemical composition of spacecraft thermal control coatings and materials. The investigation of these systems and the compilation of an associated UV reflectance and luminescence database were conducted using the Stardust Sample Return Capsule (SRC), located at the Johnson Space Center. Spectral responses of the surfaces of the Stardust forebody and aftbody in both reflectance and fluorescence modes were examined post-flight. In this paper, we report on two primary findings of in-field diffuse UV spectroscopy and imaging: (1) deduction of the thermal history of thermal control coatings of the forebody and (2) bond line variations in the aftbody. In the forebody, the thermal history of thermal control coatings may be deduced from the presence of particular semiconducting defect states associated with ZnO, a common emissivity constituent in thermal control coatings. A spatial dependence of this history was mapped for these regions. In the aftbody, luminescing defect states, associated with Si and SiO2 color centers were found along regions of bond variability.

Diffusion Performance of Fertilizer Nutrient through Polymer Latex Film.

PubMed

An, Di; Yang, Ling; Liu, Boyang; Wang, Ting-Jie; Kan, Chengyou

2017-12-20

Matching the nutrient release rate of coated fertilizer with the nutrient uptake rate of the crop is the best way to increase the utilization efficiency of nutrients and reduce environmental pollution from the fertilizer. The diffusion property and mechanism of nutrients through the film are the theoretical basis for the product pattern design of coated fertilizers. For the coated fertilizer with a single-component nutrient, an extended solution-diffusion model was used to describe the difference of nutrient release rate, and the release rate is proportional to the permeation coefficient and the solubility of the nutrient. For the double- and triple-component fertilizer of N-K, N-P, and N-P-K, because of the interaction among nutrient molecules and ions, the release rates of different nutrients were significantly affected by the components in the composite fertilizer. Coating the single-component fertilizer (i.e., nitrogen fertilizer, phosphate fertilizer, and potash fertilizer) first and subsequently bulk blending is expected to be a promising way to adjust flexibly the nutrient release rate to meet the nutrient uptake rate of the crop.

Preliminary study of a solar selective coating system using black cobalt oxide for high temperature solar collectors

NASA Technical Reports Server (NTRS)

Mcdonald, G.

1980-01-01

Black cobalt oxide coatings (high solar absorptance layer) were deposited on thin layers of silver or gold (low emittance layer) which had been previously deposited on oxidized (diffusion barrier layer) stainless steel substrates. The reflectance properties of these coatings were measured at various thicknesses of cobalt for integrated values of the solar and infrared spectrum. The values of absorptance and emittance were calculated from the measured reflectance values, before and after exposure in air at 650 C for approximately 1000 hours. Absorptance and emittance were interdependent functions of the weight of cobalt oxide. Also, these cobalt oxide/noble metal/oxide diffusion barrier coatings have absorptances greater than 0.90 and emittances of approximately 0.20 even after about 1000 hours at 650 C.

Corrosion behavior of binary titanium aluminide intermetallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saffarian, H.M.; Gan, Q.; Hadkar, R.

1996-08-01

The corrosion behavior of arc-melted binary titanium aluminide intermetallics TiAl, Ti{sub 2}Al, and TiAl{sub 3} in aqueous sodium sulfate and sodium chloride solutions was measured and compared to that of pure Ti and Al. Effects of electrolyte composition (e.g., sulfate [0.25 M SO{sub 4}{sup 2}{sup {minus}}], chloride [0.1 to 1.0 M Cl{sup {minus}}], and pH [3 to 10]) were examined. Anodic polarization of titanium aluminides in aqueous SO{sub 4}{sup 2}{sup {minus}} solutions was similar (showing passive behavior), but no pitting or pitting potential (E{sub pit}) was observed. In aqueous NaCl, however, titanium aluminides were susceptible to pitting, and E{sub pit}more » decreased with increasing Al content (i.e., Ti{sub 3}Al had the highest E{sub pit} and, therefore, a greater resistance to pitting, followed by TiAl and TiAl{sub 3}). For TiAl, E{sub pit} was slightly dependent upon pH or Cl{sup {minus}} concentration. Pit morphology and E{sub pit} values were quite different for TiAl compared to Ti{sub 3}Al. TiAl showed numerous small pits, whereas Ti{sub 3}Al exhibited fewer but larger and deeper pits. The larger pit density for TiAl was associated with Al-rich interdendrite regions. One interesting feature of the anodic polarization curves for Ti{sub 3}Al was a small anodic peak frequently observed at {approximately}1.4 V{sub SCE} to 1.8 V{sub SCE}. Results suggested this peak was associated with pit initiation, since pitting initiated concurrently with the peak or immediately afterward.« less

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleishhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2003-12-09

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2000-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr.ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Aqueous corrosion and corrosion-sensitive embrittlement of Fe{sub 3}Al-based and lean-aluminum iron aluminides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.G.; Buchanan, R.A.

Aqueous corrosion and corrosion-sensitive embrittlement of iron aluminides were characterized as functions of environment, alloying content, notch sensitivity, and strain rate. Polarization resistance and cyclic anodic polarization evaluations were performed in 3.5 wt % NaCl, 200 ppM Cl{sup {minus}} (pH = 4), and 1 N NaOH solutions. In the mild acid-chloride solution [200 ppM Cl{sup {minus}} (pH = 4)], the pitting-corrosion resistance of the new lean-aluminum iron aluminides (FAP-Y and CM-Mo) was comparable to that of the Fe{sub 3}Al-based FAL-Mo. In the higher-chloride 3.5 wt % NaCl, the resistance of CM-Mo was slightly less but FAP-Y showed quite similar behaviormore » to FAL-Mo. In 1 N NaOH solution, all materials exhibited ideal passive behavior. Under slow-strain-rate test conditions in the mild acid-chloride electrolyte, prior work had shown the ductilities (% elongations) of Fe{sub 3}Al-based materials to be {approximately}7% and {approximately}1% at the freely-corroding and hydrogen-charging potentials, respectively. Present studied on the lean-aluminum materials have shown the ductilities to be {approximately}17% and {approximately}5%, respectively. Thus, the present results indicate that these new materials have reasonably-good aqueous-corrosion properties in chloride environments and significantly-enhanced ductilities under aqueous corrosion conditions. The strain rate and notch sensitivities of high-aluminum iron aluminide (FA-129) were investigated by performing slow-strain-rate tests. The notch sensitivity was independent of strain rate and the notch sensitivity in the aqueous environment was similar to that in air.« less

Boat Hull Blisters: Repair Techniques and Long Term Effects on Hull Degradation

DTIC Science & Technology

1988-08-01

Swelling Stresses Produced by Diffusion; Long Term Damage by Water Absorption ; Effects of Gel Coat on Leaching of Water Soluble Material from...leinforcesents 5. Swelling Stresses Produced by Diffusion 6. Long Term Damage by Water Absorption 7. Effects of Gel Coat on Leaching of Water Soluble...the importance of bilge side water pick-up is emphasized. A second method for preventing blister formation is to eliminate or minimize the water soluble

Dip-coating of nano-sized CeO2 on SiC membrane and its effect on thermal diffusivity.

PubMed

Park, Jihye; Jung, Miewon

2014-05-01

CeO2-SiC mixed composite membrane was fabricated with porous SiC ceramic and cerium oxide powder synthesized by sol-gel process. This CeO2-SiC membrane and SiC membrane which is made by the purified SiC ceramic were pressed and sintered in Ar atmosphere. And then, the SiC membrane was dip-coated by cerium oxide precursor sol solution and heat-treated in air. The surface morphology, particle size, porosity and structure analysis of the mixing and dip-coating SiC membrane were monitored by FE-SEM and X-ray diffraction analysis. Surface area, pore volume and pore diameter were determined by BET instrument. Thermal diffusivity was measured by laser flash method with increasing temperature. The relation between porosity and thermal diffusivity from different preparation process has been discussed on this study.

Methods to improve the PVD coatability of brass by using diffusion barriers

NASA Astrophysics Data System (ADS)

Langer, Bernd

Previous work involving PVD coatings on brass has used a combination of multilayers consisting of electroplated films like nickel or chromium and deposited decorative PVD coatings like TiN, TiAIN or ZrN systems. The disadvantages of these systems are the combination of wet electrochemistry and high tech vacuum processes. Furthermore the allergic reaction to nickel and the toxic nature of Cr(VI) must be considered.There is a need for intermediate layers to 'seal-off the brass in order to avoid the evaporation of zinc in vacuum using a diffusion barrier. Furthermore the intermediate layers are required to act as a corrosion barrier.This thesis reports on the development of PVD coatings on heat sensitive brass substrate materials utilising ABS technology with Al, CuAl8 and Nb targets as vapour sources.The brass pretreatment includes careful grinding, polishing and cleaning steps as well as steered arc metal ion etching using the above target materials. The coatings are produced at temperatures between 100 and 250°C in the unbalanced magnetron mode, including layers made from Al, Al-Nb, CuA18, CuAl8-Nb and Nb.Scratch adhesion and Rockwell indentation tests are found not to be directly applicable to the system of soft brass and ductile coating(s). Therefore a new classification for both scratch and indentation tests was defined. The best adhesion was shown by the CuA18 coatings on brass. Corrosion tests showed good results for the Al coatings and poor results for the pure Nb coatings directly applied on brass. The best corrosion result was obtained with a CuAl8-Nb layer system. This layer system also offers very good barrier behaviour concerning Zn diffusion.Other investigations like Glow Discharge Optical Emission Spectroscopy (GDOES), Scanning Electron Microscopy (SEM) imaging, Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) were undertaken to characterise the new coating systems for brass.

Microstructure, Tensile Adhesion Strength and Thermal Shock Resistance of TBCs with Different Flame-Sprayed Bond Coat Materials Onto BMI Polyimide Matrix Composite

NASA Astrophysics Data System (ADS)

Abedi, H. R.; Salehi, M.; Shafyei, A.

2017-10-01

In this study, thermal barrier coatings (TBCs) composed of different bond coats (Zn, Al, Cu-8Al and Cu-6Sn) with mullite top coats were flame-sprayed and air-plasma-sprayed, respectively, onto bismaleimide matrix composites. These polyimide matrix composites are of interest to replace PMR-15, due to concerns about the toxicity of the MDA monomer from which PMR-15 is made. The results showed that pores and cracks appeared at the bond coat/substrate interface for the Al-bonded TBC because of its high thermal conductivity and diffusivity resulting in transferring of high heat flux and temperature to the polymeric substrate during top coat deposition. The other TBC systems due to the lower conductivity and diffusivity of bonding layers could decrease the adverse thermal effect on the polymer substrate during top coat deposition and exhibited adhesive bond coat/substrate interfaces. The tensile adhesion test showed that the adhesion strength of the coatings to the substrate is inversely proportional to the level of residual stress in the coatings. However, the adhesion strength of Al bond-coated sample decreased strongly after mullite top coat deposition due to thermal damage at the bond coat/substrate interface. TBC system with the Cu-6Sn bond coat exhibited the best thermal shock resistance, while Al-bonded TBC showed the lowest. It was inferred that thermal mismatch stresses and oxidation of the bond coats were the main factors causing failure in the thermal shock test.

High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

NASA Technical Reports Server (NTRS)

2003-01-01

Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat is lower than that of the commercially used coating alloy 16-6. To examine the potential of NiAl-AlN-CoCrAlY as a bond coat, we subjected two samples to cyclic furnace testing. The furnace cycle consisted of 45 min at 1163 C (2125 F ) followed by 15 min of cooling out of the furnace. The current NASA baseline TBC is a NiCrAlY bond coat below the 7YSZ top coat. The average TBC life for this baseline coating on Ren N5 is 188 plus or minus 19 cycles. NiAl-AlN-CoCrAlY specimens coated with the same 7YSZ top coat were still intact even after 1000 cycles. Therefore, the NiAl-AlN-CoCrAlY as a bulk substrate material, exhibits more than 5 times the life of the current state-of-the-art material. The next step is to evaluate this material as a coating on the same superalloy substrate.

Article having an improved platinum-aluminum-hafnium protective coating

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore Aswatha (Inventor); Williams, Jeffrey Lawrence (Inventor)

2005-01-01

An article protected by a protective coating has a substrate and a protective coating having an outer layer deposited upon the substrate surface and a diffusion zone formed by interdiffusion of the outer layer and the substrate. The protective coating includes platinum, aluminum, no more than about 2 weight percent hafnium, and substantially no silicon. The outer layer is substantially a single phase.

Cermet Coatings for Solar Stirling Space Power

NASA Technical Reports Server (NTRS)

Jaworske, Donald A.; Raack, Taylor

2004-01-01

Cermet coatings, molecular mixtures of metal and ceramic are being considered for the heat inlet surface of a solar Stirling space power converter. This paper will discuss the solar absorption characteristics of as-deposited cermet coatings as well as the solar absorption characteristics of the coatings after heating. The role of diffusion and island formation, during the deposition process and during heating will also be discussed.

Titanium Aluminide Scramjet Inlet Flap Subelement Benchmark Tested

NASA Technical Reports Server (NTRS)

Krause, David L.; Draper, Susan L.

2005-01-01

A subelement-level ultimate strength test was completed successfully at the NASA Glenn Research Center (http://www.nasa.gov/glenn/) on a large gamma titanium aluminide (TiAl) inlet flap demonstration piece. The test subjected the part to prototypical stress conditions by using unique fixtures that allowed both loading and support points to be located remote to the part itself (see the photograph). The resulting configuration produced shear, moment, and the consequent stress topology proportional to the design point. The test was conducted at room temperature, a harsh condition for the material because of reduced available ductility. Still, the peak experimental load-carrying capability exceeded original predictions.

Filler metal alloy for welding cast nickel aluminide alloys

DOEpatents

Santella, M.L.; Sikka, V.K.

1998-03-10

A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

Piercing mandrel strengthening by surfacing with nickel aluminide-based alloy

NASA Astrophysics Data System (ADS)

Zorin, I. V.; Dubtsov, Yu N.; Sokolov, G. N.; Artem'ev, A. A.; Lysak, V. I.; Elsukov, S. N.

2017-02-01

Electrode composite wire (CW) was used for argon-arc surfacing of a thermal-resisting nickel aluminide-based alloy (Ni-Al-Cr-W-Mo-Ta system) on the butt-end surface of the non-water-cooled piercing mandrel. It was shown that multipassing surfacing forms a defect-free deposited metal based on the γ’-Ni3Al phase of various structural origins. Using high-temperature sclerometry and thermal fatigue testing methods, the metal deposited with CW containing ultrafine particle of 0.3-0.4 % wt. WC carbide features increased resistance to thermal and force effects at temperatures up to 1200 °C.

Laser Powder Welding of a Ti52Al46.8Cr1Si0.2Titanium Aluminide Alloy at Elevated Temperature

NASA Astrophysics Data System (ADS)

Smal, C. A.; Meacock, C. G.; Rossouw, H. J.

2011-04-01

A method for the joining of a Ti52Al46.8Cr1Si0.2Titanium Aluminide alloy by laser powder welding is presented. The technique acts to join materials by consolidating powder with focused laser beam to form weld beads that fill a V joint. In order to avoid the occurrence of residual thermal stresses and hence cracking of the brittle material, the weld plates were heated to a temperature of 1173 K (= 900 °C) by an ohmic heating device, welded and then slowly cooled to produce pore and crack free welds.

Preliminary investigation of inertia friction welding B2 aluminides

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Moore, Thomas J.; Kuruzar, Daniel L.

1987-01-01

An attempt is made to achieve inertia friction-welding in FeAl and NiAl samples, taking into account their intermetallics' compositions, extrusion parameters, and microstructural data. The energy required for the weld is stored in a rotating flywheel mass attached to one of the two pieces to be joined; when enough energy is introduced, the flywheel is disconnected and an axial load is applied which forces the spinning piece against the stationary one, converting the energy into heat by means of friction. Due to the inherent brittleness of the aluminides, a step-load program was used in which an initial, low-pressure heat buildup increased the work pieces' ductility.

Multiscale tomographic analysis of heterogeneous cast Al-Si-X alloys.

PubMed

Asghar, Z; Requena, G; Sket, F

2015-07-01

The three-dimensional microstructure of cast AlSi12Ni and AlSi10Cu5Ni2 alloys is investigated by laboratory X-ray computed tomography, synchrotron X-ray computed microtomography, light optical tomography and synchrotron X-ray computed microtomography with submicrometre resolution. The results obtained with each technique are correlated with the size of the scanned volumes and resolved microstructural features. Laboratory X-ray computed tomography is sufficient to resolve highly absorbing aluminides but eutectic and primary Si remain unrevealed. Synchrotron X-ray computed microtomography at ID15/ESRF gives better spatial resolution and reveals primary Si in addition to aluminides. Synchrotron X-ray computed microtomography at ID19/ESRF reveals all the phases ≥ ∼1 μm in volumes about 80 times smaller than laboratory X-ray computed tomography. The volumes investigated by light optical tomography and submicrometre synchrotron X-ray computed microtomography are much smaller than laboratory X-ray computed tomography but both techniques provide local chemical information on the types of aluminides. The complementary techniques applied enable a full three-dimensional characterization of the microstructure of the alloys at length scales ranging over six orders of magnitude. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Ni-Al phase transformation of dual layer coating prepared by pack cementation and electrodeposition

NASA Astrophysics Data System (ADS)

Afandi, A.; Sugiarti, E.; Ekaputra, R.; Sudiro, T.; Thosin, K. A. Z.

2018-03-01

In this work, Fe-Cr alloys were coated via Aluminum (Al) pack cementation, followed by Nickel (Ni) electrodeposition. The process of pack cementation was done with mixing powders of Al, Al203 and NH4Cl with weight percentage of 15%, 85%, and 5% respectively. To control successful Al diffusion to the substrate, pack cementation was conducted for 7 hours with two holding temperatures treatment at 400 °C for 4 hours, and 800 ° C hours for 2 hours. Subsequently, the electrodeposition of Ni was applied with the solution consisting of NiSO4, H3BO3, and NiCl2. The samples were placed in the cathode, and then dipped in the solutions, while Ni plate used as anode. Successfully the samples were coated by dual Al-Ni layers, the samples were slowly heat treated at 900 °C for 10 hours. The inter-diffusion of Al and Ni were characterized with SEM/EDX to investigate the distribution of the elements. Mechanical properties of the coated substrates were analyzed with Hardness Vickers (HV). It was found the hardness of the substrate increased significantly, from originally 255 HV to the 1177 HV after pack cementation. The hardness of the substrates has decreased to 641 HV after Ni plating, but subsequent heat treatment has been able to increase the hardness to 842 HV. This phenomenon can be correlated to the inward Al diffusion, and outward Fe, Cr diffusion. The formation of intermetallic compounds due to Al inward and Fe, Cr outward diffusion were discussed in details.

Evaluation of advanced bladder technology

NASA Technical Reports Server (NTRS)

Christensen, M. V.; Pasternak, R. A.

1972-01-01

Research conducted during this period is reported. Studies presented include: (1) diffusion and permeation of CO2, O2, N2, and NO2 through polytetra fluoroethylene; (2) diffusion, permeation and solubility of simple gases (CO2, O2, N2, CH4, C2H6, C3H8, and C2H4) through a copolymer of hexafluoro propylene and tetrafluoro ethylene (FEP); (3) viscous flow and diffusion of gases throug small apertures; (4) diffusion and permeation of O2, N2, CO2, CH4, C2H6, and C3H8 through nitroso rubber; and (5) results of gas transport studies with carborane siloxane, nitroso rubber, silicone membrane, krytox coating on teflon, and FEP coated glass cloth. Publications generated under this program are listed.

Development and application of an exchange model for anisotropic water diffusion in the microporous MOF aluminum fumarate

NASA Astrophysics Data System (ADS)

Splith, Tobias; Fröhlich, Dominik; Henninger, Stefan K.; Stallmach, Frank

2018-06-01

Diffusion of water in aluminum fumarate was studied by means of pulsed field gradient (PFG) nuclear magnetic resonance (NMR). Due to water molecules exchanging between the intracrystalline anisotropic pore space and the isotropic intercrystalline void space the model of intracrystalline anisotropic diffusion fails to describe the experimental PFG NMR data at high observation times. Therefore, the two-site exchange model developed by Kärger is extended to the case of exchange between an anisotropic and an isotropic site. This extended exchange model is solved by numerical integration. It describes the experimental data very well and yields values for the intracrystalline diffusion coefficient and the mean residence times of the respective sites. Further PFG NMR studies were performed with coatings consisting of small aluminum fumarate crystals, which are used in adsorptive heat transformation applications. The diffusion coefficients of water in the small crystal coating are compared to the values expected from the extended two-site exchange model and from the model of long-range diffusion.

The effect of heat treatment on structural and electronic properties of niobium nitride prepared by a thermal diffusion method

DOE PAGES

Farha, Ashraf Hassan; Ozkendir, Osman Murat; Elsayed-Ali, Hani E.; ...

2016-11-15

NbN coatings are prepared onto Nb substrate by thermal diffusion at high temperatures. The formation of NbN coating by thermal diffusion was studied in the range of 1250-1500 °C at constant nitrogen background gas pressure (1.3x10 -3 Pa) and processing time (180 min). The electronic and crystal structures of the NbN coatings were investigated. It was found that nitrogen diffuses into Nb forming the Nb-N solid solution (bcc) a-NbN phase that starts to appear above 1250 °C. Increasing the processing temperature gives richer a-phase concentration. Besides, X-ray absorption spectroscopy (XAS) was performed to study the electronic structure of the NbNmore » layer. The results of the electronic structural study corroborate the crystal structural analysis. The Nb M 3,2 edge X-ray absorption spectroscopy (XAS) spectrum shows strong temperature dependence. At the highest processing temperature (1500 °C), the number of d holes increased. Nitrogen diffusion into Nb is resulting to increase electrostatic interaction between d electron and core hole. Lastly, for the studied conditions, only the α-NbN was observed in the X-ray diffraction patterns.« less

The effect of heat treatment on structural and electronic properties of niobium nitride prepared by a thermal diffusion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farha, Ashraf Hassan; Ozkendir, Osman Murat; Elsayed-Ali, Hani E.

NbN coatings are prepared onto Nb substrate by thermal diffusion at high temperatures. The formation of NbN coating by thermal diffusion was studied in the range of 1250-1500 °C at constant nitrogen background gas pressure (1.3x10 -3 Pa) and processing time (180 min). The electronic and crystal structures of the NbN coatings were investigated. It was found that nitrogen diffuses into Nb forming the Nb-N solid solution (bcc) a-NbN phase that starts to appear above 1250 °C. Increasing the processing temperature gives richer a-phase concentration. Besides, X-ray absorption spectroscopy (XAS) was performed to study the electronic structure of the NbNmore » layer. The results of the electronic structural study corroborate the crystal structural analysis. The Nb M 3,2 edge X-ray absorption spectroscopy (XAS) spectrum shows strong temperature dependence. At the highest processing temperature (1500 °C), the number of d holes increased. Nitrogen diffusion into Nb is resulting to increase electrostatic interaction between d electron and core hole. Lastly, for the studied conditions, only the α-NbN was observed in the X-ray diffraction patterns.« less

Barrier Coatings for Refractory Metals and Superalloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

SM Sabol; BT Randall; JD Edington

2006-02-23

In the closed working fluid loop of the proposed Prometheus space nuclear power plant (SNPP), there is the potential for reaction of core and plant structural materials with gas phase impurities and gas phase transport of interstitial elements between superalloy and refractory metal alloy components during service. Primary concerns are surface oxidation, interstitial embrittlement of refractory metals and decarburization of superalloys. In parallel with kinetic investigations, this letter evaluates the ability of potential coatings to prevent or impede communication between reactor and plant components. Key coating requirements are identified and current technology coating materials are reviewed relative to these requirements.more » Candidate coatings are identified for future evaluation based on current knowledge of design parameters and anticipated environment. Coatings were identified for superalloys and refractory metals to provide diffusion barriers to interstitial transport and act as reactive barriers to potential oxidation. Due to their high stability at low oxygen potential, alumina formers are most promising for oxidation protection given the anticipated coolant gas chemistry. A sublayer of iridium is recommended to provide inherent diffusion resistance to interstitials. Based on specific base metal selection, a thin film substrate--coating interdiffusion barrier layer may be necessary to meet mission life.« less

Investigation of the Phase Formation of AlSi-Coatings for Hot Stamping of Boron Alloyed Steel

NASA Astrophysics Data System (ADS)

Veit, R.; Hofmann, H.; Kolleck, R.; Sikora, S.

