Effect of reactive element oxide coating on the high temperature oxidation behaviour of FeCrAl alloys

NASA Astrophysics Data System (ADS)

Cueff, R.; Buscail, H.; Caudron, E.; Riffard, F.; Issartel, C.; El Messki, S.

2004-05-01

The influence of yttrium oxide coating (processed by the sol-gel method) on the oxidation behaviour of a commercial FeCrAl alloy (Kanthal A1) has been investigated during isothermal exposures in air at 1373 K. The scale growth kinetics of the uncoated alloy obey a parabolic rate law during the whole oxidation test, whereas the kinetic curves of the Y-coated specimen exhibit an initial transient stage for the first few hours, followed by a parabolic regime. The yttrium sol-gel coating deposited on the bare alloy does not provide the beneficial effect usually ascribed to reactive elements. No oxidation rate improvement of the coated alloy is observed, the parabolic rate constant values are