2011-01-01

Hot stamping of boron alloyed steel is gaining more and more importance for the production of high strength automotive body parts. Within hot stamping of quenchenable steels the blank is heated up to austenitization temperature, transferred to the tool, formed rapidly and quenched in the cooled tool. To avoid scale formation during the heating process of the blank, the sheet metal can be coated with an aluminium-silicum alloy. The meltimg temperature of this coating is below the austenitization temperature of the base material. This means, that a diffusion process between base material and coating has to take place during heating, leading to a higher melting temperature of the coating. In conventional heating devices, like roller hearth furnaces, the diffusion process is reached by relatively low heating rates. New technologies, like induction heating, reach very high heating rates and offer great potentials for the application in hot stamping. Till now it is not proofed, that this technology can be used with aluminum-silicon coated materials. This paper will present the results of comparative heating tests with a conventional furnace and an induction heating device. For different time/temperature-conditions the phase formation within the coating will be described.

Method of coating the interior surface of hollow objects with a diffusion coating

DOEpatents

Knowles, Shawn D.; Senor, David J.; Forbes, Steven V.; Johnson, Roger N.; Hollenberg, Glenn W.

2005-03-15

A method for forming a diffusion coating on the interior of surface of a hollow object wherein a filament, extending through a hollow object and adjacent to the interior surface of the object, is provided, with a coating material, in a vacuum. An electrical current is then applied to the filament to resistively heat the filament to a temperature sufficient to transfer the coating material from the filament to the interior surface of the object. The filament is electrically isolated from the object while the filament is being resistively heated. Preferably, the filament is provided as a tungsten filament or molybdenum filament. Preferably, the coating materials are selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Ge, Hg, In, K, Li, Mg, Mn, Na, Ni P, Pb, Pd, Pr, S, Sb, Sc, Se, Si, Sn, Sr, Te, Tl, Y, Yb, Zn, and combinations thereof. The invention additionally allows for the formation of nitrides, hydrides, or carbides of all the possible coating materials, where such compounds exist, by providing a partial pressure of nitrogen, hydrogen, hydrocarbons, or combination thereof, within the vacuum.

Gradient complex protective coatings for single-crystal turbine blades of high-heat gas turbine engines

NASA Astrophysics Data System (ADS)

Kuznetsov, V. P.; Lesnikov, V. P.; Muboyadzhyan, S. A.; Repina, O. V.

2007-05-01

Complex diffusion-condensation protective coatings characterized by gradient distribution of alloying elements over the thickness due to formation of a diffusion barrier layer on the surface of blades followed by deposition of condensation alloyed layers based on the Ni-Co-Cr-Al-Y system and an external layer based on a NiAl alloyed β-phase and a ZrO2: Y2O3 ceramics are presented. A complex gradient coating possessing unique protective properties at t = 1100-1200°C for single-crystal blades from alloy ZhS36VI for advanced gas turbine engines with gas temperature of 1550°C at the inlet to the turbine is described.

Production of Transitional Diffused Layers by Electrospark Coating

NASA Astrophysics Data System (ADS)

Smolentsev, Vladislav P.; Boldyrev, Alexander I.; Smolentsev, Evgeniy V.; Boldyrev, Alexander A.; Mozgalin, Vladislav L.

2018-03-01

The article presents a new method for production of diffused transitional layers with nano- and microthickness by local removal of nanofilms on aluminum alloys. This allows procuring of high-quality coatings on fusible alloys (for example, on aluminum ones) by materials, the melting point of which is 2-3 times higher than that of the basis (for example, of cast iron). This permits imparting new useful properties to workpieces made from light alloys with decent values for electrochemical working. The authors show that application of coatings provides minimum heating of workpieces. This enables the regulation in temperature condition of operating environment and permits efficiency improving during the process of electrochemical working by means of higher density current supply.

Calcium phosphate coating on titanium using laser and plasma spray

NASA Astrophysics Data System (ADS)

Roy, Mangal

Though calcium phosphate (CaP) coated implants are commercially available, its acceptance is still not wide spread due to challenges related to weaker interfacial bonding between metal and ceramic, and low crystallinity of hydroxyapatite (HA). The objectives of this research are to improve interfacial strength, crystallinity, phase purity and bioactivity of CaP coated metallic implants for orthopaedic applications. The rationale is that forming a diffuse and gradient metal-ceramic interface will improve the interfacial strength. Moreover, reducing CaP particles exposure to high temperature during coating preparation, can lead to improvement in both crystallinity and phase purity of CaP. In this study, laser engineered net shaping (LENS(TM)) was used to coat Ti metal with CaP. LENS(TM) processing enabled generation of Ti+TCP (tricalcium phosphate) composite coating with diffused interface, that also increased the coating hardness to 1049+/-112 Hv compared to a substrate hardness of 200+/-15 Hv. In vitro bone cell-material interaction studies confirmed the bioactivity of TCP coatings. Antimicrobial properties of the TCP coatings were improved by silver (Ag) electrodeposition. Along with LENS(TM), radio frequency induction plasma spray, equipped with supersonic plasma nozzle, was used to prepare HA coatings on Ti with improved crystallinity and phase purity. The coating was made of multigrain HA particles of ˜200 nm in size, which consisted of 15--20 nm HA grains. In vitro bone cell-material interaction and in vivo rat model studies confirmed the HA coatings to be bioactive. Furthermore, incorporation of Sr2+ improved bone cell of HA coatings interaction. A combination of LENS(TM) and plasma spray was used to fabricate a compositionally graded HA coatings on Ti where the microstructure varied from pure HA at the surface to pure Ti substrate with a diffused Ti+TCP composite region in between. The plasma spray system was used to synthesize spherical HA nano powder from HA sol, where the production rate was 20 g/h, which is only 16% of the total powder produced. The effects of Sr2+ and Mg2+ doping on bone cell-CaP interaction was further studied with osteoclast cells. Mg2+ doing was found to be an effective way of controlling osteoclast differentiation.

Light diffusing films fabricated by strawberry-like PMMA/SiO₂ composite microspheres for LED application.

PubMed

Guo, Shuang; Zhou, Shuxue; Li, Huijing; You, Bo

2015-06-15

This paper presents a facile method to fabricate volumetric light diffusing films with high transmittance and haze simultaneously by mimicking the micro- and nanostructure of compound eyes. Strawberry-like polymethyl methacrylate/SiO2 composite microspheres were first prepared via the electrostatic attraction between positively charged PMMA spheres and negatively charged SiO2 nanoparticles, and further blended with polyacrylate latex to produce light diffusing coatings. A novel light diffusing film with hemispherical surface was built by casting the light diffusing coatings on optical-grade PET film. Effects of the sizes of PMMA spheres and SiO2 nanoparticles on the optical properties of light diffusing film were investigated by a haze meter and application on a LED lamp. The best result (transmittance 94.6% and haze 84.2%) was achieved for the strawberry-like composite microspheres based on 1 μm PMMA spheres and 50 nm SiO2 nanoparticles. The light-diffusing mechanism of the strawberry-like microspheres in the film was discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

Method for improving the oxidation-resistance of metal substrates coated with thermal barrier coatings

DOEpatents

Thompson, Anthony Mark; Gray, Dennis Michael; Jackson, Melvin Robert

2002-01-01

A method for providing a protective coating on a metal-based substrate is disclosed. The method involves the application of an aluminum-rich mixture to the substrate to form a discontinuous layer of aluminum-rich particles, followed by the application of a second coating over the discontinuous layer of aluminum-rich particles. Aluminum diffuses from the aluminum-rich layer into the substrate, and into any bond coat layer which is subsequently applied. Related articles are also described.

Diffusely Reflecting Paints Containing TFE

NASA Technical Reports Server (NTRS)

Shai, M. C.; Schutt, J. B.

1985-01-01

Highly reflective, diffused coatings developed by incorporating polytetrafluoroethylene (TFE) pigment with alcohol-soluble binders. Alcohol and binder mixed together in blender before adding TFE. TFE preferably outgassed in mechanical-pump vacuum for typical interval of 4 hours before adding to liquid. Like wetting agent, vacuum treatment helps to prevent clumping of TFE and eases dispersion throughout mixture. Mixture blended for 3 to 5 minutes before used. Coatings useful on reflectance-standard surfaces for calibrating radiometric instruments in both laboratory and field. Paints washable and usable as optical reference surfaces.

Experience of high-nitrogenous steel powder application in repairs and surface hardening of responsible parts for power equipment by plasma spraying

NASA Astrophysics Data System (ADS)

Kolpakov, A. S.; Kardonina, N. I.

2016-02-01

The questions of the application of novel diffusion-alloying high-nitrogenous steel powders for repair and surface hardening of responsible parts of power equipment by plasma spraying are considered. The appropriateness of the method for operative repair of equipment and increasing its service life is justified. General data on the structure, properties, and manufacture of nitrogen-, aluminum-, and chromium-containing steel powders that are economically alloyed using diffusion are described. It is noted that the nitrogen release during the decomposition of iron nitrides, when heating, protects the powder particles from oxidation in the plasma jet. It is shown that the coating retains 50% of nitrogen that is contained in the powder. Plasma spraying modes for diffusion-alloying high-nitrogenous steel powders are given. The service properties of plasma coatings based on these powders are analyzed. It is shown that the high-nitrogenous steel powders to a nitrogen content of 8.9 wt % provide the necessary wear resistance and hardness of the coating and the strength of its adhesion to the substrate and corrosion resistance to typical aggressive media. It is noted that increasing the coating porosity promotes stress relaxation and increases its thickness being limited with respect to delamination conditions in comparison with dense coatings on retention of the low defectiveness of the interface and high adhesion to the substrate. The examples of the application of high-nitrogenous steel powders in power engineering during equipment repairs by service companies and overhaul subdivisions of heat power plants are given. It is noted that the plasma spraying of diffusion-alloyed high-nitrogenous steel powders is a unique opportunity to restore nitrided steel products.

Influence of temperature on oxidation mechanisms of fiber-textured AlTiTaN coatings.

PubMed

Khetan, Vishal; Valle, Nathalie; Duday, David; Michotte, Claude; Delplancke-Ogletree, Marie-Paule; Choquet, Patrick

2014-03-26

The oxidation kinetics of AlTiTaN hard coatings deposited at 265 °C by DC magnetron sputtering were investigated between 700 and 950 °C for various durations. By combining dynamic secondary ion mass spectrometry (D-SIMS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) investigations of the different oxidized coatings, we were able to highlight the oxidation mechanisms involved. The TEM cross-section observations combined with XRD analysis show that a single amorphous oxide layer comprising Ti, Al, and Ta formed at 700 °C. Above 750 °C, the oxide scale transforms into a bilayer oxide comprising an Al-rich upper oxide layer and a Ti/Ta-rich oxide layer at the interface with the coated nitride layer. From the D-SIMS analysis, it could be proposed that the oxidation mechanism was governed primarily by inward diffusion of O for temperatures of ≤700 °C, while at ≥750 °C, it is controlled by outward diffusion of Al and inward diffusion of O. Via a combination of structural and chemical analysis, it is possible to propose that crystallization of rutile lattice favors the outward diffusion of Al within the AlTiTa mixed oxide layer with an increase in the temperature of oxidation. The difference in the mechanisms of oxidation at 700 and 900 °C also influences the oxidation kinetics with respect to oxidation time. Formation of a protective alumina layer decreases the rate of oxidation at 900 °C for long durations of oxidation compared to 700 °C. Along with the oxidation behavior, the enhanced thermal stability of AlTiTaN compared to that of the TiAlN coating is illustrated.

Encapsulation of thermal energy storage media

DOEpatents

Dhau, Jaspreet; Goswami, Dharendra; Jotshi, Chand K.; Stefanakos, Elias K.

2017-09-19

In one embodiment, a phase change material is encapsulated by forming a phase change material pellet, coating the pellet with flexible material, heating the coated pellet to melt the phase change material, wherein the phase change materials expands and air within the pellet diffuses out through the flexible material, and cooling the coated pellet to solidify the phase change material.

Enhancement of the Rate Capability of LiFePO4 by a New Highly Graphitic Carbon-Coating Method.

PubMed

Song, Jianjun; Sun, Bing; Liu, Hao; Ma, Zhipeng; Chen, Zhouhao; Shao, Guangjie; Wang, Guoxiu

2016-06-22

Low lithium ion diffusivity and poor electronic conductivity are two major drawbacks for the wide application of LiFePO4 in high-power lithium ion batteries. In this work, we report a facile and efficient carbon-coating method to prepare LiFePO4/graphitic carbon composites by in situ carbonization of perylene-3,4,9,10-tetracarboxylic dianhydride during calcination. Perylene-3,4,9,10-tetracarboxylic dianhydride containing naphthalene rings can be easily converted to highly graphitic carbon during thermal treatment. The ultrathin layer of highly graphitic carbon coating drastically increased the electronic conductivity of LiFePO4. The short pathway along the [010] direction of LiFePO4 nanoplates could decrease the Li(+) ion diffusion path. In favor of the high electronic conductivity and short lithium ion diffusion distance, the LiFePO4/graphitic carbon composites exhibit an excellent cycling stability at high current rates at room temperature and superior performance at low temperature (-20 °C).

Microstructural characterization of a thin film ZrN diffusion barrier in an As-fabricated U-7Mo/Al matrix dispersion fuel plate

NASA Astrophysics Data System (ADS)

Keiser, Dennis D.; Perez, Emmanuel; Wiencek, Tom; Leenaers, Ann; Van den Berghe, Sven

2015-03-01

The United States High Performance Research Reactor Fuel Development program is developing low enriched uranium fuels for application in research and test reactors. One concept utilizes U-7 wt.% Mo (U-7Mo) fuel particles dispersed in Al matrix, where the fuel particles are coated with a 1 μm-thick ZrN coating. The ZrN serves as a diffusion barrier to eliminate a deleterious reaction that can occur between U-7Mo and Al when a dispersion fuel is irradiated under aggressive reactor conditions. To investigate the final microstructure of a physically-vapor-deposited ZrN coating in a dispersion fuel plate after it was fabricated using a rolling process, characterization samples were taken from a fuel plate that was fabricated at 500 °C using ZrN-coated U-7Mo particles, Al matrix and AA6061 cladding. Scanning electron and transmission electron microscopy analysis were performed. Data from these analyses will be used to support future microstructural examinations of irradiated fuel plates, in terms of understanding the effects of irradiation on the ZrN microstructure, and to determine the role of diffusion barrier microstructure in eliminating fuel/matrix interactions during irradiation. The as-fabricated coating was determined to be cubic-ZrN (cF8) phase. It exhibited a columnar microstructure comprised of nanometer-sized grains and a region of relatively high porosity, mainly near the Al matrix. Small impurity-containing phases were observed at the U-7Mo/ZrN interface, and no interaction zone was observed at the ZrN/Al interface. The bonding between the U-7Mo and ZrN appeared to be mechanical in nature. A relatively high level of oxygen was observed in the ZrN coating, extending from the Al matrix in the ZrN coating in decreasing concentration. The above microstructural characteristics are discussed in terms of what may be most optimal for a diffusion barrier in a dispersion fuel plate application.

Impact resistance and energies of intermetallic bonded diamond composites and polycrystalline diamond compacts and their comparison

NASA Astrophysics Data System (ADS)

Gorla, Sai Prasanth

Chemistry of intermetallic bonded diamond is studied. The impact resistance and energies of intermetallic bonded diamond is compared to current poly crystalline diamond compacts. IBD's are found to have high standards of hardness and have more impact energies absorbed. Intermetallic bonded diamond composite comprises of diamond particles dispersed in Tungsten carbide using Nickel aluminide (Ni3Al) as binder. In previous research conducted on IBD's, diamonds are successfully dispersed in intermetallic alloy of nickel aluminide and processed at 1350°C such that diamond particles remain intact without forming graphite. Composites are formed by milling, pressing the intermetallic binder and diamond particles and sintering at high temperature conditions.

High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

DOEpatents

Maziasz, P.J.; Goodwin, G.M.; Liu, C.T.

1996-08-13

This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding. 13 figs.

High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

DOEpatents

Maziasz, Philip J.; Goodwin, Gene M.; Liu, Chain T.

1996-01-01

This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding.

Interface-related deformation phenomena in intermetallic γ-titanium aluminides

NASA Astrophysics Data System (ADS)

Appel, F.; Wagner, R.

1993-01-01

The development of titanium aluminides towards higher ductility concentrates on Ti-rich alloys which are composed of the intermetallic phases γ(TiAl) and α2(Ti3Al). The two phases form a lamellar microstructure with various types of interfaces. The deformation behaviour of these materials was investigated by compression tests, which were performed for different orientations of the interfacial boundaries with respect to the sample axis. With regard to the mechanical properties the structure of the interfaces and the micromechanisms of deformation were studied by conventional and high resolution electron microscopy. Accordingly, the interfacial boundaries impede the propagation of slip across the lamellae, leading to an athermal contribution to the flow stress.

Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic stack test fixture, part III: Stability and microstructure of Ce-(Mn,Co)-spinel coating, AISI441 interconnect, alumina coating, cathode and anode

NASA Astrophysics Data System (ADS)

Chou, Yeong-Shyung; Stevenson, Jeffry W.; Choi, Jung-Pyung

2014-07-01

A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing under realistic conditions. Part III of the work investigated the stability of Ce-(Mn,Co) spinel coating, AISI441 metallic interconnect, alumina coating, and cell's degradation. After 6000 h test, the spinel coating showed densification with some diffusion of Cr. At the metal interface, segregation of Si and Ti was observed, however, no continuous layer formed. The alumina coating for perimeter sealing areas appeared more dense and thick at the air side than the fuel side. Both the spinel and alumina coatings remained bonded. EDS analysis of Cr within the metal showed small decrease in concentration near the coating interface and would expect to cause no issue of Cr depletion. Inter-diffusion of Ni, Fe, and Cr between spot-welded Ni wire and AISI441 interconnect was observed and Cr-oxide scale formed along the circumference of the weld. The microstructure of the anode and cathode was discussed relating to degradation of the top and middle cells. Overall, the Ce-(Mn,Co) spinel coating, alumina coating, and AISI441 steel showed the desired long-term stability and the developed generic stack fixture proved to be a useful tool to validate candidate materials for SOFC.

Characterization of Secondary Mineral Grain Coatings and their Role as Diffusion-controlled Sinks and Sources for Metal Contaminants

NASA Astrophysics Data System (ADS)

Davis, J. A.; Guo, H.; Lai, B.; Kemner, K. M.; Ercius, P.; Fox, P. M.; Singer, D. M.; Minor, A.; Waychunas, G.

2012-12-01

Many important geochemical reactions occur at the mineral-water interface, including sorption and desorption reactions of contaminants. Fundamental knowledge of the kinetics of these processes is based primarily on experimental observations of reactions at faces of single crystals or macroscopic data from pure mineral powder suspensions. Sorption reactions at crystal faces are generally very fast, on the order of microseconds or less, with reaction times often limited only by film diffusion at the mineral-water interface. In well-stirred suspensions of aquifer sediments, however, sorptive equilibrium can take many hours or days to achieve steady-state concentrations. We have examined the potential reasons for sorption rate limitation using uranium(VI) sorption by sediments from a sandy aquifer in Savannah River, South Carolina (USA). U(VI) sorption by sand-sized grains from the aquifer is dominated by reaction with secondary mineral coatings on quartz and feldspar grains. The coatings studied were on the order of 15 microns in thickness (i.e., from quartz grain to aqueous solution) and composed primarily of clay minerals and hematite of varying particle size. Microfocused-XRF imaging of elemental concentrations (e.g., U, Fe) of polished cross-sections of the grain/coating contact showed strong spatial correlations of U and Fe within the coatings, regardless of the length of reaction time (30 minutes to 4 weeks). The spatial resolution of the μ-XRF technique is of the order of 2 microns in horizontal directions, but the uncertainty of the observed spatial gradients is high due to grain curvature away from the polished surface and fluorescence contributed from the entire 30 micron thickness of a typical grain/epoxy thin section. TEM characterization of focused-ion-beam (FIB), vertically-extracted samples of the grain-coating contact shows that complex pore networks exist within the coatings of variable dimensions and unknown connectivity. Using scanning TEM (STEM) tomography, it can be seen that there are large numbers of pore throat sizes less than 10 nm within the coatings. We hypothesize that diffusion through these pores, which likely have electrically charged surfaces, controls the observed macroscopic rates of U(VI) sorption in batch experiments with sand grains. Evidence to support this hypothesis was observed by studying U and Fe fluorescence spatial variation within FIB samples (1 micron thick) at 200 nm spatial resolution. With this greater spatial resolution, it is possible to see U concentration variations within the coatings that are dependent on the time of sorption reaction, and illustrates how the coating environment constitutes a diffusion constraint to achieve adsorptive equilibrium between an aqueous phase and the mineral surfaces. Including this diffusion constraint within conceptual models for reactive contaminant transport may be significant at the field scale, because secondary mineral coatings are potentially both sinks and sources of contaminants depending on the history of a contaminated site. This is important in resolving long-term transport predictions at DOE sites, such as Hanford and Savannah River, where equilibrium versus kinetic reactive transport models are being evaluated.

Towards a versatile technique for tracking nanoparticle-mucus interaction: a step on the road

NASA Astrophysics Data System (ADS)

Nafee, N.; Schneider, M.

2014-02-01

Respiratory mucus is one of the main barriers for nanoparticle-based pulmonary delivery systems. This holds true especially for lung diseases like cystic fibrosis, where a very tenacious thick mucus layer hinders particle diffusion to the lung epithelium or the target area. Typically, mean square displacement of particles is used for mobility evaluation. In contrast, our objective is to develop a feasible technique to track directed particle penetration as a prerequisite for efficient pulmonary nanotherapy. Therefore, particle diffusion in artificial mucus was monitored based on confocal laser scanning microscopy (CLSM) and particle-mucus interaction was observed. As pharmaceutical relevant and benign materials, solid lipid nanoparticles (SLNs) were prepared by hot-melt emulsification using glyceryl behenate and different stabilizing agents such as poloxamer-407, tween-80, and polyvinyl alcohol (PVA). The diffusion of labeled SLNs in stained artificial sputum representing CF-patient sputum was verified by 3D time laps imaging. Thus, the effect of coating, particle size and mucus viscosity on nanoparticle diffusion was studied. Using image analysis software "Image J", the total fluorescent signal after 30 min in case of poloxamer-coated SLNs was 5 and 100 folds higher than tween- and PVA-coated SLNs, respectively. Nevertheless, increasing mucus viscosity reduced the diffusion of tweencoated SLNs by a factor of 10. Studying particle-mucus interaction by CLSM can be considered a promising and versatile technique.

An evaluation of fiber-reinforced titanium matrix composites for advanced high-temperature aerospace applications

NASA Astrophysics Data System (ADS)

Larsen, James M.; Russ, Stephan M.; Jones, J. W.

1995-12-01

The current capabilities of continuous silicon-carbide fiber-reinforced titanium matrix composites (TMCs) are reviewed with respect to application needs and compared to the capabilities of conventional high-temperature monolithic alloys and aluminides. In particular, the properties of a firstgeneration titanium aluminide composite, SCS-6/Ti-24Al-11Nb, and a second-generation metastable beta alloy composite, SCS-6/TIMETAL 21S, are compared with the nickel-base superalloy IN100, the high-temperature titanium alloy Ti-1100, and a relatively new titanium aluminide alloy. Emphasis is given to life-limiting cyclic and monotonie properties and to the influence of time-dependent deformation and environmental effects on these properties. The composite materials offer a wide range of performance capabilities, depending on laminate architecture. In many instances, unidirectional composites exhibit outstanding properties, although the same materials loaded transverse to the fiber direction typically exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property under consideration, composite cross-ply laminates often show no improvement over the capability of conventional monolithic materials. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to the specific application needs if these materials are to be attractive candidates to replace more conventional materials.

Effect of powder reactivity on fabrication and properties of NiAl/Al2O3 composite coated on cast iron using spark plasma sintering

NASA Astrophysics Data System (ADS)

Beyhaghi, Maryam; Kiani-Rashid, Ali-Reza; Kashefi, Mehrdad; Khaki, Jalil Vahdati; Jonsson, Stefan

2015-07-01

Powder mixtures of Ni, NiO and Al are ball milled for 1 and 10 h. X-ray diffractometry and differential thermal analysis show that while ball milling for 1 h produced mechanically activated powder; 10 h ball milling produced NiAl and Al2O3 phases. Dense NiAl/Al2O3 composite coatings are formed on gray cast iron substrate by spark plasma sintering (SPS) technique. The effect of powder reactivity on microstructure, hardness and scratch hardness of NiAl/Al2O3 coatings after SPS is discussed. Results show that in the coating sample made of mechanically activated powder in situ synthesis of NiAl/Al2O3 composite coating is fulfilled and a thicker well-formed diffusion bond layer at the interface between coating and substrate is observed. The diffusion of elements across the bond layers and phase evolution in the bond layers were investigated. No pores or cracks were observed at the interface between coating layer and substrate in any of samples. Higher Vickers hardness and scratch hardness values in coating made of 10 h ball milled powder than in coating fabricated from 1 h ball milled powder are attributed to better dispersion of Al2O3 reinforcement particles in NiAl matrix and nano-crystalline structure of NiAl matrix. Scratched surface of coatings did not reveal any cracking or spallation at coating-substrate interface indicating their good adherence at test conditions.

Kinetic Monte Carlo Simulation of Oxygen Diffusion in Ytterbium Disilicate

NASA Technical Reports Server (NTRS)

Good, Brian S.

2015-01-01

Ytterbium disilicate is of interest as a potential environmental barrier coating for aerospace applications, notably for use in next generation jet turbine engines. In such applications, the transport of oxygen and water vapor through these coatings to the ceramic substrate is undesirable if high temperature oxidation is to be avoided. In an effort to understand the diffusion process in these materials, we have performed kinetic Monte Carlo simulations of vacancy-mediated and interstitial oxygen diffusion in Ytterbium disilicate. Oxygen vacancy and interstitial site energies, vacancy and interstitial formation energies, and migration barrier energies were computed using Density Functional Theory. We have found that, in the case of vacancy-mediated diffusion, many potential diffusion paths involve large barrier energies, but some paths have barrier energies smaller than one electron volt. However, computed vacancy formation energies suggest that the intrinsic vacancy concentration is small. In the case of interstitial diffusion, migration barrier energies are typically around one electron volt, but the interstitial defect formation energies are positive, with the result that the disilicate is unlikely to exhibit experience significant oxygen permeability except at very high temperature.

Ag out-surface diffusion in crystalline SiC with an effective SiO 2 diffusion barrier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, H.; Xiao, H. Y.; Zhu, Z.

2015-05-07

For applications of tristructural isotropic (TRISO) fuel particles in high temperature reactors, release of radioactive Ag isotope ( 110mAg) through the SiC coating layer is a safety concern. In order to understand the diffusion mechanism, Ag ion implantations near the surface and in the bulk were performed by utilizing different ion energies and energy-degrader foils. High temperature annealing was carried out on the as-irradiated samples to study the possible out-surface diffusion. Before and after annealing, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) measurements were employed to obtain the elemental profiles of the implanted samples. Our results suggestmore » little migration of buried Ag in the bulk, and an out-diffusion of the implanted Ag in the near-surface region of single crystal SiC. It is also found that a SiO 2 layer, which was formed during annealing, may serve as an effective barrier to reduce or prevent Ag out diffusion through the SiC coating layer.« less

Ag Out-surface Diffusion In Crystalline SiC With An Effective SiO2 Diffusion Barrier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, H.; Xiao, Haiyan Y.; Zhu, Zihua

2015-09-01

For applications of tristructural isotropic (TRISO) fuel particles in high temperature reactors, release of radioactive Ag isotope (110mAg) through the SiC coating layer is a safety concern. To understand the diffusion mechanism, Ag ion implantations near the surface and in the bulk were performed by utilizing different ion energies and energy-degrader foils. High temperature annealing was carried out on the as-irradiated samples to study the possible out-surface diffusion. Before and after annealing, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) measurements were employed to obtain the elemental profiles of the implanted samples. The results suggest little migration ofmore » buried Ag in the bulk, and an out-diffusion of the implanted Ag in the near-surface region of single crystal SiC. It is also found that a SiO2 layer, which was formed during annealing, may serve as an effective barrier to reduce or prevent Ag out diffusion through the SiC coating layer.« less

Gas diffusion layers coated with a microporous layer containing hydrophilic carbon nanotubes for performance enhancement of polymer electrolyte fuel cells under both low and high humidity conditions

NASA Astrophysics Data System (ADS)

Kitahara, Tatsumi; Nakajima, Hironori; Okamura, Kosuke

2015-06-01

Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) composed of carbon black and polytetrafluoroethylene (PTFE) have been commonly used to improve the water management characteristics of polymer electrolyte fuel cells (PEFCs). However, the hydrophobic MPL coated GDL designed to prevent dehydration of the membrane under low humidity conditions is generally inferior at reducing flooding under high humidity conditions. It is therefore important to develop a robust MPL coated GDL that can enhance the PEFC performance regardless of the humidity conditions. In the present study, a GDL coated with an MPL containing hydrophilic carbon nanotubes (CNTs) was developed. The less hydrophobic pores incorporating CNTs are effective at conserving the membrane humidity under low humidity conditions. The MPL with CNTs is also effective at expelling excess water from the catalyst layer while maintaining oxygen flow pathways from the GDL substrate, allowing the mean flow pore diameter to be decreased to 2 μm without reducing the ability of the MPL to prevent flooding under high humidity conditions. An MPL coated GDL with a CNT content of 4 mass% exhibits significantly higher performance under both low and high humidity conditions than a hydrophobic MPL coated GDL.

Characterization of Microstructure and Thermal Properties of YSZ Coatings Obtained by Axial Suspension Plasma Spraying (ASPS)

NASA Astrophysics Data System (ADS)

Ganvir, Ashish; Curry, Nicholas; Björklund, Stefan; Markocsan, Nicolaie; Nylén, Per

2015-10-01

The paper aims at demonstrating various microstructures which can be obtained using the suspension spraying technique and their respective significance in enhancing the thermal insulation property of a thermal barrier coating. Three different types of coating microstructures are discussed which were produced by the Axial Suspension Plasma Spraying. Detailed characterization of coatings was then performed. Optical and scanning electron microscopy were utilized for microstructure evaluations; x-ray diffraction for phase analysis; water impregnation, image analysis, and mercury intrusion porosimetry for porosity analysis, and laser flash analysis for thermal diffusivity measurements were used. The results showed that Axial Suspension Plasma Spraying can generate vertically cracked, porous, and feathery columnar-type microstructures. Pore size distribution was found in micron, submicron, and nanometer range. Higher overall porosity, the lower density of vertical cracks or inter-column spacing, and higher inter-pass porosity favored thermal insulation property of the coating. Significant increase in thermal diffusivity and conductivity was found at higher temperature, which is believed to be due to the pore rearrangement (sintering and pore coarsening). Thermal conductivity values for these coatings were also compared with electron beam physical vapor deposition (EBPVD) thermal barrier coatings from the literature and found to be much lower.

Microstructure characteristics of Ni/WC composite cladding coatings

NASA Astrophysics Data System (ADS)

Yang, Gui-rong; Huang, Chao-peng; Song, Wen-ming; Li, Jian; Lu, Jin-jun; Ma, Ying; Hao, Yuan

2016-02-01

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr7C3/Cr23C6, CrB, and Ni+Ni3Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.

Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.

1997-04-01

A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductilitymore » and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.« less

Evaluation of Antibacterial Effects of Silver-Coated Stainless Steel Orthodontic Brackets.

PubMed

Arash, Valiollah; Keikhaee, Fatemeh; Rabiee, Sayed Mahmood; Rajabnia, Ramazan; Khafri, Soraya; Tavanafar, Saeid

2016-01-01

White spots and enamel demineralization around orthodontic brackets are among the most important complications resulting from orthodontic treatments. Since the antibacterial properties of metals and metallic particles have been well documented, the aim of this study was to assess the antibacterial effect of stainless steel orthodontic brackets coated with silver (Ag) particles. In this study, 40 standard metal brackets were divided into two groups of 20 cases and 20 controls. The brackets in the case group were coated with Ag particles using an electroplating method. Atomic force microscopy and scanning electron microscopy were used to assess the adequacy of the coating process. In addition, antibacterial tests, i.e., disk diffusion and direct contact tests were performed at three, six, 24, and 48 hours, and 15 and 30 days using a Streptococcus mutans strain. The results were analyzed using Student's t-test and repeated measures ANOVA. Analyses via SEM and AFM confirmed that excellent coatings were obtained by using an electroplating method. The groups exhibited similar behavior when subjected to the disk diffusion test in the agar medium. However, the bacterial counts of the Ag-coated brackets were, in general, significantly lower (P<0.001) than those of their non-coated counterparts. Brackets coated with Ag, via an electroplating method, exhibited antibacterial properties when placed in direct contact with Streptococcus mutans. This antibacterial effect persisted for 30 days after contact with the bacteria.

Diffusivities of Ag, Cs, Sr, and Kr in TRISO fuel particles and graphite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collin, Blaise Paul

Tri-structural isotropic (TRISO) coated particles have been developed and studied since the late 1950s when the concept of coated particles was invented by Roy Huddle of the United Kingdom Atomic Energy Authority. Several decades of work by half a dozen countries on fission product transport in TRISO fuel through numerous irradiation and heating experiments have led to several recommendations of transport data and to the adoption of various sets of diffusion coefficients. In 1997, the International Atomic Energy Agency (IAEA) gathered all these historical results and issued a technical document (TECDOC-978 [IAEA]) that summarizes these sets of recommended diffusion coefficients.more » Table 1 shows the reference literature articles for the diffusivities that have historically been recommended by the American and German TRISO fuel development programs and that are summarized in the IAEA report (see section 7 for full references of these articles).« less

Kinetic Monte Carlo Simulations of Oxygen Diffusion in Environmental Barrier Coating Materials

NASA Technical Reports Server (NTRS)

Good, Brian S.

2017-01-01

Ceramic Matrix Composite (CMC) materials are of interest for use in next-generation turbine engine components, offering a number of significant advantages, including reduced weight and high operating temperatures. However, in the hot environment in which such components operate, the presence of water vapor can lead to corrosion and recession, limiting the useful life of the components. Such degradation can be reduced through the use of Environmental Barrier Coatings (EBCs) that limit the amount of oxygen and water vapor reaching the component. Candidate EBC materials include Yttrium and Ytterbium silicates. In this work we present results of kinetic Monte Carlo (kMC) simulations of oxygen diffusion, via the vacancy mechanism, in Yttrium and Ytterbium disilicates, along with a brief discussion of interstitial diffusion.

Thickness limitations in carbon nanotube reinforced silicon nitride coatings synthesized by vapor infiltration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eres, Gyula

Chemical vapor infiltration is a convenient method for synthesizing carbon nanotube (CNT)-reinforced ceramic coatings. The thickness over which infiltration is relatively uniform is limited by gas phase diffusion in the pore structure. These effects were investigated in two types of silicon nitride matrix composites. With CNTs that were distributed uniformly on the substrate surface dense coatings were limited to thicknesses of several microns. With dual structured CNT arrays produced by photolithography coatings up to 400 gm thick were obtained with minimal residual porosity. Gas transport into these dual structured materials was facilitated by creating micron sized channels between "CNT pillars"more » (i.e. each pillar consisted of a large number of individual CNTs). The experimental results are consistent with basic comparisons between the rates of gas diffusion and silicon nitride growth in porous structures. This analysis also provides a general insight into optimizing infiltration conditions during the fabrication of thick CNT-reinforced composite coatings. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent.

PubMed

Ye, ShuJun; Song, MingHui; Kumakura, Hiroaki

2015-01-30

A 3 nm coronene coating and a 4 nm amorphous carbon coating with a uniform shell-core encapsulation structure for nanosized boron (B) powders are formed by a simple process in which coronene is directly mixed with boron particles without a solvent and heated at 520 °C for 1 h or at 630 °C for 3 h in a vacuum-sealed silica tube. Coronene has a melting point lower than its decomposition temperature, which enables liquid coronene to cover B particles by liquid diffusion and penetration without the need for a solvent. The diffusion and penetration of coronene can extend to the boundaries of particles and to inside the agglomerated nanoparticles to form a complete shell-core encapsulated structure. As the temperature is increased, thermal decomposition of coronene on the B particles results in the formation of a uniform amorphous carbon coating layer. This novel and simple nanometer-level uniform amorphous carbon coating method can possibly be applied to many other powders; thus, it has potential applications in many fields at low cost.

Interdiffusion behaviors in doped molybdenum uranium and aluminum or aluminum silicon dispersion fuels: Effects of the microstructure

NASA Astrophysics Data System (ADS)

Allenou, J.; Tougait, O.; Pasturel, M.; Iltis, X.; Charollais, F.; Anselmet, M. C.; Lemoine, P.

2011-09-01

Si addition to Al is considered as a promising route to reduce (U,Mo)-Al interaction kinetics, due to its accumulation in the interaction layer, yielding the formation of silicide phases. The (U,Mo) alloy microstructure, and especially its homogenization state, could play a role on this accumulation process. The addition of a third element in γ(U,Mo) could also influence diffusion mechanisms of Al and Si. These two parameters were studied by means of diffusion couple experiments by joining γU based alloys with Al and (Al,Si) alloy. Chemical elements X added into γ(U,Mo) were thoroughly chosen on the following criteria: (i) the potential solubility of the alloying element into the γ(U,Mo) matrix, (ii) its capability to form the ternary aluminides based on the CeCr 2Al 20 and Ho 6Mo 4Al 43 - types, and (iii) the feasibility to control the microstructure of the alloys. On this basis, a test matrix is defined. It concerns γ(U80,Mo15,X5) alloys (in at.%) with X = Y, Cu, Zr, Ti or Cr. These alloys were homogenized and coupled with Al or (Al,Si) alloy. Results evidenced, first, the importance of the state of homogenization of the γ(U,Mo) binary alloy on interaction processes with (Al,Si) alloy, and the benefit on the diffusion of Si through the interaction layer, as observed on the elementary concentration profiles, when the third element X has some solubility into γ(U,Mo) alloy.

Silk Fibroin as Edible Coating for Perishable Food Preservation

NASA Astrophysics Data System (ADS)

Marelli, B.; Brenckle, M. A.; Kaplan, D. L.; Omenetto, F. G.

2016-05-01

The regeneration of structural biopolymers into micelles or nanoparticles suspended in water has enabled the design of new materials with unique and compelling properties that can serve at the interface between the biotic and the abiotic worlds. In this study, we leveraged silk fibroin quintessential properties (i.e. polymorphism, conformability and hydrophobicity) to design a water-based protein suspension that self-assembles on the surface of food upon dip coating. The water-based post-processing control of the protein polymorphism enables the modulation of the diffusion of gases through the silk fibroin thin membranes (e.g. O2 and CO2 diffusion, water vapour permeability), which is a key parameter to manage food freshness. In particular, an increased beta-sheet content corresponds to a reduction in oxygen diffusion through silk fibroin thin films. By using the dip coating of strawberries and bananas as proof of principle, we have shown that the formation of micrometre-thin silk fibroin membranes around the fruits helps the management of postharvest physiology of the fruits. Thus, silk fibroin coatings enhance fruits’ shelf life at room conditions by reducing cell respiration rate and water evaporation. The water-based processing and edible nature of silk fibroin makes this approach a promising alternative for food preservation with a naturally derived material.

Silk Fibroin as Edible Coating for Perishable Food Preservation

PubMed Central

Marelli, B.; Brenckle, M. A.; Kaplan, D. L.; Omenetto, F. G.

2016-01-01

The regeneration of structural biopolymers into micelles or nanoparticles suspended in water has enabled the design of new materials with unique and compelling properties that can serve at the interface between the biotic and the abiotic worlds. In this study, we leveraged silk fibroin quintessential properties (i.e. polymorphism, conformability and hydrophobicity) to design a water-based protein suspension that self-assembles on the surface of food upon dip coating. The water-based post-processing control of the protein polymorphism enables the modulation of the diffusion of gases through the silk fibroin thin membranes (e.g. O2 and CO2 diffusion, water vapour permeability), which is a key parameter to manage food freshness. In particular, an increased beta-sheet content corresponds to a reduction in oxygen diffusion through silk fibroin thin films. By using the dip coating of strawberries and bananas as proof of principle, we have shown that the formation of micrometre-thin silk fibroin membranes around the fruits helps the management of postharvest physiology of the fruits. Thus, silk fibroin coatings enhance fruits’ shelf life at room conditions by reducing cell respiration rate and water evaporation. The water-based processing and edible nature of silk fibroin makes this approach a promising alternative for food preservation with a naturally derived material. PMID:27151492

A combination of interdisciplinary analytical tools for evaluation of multi-layered coatings on medical grade stainless steel for biomedical applications.

PubMed

Maver, Uroš; Xhanari, Klodian; Žižek, Marko; Korte, Dorota; Gradišnik, Lidija; Franko, Mladen; Finšgar, Matjaž

2018-05-03

In this comprehensive study several analytical techniques were used in order to evaluate multi--layered biomedical surface coatings composed of a drug (diclofenac) and a polymer (chitosan). Such a thorough examination is of paramount importance in order to assure safety and prove efficiency of potential biomedical materials already at the in vitro level, hence leading to their potentially faster introduction to clinical trials. For the first time a novel technique based on thermal diffusivity and conductivity measurement (photothermal beam deflection spectroscopy - BDS) was employed in order to analyse in a non-destructive way the thickness of respective layers, together with their thermal diffusivity and conductivity. In addition to attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), BDS confirmed successive surface layers of the prepared coatings. Scanning electron microscopy and atomic force microscopy were used to examine structural information on the macro- and micro/nano-scale, respectively. Surface hydrophilicity was measured with the contact angle analysis, which clearly showed differences in hydrophilicity between coated and non-coated samples. Considering the targeted application of the prepared coatings (as implant in orthopaedic treatments), the in vitro drug release was analysed spectrophotometrically to examine the coatings potential for a controlled drug release. Furthermore, the material was also tested by electrochemical impedance spectroscopy and cyclic polarisation techniques, which were able to detect even minor differences between the performance of the coated and non-coated materials. As the final test, the biocompatibility of the coatings with human osteoblasts was determined. Copyright © 2018. Published by Elsevier B.V.

An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

NASA Technical Reports Server (NTRS)

Shanabarger, Mickey R.

1993-01-01

The goal of this program was to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. Although hydrogen degradation of metallic materials is believed to result from dissolved protonic hydrogen, the heterogeneous hydrogen interface transport processes often dominate the kinetics of degradation. The initial step in the interface transport process is the dissociative chemisorption of the molecular species at the metal surface followed by hydrogen absorption into and transport through the bulk. The interaction of hydrogen with the surfaces of alpha-2(Ti3Al) titanium aluminide, gamma(TiAl) titanium aluminide, and beryllium were studied.

Two phase titanium aluminide alloy

DOEpatents

Deevi, Seetharama C.; Liu, C. T.

2001-01-01

A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, Claudette G.; Liu, Chain T.

1990-01-01

An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, C.G.; Liu, C.T.

1990-10-09

An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.

COATING URANIUM FROM CARBONYLS

DOEpatents

Gurinsky, D.H.; Storrs, S.S.

1959-07-14

Methods are described for making adherent corrosion resistant coatings on uranium metal. According to the invention, the uranium metal is heated in the presence of an organometallic compound such as the carbonyls of nickel, molybdenum, chromium, niobium, and tungsten at a temperature sufficient to decompose the metal carbonyl and dry plate the resultant free metal on the surface of the uranium metal body. The metal coated body is then further heated at a higher temperature to thermally diffuse the coating metal within the uranium bcdy.

Sealed glass coating of high temperature ceramic superconductors

DOEpatents

Wu, W.; Chu, C.Y.; Goretta, K.C.; Routbort, J.L.

1995-05-02

A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor is disclosed. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor. 8 figs.

Sealed glass coating of high temperature ceramic superconductors

DOEpatents

Wu, Weite; Chu, Cha Y.; Goretta, Kenneth C.; Routbort, Jules L.

1995-01-01

A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor.

Method of forming metallic coatings on polymeric substrates

DOEpatents

Liepins, Raimond

1984-01-01

Very smooth polymeric coatings or films graded in atomic number and density an readily be formed by first preparing the coating or film from the desired monomeric material and then contacting it with a fluid containing a metal or a mixture of metals for a time sufficient for such metal or metals to sorb and diffuse into the coating or film. Metal resinate solutions are particularly advantageous for this purpose. A metallic coating can in turn be produced on the metal-loaded film or coating by exposing it to a low pressure plasma of air, oxygen, or nitrous oxide. The process permits a metallic coating to be formed on a heat sensitive substrate without the use of elevated temperatures.

Method of forming graded polymeric coatings or films

DOEpatents

Liepins, Raimond

1983-01-01

Very smooth polymeric coatings or films graded in atomic number and density can readily be formed by first preparing the coating or film from the desired monomeric material and then contacting it with a fluid containing a metal or a mixture of metals for a time sufficient for such metal or metals to sorb and diffuse into the coating or film. Metal resinate solutions are particularly advantageous for this purpose. A metallic coating can in turn be produced on the metal-loaded film or coating by exposing it to a low pressure plasma of air, oxygen, or nitrous oxide. The process permits a metallic coating to be formed on a heat sensitive substrate without the use of elevated temperatures.

Effect of Zinc Phosphate on the Corrosion Behavior of Waterborne Acrylic Coating/Metal Interface

PubMed Central

Wan, Hongxia; Song, Dongdong; Li, Xiaogang; Zhang, Dawei; Gao, Jin; Du, Cuiwei

2017-01-01

Waterborne coating has recently been paid much attention. However, it cannot be used widely due to its performance limitations. Under the specified conditions of the selected resin, selecting the function pigment is key to improving the anticorrosive properties of the coating. Zinc phosphate is an environmentally protective and efficient anticorrosion pigment. In this work, zinc phosphate was used in modifying waterborne acrylic coatings. Moreover, the disbonding resistance of the coating was studied. Results showed that adding zinc phosphate can effectively inhibit the anode process of metal corrosion and enhance the wet adhesion of the coating, and consequently prevent the horizontal diffusion of the corrosive medium into the coating/metal interface and slow down the disbonding of the coating. PMID:28773013

Effectiveness of Diffusion Barrier Coatings for Mo-Re Embedded in C/SiC and C/C

NASA Technical Reports Server (NTRS)

Glass, David E.; Shenoy, Ravi N.; Wang, Zeng-Mei; Halbig, Michael C.

2001-01-01

Advanced high-temperature cooling applications may often require the elevated-temperature capability of carbon/silicon carbide or carbon/carbon composites in combination with the hermetic capability of metallic tubes. In this paper, the effects of C/SiC and C/C on tubes fabricated from several different refractory metals were evaluated. Though Mo, Nb, and Re were evaluated in the present study, the primary effort was directed toward two alloys of Mo-Re, namely, arc cast Mo-41Re and powder metallurgy Mo-47.5Re. Samples of these refractory metals were subjected to either the PyC/SiC deposition or embedding in C/C. MoSi2(Ge), R512E, and TiB2 coatings were included on several of the samples as potential diffusion barriers. The effects of the processing and thermal exposure on the samples were evaluated by conducting burst tests, microhardness surveys, and scanning electron microscopic examination (using either secondary electron or back scattered electron imaging and energy dispersive spectroscopy). The results showed that a layer of brittle Mo-carbide formed on the substrates of both the uncoated Mo-41Re and the uncoated Mo-47.5Re, subsequent to the C/C or the PyC/SiC processing. Both the R512E and the MoSi2(Ge) coatings were effective in preventing not only the diffusion of C into the Mo-Re substrate, but also the formation of the Mo-carbides. However, none of the coatings were effective at preventing both C and Si diffusion without some degradation of the substrate.

Evaluation of oxide-coated iridium-rhenium chambers

NASA Astrophysics Data System (ADS)

Reed, Brian D.

1994-03-01

Iridium-coated rhenium (Ir-Re) provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase Ir-Re rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated Ir-Re, 22-N rocket chambers were tested with gaseous hydrogen/gaseous oxygen (GHz/G02) propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia (HfO2) or zirconia (ZrO2). Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of ZrO2 infiltrated with sol gel HfO2. The other chamber had a coating composed of an Ir-oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. Testing the Ir-oxide composite-coated chamber included over 29 min at mixture ratio 16. The thicker walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner walled coatings did not experience the macrocracking and chipping of the chambers that was seen with the thick, monolithic coatings. However, burn-throughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stoichiometric. The burn-throughs were probably the result of oxygen diffusion through the oxide coating that allowed the underlying Ir and Re layers to be oxidized. The results of this test program indicated that the thin-walled oxide coatings are better suited for repeated thermal cycling than the thick-walled coating, while thicker coatings may be required for operation in aggressively oxidizing environments.

Evaluation of oxide-coated iridium-rhenium chambers

NASA Technical Reports Server (NTRS)

Reed, Brian D.

1994-01-01

Iridium-coated rhenium (Ir-Re) provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase Ir-Re rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated Ir-Re, 22-N rocket chambers were tested with gaseous hydrogen/gaseous oxygen (GHz/G02) propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia (HfO2) or zirconia (ZrO2). Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of ZrO2 infiltrated with sol gel HfO2. The other chamber had a coating composed of an Ir-oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. Testing the Ir-oxide composite-coated chamber included over 29 min at mixture ratio 16. The thicker walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner walled coatings did not experience the macrocracking and chipping of the chambers that was seen with the thick, monolithic coatings. However, burn-throughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stoichiometric. The burn-throughs were probably the result of oxygen diffusion through the oxide coating that allowed the underlying Ir and Re layers to be oxidized. The results of this test program indicated that the thin-walled oxide coatings are better suited for repeated thermal cycling than the thick-walled coating, while thicker coatings may be required for operation in aggressively oxidizing environments.

Testing and evaluation of oxide-coated iridium/rhenium chambers

NASA Technical Reports Server (NTRS)

Reed, Brian D.

1993-01-01

Iridium-coated rhenium provides long life operation of radiation-cooled rockets at temperatures up to 2200 C. Ceramic oxide coatings could be used to increase iridium/rhenium rocket lifetimes and allow operation in highly oxidizing environments. Ceramic oxide coatings promise to serve as both thermal and diffusion barriers for the iridium layer. Seven ceramic oxide-coated iridium/rhenium, 22 N rocket chambers were tested on gaseous hydrogen/gaseous oxygen propellants. Five chambers had thick (over 10 mils), monolithic coatings of either hafnia or zirconia. Two chambers had coatings with thicknesses less than 5 mils. One of these chambers had a thin-walled coating of zirconia infiltrated with sol gel hafnia. The other chamber had a coating composed of an iridium/oxide composite. The purpose of this test program was to assess the ability of the oxide coatings to withstand the thermal shock of combustion initiation, adhere under repeated thermal cycling, and operate in aggressively oxidizing environments. All of the coatings survived the thermal shock of combustion and demonstrated operation at mixture ratios up to 11. The iridium/oxide composite coated chamber included testing for over 29 minutes at mixture ratio 16. The thicker-walled coatings provided the larger temperature drops across the oxide layer (up to 570 C), but were susceptible to macrocracking and eventual chipping at a stress concentrator. The cracks apparently resealed during firing, under compression of the oxide layer. The thinner-walled coatings did not experience the macrocracking and chipping of the chambers seen with the thick, monolithic coatings. However, burnthroughs in the throat region did occur in both of the thin-walled chambers at mixture ratios well above stochiometric. The burn-throughs were probably the result of oxygen-diffusion through the oxide coating that allowed the underlying iridium and rhenium layers to be oxidized. The results of this test program indicated that the thin-walled oxide coatings are better suited for repeated thermal cycling than the thick-walled coating, while thicker coatings may be required for operation in aggressively oxidizing environments.

Grain-boundary type and distribution in silicon carbide coatings and wafers

NASA Astrophysics Data System (ADS)

Cancino-Trejo, Felix; López-Honorato, Eddie; Walker, Ross C.; Ferrer, Romelia Salomon

2018-03-01

Silicon carbide is the main diffusion barrier against metallic fission products in TRISO (tristructural isotropic) coated fuel particles. The explanation of the accelerated diffusion of silver through SiC has remained a challenge for more than four decades. Although, it is now well accepted that silver diffuse through SiC by grain boundary diffusion, little is known about the characteristics of the grain boundaries in SiC and how these change depending on the type of sample. In this work five different types (coatings and wafers) of SiC produced by chemical vapor deposition were characterized by electron backscatter diffraction (EBSD). The SiC in TRISO particles had a higher concentration of high angle grain boundaries (aprox. 70%) compared to SiC wafers, which ranged between 30 and 60%. Similarly, SiC wafers had a higher concentration of low angle grain boundaries ranging between 15 and 30%, whereas TRISO particles only reached values of around 7%. The same trend remained when comparing the content of coincidence site lattice (CSL) boundaries, since SiC wafers showed a concentration of more than 30%, whilst TRISO particles had contents of around 20%. In all samples the largest fractions of CSL boundaries (3 ≤ Σ ≤ 17) were the Σ3 boundaries. We show that there are important differences between the SiC in TRISO particles and SiC wafers which could explain some of the differences observed in diffusion experiments in the literature.

The Lattice and Thermal Radiation Conductivity of Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Spuckler, Charles M.

2008-01-01

The lattice and radiation conductivity of thermal barrier coatings was evaluated using a laser heat flux approach. A diffusion model has been established to correlate the apparent thermal conductivity of the coating to the lattice and radiation conductivity. The radiation conductivity component can be expressed as a function of temperature and the scattering and absorption properties of the coating material. High temperature scattering and absorption of the coating systems can also be derived based on the testing results using the modeling approach. The model prediction is found to have good agreement with experimental observations.

The effect of intestinal bacteria adherence on drug diffusion through solid films under stationary conditions.

PubMed

Rubinstein, A; Radai, R; Friedman, M; Fischer, P; Rokem, J S

1997-04-01

To study the in vitro and in vivo the role of surface bacterial adhesion on the diffusion of model drugs at stationary conditions. Salicylic acid (SA) diffusion through ethyl cellulose (EC) films was measured in vitro in side-by-side diffusion cells with and without E. coli of intestinal origin. Insulin (I) release from paper strips coated or uncoated with pectin films, with or without antibiotic treatment, was measured in vivo in conscious rats after cecal implantation by comparing blood glucose levels at Tmax of the pharmacodynamic effect. During five hours of diffusion studies which were performed immediately following incubation of EC films with bacteria, the diffusion rate of SA throughout the films was 2.72-fold lower in the presence of bacteria compared with the diffusion rate in the control studies conducted without bacteria. The mean blood glucose levels dropped in the rat to 40.6 +/- 21.6% of glucose basal levels within 2.4 +/- 1.4 h when uncoated I solid carriers were used. Glucose levels did not change for pectin-coated dosage forms. After antibiotic treatment which prevented the formation of bacterial biofilm on the surface of the I solid dosage forms, blood glucose levels dropped to 22.0 +/- 4.7% and 50.9 +/- 20.5% of glucose basal levels within 7.4 +/- 2.6 h and 1.8 +/- 0.9 h for pectin uncoated or coated dosage forms, respectively. Maximum bacterial adherence occurred at stationary conditions (RPM = 0), while at maximum agitation (200 RPM), almost no adherence occurred. (a) Bacterial adherence shows down the diffusion rate of SA through EC films; (b) Under stationary conditions bacterial adherence may also interfere with drug release from biodegradable (pectin) films; (c) Successful functioning of biodegradable colon-specific delivery systems depends on agitation and surface friction in the lumen of the colon.

Fate of Zinc Oxide Nanoparticles Coated onto Macronutrient Fertilizers in an Alkaline Calcareous Soil

PubMed Central

Milani, Narges; Hettiarachchi, Ganga M.; Kirby, Jason K.; Beak, Douglas G.; Stacey, Samuel P.; McLaughlin, Mike J.

2015-01-01

Zinc oxide (ZnO) nanoparticles may provide a more soluble and plant available source of Zn in Zn fertilizers due to their greater reactivity compared to equivalent micron- or millimetre-sized (bulk) particles. However, the effect of soil on solubility, spatial distribution and speciation of ZnO nanoparticles has not yet been investigated. In this study, we examined the diffusion and solid phase speciation of Zn in an alkaline calcareous soil following application of nanoparticulate and bulk ZnO coated fertilizer products (monoammonium phosphate (MAP) and urea) using laboratory-based x-ray techniques and synchrotron-based μ-x-ray fluorescence (μ–XRF) mapping and absorption fine structure spectroscopy (μ–XAFS). Mapping of the soil-fertilizer reaction zones revealed that most of the applied Zn for all treatments remained on the coated fertilizer granule or close to the point of application after five weeks of incubation in soil. Zinc precipitated mainly as scholzite (CaZn2(PO4)2.2H2O) and zinc ammonium phosphate (Zn(NH4)PO4) species at the surface of MAP granules. These reactions reduced dissolution and diffusion of Zn from the MAP granules. Although Zn remained as zincite (ZnO) at the surface of urea granules, limited diffusion of Zn from ZnO-coated urea granules was also observed for both bulk and nanoparticulate ZnO treatments. This might be due to either the high pH of urea granules, which reduced solubility of Zn, or aggregation (due to high ionic strength) of released ZnO nanoparticles around the granule/point of application. The relative proportion of Zn(OH)2 and ZnCO3 species increased for all Zn treatments with increasing distance from coated MAP and urea granules in the calcareous soil. When coated on macronutrient fertilizers, Zn from ZnO nanoparticles (without surface modifiers) was not more mobile or diffusible compared to bulk forms of ZnO. The results also suggest that risk associated with the presence of ZnO NPs in calcareous soils would be the same as bulk sources of ZnO. PMID:25965385

Use of the quartz crystal microbalance to determine the monomeric friction coefficient of polyimides

NASA Technical Reports Server (NTRS)

Bechtold, Mary M.

1995-01-01

When a thin film of polymer is coated on to a quartz crystal microbalance (QCM), the QCM can be used to detect the rate of increase in weight of the polymer film as the volatile penetrant diffuses into the polymer. From this rate information the diffusion coefficient of the penetrant into the polymer can be computed. Calculations requiring this diffusion coefficient lead to values which approximate the monomeric friction coefficient of the polymer. This project has been concerned with the trial of crystal oscillating circuits suitable for driving polymer coated crystals in an atmosphere of penetrant. For these studies done at room temperature, natural rubber was used as an easily applied polymer that is readily penetrated by toluene vapors, qualities anticipated with polyimides when they are tested at T(g) in the presence of toluene. Three quartz crystal oscillator circuits were tested. The simplest circuit used +/- 5 volt dc and had a transistor to transistor logic (TTL) inverter chip that provides a 180 deg phase shift via a feed back loop. This oscillator circuit was stable but would not drive the crystal when the crystal was coated with polymer and subjected to toluene vapors. Removal of a variable resistor from this circuit increased stability but did not otherwise increase performance. Another driver circuit tested contained a two stage differential input, differential output, wide band video amplifier and also contain a feed back loop. The circuit voltage could not be varied and operated at +/- 5 volts dc; this circuit was also stable but failed to oscillate the polymer coated crystal in an atmosphere saturated with toluene vapors. The third oscillator circuit was of similar construction and relied on the same video amplifier but allowed operation with variable voltage. This circuit would drive the crystal when the crystal was submerged in liquid toluene and when the crystal was coated with polymer and immersed in toluene vapors. The frequency readings obtained when using this oscillating circuit are highly variable. This circuit requires further modification to stabilize frequency readings before its use in studies to determine the diffusion coefficient of penetrant molecules into a polymer film coated on a QCM.

Oxidation study of coated Crofer 22 APU steel in dry oxygen

NASA Astrophysics Data System (ADS)

Molin, Sebastian; Chen, Ming; Hendriksen, Peter Vang

2014-04-01

The effect of a dual layer coating composed of a layer of a Co3O4 and a layer of a La0.85Sr0.15MnO3/Co3O4 mixture on the high temperature corrosion of the Crofer 22 APU alloy is reported. Oxidation experiments were performed in dry oxygen at three temperatures: 800 °C, 850 °C and 900 °C for periods up to 1000 h. Additionally at 850 °C a 5000 h long oxidation test was performed to evaluate longer term suitability of the proposed coating. Corrosion kinetics were evaluated by measuring mass gain during oxidation. The corrosion kinetics for the coated samples are analyzed in terms of a parabolic rate law. Microstructural features were investigated by scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffractometry. The coating is effective in reducing the corrosion rate and in ensuring long lifetime of coated alloys. The calculated activation energy for the corrosion process is around 1.8 eV. A complex Co-Mn-Cr spinel is formed caused by diffusion of Cr and Mn from the alloy into the Co3O4 coating and by additional diffusion of Mn from the LSM layer. Adding a layer of LSM/Co3O4, acting as an additional Mn source, on top of the cobalt spinel is beneficial for the improved corrosion resistance.

Evaluation of Antibacterial Effects of Silver-Coated Stainless Steel Orthodontic Brackets

PubMed Central

Arash, Valiollah; Keikhaee, Fatemeh; Rajabnia, Ramazan; Khafri, Soraya; Tavanafar, Saeid

2016-01-01

Objectives: White spots and enamel demineralization around orthodontic brackets are among the most important complications resulting from orthodontic treatments. Since the antibacterial properties of metals and metallic particles have been well documented, the aim of this study was to assess the antibacterial effect of stainless steel orthodontic brackets coated with silver (Ag) particles. Materials and Methods: In this study, 40 standard metal brackets were divided into two groups of 20 cases and 20 controls. The brackets in the case group were coated with Ag particles using an electroplating method. Atomic force microscopy and scanning electron microscopy were used to assess the adequacy of the coating process. In addition, antibacterial tests, i.e., disk diffusion and direct contact tests were performed at three, six, 24, and 48 hours, and 15 and 30 days using a Streptococcus mutans strain. The results were analyzed using Student’s t-test and repeated measures ANOVA. Results: Analyses via SEM and AFM confirmed that excellent coatings were obtained by using an electroplating method. The groups exhibited similar behavior when subjected to the disk diffusion test in the agar medium. However, the bacterial counts of the Ag-coated brackets were, in general, significantly lower (P<0.001) than those of their non-coated counterparts. Conclusions: Brackets coated with Ag, via an electroplating method, exhibited antibacterial properties when placed in direct contact with Streptococcus mutans. This antibacterial effect persisted for 30 days after contact with the bacteria. PMID:27536328

Sealing nuclear graphite with pyrolytic carbon

NASA Astrophysics Data System (ADS)

Feng, Shanglei; Xu, Li; Li, Li; Bai, Shuo; Yang, Xinmei; Zhou, Xingtai

2013-10-01

Pyrolytic carbon (PyC) coatings were deposited on IG-110 nuclear graphite by thermal decomposition of methane at ∼1830 °C. The PyC coatings are anisotropic and airtight enough to protect IG-110 nuclear graphite against the permeation of molten fluoride salts and the diffusion of gases. The investigations indicate that the sealing nuclear graphite with PyC coating is a promising method for its application in Molten Salt Reactor (MSR).

Influence of surface coating on the intracellular behaviour of gold nanoparticles: a fluorescence correlation spectroscopy study.

PubMed

Silvestri, A; Di Silvio, D; Llarena, I; Murray, R A; Marelli, M; Lay, L; Polito, L; Moya, S E

2017-10-05

In the biomedical applications of nanoparticles (NPs), the proper choice of surface chemistry is a crucial aspect in their design. The nature of the coating can heavily impact the interaction of NPs with biomolecules, affect the state of aggregation, and ultimately determine their biological fate. As such, protein corona formation and the aggregation behaviour of gold NPs (Au NPs) are studied here. Au NPs are prepared with four distinct surface functionalisations, namely mercaptosuccinic acid (MSA), N-4-thiobutyroil glucosamine, HS-PEG 5000 and HS-alkyl-PEG 600 . Corona formation, aggregation, and the intracellular behaviour of the Au NPs are then investigated by means of Fluorescence Correlation Spectroscopy (FCS) in cell culture media and in live cells. To evaluate the state of aggregation and the formation of a protein corona, the Au NPs are incubated in cell media and the diffusion coefficient is determined via FCS. The in vitro behaviour is compared with the level of aggregation of the NPs in cells. Diffusion times of the NPs are estimated at different positions in the cell after a one hour incubation period. It is found that the majority of MSA and glucose-Au NPs are present inside the cell as slowly diffusing species with diffusion times (τ D ) greater than 6000 μs (hydrodynamic diameter >250 nm). PEGylated Au NPs adsorb a small amount of protein and manifest low agglomeration both in media and in living cells. In particular, the HS-alkyl-PEG 600 coating shows an excellent correlation between lower protein adsorption, 4-fold lower compared to the MSA coated NPs, and limited intracellular aggregation. In the case of single HS-alkyl-PEG 600 coated NPs, it is found that typical intracellular τ D values range from 500 to 1500 μs, indicating that these particles display reduced aggregation in the intracellular environment.

Impact of surface coating and environmental conditions on the fate and transport of silver nanoparticles in the aquatic environment.

PubMed

Ellis, Laura-Jayne A; Valsami-Jones, Eugenia; Lead, Jamie R; Baalousha, Mohammed

2016-10-15

The role of surface coating (polyvinylpyrrolidone (PVP) and citrate) and water chemistry on the fate and behavior of AgNPs in aquatic microcosms is reported in this study. The migration and transformation of the AgNPs was examined in low (ultrapure water-UPW) and high ionic strength (moderately hard water - MHW) preparations, and in the presence of modeled natural organic matter (NOM) of Suwannee River Fulvic Acid (SRFA). The migration and fate of the AgNPs in the microcosms was validated using a sedimentation-diffusion model and the aggregation behavior was monitored by UV-visible spectrometry (UV-vis). Dissolved and particulate Ag concentrations (% Ag) were analyzed by ultrafiltration methods. Imaging of the AgNPs was captured using transmission electron microscopy (TEM). Results indicate that PVP-coated AgNPs (PVP-AgNPs) remained stable for 28days with similarly distributed concentrations of the PVP-AgNPs throughout the columns in each of the water conditions after approximately 96h (4days). The sedimentation-diffusion model confirmed PVP-AgNP stability in each condition, by showing diffusion dominated transport by using the original unaltered AgNP sizes to fit the parameters. In comparison, citrate AgNPs were largely unstable in the more complex water preparations (MHW). In MHW, aggregation dominated behavior followed by sedimentation/dissolution controlled transport was observed. The addition of SRFA to MHW resulted in small stabilizing effects, to the citrate coated AgNPs, producing smaller sized AgNPs (TEM) and mixed sedimentation and diffusion migration compared the studies absent of SRFA. The results suggest that surface coating and solution chemistry has a major impact on AgNP stability, furthermore the corresponding modeling will support the experimental understanding of the overall fate of AgNPs in the environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Atomic Layer Deposition for Coating of High Aspect Ratio TiO2 Nanotube Layers

PubMed Central

2016-01-01

We present an optimized approach for the deposition of Al2O3 (as a model secondary material) coating into high aspect ratio (≈180) anodic TiO2 nanotube layers using the atomic layer deposition (ALD) process. In order to study the influence of the diffusion of the Al2O3 precursors on the resulting coating thickness, ALD processes with different exposure times (i.e., 0.5, 2, 5, and 10 s) of the trimethylaluminum (TMA) precursor were performed. Uniform coating of the nanotube interiors was achieved with longer exposure times (5 and 10 s), as verified by detailed scanning electron microscopy analysis. Quartz crystal microbalance measurements were used to monitor the deposition process and its particular features due to the tube diameter gradient. Finally, theoretical calculations were performed to calculate the minimum precursor exposure time to attain uniform coating. Theoretical values on the diffusion regime matched with the experimental results and helped to obtain valuable information for further optimization of ALD coating processes. The presented approach provides a straightforward solution toward the development of many novel devices, based on a high surface area interface between TiO2 nanotubes and a secondary material (such as Al2O3). PMID:27643411

Low emissivity high-temperature tantalum thin film coatings for silicon devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rinnerbauer, Veronika; Senkevich, Jay J.; Joannopoulos, John D.

The authors study the use of thin ( ~230 nm ) tantalum (Ta) layers on silicon (Si) as a low emissivity (high reflectivity) coating for high-temperature Si devices. Such coatings are critical to reduce parasitic radiation loss, which is one of the dominant loss mechanisms at high temperatures (above 700 °C ). The key factors to achieve such a coating are low emissivity in the near infrared and superior thermal stability at high operating temperatures. The authors investigated the emissivity of Ta coatings deposited on Si with respect to deposition parameters, and annealing conditions, and temperature. The authors found thatmore » after annealing at temperatures ≥900 °C the emissivity in the near infrared ( 1–3 μm ) was reduced by a factor of 2 as compared to bare Si. In addition, the authors measured thermal emission at temperatures from 700 to 1000 °C , which is stable up to a heater temperature equal to the annealing temperature. Furthermore, Auger electron spectroscopy profiles of the coatings before and after annealing were taken to evaluate thermal stability. A thin (about 70 nm) Ta₂O₅ layer was found to act as an efficient diffusion barrier between the Si substrate and the Ta layer to prevent Si diffusion.« less

Design, analysis, and fabrication of oxide-coated iridium/rhenium combustion chambers

NASA Technical Reports Server (NTRS)

Jang, Q.; Tuffias, R. H.; Laferla, R.; Ghoniem, N. M.

1993-01-01

Iridium-coated rhenium (Ir/Re) combustion chambers provide high temperature, oxidation-resistant operation for radiation-cooled liquid-fueled rocket engines. A 22-N (5-lb(sub f)) chamber has been operated for 15 hours at 2200 C (4000 F) using nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) propellant, with negligible internal erosion. The oxidation resistance of these chambers could be further increased by the addition of refractory oxide coatings, providing longer life and/or operation in more oxidizing and higher temperature environments. The oxide coatings would serve as a thermal and diffusion barrier for the iridium coating, lowering the temperature of the iridium layer while also preventing the ingress of oxygen and egress of iridium oxides. This would serve to slow the failure mechanisms of Ir/Re chambers, namely the diffusion of rhenium to the inner surface and the oxidation of iridium. Such protection could extend chamber lifetimes by tens or perhaps hundreds of hours, and allow chamber operation on stoichiometric or higher mixture ratio oxygen/hydrogen (O2/H2) propellant. Extensive thermomechanical, thermochemical, and mass transport modeling was performed as a key material/structure design tool. Based on the results of these analyses, several 22-N oxide-coated Ir/Re chambers were fabricated and delivered to NASA Lewis Research Center for hot-fire testing.

Very Long Term Oxidation of Titanium Aluminides Investigated

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; Brady, Michael P.; Smialek, James L.; Retallick, William B.

2000-01-01

Titanium aluminides (TiAl) are of great interest for intermediate-temperature (600 to 850 C) aerospace and power-generation applications because they offer significant weight savings over today's nickel alloys. TiAl alloys are being investigated for low-pressure turbine blade applications, exhaust nozzle components, and compressor cases in advanced subsonic and supersonic engines. Significant progress has been made in understanding the fundamental aspects of the oxidation behavior of binary TiAl alloys. However, most of this work has concentrated on short term (<1000 hr), high-temperature (900 to 1000 C) exposures. Also, there is not much data available in the literature regarding the oxidation behavior of the quaternary and higher order engineering alloys. This is especially true for the very long term, low-temperature conditions likely to be experienced during aerospace applications. An investigation at the NASA Glenn Research Center at Lewis Field was undertaken to characterize the long-term oxidation behavior of various model and advanced titanium aluminides for periods up to 7000 hr at 704 C in air using a high-resolution field emission scanning electron microscope. Also, a unique surface treatment technique developed to improve the oxidation resistance of TiAl was evaluated. The alloys included in this investigation are listed in the table. The table also shows typical alloy compositions and the specific weight changes and scale thickness measured for each alloy after exposure to 700 C for 7000 hr in air.

Thermal and Irradiation Creep Behavior of a Titanium Aluminide in Advanced Nuclear Plant Environments

NASA Astrophysics Data System (ADS)

Magnusson, Per; Chen, Jiachao; Hoffelner, Wolfgang

2009-12-01

Titanium aluminides are well-accepted elevated temperature materials. In conventional applications, their poor oxidation resistance limits the maximum operating temperature. Advanced reactors operate in nonoxidizing environments. This could enlarge the applicability of these materials to higher temperatures. The behavior of a cast gamma-alpha-2 TiAl was investigated under thermal and irradiation conditions. Irradiation creep was studied in beam using helium implantation. Dog-bone samples of dimensions 10 × 2 × 0.2 mm3 were investigated in a temperature range of 300 °C to 500 °C under irradiation, and significant creep strains were detected. At temperatures above 500 °C, thermal creep becomes the predominant mechanism. Thermal creep was investigated at temperatures up to 900 °C without irradiation with samples of the same geometry. The results are compared with other materials considered for advanced fission applications. These are a ferritic oxide-dispersion-strengthened material (PM2000) and the nickel-base superalloy IN617. A better thermal creep behavior than IN617 was found in the entire temperature range. Up to 900 °C, the expected 104 hour stress rupture properties exceeded even those of the ODS alloy. The irradiation creep performance of the titanium aluminide was comparable with the ODS steels. For IN617, no irradiation creep experiments were performed due to the expected low irradiation resistance (swelling, helium embrittlement) of nickel-base alloys.

Microstructure of thermally grown and deposited alumina films probed with positrons

NASA Astrophysics Data System (ADS)

Somieski, Bertram; Hulett, Lester D.; Xu, Jun; Pint, Bruce A.; Tortorelli, Peter F.; Nielsen, Bent; Asoka-Kumar, Palakkal; Suzuki, Ryoichi; Ohdaira, Toshiyuki

1999-03-01

Aluminum oxide films used for corrosion protection of iron and nickel aluminides were generated by substrate oxidation as well as plasma and physical vapor depositions. The films grown by oxidation were crystalline. The others were amorphous. Defect structures of the films were studied by positron spectroscopy techniques. Lifetimes of the positrons, and Doppler broadening of the γ photons generated by their annihilation, were measured as functions of the energies with which they were injected. In this manner, densities and sizes of the defects were determined as functions of depths from the outer surfaces of the films. Alumina films generated by oxidation had high densities of open volume defects, mainly consisting of a few aggregated vacancies. In the outer regions of the films the structures of the defects did not depend on substrate compositions. Positron lifetime measurements, and the S and W parameters extracted from Doppler broadening spectra, showed uniform distributions of defects in the crystalline Al2O3 films grown on nickel aluminide substrates, but these data indicated intermediate layers of higher defect contents at the film/substrate interfaces of oxides grown on iron aluminide substrates. Amorphous films generated by plasma and physical vapor deposition had much larger open volume defects, which caused the average lifetimes of the injected positrons to be significantly longer. The plasma deposited film exhibited a high density of large cavities.

Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

NASA Technical Reports Server (NTRS)

Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

2006-01-01

Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

Coated graphite articles useful in metallurgical processes and method for making same

DOEpatents

Holcombe, Cressie E.; Bird, Eugene L.

1995-01-01

Graphite articles including crucibles and molds used in metallurgical processes involving the melting and the handling of molten metals and alloys that are reactive with carbon when in a molten state and at process temperatures up to about 2000.degree. C. are provided with a multiple-layer coating for inhibiting carbon diffusion from the graphite into the molten metal or alloys. The coating is provided by a first coating increment of a carbide-forming metal on selected surfaces of the graphite, a second coating increment of a carbide forming metal and a refractory metal oxide, and a third coating increment of a refractory metal oxide. The second coating increment provides thermal shock absorbing characteristics to prevent delamination of the coating during temperature cycling. A wash coat of unstabilized zirconia or titanium nitride can be applied onto the third coating increment to facilitate release of melts from the coating.

Influences of superalloy composition and Pt content on the oxidation behavior of gamma–gamma prime NiPtAl bond coatings

DOE PAGES

Haynes, James A.; Unocic, Kinga A.; Lance, Michael J.; ...

2016-09-13

Here, the effects of superalloy composition and Pt content on the high-temperature oxidation behavior of γ–γ’ NiPtAl diffusion coatings were investigated over the temperature range of 1050–1150 °C. Simple NiPtAl diffusion coatings with 7 or 12 µm electroplated Pt thickness were evaluated in 1-h cycles in dry O 2 for up to 2500 cycles on four superalloys: directionally solidified (DS) alloy 142, 1st generation single-crystal (SX) alloy 1483, and 2nd generation SX alloys X4 and N5. Coatings on high-Hf alloy 142 experienced severe internal oxidation of Hf at all temperatures. Coatings on ~5 at.% Ti alloy 1483 were protective atmore » 1050 °C, but exhibited severe scale spallation at 1100 °C, with extensive formation of Ti- and Ni-rich oxides at the gas interface. Coatings with 7-µm Pt on X 4 were extremely protective at 1100 °C, but failed rapidly at 1150 °C, which also was associated with the formation of Ti-rich oxides. Increasing the coating Pt content on X 4 improved the 1150 °C oxidation behavior. Coatings on Ti-free N 5 showed the best performance at 1150 °C, especially with 12-µm Pt. Although γ–γ’ coatings can exhibit outstanding cyclic oxidation resistance with minimal Al depletion, they appear to be sensitive to substrate composition, as well as eventual Pt depletion due to interdiffusion.« less

Life prediction methodology for thermal-mechanical fatigue and elevated temperature creep design

NASA Astrophysics Data System (ADS)

Annigeri, Ravindra

Nickel-based superalloys are used for hot section components of gas turbine engines. Life prediction techniques are necessary to assess service damage in superalloy components resulting from thermal-mechanical fatigue (TMF) and elevated temperature creep. A new TMF life model based on continuum damage mechanics has been developed and applied to IN 738 LC substrate material with and without coating. The model also characterizes TMF failure in bulk NiCoCrAlY overlay and NiAl aluminide coatings. The inputs to the TMF life model are mechanical strain range, hold time, peak cycle temperatures and maximum stress measured from the stabilized or mid-life hysteresis loops. A viscoplastic model is used to predict the stress-strain hysteresis loops. A flow rule used in the viscoplastic model characterizes the inelastic strain rate as a function of the applied stress and a set of three internal stress variables known as back stress, drag stress and limit stress. Test results show that the viscoplastic model can reasonably predict time-dependent stress-strain response of the coated material and stress relaxation during hold times. In addition to the TMF life prediction methodology, a model has been developed to characterize the uniaxial and multiaxial creep behavior. An effective stress defined as the applied stress minus the back stress is used to characterize the creep recovery and primary creep behavior. The back stress has terms representing strain hardening, dynamic recovery and thermal recovery. Whenever the back stress is greater than the applied stress, the model predicts a negative creep rate observed during multiple stress and multiple temperature cyclic tests. The model also predicted the rupture time and the remaining life that are important for life assessment. The model has been applied to IN 738 LC, Mar-M247, bulk NiCoCrAlY overlay coating and 316 austenitic stainless steel. The proposed model predicts creep response with a reasonable accuracy for wide range of loading cases such as uniaxial tension, tension-torsion and tension-internal pressure loading.

The Lattice and Thermal Radiation Conductivity of Thermal Barrier Coatings: Models and Experiments

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Spuckler, Charles M.

2010-01-01

The lattice and radiation conductivity of ZrO2-Y2O3 thermal barrier coatings was evaluated using a laser heat flux approach. A diffusion model has been established to correlate the coating apparent thermal conductivity to the lattice and radiation conductivity. The radiation conductivity component can be expressed as a function of temperature, coating material scattering, and absorption properties. High temperature scattering and absorption of the coating systems can be also derived based on the testing results using the modeling approach. A comparison has been made for the gray and nongray coating models in the plasma-sprayed thermal barrier coatings. The model prediction is found to have a good agreement with experimental observations.

Corrosion Performance of Nano-ZrO₂ Modified Coatings in Hot Mixed Acid Solutions.

PubMed

Xu, Wenhua; Wang, Zhenyu; Han, En-Hou; Wang, Shuai; Liu, Qian

2018-06-01

A nano-ZrO₂ modified coating system was prepared by incorporation of nano-ZrO₂ concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO₂ content were specially focused on. The results showed that 1% and 3% nano-ZrO₂ addition enhanced the corrosion resistance of the coatings, while 5% nano-ZrO₂ addition declined it. The coating with 3% nano-ZrO₂ presented the minimum amount of species diffusion, the lowest average roughness (5.94 nm), and the highest C/O ratio (4.55) and coating resistance, and it demonstrated the best corrosion performance among the coating specimens.

Atomic layer deposition to prevent metal transfer from implants: An X-ray fluorescence study

NASA Astrophysics Data System (ADS)

Bilo, Fabjola; Borgese, Laura; Prost, Josef; Rauwolf, Mirjam; Turyanskaya, Anna; Wobrauschek, Peter; Kregsamer, Peter; Streli, Christina; Pazzaglia, Ugo; Depero, Laura E.

2015-12-01

We show that Atomic Layer Deposition is a suitable coating technique to prevent metal diffusion from medical implants. The metal distribution in animal bone tissue with inserted bare and coated Co-Cr alloys was evaluated by means of micro X-ray fluorescence mapping. In the uncoated implant, the migration of Co and Cr particles from the bare alloy in the biological tissues is observed just after one month and the number of particles significantly increases after two months. In contrast, no metal diffusion was detected in the implant coated with TiO2. Instead, a gradient distribution of the metals was found, from the alloy surface going into the tissue. No significant change was detected after two months of aging. As expected, the thicker is the TiO2 layer, the lower is the metal migration.

Titanium Aluminide Technologies Successfully Transferred From HSR Program to RLV VentureStar Program

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.

2000-01-01

Through a cost-share contract, BFGoodrich Aerostructures group successfully fabricated three titanium aluminide (gamma TiAl) truss core structures using technologies pioneered in the High-Speed Research (HSR) program at the NASA Glenn Research Center at Lewis Field. The truss core subelement is approximately 60-cm (24-in.) long by 14-cm (5.5-in.) wide by 6-cm (2.5-in.) deep. To fabricate this subelement, BFGoodrich first obtained gamma TiAl sheets from Plansee (Austria) which produced the sheets using techniques developed collaboratively by Glenn, Pratt & Whitney, and Plansee. This new gamma TiAl production technology has significantly lowered the cost of gamma TiAl sheet (approx. 75-percent decrease) and has made the production of larger gamma TiAl sheets possible (approx. 60-percent increase).

Recrystallization and grain growth in NiAl

NASA Technical Reports Server (NTRS)

Haff, G. R.; Schulson, E. M.

1982-01-01

Aluminide intermetallics, because of their strength, microstructural stability, and oxidation resistance at elevated temperatures, represent potential structural materials for use in advanced energy conversion systems. This inherent potential of the intermetallics can currently not be realized in connection with the general brittleness of the materials under ambient conditions. It is pointed out, however, that brittleness is not an inherent characteristic. Single crystals are ductile and polycrystals may be, too, if their grains are fine enough. The present investigation is concerned with an approach for reducing material brittleness, taking into account thermal-mechanically induced grain refinement in NiAl, a B2 aluminide which melts at 1638 C and which retains complete order to its melting point. Attention is given to the kinetics of recrystallization and grain growth of warm-worked, nickel-rich material.

Features of degradation and recovery of the optical properties of coatings based on ZnO powder modified with nanoparticles after irradiation

NASA Astrophysics Data System (ADS)

Mikhailov, M.; Neschimenko, V.; Sokolovskiy, A.

2018-04-01

The effect of electron irradiation with energy of 30 keV and fluence up to 7 × 1016 cm-2 on diffuse reflection spectra in situ of coatings based on ZnO powders unmodified and modified with zirconium dioxide and aluminum oxide nanopowders was investigated. The higher radiation stability of coatings based on modified pigments in comparison to unmodified pigments has been established. A significant recovery of the reflection spectra of irradiated coatings after exposure to residual vacuum and air was shown.

On the kinetics of the pack - Aluminization process

NASA Technical Reports Server (NTRS)

Sivakumar, R.; Seigle, L. L.

1976-01-01

An investigation has been made of the aluminization of unalloyed Ni in fluoride-activated packs of varying Al activity. In packs of low Al activity, in which the ratio of Al to Ni was less than 50 at. pct, the specimen surface quickly came to equilibrium with the pack and remained close to equilibrium for the duration of normal coating runs. In these packs the kinetics of aluminization was controlled by diffusion in the solid. In packs of higher Al activity the surface of the specimen did not come to equilibrium with the pack and the kinetics of the process was governed by a combination of solid and gas diffusion rates. Under most conditions however, the surface composition was time-invariant and a steady-state appeared to exist at the pack-coating interface. By combining Levine and Caves' model for gaseous diffusion in pure-Al packs with calculations of solid diffusion rates some success has been achieved in explaining the results.

Liquid phase diffusion bonding of A1070 by using metal formate coated Zn sheet

NASA Astrophysics Data System (ADS)

Ozawa, K.; Koyama, S.; shohji, I.

2017-05-01

Aluminium alloy have high strength and easily recycle due to its low melting point. Therefore, aluminium is widely used in the manufacturing of cars and electronic devices. In recent years, the most common way for bonding aluminium alloy is brazing and friction stir welding. However, brazing requires positional accuracy and results in the formation of voids by the flax residue. Moreover, aluminium is an excellent heat radiating and electricity conducting material; therefore, it is difficult to bond together using other bonding methods. Because of these limitations, liquid phase diffusion bonding is considered to the suitable method for bonding aluminium at low temperature and low bonding pressure. In this study, the effect of metal formate coating processing of zinc surface on the bond strength of the liquid phase diffusion bonded interface of A1070 has been investigated by SEM observation of the interfacial microstructures and fractured surfaces after tensile test. Liquid phase diffusion bonding was carried out under a nitrogen gas atmosphere at a bonding temperature of 673 K and 713 K and a bonding load of 6 MPa (bonding time: 15 min). As a result of the metal formate coating processing, a joint having the ultimate tensile strength of the base aluminium was provided. It is hypothesized that this is because metallic zinc is generated as a result of thermal decomposition of formate in the bonded interface at lower bonding temperatures.

Process to produce lithium-polymer batteries

DOEpatents

MacFadden, Kenneth Orville

1998-01-01

A polymer bonded sheet product suitable for use as an electrode in a non-aqueous battery system. A porous electrode sheet is impregnated with a solid polymer electrolyte, so as to diffuse into the pores of the electrode. The composite is allowed to cool, and the electrolyte is entrapped in the porous electrode. The sheet products composed have the solid polymer electrolyte composition diffused into the active electrode material by melt-application of the solid polymer electrolyte composition into the porous electrode material sheet. The solid polymer electrolyte is maintained at a temperature that allows for rapid diffusion into the pores of the electrode. The composite electrolyte-electrode sheets are formed on current collectors and can be coated with solid polymer electrolyte prior to battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte coating has low resistance.

Diffusion bonding

DOEpatents

Anderson, Robert C.

1976-06-22

1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

Evaluation of SmCo and SmCoN magnetron sputtering coatings for SOFC interconnect applications

NASA Astrophysics Data System (ADS)

Wu, Junwei; Li, Chengming; Johnson, Christopher; Liu, Xingbo

Cobalt or cobalt containing coatings are promising for SOFC interconnect applications because of their high conductivity. We have investigated SmCo and SmCoN coatings deposited by magnetron sputtering from a SmCo (5% Sm) target on to Crofer 22 APU substrates. The composition, structure, surface morphology, and electrical conductivity of the coated substrates were characterized by SEM/EDX, XRD and ASR measurements. Addition of Sm enhances the oxidation resistance and the Cr retention capability of the coatings. The use of nitride as a precursor stabilizes Sm during oxidation of the films, thus inhibiting diffusion of Fe, resulting in a more compact coating and lowering ASR. The combined advantages of Sm addition to cobalt and the use of a nitride as a precursor, makes SmCoN coatings a promising new interconnect coating material.

Preliminary evaluation of an aqueous wax emulsion for controlled-release coating.

PubMed

Walia, P S; Stout, P J; Turton, R

1998-02-01

The purpose of this work was to evaluate the use of an aqueous carnauba wax emulsion (Primafresh HS, Johnson Wax) in a spray-coating process. This involved assessing the effectiveness of the wax in sustaining the release of the drug, theophylline. Second, the process by which the drug was released from the wax-coated pellets was modeled. Finally, a method to determine the optimum blend of pellets with different wax thicknesses, in order to yield a zero-order release profile of the drug, was addressed. Nonpareil pellets were loaded with theophylline using a novel powder coating technique. These drug-loaded pellets were then coated with different levels of carnauba wax in a 6-in. diameter Plexiglas fluid bed with a 3.5-in. diameter Wurster partition. Drug release was measured using a spin-filter dissolution device. The study resulted in continuous carnauba wax coatings which showed sustained drug release profile characteristics typical of a barrier-type, diffusion-controlled system. The effect of varying wax thickness on the release profiles was investigated. It was observed that very high wax loadings would be required to achieve long sustained-release times. The diffusion model, developed to predict the release of the drug, showed good agreement with the experimental data. However, the data exhibited an initial lag-time for drug release which could not be predicted a priori based on the wax coating thickness. A method of mixing pellets with different wax thicknesses was proposed as a way to approximate zero-order release.

Lubricating Properties of Some Bonded Fluoride and Oxide Coatings for Temperature to 1500 F

NASA Technical Reports Server (NTRS)

Sliney, Harold E.

1960-01-01

The lubricating properties of some experimental ceramic coatings, diffusion-bonded fluoride coatings, and ceramic-bonded fluoride coatings were determined. The experiments were conducted in an air atmosphere at a sliding velocity of 430 feet per minute and at temperatures from 75 to 1500 F. Several ceramic coatings provided substantial reductions in friction coefficient and rider wear (compared with the unlubricated metals). For example, a cobaltous oxide (CoO) base coating gave friction coefficients of 0.24 to 0.36 within the temperature range of 75 to 1400 F; serious galling and welding of the metal surfaces were prevented. The friction coefficients were higher than the arbitrary maximum (0.2) usually considered for effective boundary lubrication. However, when a moderately high friction coefficient can be tolerated, this type of coating may be a useful antiwear composition. Diffusion-bonded calcium fluoride (CaF2) on Haynes Stellite 21 and on Inconel X gave friction coefficients of 0.1 to 0.2 at 1500 F. Endurance life was dependent on the thermal history of the coating; life improved with increased exposure time at elevated temperatures prior to running. Promising results were obtained with ceramic-bonded CaF2 on Inconel X. Effective lubrication and good adherence were obtained with a 3 to 1 ratio of CaF2 to ceramic. A very thin sintered and burnished film of CaF2 applied to the surface of this coating further improved lubrication, particularly above 1350 F. The friction coefficient was 0.2 at 500 F and decreased with increasing temperature to 0.06-at 1500 F. It was 0.25 at 75 F and 0.22 at 250 F.

Bio-based coatings as potential barriers to chemical contaminants from recycled paper and board for food packaging.

PubMed

Guazzotti, V; Marti, A; Piergiovanni, L; Limbo, S

2014-01-01

Partition and diffusion experiments were carried out with paper and board samples coated with different biopolymers. The aim was to evaluate the physicochemical behaviour and barrier properties of bio-coatings against migration of typical contaminants from recycled paper packaging. Focus was directed towards water-based, renewable biopolymers, such as modified starches (cationic starch and cationic waxy starch), plant and animal proteins (gluten and gelatine), poured onto paper with an automatic applicator. Additionally, a comparison with polyethylene-laminated paper was performed. Microstructural observations of the bio-coated paper allowed the characterisation of samples. From the partitioning studies, considerable differences in the adsorption behaviour of the selected contaminants between bio-coated or uncoated paper and air were highlighted. For both the polar and non-polar compounds considered (benzophenone and diisobutyl phthalate, respectively), the lowest values of partition coefficients were found when paper was bio-coated, making it evident that biopolymers acted as chemical/physical barriers towards these contaminants. These findings are discussed considering the characteristics of the tested biopolymers. Diffusion studies into the solid food simulant poly 2,6-diphenyl-p-phenylene oxide, also known as Tenax(®), confirmed that all the tested biopolymers slowed down migration. The Weibull kinetic model was fitted to the experimental data to compare migration from paper and bio-coated paper. Values found for β, an index determining the pattern of curvature, ranged from 1.1 to 1.7 for uncoated and polyethylene paper, whereas for bio-coated papers they ranged from 2.2 to 4.9, corresponding to the presence of an evident lag phase due to barrier properties of the tested bio-coatings.

Electrodeposited MCrAlY Coatings for Gas Turbine Engine Applications

NASA Astrophysics Data System (ADS)

Zhang, Y.

2015-11-01

Electrolytic codeposition is a promising alternative process for fabricating MCrAlY coatings. The coating process involves two steps, i.e., codeposition of CrAlY-based particles and a metal matrix of Ni, Co, or (Ni,Co), followed by a diffusion heat treatment to convert the composite coating to the desired MCrAlY microstructure. Despite the advantages such as low cost and non-line-of-sight, this coating process is less known than electron beam-physical vapor deposition and thermal spray processes for manufacturing high-temperature coatings. This article provides an overview of the electro-codeposited MCrAlY coatings for gas turbine engine applications, highlighting the unique features of this coating process and some important findings in the past 30 years. Challenges and research opportunities for further optimization of this type of MCrAlY coatings are also discussed.

In situ catalytic synthesis of high-graphitized carbon-coated LiFePO4 nanoplates for superior Li-ion battery cathodes.

PubMed

Ma, Zhipeng; Fan, Yuqian; Shao, Guangjie; Wang, Guiling; Song, Jianjun; Liu, Tingting

2015-02-04

The low electronic conductivity and one-dimensional diffusion channel along the b axis for Li ions are two major obstacles to achieving high power density of LiFePO4 material. Coating carbon with excellent conductivity on the tailored LiFePO4 nanoparticles therefore plays an important role for efficient charge and mass transport within this material. We report here the in situ catalytic synthesis of high-graphitized carbon-coated LiFePO4 nanoplates with highly oriented (010) facets by introducing ferrocene as a catalyst during thermal treatment. The as-obtained material exhibits superior performances for Li-ion batteries at high rate (100 C) and low temperature (-20 °C), mainly because of fast electron transport through the graphitic carbon layer and efficient Li(+)-ion diffusion through the thin nanoplates.

Interdiffusion behavior between NiAlHf coating and Ni-based single crystal superalloy with different crystal orientations

NASA Astrophysics Data System (ADS)

Wang, Ruili; Gong, Xueyuan; Peng, Hui; Ma, Yue; Guo, Hongbo

2015-01-01

NiAlHf coatings were deposited onto Ni-based single crystal (SC) superalloy with different crystal orientations by electron beam physical vapor deposition (EB-PVD). The effects of the crystal orientations of the superalloy substrate on inter-diffusion behavior between the substrate and the NiAlHf coating were investigated. Substrate diffusion zone (SDZ) containing needle-like μ phases and interdiffusion zone (IDZ) mainly consisting of the ellipsoidal and rod-like μ phases were formed in the SC alloy after heat-treatment 10 h at 1100 °C. The thickness of secondary reaction zone (SRZ) formed in the SC alloy with (0 1 1) crystal orientation is about 14 μm after 50 h heat-treatment at 1100 °C, which is relatively thicker than that in the SC alloy with (0 0 1) crystal orientation, whereas the IDZ revealed similar thickness.

Nanoparticle diffusion in, and microrheology of, the bovine vitreous ex vivo

PubMed Central

Xu, Qingguo; Boylan, Nicholas J.; Suk, Jung Soo; Wang, Ying-Ying; Nance, Elizabeth; Yang, Jeh-Chang; McDonnell, Peter; Cone, Richard; Duh, Elia J.; Hanes, Justin

2013-01-01

Intravitreal injection of biodegradable nanoparticles (NP) holds promise for gene therapy and drug delivery to the back of the eye. In some cases, including gene therapy, NP need to diffuse rapidly from the site of injection in order to reach targeted cell types in the back of the eye, whereas in other cases it may be preferred for the particles to remain at the injection site and slowly release drugs that may then diffuse to the site of action. We studied the movements of polystyrene (PS) nanoparticles of various sizes and surface chemistries in fresh bovine vitreous. PS NP as large as 510 nm rapidly penetrated the vitreous gel when coated with polyethylene glycol (PEG), whereas the movements of NP 1190 nm in diameter or larger were highly restricted regardless of surface chemistry owing to steric obstruction. PS NP coated with primary amine groups (–NH2) possessed positively charged surfaces at the pH of bovine vitreous (pH = 7.2), and were immobilized within the vitreous gel. In comparison, PS NP coated with –COOH (possessing negatively charged surfaces) in the size range of 100–200 nm and at particle concentrations below 0.0025% (w/v) readily diffused through the vitreous meshwork; at higher concentrations (~0.1% w/v), these nanoparticles aggregated within vitreous. Based on the mobility of different sized PS-PEG NP, we estimated the average mesh size of fresh bovine vitreous to be ~550 ± 50 nm. The bovine vitreous behaved as an impermeable elastic barrier to objects sized 1190 nm and larger, but as a highly permeable viscoelastic liquid to non-adhesive objects smaller than 510 nm in diameter. Guided by these studies, we next sought to examine the transport of drug- and DNA-loaded nanoparticles in bovine vitreous. Biodegradable NP with diameter of 227 nm, composed of a poly(lactic-co-glycolic acid) (PLGA)-based core coated with poly(vinyl alcohol) rapidly penetrated vitreous. Rod-shaped, highly-compacted CK30PEG10k/DNA with PEG coating (neutral surface charge; diameter ~60 nm) diffused rapidly within vitreous. These findings will help guide the development of nanoparticle-based therapeutics for the treatment of vision-threatening ocular diseases. PMID:23369761

Effect of water vapor on evolution of a thick Pt-layer modified oxide on the NiCoCrAl alloy at high temperature

NASA Astrophysics Data System (ADS)

Song, Peng; He, Xuan; Xiong, Xiping; Ma, Hongqing; Song, Qunling; Lü, Jianguo; Lu, Jiansheng

2018-03-01

To investigate the effect of water vapor on the novel Pt-containing oxide growth behavior, Pt-addition within the oxide layer on the surface of NiCoCrAl coating and furnace cycle tests were carried out at 1050 °C in air and air plus water vapor. The thick Pt-containing oxide layer on NiCoCrAl exhibits a different oxidation growth behavior compared to the conventional Pt-diffusion metallic coatings. The Pt-containing oxide after oxidation in air plus water vapor showed a much thicker oxide layer compare to the ones without Pt addition, and also presented a much better coating adhesion. During the oxidation process in air, Pt promotes the spinel (NiCr2O4) formation. However, the Cr2O3 formed in air with water vapor and fixed Pt within the complex oxide layer. The water vapor promoted the Ni and Co outer-diffusion, and combined with Pt to form CoPt compounds on the surface of the NiCoCrAl coating system.

Tritium permeation through austenitic stainless steel with chemically densified coating as a tritium permeation barrier

NASA Astrophysics Data System (ADS)

Terai, Takayuki; Yoneoka, Toshiaki; Tanaka, Hirohisa; Kawamura, Hiroshi; Nakamichi, Masaru; Miyajima, Kiyoshi

1994-09-01

Chemically densified coating formed on the surface of austenitic stainless steel (SUS 316) was examined for compatibility with molten lithium-lead eutectic alloy (Li17Pb83) and tritium permeability. The chemically densified coating (CDC) consisting of SiO 2 particles and a Cr 2O 3 matrix with a thickness of 60 μm was unstable in contact with the molten alloy as predicted from a thermodynamic calculation at 600°C, and it was degraded in several days. In an in-pile experiment, specimens with the coating on the front surface or the rear surface were immersed in Li17Pb83 molten alloy, and their tritium permeabilities were measured. The permeability of the former was reduced to {1}/{10} of the ideal value in the diffusion-limited case, while that of the latter was less than {1}/{100} of the diffusion-limited value even in a pure H 2 atmosphere. It is concluded that CDC is quite effective to reduce tritium permeability in the condition of not contacting molten Li17Pb83 alloy.

Changes of composition and microstructure of joint interface of tungsten coated carbon by high heat flux

NASA Astrophysics Data System (ADS)

Tokunaga, K.; Matsubara, T.; Miyamoto, Y.; Takao, Y.; Yoshida, N.; Noda, N.; Kubota, Y.; Sogabe, T.; Kato, T.; Plöchl, L.

2000-12-01

Tungsten coatings of 0.5 and 1 mm thickness were successfully deposited by the vacuum plasma spraying (VPS) technique on carbon/carbon fiber composite (CFC), CX-2002U and isotropic fine grained graphite, IG-430U. High heat flux experiments by irradiation of electron beam with uniform profile were performed on the coated samples in order to prove the suitability and load limit of such coating materials. The cross-sectional composition and structure of the interface of VPS-W and carbon material samples were investigated. Compositional analyses showed that the Re/W multi-layer acts as diffusion barrier for carbon and suppresses tungsten carbide formation in the VPS-W layer at high temperature about 1300°C. Microstructure of the joint interface of the sample changed in the case of a peak temperature of about 2800°C. The multi-layer structure completely disappeared and compositional distribution was almost uniform in the interface of the sample after melting and resolidification. The diffusion barrier for carbon is not expected to act in this stage.

Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

NASA Astrophysics Data System (ADS)

Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

2016-07-01

The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

Electrodeposition of Ni(OH)2 reinforced polyaniline coating for corrosion protection of 304 stainless steel

NASA Astrophysics Data System (ADS)

Jiang, Li; Syed, Junaid Ali; Gao, Yangzhi; Lu, Hongbin; Meng, Xiangkang

2018-05-01

In the present paper, polyaniline (PANI) coating was electropolymerized in the presence of phosphoric acid with subsequent deposition of Ni(OH)2 particles. The Ni(OH)2 reinforced PANI coating significantly enhances the corrosion resistance of 304 stainless steel (304SS) in comparison with the pristine PANI coating. The galvanostatically deposited Ni(OH)2 particles fill the pores of the pristine PANI coating and improves the coatings hydrophobicity which decreases the diffusion of aggressive media. Importantly, the Rp values of Ni(OH)2 reinforced PANI coating is much higher than that of pristine PANI coating and the Ni(OH)2 reinforced PANI coating presents a long-term anti-corrosive ability (360 h) in 3.5 wt% NaCl solution. The prolonged corrosion protection of Ni(OH)2 reinforced PANI coating is attributed to the improved physical barrier as well as the facile formation of passive oxide film that sustain the anodic protection of the coating.

Theoretical studies of aluminum and aluminide alloys using CALPHAD and first-principles approach

NASA Astrophysics Data System (ADS)

Jiang, Chao

Heat-treatable aluminum alloys have been widely used in the automobile and aerospace industries as structural materials due to their light weight and high strength. To study the age-hardening process in heat-treatable aluminum alloys, the Gibbs energies of the strengthening metastable phases, e.g. theta ' and theta″, are critical. However, those data are not included in the existing thermodynamic databases for aluminum alloys due to the semi-empirical nature of the CALPHAD approach. In the present study, the thermodynamics of the Al-Cu system, the pivotal age-hardening system, is remodeled using a combined CALPHAD and first-principles approach. The formation enthalpies and vibrational formation entropies of the stable and metastable phases in the Al-Cu system are provided by first-principles calculations. Special Quasirandom Structures (SQS's) are applied to model the substitutionally random fee and bee alloys. SQS's for binary bee alloys are developed and tested in the present study. Finally, a self-consistent thermodynamic description of the Al-Cu system including the two metastable theta″ and theta' phases is obtained. During welding of heat-treatable aluminum alloys, a detrimental phenomenon called constitutional liquation, i.e. the local eutectic melting of second-phase particles in a matrix at temperatures above the eutectic temperature but below the solidus of the alloy, may occur in the heat-affected zone (HAZ). In the present study, diffusion code DICTRA coupled with realistic thermodynamic and kinetic databases is used to simulate the constitutional liquation in the model Al-Cu system. The simulated results are in quantitative agreement with experiments. The critical heating rate to avoid constitutional liquation is also determined through computer simulations. Besides the heat-treatable aluminum alloys, intermetallic compounds based on transition metal aluminides, e.g. NiAl and FeAl, are also promising candidates for the next-generation of high-temperature structural materials for aerospace applications due to their high melting temperature and good oxidation resistance. Many important properties of B2 aluminides are governed by the existences of point defects. In the present study, Special Quasirandom Structures (SQS's) are developed to model non-stoichiometric B2 compounds containing large concentrations of constitutional point defects. The SQS's are then applied to study B2 NiAl. The first-principles SQS results provide formation enthalpies, equilibrium lattice parameters and elastic constants of B2 NiAl which agree satisfactorily with the existing experimental data in the literature. It is unambiguously shown that, at T = 0K and zero pressure, Ni vacancies and antisite Ni atoms are the energetically favorable point defects in Al-rich and Ni-rich B2 NiAl, respectively. Remarkably, it is predicted that high defect concentrations can lead to structural instability of B2 NiAl, which explains well the martensitic transformation observed in this compound at high Ni concentrations.

Assessment of Titanium Aluminide Alloys for High-Temperature Nuclear Structural Applications

NASA Astrophysics Data System (ADS)

Zhu, Hanliang; Wei, Tao; Carr, David; Harrison, Robert; Edwards, Lyndon; Hoffelner, Wolfgang; Seo, Dongyi; Maruyama, Kouichi

2012-12-01

Titanium aluminide (TiAl) alloys exhibit high specific strength, low density, good oxidation, corrosion, and creep resistance at elevated temperatures, making them good candidate materials for aerospace and automotive applications. TiAl alloys also show excellent radiation resistance and low neutron activation, and they can be developed to have various microstructures, allowing different combinations of properties for various extreme environments. Hence, TiAl alloys may be used in advanced nuclear systems as high-temperature structural materials. Moreover, TiAl alloys are good materials to be used for fundamental studies on microstructural effects on irradiation behavior of advanced nuclear structural materials. This article reviews the microstructure, creep, radiation, and oxidation properties of TiAl alloys in comparison with other nuclear structural materials to assess the potential of TiAl alloys as candidate structural materials for future nuclear applications.

Modeling of High-Strain-Rate Deformation, Fracture, and Impact Behavior of Advanced Gas Turbine Engine Materials at Low and Elevated Temperatures

NASA Technical Reports Server (NTRS)

Shazly, Mostafa; Nathenson, David; Prakash, Vikas

2003-01-01

Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention, and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, Gamma-met PX has been developed by GKSS, Germany. These alloys have been observed to have superior strengths at elevated temperatures and quasi-static deformation rates and good oxidation resistance at elevated temperatures when compared with other gamma titanium aluminides. The present paper discusses results of a study to understand dynamic response of gamma-met PX in uniaxial compression. The experiments were conducted by using a modified split Hopkinson pressure bar between room temperature and 900 C and strain rates of up to 3500 per second. The Gamma met PX alloy showed superior strength when compared to nickel based superalloys and other gamma titanium aluminides at all test temperatures. It also showed strain and strain-rate hardening at all levels of strain rates and temperatures and without yield anomaly up to 900 C. After approximately 600 C, thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 and 900 C. However, these flow stress levels are comparatively higher in Gamma met PX than those observed for other TiAl alloys.

Compositionally modulated multilayer diamond-like carbon coatings with AlTiSi multi-doping by reactive high power impulse magnetron sputtering

NASA Astrophysics Data System (ADS)

Dai, Wei; Gao, Xiang; Liu, Jingmao; Kwon, Se-Hun; Wang, Qimin

2017-12-01

Diamond-like carbon (DLC) coatings with AlTiSi multi-doping were prepared by a reactive high power impulse magnetron sputtering with using a gas mixture of Ar and C2H2 as precursor. The composition, microstructure, compressive stress, and mechanical property of the as-deposited DLC coatings were studied systemically by using SEM, XPS, TEM, Raman spectrum, stress-tester, and nanoindentation as a function of the Ar fraction. The results show that the doping concentrations of the Al, Ti and Si atoms increased as the Ar fraction increased. The doped Ti and Si preferred to bond with C while the doped Al mainly existed in oxidation state without bonding with C. As the doping concentrations increased, TiC carbide nanocrystals were formed in the DLC matrix. The microstructure of coatings changed from an amorphous feature dominant AlTiSi-DLC to a carbide nanocomposite AlTiSi-DLC with TiC nanoparticles embedding. In addition, the coatings exhibited the compositionally modulated multilayer consisting of alternate Al-rich layer and Al-poor layer due to the rotation of the substrate holder and the diffusion behavior of the doped Al which tended to separate from C and diffuse towards the DLC matrix surface owing to its weak interactions with C. The periodic Al-rich layer can effectively release the compressive stress of the coatings. On the other hand, the hard TiC nanoparticles were conducive to the hardness of the coatings. Consequently, the DLC coatings with relatively low residual stress and high hardness could be acquired successfully through AlTiSi multi-doping. It is believed that the AlCrSi multi-doping may be a good way for improving the comprehensive properties of the DLC coatings. In addition, we believe that the DLC coatings with Al-rich multilayered structure have a high oxidation resistance, which allows the DLC coatings application in high temperature environment.

Characterization and durability testing of plasma-sprayed zirconia-yttria and hafnia-yttria thermal barrier coatings. Part 1: Effect of spray parameters on the performance of several lots of partially stabilized zirconia-yttria powder

NASA Technical Reports Server (NTRS)

Miller, Robert A.; Leissler, George W.; Jobe, J. Marcus

1993-01-01

Initial experiments conducted on thermal barrier coatings prepared in the newly upgraded research plasma spray facility and the burner rig test facilities are discussed. Part 1 discusses experiments which establish the spray parameters for three baseline zirconia-yttria coatings. The quality of five similar coating lots was judged primarily by their response to burner rig exposure supplemented by data from other sources such as specimen characterizations and thermal diffusivity measurements. After allowing for burner rig variability, although there appears to be an optimum density (i.e., optimum microstructure) for maximum burner rig life, the distribution tends to be rather broad about the maximum. In Part 2, new hafnia-yttria-based coatings were evaluated against both baseline and alternate zirconia-yttria coatings. The hafnia-yttria coatings and the zirconia-yttria coatings that were prepared by an alternate powder vendor were very sensitive to plasma spray parameters, in that high-quality coatings were only obtained when certain parameters were employed. The reasons for this important observation are not understood. Also not understood is that the first of two replicate specimens sprayed for Part 1 consistently performed better than the second specimen. Subsequent experiments did not display this spray order affect, possibly because a chiller was installed in the torch cooling water circuit. Also, large changes in coating density were observed after switching to a new lot of electrodes. Analyses of these findings were made possible, in part, because of the development of a sensitive density measurement technique described herein in detail. The measured thermal diffusivities did not display the expected strong relationship with porosity. This surprising result was believed to have been caused by increased microcracking of the denser coatings on the stainless steel substrates.

Theoretical analysis of the performance of glucose sensors with layer-by-layer assembled outer membranes.

PubMed

Croce, Robert A; Vaddiraju, Santhisagar; Papadimitrakopoulos, Fotios; Jain, Faquir C

2012-10-01

The performance of implantable electrochemical glucose sensors is highly dependent on the flux-limiting (glucose, H(2)O(2), O(2)) properties of their outer membranes. A careful understanding of the diffusion profiles of the participating species throughout the sensor architecture (enzyme and membrane layer) plays a crucial role in designing a robust sensor for both in vitro and in vivo operation. This paper reports the results from the mathematical modeling of Clark's first generation amperometric glucose sensor coated with layer-by-layer assembled outer membranes in order to obtain and compare the diffusion profiles of various participating species and their effect on sensor performance. Devices coated with highly glucose permeable (HAs/Fe(3+)) membranes were compared with devices coated with PSS/PDDA membranes, which have an order of magnitude lower permeability. The simulation showed that the low glucose permeable membrane (PSS/PDDA) sensors exhibited a 27% higher amperometric response than the high glucose permeable (HAs/Fe(3+)) sensors. Upon closer inspection of H(2)O(2)diffusion profiles, this non-typical higher response from PSS/PDDA is not due to either a larger glucose flux or comparatively larger O(2) concentrations within the sensor geometry, but rather is attributed to a 48% higher H(2)O(2) concentration in the glucose oxidase enzyme layer of PSS/PDDA coated sensors as compared to HAs/Fe(3+) coated ones. These simulated results corroborate our experimental findings reported previously. The high concentration of H(2)O(2) in the PSS/PDDA coated sensors is due to the low permeability of H(2)O(2) through the PSS/PDDA membrane, which also led to an undesired increase in sensor response time. Additionally, it was found that this phenomenon occurs for all enzyme thicknesses investigated (15, 20 and 25 nm), signifying the need for a holistic approach in designing outer membranes for amperometric biosensors.

Dexamethasone diffusion across contact lenses is inhibited by Staphylococcus epidermidis biofilms in vitro.

PubMed

Brothers, Kimberly M; Nau, Amy C; Romanowski, Eric G; Shanks, Robert M Q

2014-10-01

This study was designed to measure the impact of bacterial biofilms on diffusion of an ocular therapeutic through silicone hydrogel bandage lenses in vitro. An assay was designed to study the passage of a commonly used steroid, dexamethasone, through silicone hydrogel soft contact lenses. Diffused dexamethasone was measured using a spectrophotometer over a period of 18 hours and quantified using a standard curve. This assay was performed with control and Staphylococcus epidermidis biofilm-coated contact lenses comprised of lotrafilcon A and methafilcon. Biofilms were formed in brain heart infusion broth supplemented with D-glucose. The presented data validate a simple in vitro model that can be used to measure the penetration of a topical therapeutic through silicone hydrogel soft contact lenses. Using this model, we measured a reduction in dexamethasone diffusion up to 88% through S. epidermidis biofilm-coated silicone hydrogel lenses compared with control lenses. The results of this in vitro study demonstrate that bacterial biofilms impede dexamethasone diffusion through silicone hydrogel contact lenses and warrant future studies regarding the clinical benefit of using ocular therapeutics in the setting of bandage contact lens use for corneal epithelial defects.

Dexamethasone diffusion across contact lenses is inhibited by Staphylococcus epidermidis biofilms in vitro

PubMed Central

Brothers, Kimberly M.; Nau, Amy C.; Romanowski, Eric G.; Shanks, Robert M. Q.

2014-01-01

Purpose This study was designed to measure the impact of bacterial biofilms on diffusion of an ocular therapeutic through silicone hydrogel bandage lenses in vitro. Methods An assay was designed to study the passage of a commonly used steroid dexamethasone through the silicone hydrogel soft contact lenses. Diffused dexamethasone was measured using a spectrophotometer over a period of 18 hours and quantified using a standard curve. This assay was performed with control and Staphylococcus epidermidis biofilm-coated contact lenses composed of lotrafilcon A and methafilcon. Biofilms were formed in brain heart infusion broth supplemented with D-glucose. Results The presented data validate a simple in vitro model that can be used to measure penetration of a topical therapeutic through silicone hydrogel soft contact lenses. Using this model we measured a reduction of dexamethasone diffusion by up to 88% through S. epidermidis biofilm-coated silicon hydrogel lenses compared to control lenses. Conclusions The results of this in vitro study demonstrate that bacterial biofilms impede dexamethasone diffusion through silicon hydrogel contact lenses, and warrant future studies regarding the clinical benefit of using ocular therapeutics in the setting of bandage contact lens use for corneal epithelial defects. PMID:25090165

Solution processable broadband transparent mixed metal oxide nanofilm optical coatings via substrate diffusion doping.

PubMed

Glynn, Colm; Aureau, Damien; Collins, Gillian; O'Hanlon, Sally; Etcheberry, Arnaud; O'Dwyer, Colm

2015-12-21

Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings. Here, we report a facile solution processed technique for the formation of a transparent thin film through an inter-diffusion process involving substrate dopant species at a range of low annealing temperatures compatible with processing conditions required by many state-of-the-art devices. The inter-diffusion process facilitates the movement of Si, Na and O species from the substrate into the as-deposited vanadium oxide thin film forming a composite fully transparent V0.0352O0.547Si0.4078Na0.01. Thin film X-ray diffraction and Raman scattering spectroscopy show the crystalline component of the structure to be α-NaVO3 within a glassy matrix. This optical coating exhibits high broadband transparency, exceeding 90-97% absolute transmission across the UV-to-NIR spectral range, while having low roughness and free of surface defects and pinholes. The production of transparent films for advanced optoelectronic devices, optical coatings, and low- or high-k oxides is important for planar or complex shaped optics or surfaces. It provides opportunities for doping metal oxides to ternary, quaternary or other mixed metal oxides on glass, encapsulants or other substrates that facilitate diffusional movement of dopant species.

Process to produce lithium-polymer batteries

DOEpatents

MacFadden, K.O.

1998-06-30

A polymer bonded sheet product is described suitable for use as an electrode in a non-aqueous battery system. A porous electrode sheet is impregnated with a solid polymer electrolyte, so as to diffuse into the pores of the electrode. The composite is allowed to cool, and the electrolyte is entrapped in the porous electrode. The sheet products composed have the solid polymer electrolyte composition diffused into the active electrode material by melt-application of the solid polymer electrolyte composition into the porous electrode material sheet. The solid polymer electrolyte is maintained at a temperature that allows for rapid diffusion into the pores of the electrode. The composite electrolyte-electrode sheets are formed on current collectors and can be coated with solid polymer electrolyte prior to battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte coating has low resistance. 1 fig.

Reaction diffusion in the NiCrAl and CoCrAl systems

NASA Technical Reports Server (NTRS)

Levine, S. R.

1978-01-01

The paper assesses the effect of overlay coating and substrate composition on the kinetics of coating depletion by interdiffusion. This is accomplished by examining the constitution, kinetics and activation energies for a series of diffusion couples primarily of the NiCrAl/Ni-10Cr or CoCrAl/Ni-10Cr type annealed at temperatures in the range 1000-1205 C for times up to 500 hr. A general procedure is developed for analyzing diffusion in multicomponent multiphase systems. It is shown that by introducing the concept of beta-source strength, which can be determined from appropriate phase diagrams, the Wagner solution for consumption of a second phase in a semiinfinite couple is successfully applied to the analysis of MCrAl couples. Thus, correlation of beta-recession rate constants with couple composition, total and diffusional activation energies, and interdiffusion coefficients are determined.

Feasibility study of electrophoresis deposition of DyF3 on Nd-Fe-B particles for coercivity enhancement

NASA Astrophysics Data System (ADS)

Kim, K. M.; Kang, M. S.; Kwon, H. W.; Lee, J. G.; Yu, J. H.

2018-05-01

Feasibility of the electrophoresis deposition (EPD) technique for homogeneous and adhesive deposition of DyF3 particles on the Nd-Fe-B-type particles was studied, and coercivity enhancement in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD was investigated. HDDR-treated Nd12.5Fe80.6B6.4Ga0.3Nb0.2 particles were deposited with DyF3 particles by EPD. More homogeneous and adhesive deposition of DyF3 particles on the surface of Nd-Fe-B particles was made by the EPD with respect to conventional dip-coating, and this led to more active and homogeneous diffusion of Dy. More profound coercivity enhancement was achieved in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD compared to dip-coated particles.

Effect of Carbon Coating on Li4TiO12 of Anode Material for Hybrid Capacitor.

PubMed

Lee, Jong-Kyu; Lee, Byung-Gwan; Yoon, Jung-Rag

2015-11-01

The carbon-coated Li4Ti5O12 of anode material for hybrid capacitor was prepared by controlling carbonization time at 700 degrees C in nitrogen. With increasing of carbonization time, the discharge capacity and capacitance were decreased, while the equivalent series resistance was not changed remarkably. The rate capability and cycle performance of carbon-coated Li4Ti5O12 were larger than that of Li4Ti5O12. Carbon coating improved conductivity as well as Li-ion diffusion, and thus also resulted in good rate capabilities and cycle stability. The effects of carbon coating on the gas generation of hybrid capacitor were also discussed.

Response of Cr and Cr-Al coatings on Zircaloy-2 to high temperature steam

NASA Astrophysics Data System (ADS)

Zhong, Weicheng; Mouche, Peter A.; Heuser, Brent J.

2018-01-01

The oxidation behavior of chromium (Cr) and chromium-aluminum (CrAl) coatings with various compositions deposited on Zircaloy-2 to 700 °C high-temperature steam (HTS) exposure has been investigated. CrAl coatings with higher Al compositions demonstrate lower oxidation weight gain. A layer of γ-alumina developed on the CrAl coatings with Al composition over 43 at%, while Al2O3 and Cr2O3 developed on CrAl coatings with Al composition below 33 at%. Oxidation of Zircaloy-2 substrate was inhibited by the 1um coatings to 20 h HTS exposure. Coating constituent elements diffused into the substrate and formed intermetallic phases with the Zircaloy substrate. Thicker layers of intermetallic phases developed on the coatings with higher Al composition. The intermetallic phases included Fe and Ni, indicating the dissolution of second phase particles (SPPs) during HTS exposure.

In-pile test results of U-silicide or U-nitride coated U-7Mo particle dispersion fuel in Al

NASA Astrophysics Data System (ADS)

Kim, Yeon Soo; Park, J. M.; Lee, K. H.; Yoo, B. O.; Ryu, H. J.; Ye, B.

2014-11-01

U-silicide or U-nitride coated U-Mo particle dispersion fuel in Al (U-Mo/Al) was in-pile tested to examine the effectiveness of the coating as a diffusion barrier between the U-7Mo fuel kernels and Al matrix. This paper reports the PIE data and analyses focusing on the effectiveness of the coating in terms of interaction layer (IL) growth and general fuel performance. The U-silicide coating showed considerable success, but it also provided evidence for additional improvement for coating process. The U-nitride coated specimen showed largely inefficient results in reducing IL growth. From the test, important observations were also made that can be utilized to improve U-Mo/Al fuel performance. The heating process for coating turned out to be beneficial to suppress fuel swelling. The use of larger fuel particles confirmed favorable effects on fuel performance.

Corrosion properties of zirconium-based ceramic coatings for micro-bearing and biomedical applications

NASA Astrophysics Data System (ADS)

Walkowicz, J.; Zavaleyev, V.; Dobruchowska, E.; Murzynski, D.; Donkov, N.; Zykova, A.; Safonov, V.; Yakovin, S.

2016-03-01

Ceramic oxide ZrO2 and oxynitride ZrON coatings are widely used as protective coatings against diffusion and corrosion. The enhancement of the coatings' mechanical properties, as well as their wear and corrosion resistance, is very important for their tribological performance. In this work, ZrO2 and ZrON coatings were deposited by magnetron sputtering on stainless steel (AISI 316) substrates. The adhesion, hardness and elastic properties were evaluated by standard methods. The surface structure of the deposited coatings was observed by electron scanning microscopy (SEM) and atomic force microscopy (AFM). The composition of the coatings was analyzed by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS). The corrosion resistance properties were evaluated using the potentiodynamic method. The results show that the corrosion parameters are significantly increased in the cases of both oxynitride and oxide coatings in comparison with the stainless steel (AISI 316) substrates.

Porous coatings from wire mesh for bone implants

DOEpatents

Sump, Kenneth R.

1986-01-01

A method of coating areas of bone implant elements and the resulting implant having a porous coating are described. Preselected surface areas are covered by a preform made from continuous woven lengths of wire. The preform is compressed and heated to assure that diffusion bonding occurs between the wire surfaces and between the surface boundaries of the implant element and the wire surfaces in contact with it. Porosity is achieved by control of the resulting voids between the bonded wire portions.

Deuterium diffusion and retention in tungsten coated with barrier layer during ion irradiation

NASA Astrophysics Data System (ADS)

Begrambekov, L. B.; Kaplevsky, A. S.; Dovganyuk, S. S.; Evsin, A. E.; Baryshnikova, I. E.

2017-12-01

The results of the comparative analysis of low-temperature desorption of deuterium from tungsten coated with aluminum and yttrium films under the irradiation by hydrogen plasma with oxygen impurity are presented. The irradiation of aluminum or yttrium coating by H2+1%O2 plasma leads to the desorption of implanted deuterium from the samples. It was shown that the number of atoms desorbed depends on the sign of enthalpy of hydrogen solution in the metal film.

Oxygen-Barrier Coating for Titanium

NASA Technical Reports Server (NTRS)

Clark, Ronald K.; Unnam, Jalaiah

1987-01-01

Oxygen-barrier coating for titanium developed to provide effective and low-cost means for protecting titanium alloys from oxygen in environment when alloys used in high-temperature mechanical or structural applications. Provides protective surface layer, which reduces extent of surface oxidation of alloy and forms barrier to diffusion of oxygen, limiting contamination of substrate alloy by oxygen. Consists of submicron layer of aluminum deposited on surface of titanium by electron-beam evaporation, with submicron layer of dioxide sputtered onto aluminum to form coat.

Thermodynamics and kinetics of reactions in protective coating systems

NASA Technical Reports Server (NTRS)

Gupta, B.; Sarkhel, A.; Shankar, S.; Seigle, L.

1975-01-01

A study of the aluminization of Ni from packs containing various percentages of unalloyed Al confirmed that the surface aluminum content of specimens aluminized tends to decrease with time and consequently a simple parabolic law for the weight-gain vs. time relationship is not obeyed. The diffusivity-composition relationship in NiAl was examined, and a set of curves is presented. A numerical method for the calculation of coating dissolution rates was developed and applied to NiAl-Ni3Al type of coatings.

Guanidine Soaps As Vehicles For Coating Ceramic Fibers

NASA Technical Reports Server (NTRS)

Philipp, Warren H.; Veitch, Lisa C.; Jaskowiak, Martha H.

1994-01-01

Soaps made from strong organic base guanidine and organic fatty acids serve as vehicles and binders for coating ceramic fibers, various smooth substrates, and other problematic surfaces with thin precious-metal or metal-oxide films. Films needed to serve as barriers to diffusion in fiber/matrix ceramic composite materials. Guanidine soaps entirely organic and burn off, leaving no residues.

The Effectiveness of Surface Coatings on Preventing Interfacial Reaction During Ultrasonic Welding of Aluminum to Magnesium

NASA Astrophysics Data System (ADS)

Panteli, Alexandria; Robson, Joseph D.; Chen, Ying-Chun; Prangnell, Philip B.

2013-12-01

High power ultrasonic spot welding (USW) is a solid-state joining process that is advantageous for welding difficult dissimilar material couples, like magnesium to aluminum. USW is also a useful technique for testing methods of controlling interfacial reaction in welding as the interface is not greatly displaced by the process. However, the high strain rate deformation in USW has been found to accelerate intermetallic compound (IMC) formation and a thick Al12Mg17 and Al3Mg2 reaction layer forms after relatively short welding times. In this work, we have investigated the potential of two approaches for reducing the IMC reaction rate in dissimilar Al-Mg ultrasonic welds, both involving coatings on the Mg sheet surface to (i) separate the join line from the weld interface, using a 100- μm-thick Al cold spray coating, and (ii) provide a diffusion barrier layer, using a thin manganese physical vapor deposition (PVD) coating. Both methods were found to reduce the level of reaction and increase the failure energy of the welds, but their effectiveness was limited due to issues with coating attachment and survivability during the welding cycle. The effect of the coatings on the joint's interface microstructure, and the fracture behavior have been investigated in detail. Kinetic modeling has been used to show that the benefit of the cold spray coating can be attributed to the reaction rate reverting to that expected under static conditions. This reduces the IMC growth rate by over 50 pct because at the weld line, the high strain rate dynamic deformation in USW normally enhances diffusion through the IMC layer. In comparison, the thin PVD barrier coating was found to rapidly break up early in USW and become dispersed throughout the deformation layer reducing its effectiveness.

Carbide coated fibers in graphite-aluminum composites

NASA Technical Reports Server (NTRS)

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1975-01-01

The study of protective-coupling layers of refractory metal carbides on the graphite fibers prior to their incorporation into composites is presented. Such layers should be directly wettable by liquid aluminum and should act as diffusion barriers to prevent the formation of aluminum carbide. Chemical vapor deposition was used to uniformly deposit thin, smooth, continuous coats of ZrC on the carbon fibers of tows derived from both rayon and polyacrylonitrile. A wet chemical coating of the fibers, followed by high-temperature treatment, was used, and showed promise as an alternative coating method. Experiments were performed to demonstrate the ability of aluminum alloys to wet carbide surfaces. Titanium carbide, zirconium carbide and carbide-coated graphite surfaces were successfully wetted. Results indicate that initial attempts to wet surfaces of ZrC-coated carbon fibers appear successful.

Immobilization of hyaluronic acid on plasma-sprayed porous titanium coatings for improving biological properties.

PubMed

Ao, Haiyong; Xie, Youtao; Qin, An; Ji, Heng; Yang, Shengbing; Huang, Liping; Zheng, Xuebin; Tang, Tingting

2014-01-01

In the present study, hyaluronic acid (HyA) was covalently immobilized onto titanium coatings to improve their biological properties. Diffuse reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to characterize the HyA-modified titanium coating. HyA-modified titanium coatings possess better cell-material interaction, and human mesenchymal stem cells present good adhesive morphologies on the surface of TC-AAH. The results of subsequent cellular evaluation showed that the immobilization of HyA on titanium coatings could improve hMSC attachment, proliferation, and differentiation. In vivo evaluation of implants in rabbit femur condyle defect model showed improvements of early osseointegration and bone-to-implant contact of TC-AAH. In conclusion, immobilization of HyA could improve biological properties of titanium coatings.

Refractometry studies of the optical properties of polymer films and the development of polymer coated refractive index sensors

NASA Astrophysics Data System (ADS)

Saunders, John Edward

Sensors for real-time monitoring of environmental contaminants are essential for protecting ecosystems and human health. Refractive index sensing is a non-selective technique that can be used to measure almost any analyte. Miniaturized refractive index sensors, such as silicon-on-insulator (SOI) microring resonators are one possible platform, but require coatings selective to the analytes of interest. A homemade prism refractometer is reported and used to characterize the interactions between polymer films and liquid or vapour-phase analytes. A camera was used to capture both Fresnel reflection and total internal reflection within the prism. For thin-films (d = 10 μm - 100 μm), interference fringes were also observed. Fourier analysis of the interferogram allowed for simultaneous extraction of the average refractive index and film thickness with accuracies of Δn = 1-7 x10-4 and Δd < 3-5%. The refractive indices of 29 common organic solvents as well as aqueous solutions of sodium chloride, sucrose, ethylene glycol, glycerol, and dimethylsulfoxide were measured at λ = 1550 nm. These measurements will be useful for future calibrations of near-infrared refractive index sensors. A mathematical model is presented, where the concentration of analyte adsorbed in a film can be calculated from the refractive index and thickness changes during uptake. This model can be used with Fickian diffusion models to measure the diffusion coefficients through the bulk film and at the film-substrate interface. The diffusion of water and other organic solvents into SU-8 epoxy was explored using refractometry and the diffusion coefficient of water into SU-8 is presented. Exposure of soft baked SU-8 films to acetone, acetonitrile and methanol resulted in rapid delamination. The diffusion of volatile organic compound (VOC) vapours into polydimethylsiloxane and polydimethyl-co-polydiphenylsiloxane polymers was also studied using refractometry. Diffusion and partition coefficients are reported for several analytes. As a model system, polydimethyl-co-diphenylsiloxane films were coated onto SOI microring resonators. After the development of data acquisition software, coated devices were exposed to VOCs and the refractive index response was assessed. More studies with other polymers are required to test the viability of this platform for environmental sensing applications.

Development of Surfaces Optically Suitable for Flat Solar Panels. [using a reflectometer which separately evaluates spectral and diffuse reflectivities of surfaces

NASA Technical Reports Server (NTRS)

1979-01-01

A reflectometer which can separately evaluate the spectral and diffuse reflectivities of surfaces is described. A phase locked detection system for the reflectometer is also described. A selective coating on aluminum potentially useful for flat plate solar collector applications is presented. The coating is composed of strongly bound copper oxide (divalent) and is formed by an etching process performed on an aluminum alloy with high copper content. Fabrication costs are expected to be small due to the one stop fabrication process. A number of conclusions gathered from the literature as to the required optical properties of flat plate solar collectors are discussed.

High temperature coatings for gas turbines

DOEpatents

Zheng, Xiaoci Maggie

2003-10-21

Coating for high temperature gas turbine components that include a MCrAlX phase, and an aluminum-rich phase, significantly increase oxidation and cracking resistance of the components, thereby increasing their useful life and reducing operating costs. The aluminum-rich phase includes aluminum at a higher concentration than aluminum concentration in the MCrAlX alloy, and an aluminum diffusion-retarding composition, which may include cobalt, nickel, yttrium, zirconium, niobium, molybdenum, rhodium, cadmium, indium, cerium, iron, chromium, tantalum, silicon, boron, carbon, titanium, tungsten, rhenium, platinum, and combinations thereof, and particularly nickel and/or rhenium. The aluminum-rich phase may be derived from a particulate aluminum composite that has a core comprising aluminum and a shell comprising the aluminum diffusion-retarding composition.

Using Diffusion Bonding in Making Piezoelectric Actuators

NASA Technical Reports Server (NTRS)

Sager, Frank E.

2003-01-01

A technique for the fabrication of piezoelectric actuators that generate acceptably large forces and deflections at relatively low applied voltages involves the stacking and diffusion bonding of multiple thin piezoelectric layers coated with film electrodes. The present technique stands in contrast to an older technique in which the layers are bonded chemically, by use of urethane or epoxy agents. The older chemical-bonding technique entails several disadvantages, including the following: It is difficult to apply the bonding agents to the piezoelectric layers. It is difficult to position the layers accurately and without making mistakes. There is a problem of disposal of hazardous urethane and epoxy wastes. The urethane and epoxy agents are nonpiezoelectric materials. As such, they contribute to the thickness of a piezoelectric laminate without contributing to its performance; conversely, for a given total thickness, the performance of the laminate is below that of a unitary piezoelectric plate of the same thickness. The figure depicts some aspects of the fabrication of a laminated piezoelectric actuator by the present diffusion- bonding technique. First, stock sheets of the piezoelectric material are inspected and tested. Next, the hole pattern shown in the figure is punched into the sheets. Alternatively, if the piezoelectric material is not a polymer, then the holes are punched in thermoplastic films. Then both faces of each punched piezoelectric sheet or thermoplastic film are coated with a silver-ink electrode material by use of a silkscreen printer. The electrode and hole patterns are designed for minimal complexity and minimal waste of material. After a final electrical test, all the coated piezoelectric layers (or piezoelectric layers and coated thermoplastic films) are stacked in an alignment jig, which, in turn, is placed in a curved press for the diffusion-bonding process. In this process, the stack is pressed and heated at a specified curing temperature and pressure for a specified curing time. The pressure, temperature, and time depend on the piezoelectric material selected. At the end of the diffusion-bonding process, the resulting laminated piezoelectric actuator is tested to verify the adequacy of the mechanical output as a function of an applied DC voltage.

Diffusion and phase transformation behavior in poly-synthetically-twinned (PST) titanium-aluminum/titanium diffusion couple

NASA Astrophysics Data System (ADS)

Pan, Ling

Motivated by the great potential applications of gamma titanium aluminide based alloys and the important effect of diffusion on the properties of gamma-TiAl/alpha2-Ti3Al two-phase lamellar structure, we conduct this thesis research to explore the microstructural evolution and interdiffusion behavior, and their correlations in multi-phase solid state diffusion couples made up of pure titanium and polysynthetically-twinned (PST) Ti-49.3 at.% Al "single" crystal, in the temperature range of 973--1173 K. The diffusion couples are prepared by high vacuum hot-pressing, with the diffusion direction parallel to the lamellar planes. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) are employed to observe the microstructure at various interfaces/interphases. A reaction zone (RZ) of polycrystalline alpha 2-Ti3Al phase forms along the PST Ti-Al/Ti bonding interface having a wavy interface with the PST crystal and exhibits deeper penetration in alpha2 lamellae, consisting of many fine alpha2 and secondary gamma laths, than in primary gamma lamellae. Direct measurement of the RZ thickness on SEM back-scattered electron images reveals a parabolic growth of the RZ, indicating a macroscopically diffusion-controlled growth. Concentration profiles from Ti, through the RZ, into the alpha2 lamellae of the PST crystal are measured by quantitative energy-dispersive x-ray spectroscopy (EDS) in a scanning transmission electron microscope (STEM). A plateau of composition adjacent to the RZ/(mixed alpha2 lath in PST) interface forms in the deeply penetrated RZ grains, implying a diffusion barrier crossing the interface and some extent of interface control in the RZ grain growth. The interdiffusion coefficient is evaluated both independent of composition and as a function of composition. No significant concentration dependence of the interdiffusion coefficients is observed using Boltzmann-Matano analysis. The temperature dependence of the interdiffusion coefficients obeys the Arrhenius relationship with a pre-exponential factor of D 0 = (7.56 +/- 7.14) x 10-5 m2/s and an activation enthalpy of Q = 255.6+8.9-8.3 kJ/mol = (2.65 +/- 0.09) eV/atom. The initial nucleation stage of the RZ grains plays an important role in the later microstructural evolution as does the local mass balance. The interfacial energy and the strain energy in the deeply penetrated RZ grains are possible reasons for the plateau.

NASA's activities in the conservation of strategic aerospace materials

NASA Technical Reports Server (NTRS)

Stephens, J. R.

1980-01-01

The United States imports 50-100 percent of certain metals critical to the aerospace industry, namely, cobalt, columbium, chromium, and tantalum. In an effort to reduce this dependence on foreign sources, NASA is planning a program called Conservation of Strategic Aerospace Materials (COSAM), which will provide technology minimizing strategic metal content in the components of aerospace structures such as aircraft engines. With a proposed starting date of October 1981, the program will consist of strategic element substitution, process technology development, and alternate materials research. NASA's two-fold pre-COSAM studies center on, first, substitution research involving nickel-base and cobalt-base superalloys (Waspaloy, Udimet-700, MAE-M247, Rene 150, HA-188) used in turbine disks, low-pressure blades, turbine blades, and combustors; and, second, alternate materials research devoted initially to investigating possible structural applications of the intermetallic alloys nickel aluminide and iron aluminide.

The Effect of Nb Addition on the Microstructure and the High-Temperature Strength of Fe3Al Aluminide

NASA Astrophysics Data System (ADS)

Kratochvíl, Petr; Švec, Martin; Král, Robert; Veselý, Jozef; Lukáč, Pavel; Vlasák, Tomáš

2018-02-01

The microstructural and high-temperature mechanical properties of Fe-26Al-xNb (x = 3 and 5 at. pct) are compared. The alloys were investigated "as cast" and after hot rolling at 1473 K (1200 °C). Scanning electron microscopes equipped with EDS and EBSD were used for the microstructure and phase identification. The addition of 3 at. pct of Nb into the Fe3Al matrix leads to the formation of C14 λ—Laves phase (Fe,Al)2Nb (LP) particles spread in the Fe3Al matrix, while an eutectic with thin lamellae of LP C14 λ—Laves phase (Fe,Al)2Nb and matrix is also formed in the iron aluminide with 5 at. pct of Nb. The presence of incoherent precipitates is connected with the enhancement of the high-temperature strength and creep resistance.

Titanium Aluminide Casting Technology Development

NASA Astrophysics Data System (ADS)

Bünck, Matthias; Stoyanov, Todor; Schievenbusch, Jan; Michels, Heiner; Gußfeld, Alexander

2017-12-01

Titanium aluminide alloys have been successfully introduced into civil aircraft engine technology in recent years, and a significant order volume increase is expected in the near future. Due to its beneficial buy-to-fly ratio, investment casting bears the highest potential for cost reduction of all competing production technologies for TiAl-LPTB. However, highest mechanical properties can be achieved by TiAl forging. In view of this, Access e.V. has developed technologies for the production of TiAl investment cast parts and TiAl die cast billets for forging purposes. While these parts meet the highest requirements, establishing series production and further optimizing resource and economic efficiency are present challenges. In order to meet these goals, Access has recently been certified according to aircraft standards, aiming at qualifying parts for production on technology readiness level 6. The present work gives an overview of the phases of development and certification.

Assessment of Fatigue Resistance of Aluminide Layers on MAR 247 Nickel Super Alloy with Full-Field Optical Strain Measurements

NASA Astrophysics Data System (ADS)

Kukla, D.; Brynk, T.; Pakieła, Z.

2017-08-01

This work presents the results of fatigue tests of MAR 247 alloy flat specimens with aluminides layers of 20 or 40 µm thickness obtained in CVD process. Fatigue test was conducted at amplitude equal to half of maximum load and ranging between 300 and 650 MPa (stress asymmetry ratio R = 0, frequency f = 20 Hz). Additionally, 4 of the tests, characterized by the highest amplitude, were accompanied with non-contact strain field measurements by means of electronic speckle pattern interferometry and digital image correlation. Results of these measurements allowed to localize the areas of deformation concentration identified as the damage points of the surface layer or advanced crack presence in core material. Identification and observation of the development of deformation in localization areas allowed to assess fatigue-related phenomena in both layer and substrate materials.

Development of Improved Iron-Aluminide Filter Tubes and Elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Judkins, R.R.; Sutton, T.G.; Miller, C.J.

2008-01-14

The purpose of this Cooperative Research and Development Agreement (CRADA) was to explore and develop advanced manufacturing techniques to fabricate sintered iron-aluminide intermetallic porous bodies used for gas filtration so as to reduce production costs while maintaining or improving performance in advanced coal gasification and combustion systems. The use of a power turbine fired with coal-derived synthesis gas requires some form of gas cleaning in order to protect turbine and downstream components from degradation by erosion, corrosion, and/or deposition. Hot-gas filtration is one form of cleaning that offers the ability to remove particles from the gases produced by gasification processesmore » without having to substantially cool and, possibly, reheat them before their introduction into the turbine. This technology depends critically on materials durability and reliability, which have been the subject of study for a number of years.« less

Plastic flow and microstructure of cast nickel aluminides at 1273 K

NASA Astrophysics Data System (ADS)

Schneibel, J. H.; Porter, W. D.; Horton, J. A.

1987-12-01

Chill-cast nickel aluminides based on Ni3Al were compression-tested in vacuum at 1273 K at strain rates ranging from 10-5 s-1 to 10-1 s-1. As the strain rate increases, the propensity for intergranular cracking increases. The ductile-to-brittle transition strain rate (DBTS) of as-cast Ni-22.5Al-0.5Hf-0.1B (at. pct) is approximately 10-1 s-1. Homogenization lowers this value by three orders of magnitude, to 10-4 s-1 (a homogenized specimen disintegrated completely at a rate of 10-3 s-1). The fine-grained structure of the as-cast alloy plays an important role in its relatively high DBTS. A hafnium-free alloy, Ni-24A1-0.1B, on the other hand, shows only a weak dependence of the DBTS on prior homogenization, and possible reasons for this finding are discussed.

Ni{sub 3}Al technology transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Viswanathan, S.; Santella, M.L.

1997-04-01

Ductile Ni{sub 3}Al and Ni{sub 3}Al-based alloys have been identified for a range of applications. These applications require the use of material in a variety of product forms such as sheet, plate, bar, wire, tubing, piping, and castings. Although significant progress has been made in the melting, casting, and near-net-shape forming of nickel aluminides, some issues still remain. These include the need for: (1) high-strength castable composition for many applications that have been identified; (2) castability (mold type, fluidity, hot-shortness, porosity, etc.); (3) weld reparability of castings; and (4) workability of cast or powder metallurgy product to sheet, bar, andmore » wire. The four issues listed above can be {open_quotes}show stoppers{close_quotes} for the commercial application of nickel aluminides. This report describes the work completed to address some of these issues during FY 1996.« less

Vacuum plasma coatings for turbine blades

NASA Technical Reports Server (NTRS)

Holmes, R. R.

1985-01-01

Turbine blades, vacuum plasma spray coated with NiCrAlY, CoCrAlY or NiCrAlY/Cr2O3, were evaluated and rated superior to standard space shuttle main engine (SSME) coated blades. Ratings were based primarily on 25 thermal cycles in the MSFC Burner Rig Tester, cycling between 1700 F (gaseous H2) and -423 F (liquid H2). These tests showed no spalling on blades with improved vacuum plasma coatings, while standard blades spalled. Thermal barrier coatings of ZrO2, while superior to standard coatings, lacked the overall performance desired. Fatigue and tensile specimens, machined from MAR-M-246(Hf) test bars identical to the blades were vacuum plasma spray coated, diffusion bond treated, and tested to qualify the vacuum plasma spray process for flight hardware testing and application. While NiCrAlY/Cr2O3 offers significant improvement over standard coatings in durability and thermal protection, studies continue with an objective to develop coatings offering even greater improvements.

PROCESS OF COATING METALS WITH BISMUTH OR BISMUTH-BASE ALLOYS

DOEpatents

Beach, J.G.

1958-01-28

A method is described for producing coatings of bismuth or bismuth alloys on a metal base. This is accomplished by electrodepositing the bismuth from an aqueous solution of BiCl/sub 3/, and by making the metal base alternately the cathode and the anode, the cathode periods being twice as long as the anode periods. In one embodiment a nickel coating is first electrodeposited in a known way, and this nickel plated piece is tae base upon which tae bismuth is deposited by the process of this patent. The coated piece is then heat treated to produce a homogeneous Ni--Bi alloy by diffusion.

Size and shape effects on diffusion and absorption of colloidal particles near a partially absorbing sphere: implications for uptake of nanoparticles in animal cells.

PubMed

Shi, Wendong; Wang, Jizeng; Fan, Xiaojun; Gao, Huajian

2008-12-01

A mechanics model describing how a cell membrane with diffusive mobile receptors wraps around a ligand-coated cylindrical or spherical particle has been recently developed to model the role of particle size in receptor-mediated endocytosis. The results show that particles in the size range of tens to hundreds of nanometers can enter cells even in the absence of clathrin or caveolin coats. Here we report further progress on modeling the effects of size and shape in diffusion, interaction, and absorption of finite-sized colloidal particles near a partially absorbing sphere. Our analysis indicates that, from the diffusion and interaction point of view, there exists an optimal hydrodynamic size of particles, typically in the nanometer regime, for the maximum rate of particle absorption. Such optimal size arises as a result of balance between the diffusion constant of the particles and the interaction energy between the particles and the absorbing sphere relative to the thermal energy. Particles with a smaller hydrodynamic radius have larger diffusion constant but weaker interaction with the sphere while larger particles have smaller diffusion constant but stronger interaction with the sphere. Since the hydrodynamic radius is also determined by the particle shape, an optimal hydrodynamic radius implies an optimal size as well as an optimal aspect ratio for a nonspherical particle. These results show broad agreement with experimental observations and may have general implications on interaction between nanoparticles and animal cells.

Size and shape effects on diffusion and absorption of colloidal particles near a partially absorbing sphere: Implications for uptake of nanoparticles in animal cells

NASA Astrophysics Data System (ADS)

Shi, Wendong; Wang, Jizeng; Fan, Xiaojun; Gao, Huajian

2008-12-01

A mechanics model describing how a cell membrane with diffusive mobile receptors wraps around a ligand-coated cylindrical or spherical particle has been recently developed to model the role of particle size in receptor-mediated endocytosis. The results show that particles in the size range of tens to hundreds of nanometers can enter cells even in the absence of clathrin or caveolin coats. Here we report further progress on modeling the effects of size and shape in diffusion, interaction, and absorption of finite-sized colloidal particles near a partially absorbing sphere. Our analysis indicates that, from the diffusion and interaction point of view, there exists an optimal hydrodynamic size of particles, typically in the nanometer regime, for the maximum rate of particle absorption. Such optimal size arises as a result of balance between the diffusion constant of the particles and the interaction energy between the particles and the absorbing sphere relative to the thermal energy. Particles with a smaller hydrodynamic radius have larger diffusion constant but weaker interaction with the sphere while larger particles have smaller diffusion constant but stronger interaction with the sphere. Since the hydrodynamic radius is also determined by the particle shape, an optimal hydrodynamic radius implies an optimal size as well as an optimal aspect ratio for a nonspherical particle. These results show broad agreement with experimental observations and may have general implications on interaction between nanoparticles and animal cells.

Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability

NASA Astrophysics Data System (ADS)

Forsén, R.; Ghafoor, N.; Odén, M.

2013-12-01

A concept to improve hardness and thermal stability of unstable multilayer alloys is presented based on control of the coherency strain such that the driving force for decomposition is favorably altered. Cathodic arc evaporated cubic TiCrAlN/Ti1-xCrxN multilayer coatings are used as demonstrators. Upon annealing, the coatings undergo spinodal decomposition into nanometer-sized coherent Ti- and Al-rich cubic domains which is affected by the coherency strain. In addition, the growth of the domains is restricted by the surrounding TiCrN layer compared to a non-layered TiCrAlN coating which together results in an improved thermal stability of the cubic structure. A significant hardness increase is seen during decomposition for the case with high coherency strain while a low coherency strain results in a hardness decrease for high annealing temperatures. The metal diffusion paths during the domain coarsening are affected by strain which in turn is controlled by the Cr-content (x) in the Ti1-xCrxN layers. For x = 0 the diffusion occurs both parallel and perpendicular to the growth direction but for x > =0.9 the diffusion occurs predominantly parallel to the growth direction. Altogether this study shows a structural tool to alter and fine-tune high temperature properties of multicomponent materials.

Accurate measurements of the thermal diffusivity of thin filaments by lock-in thermography

NASA Astrophysics Data System (ADS)

Salazar, Agustín; Mendioroz, Arantza; Fuente, Raquel; Celorrio, Ricardo

2010-02-01

In lock-in (modulated) thermography the lateral thermal diffusivity can be obtained from the slope of the linear relation between the phase of the surface temperature and the distance to the heating spot. However, this slope is greatly affected by heat losses, leading to an overestimation of the thermal diffusivity, especially for thin samples of poor thermal conducting materials. In this paper, we present a complete theoretical model to calculate the surface temperature of filaments heated by a focused and modulated laser beam. All heat losses have been included: conduction to the gas, convection, and radiation. Monofilaments and coated wires have been studied. Conduction to the gas has been identified as the most disturbing effect preventing from the direct use of the slope method to measure the thermal diffusivity. As a result, by keeping the sample in vacuum a slope method combining amplitude and phase can be used to obtain the accurate diffusivity value. Measurements performed in a wide variety of filaments confirm the validity of the conclusion. On the other hand, in the case of coated wires, the slope method gives an effective thermal diffusivity, which verifies the in-parallel thermal resistor model. As an application, the slope method has been used to retrieve the thermal conductivity of thin tubes by filling them with a liquid of known thermal properties.

Structural & oxidation behavior of TiN & AlxTi1-xN coatings deposited by CA-PVD technique

NASA Astrophysics Data System (ADS)

Thorat, Nirmala; Mundotia, Rajesh; Varma, Ranjana; Kale, Ashwin; Mhatre, Umesh; Patel, Nainesh

2018-04-01

Coatings with thermal stability at elevated temperatures are prerequisite for various high speed machining and high temperature applications. The present work compares the oxidation behavior of the AlxTi1-xN coating prepared with different Al composition. Coated samples were tested at different temperatures in the range of 400 - 800 C to study their oxidation behavior. Percentage weight gain of all the samples were evaluated using high accuracy weighing balance. The depth of oxide layers were studied using Calo-test instrument. The XRD analysis was carried out to specify the phase structure. Higher oxidation rate was observed for TiN coating at all the oxidation temperatures. Oxidation rate was higher for Al13Ti87N and Al70Ti30N coatings compared to Al60Ti40N and Al50Ti50N coatings which exhibits better oxygen diffusion barrier at all the temperature.

Crystallization of DNA-coated colloids

PubMed Central

Wang, Yu; Wang, Yufeng; Zheng, Xiaolong; Ducrot, Étienne; Yodh, Jeremy S.; Weck, Marcus; Pine, David J.

2015-01-01

DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperature-sensitive diffusion between aggregated DNA-coated colloids. PMID:26078020

Corrosion behavior of ceramic-coated ZIRLO™ exposed to supercritical water

NASA Astrophysics Data System (ADS)

Mandapaka, Kiran K.; Cahyadi, Rico S.; Yalisove, Steven; Kuang, Wenjun; Sickafus, K.; Patel, Maulik K.; Was, Gary S.

2018-01-01

The corrosion behavior of ceramic coated ZIRLO™ tubing was evaluated in a supercritical water (SCW) environment to determine its behavior in high temperature water. Two coating architectures were analyzed; a 4 bi-layer TiAlN/TiN coating with Ti bond coat, and a TiN monolithic coating with Ti bond layer on ZIRLO™ tubes using cathodic arc physical vapor deposition (CA-PVD) technique. Femtosecond laser ablation was used to introduce reproducible defects in some of the coated tubes. On exposure to deaerated supercritical water at 542 °C for 48 h, coated tubes exhibited significantly higher weight gain compared to uncoated ZIRLO™. Examination revealed formation of a uniform ZrO2 layer beneath the coating of a thickness similar to that on the uncoated tube inner surface. The defects generated during the coating process acted as preferential paths for diffusion of oxygen resulting in the oxidation of substrate ZIRLO™. However, there was no delamination of the coating. There were insignificant differences in the oxidation weight gain between laser ablated and non-ablated tubes and the laser induced defects did not spread beyond their original size.

Chloride-induced corrosion mechanism and rate of enamel- and epoxy-coated deformed steel bars embedded in mortar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Fujian; Chen, Genda; Brow, Richard K.

The chloride-induced corrosion mechanisms of uncoated, pure enamel (PE)-coated, mixed enamel (ME)-coated, double enamel (DE)-coated, and fusion bonded epoxy (FBE)-coated deformed steel bars embedded in mortar cylinders are investigated in 3.5 wt.% NaCl solution and compared through electrochemical tests and visual inspection. Corrosion initiated after 29 or 61 days of tests in all uncoated and enamel-coated steel bars, and after 244 days of tests in some FBE-coated steel bars. In active stage, DE- and FBE-coated steel bars are subjected to the highest and lowest corrosion rates, respectively. The uncoated and ME-coated steel bars revealed relatively uniform corrosion while the PE-,more » DE-, and FBE-coated steel bars experienced pitting corrosion around damaged coating areas. Due to the combined effect of ion diffusion and capillary suction, wet–dry cyclic immersion caused more severe corrosion than continuous immersion. Both exposure conditions affected the corrosion rate more significantly than the water–cement ratio in mortar design.« less

Study of cerium diffusion in undoped lithium-6 enriched glass with Rutherford backscattering spectrometry

NASA Astrophysics Data System (ADS)

Zhang, Xiaodong; Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D.; Hayward, Jason P.

2016-07-01

Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick's second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.

Permanganate diffusion and reaction in sedimentary rocks.

PubMed

Huang, Qiuyuan; Dong, Hailiang; Towne, Rachael M; Fischer, Timothy B; Schaefer, Charles E

2014-04-01

In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate. Copyright © 2014 Elsevier B.V. All rights reserved.

Fabrication and Characterization of Novel Refractory Coatings Using Combinatorial Nanocalorimetry

DTIC Science & Technology

2015-07-21

The report summarizes the results of solid-state reaction in Zr /B and Zr /B4C multilayers, oxidation of ZrB2, the effect of Nb and C doping on the...oxidation resistance of the coatings at temperatures below 1000 K, but the temperature-dependence of the diffusion rate constant suggests that Nb ...28 B4. Zr -B- Nb oxidation

Commissioning results of Nb 3Sn cavity vapor diffusion deposition system at JLab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eremeev, Grigory; Clemens, William A.; Macha, Kurt M.

2015-09-01

Nb 3Sn as a BCS superconductor with a superconducting critical temperature higher than that of niobium offers potential benefit for SRF cavities via a lower-than-niobium surface resistance at the same temperature and frequency. A Nb 3Sn vapor diffusion deposition system designed for coating of 1.5 and 1.3 GHz single-cell cavities was built and commissioned at JLab. As the part of the commissioning, RF performance at 2.0 K of a single-cell 1.5 GHz CEBAF-shaped cavity was measured before and after coating in the system. Before Nb 3Sn coating the cavity had a Q 0 of about 10 10 and was limitedmore » by the high field Q-slope at E acc ≅ 27 MV/m. Coated cavity exhibited the superconducting transition at about 17.9 K. The low-field quality factor was about 5∙10 9 at 4.3 K and 7∙10 9 at 2.0 K decreasing with field to about 1∙10 9 at E acc ≅ 8 MV/m at both temperatures. The highest field was limited by the available RF power.« less

Comparing Two Antibacterial Treatments for Bioceramic Coatings at Short Culture Times

NASA Astrophysics Data System (ADS)

Melero, H.; Madrid, C.; Fernández, J.; Guilemany, J. M.

2014-04-01

Plasma-sprayed hydroxyapatite coatings were employed industrially for decades to improve osteointegration of articular implants, but many studies have warned about the problems inherent to this procedure (mechanical properties, harmful phases). Consequently, a combination of hydroxyapatite with TiO2 sprayed by high velocity oxy-fuel spray was considered in this study. As infection after joint replacement surgery is one of the most critical concerns when considering implant performance, it is necessary to study possible ways to reduce or eliminate it. Two coating treatments were chosen for this study: addition of a percentage of ZnO and immersion in gentamicin for 24 h. Furthermore, three bacteria were considered: Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The evolution of bacteria viability in solution was measured at 0, 2, and 4 h; and plate assays were performed to study antibacterial effects by diffusion. The results show an important antibacterial effect of the as-sprayed coating, attributed to the presence of -OH radicals on the surface. The presence of ZnO did not have any additional influence on bacteria viability, but gentamicin-treated samples showed an improvement in antibacterial behavior for Gram-negative bacteria in solution, as well as a bactericidal effect in diffusion conditions.

Multilayer design of hybrid phosphor film for application in LEDs

NASA Astrophysics Data System (ADS)

Güner, Tuğrul; Köseoğlu, Devrim; Demir, Mustafa M.

2016-10-01

Crosslinked polydimethylsiloxane (PDMS) composite coatings containing luminescent micrometer-sized yellow Y3Al5O12:Ce3+ (YAG:Ce3+) particles were prepared by spraying for potential applications in solid-state lighting. Blue light was down converted by phosphor particles to produce white light, yet poor color properties of YAG:Ce3+ stemmed from a deficiency of red. When nitride-based red phosphor was simply blended into the system, the electrostatic interaction of negatively charged YAG:Ce3+ and positively charged red phosphor particles caused remarkable clustering and heterogeneity in particle dispersion. Consequently, the light is dominantly blue and shifted to cold white. In other case, phosphor particles were sprayed onto the diffused polycarbonate substrate in stacked layers. Coatings with >80% inorganic content by mass with a thickness of 60 μm were subjected to thermal crosslinking, which the presence of the phosphor particles obstructed, presumably due to the hindrance of large phosphor particles in the diffusion of PDMS precursors. The coating of YAG:Ce3+ first followed by red phosphor in stacked layers produced better light output and color properties than the coating obtained by spraying the mixture at once. Monte Carlo simulation validated the hypothesis.

Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites

NASA Astrophysics Data System (ADS)

Smith, P. R.; Graves, J. A.; Rhodes, Cg.

1994-06-01

The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti3Al ( α 2) + disordered beta (β), while the Ti-21 Al-22Nb matrix contained three phases: α2, ordered beta ( β 0), and ordered orthorhombic (O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products (i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in the α 2 + β matrix composite were much more rapid than in the O + β 0 + α 2 matrix composite. Additionally, interfacial reaction in the α 2 + β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in the O + β 0+ α 2 matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α2+ β alloy in all of these mechanical behavioral areas, on both an absolute and a specific (i.e., density corrected) basis.

Numerical analysis of heat treatment of TiCN coated AA7075 aluminium alloy

NASA Astrophysics Data System (ADS)

Srinath, M. K.; Prasad, M. S. Ganesha

2018-04-01

The Numerical analysis of heat treatments of TiCN coated AA7075 aluminium alloys is presented in this paper. The Convection-Diffusion-Reaction (CDR) equation with solutions in the Streamlined-Upward Petrov-Galerkin (SUPG) method for different parameters is provided for the understanding of the process. An experimental process to improve the surface properties of AA-7075 aluminium alloy was attempted through the coatings of TiCN and subsequent heat treatments. From the experimental process, optimized temperature and time was obtained which gave the maximum surface hardness and corrosion resistance. The paper gives an understanding and use of the CDR equation for application of the process. Expression to determine convection, diffusion and reaction parameters are provided which is used to obtain the overall expression of the heat treatment process. With the substitution of the optimized temperature and time, the governing equation may be obtained. Additionally, the total energy consumed during the heat treatment process is also developed to give a mathematical formulation of the energy consumed.

Thermal barrier coatings

DOEpatents

Alvin, Mary Anne [Pittsburg, PA

2010-06-22

This disclosure addresses the issue of providing a metallic-ceramic overlay coating that potentially serves as an interface or bond coat layer to provide enhanced oxidation resistance to the underlying superalloy substrate via the formation of a diffusion barrier regime within the supporting base material. Furthermore, the metallic-ceramic coating is expected to limit the growth of a continuous thermally grown oxide (TGO) layer that has been primarily considered to be the principal cause for failure of existing TBC systems. Compositional compatibility of the metallic-ceramic with traditional yttria-stabilized zirconia (YSZ) top coats is provided to further limit debond or spallation of the coating during operational use. A metallic-ceramic architecture is disclosed wherein enhanced oxidation resistance is imparted to the surface of nickel-based superalloy or single crystal metal substrate, with simultaneous integration of the yttria stabilized zirconia (YSZ) within the metallic-ceramic overlayer.

The Study of Indicatrices of Space Object Coatings in a Controlled Laboratory Environment

NASA Astrophysics Data System (ADS)

Koshkin, N.; Burlak, N.; Petrov, M.; Strakhova, S.

The indicatrices of light scattering by radiation balance coatings used on space objects (SO) were determined in the laboratory experiment in a controlled condition. The laboratory device for the physical simulation of photometric observations of space objects in orbit, which was used in this case to study optical properties of coating samples, is described. The features of light reflection off plane coating samples, including multi-layer insulation (MLI) blankets, metal surfaces coated with several layers of enamel EP-140, special polyacrylate enamel AK-512 and matte finish Tp-CO-2, were determined. The indicated coatings are compound reflectors which exhibit both diffuse and specular reflections. The data obtained are to be used in the development of computer optical-geometric models of space objects or their fragments (space debris) to interpret the photometry results for real space objects.

Advanced thin film thermocouples

NASA Technical Reports Server (NTRS)

Kreider, K. G.; Semancik, S.; Olson, C.

1984-01-01

The fabrication, materials characterization, and performance of thin film platinum rhodium thermocouples on gas turbine alloys was investigated. The materials chosen for the study were the turbine blade alloy systems MAR M200+Hf with NiCoCrAlY and FeCrAlY coatings, and vane alloy systems MAR M509 with FeCrAlY. Research was focussed on making improvements in the problem areas of coating substrate stability, adhesion, and insulation reliability and durability. Diffusion profiles between the substrate and coating with and without barrier coatings of Al2O3 are reported. The relationships between fabrication parameters of thermal oxidation and sputtering of the insulator and its characterization and performance are described. The best thin film thermocouples were fabricated with the NiCoCrAlY coatings which were thermally oxidized and sputter coated with Al2O3.

Thin coatings in packaging: Fundamental and practical aspects

NASA Astrophysics Data System (ADS)

Thorne, N. A.

1996-01-01

A beverage or food can is very much a functionalized product, the overall performance characteristics being achieved by the use of several materials each of which provides a specific property. Schematically, the metal substrate provides the mechanical and barrier properties, whereby the chemical resistance is provided by specific surface treatments to the metal surface and the application of a thin organic coating. Between about 4-15 μm in thickness, this organic coating has a double protective role, as it must protect the substrate from the foodstuff (corrosion) and the foodstuff from the substrate (taste..) over the required shelflife of the product. To give an idea of the industrial importance of this application, over 100 billion beverage cans per year are produced worldwide, each being individually sprayed with a protective organic layer. To perform correctly these coatings need to possess the following characteristics: —ability to be applied in thin, homogeneous layers without macroscopic or microscopic defects, —sufficient adhesion with the substrate and possess considerable interface stability —mechanical properties sufficient to withstand the can forming operations —intrinsic diffusion barrier properties necessary to prevent significant interaction with the substrate —sufficient chemical resistance to withstand any significant modification of the coating structure and hence intrinsic properties induced by the foodstuff Whereas a considerable amount of scientific attention has been applied to ``bulk'' systems, such as the mechanical properties of epoxies used for composite materials, diffusion in polymer packaging..., little published work is available concerning the specific properties of these thin coatings. The task is not helped by the commercial nature of the resin formulations used, the need to adapt these formulations to the multitude of industrial operations and the physical size of the coatings. The above coating properties will be discussed in relation to the ability to understand the underlying mechanisms involved, to measure the required properties and in the long term predict coating performance.

Application of Molecular Adsorber Coatings in Chamber A for the James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Abraham, Nithin S.

2017-01-01

As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test facility called Chamber A. This presentation summarizes the background, fabrication, installation, chemical analysis test results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination. As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test facility called Chamber A. This presentation summarizes the background, fabrication, installation, chemical analysis test results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination.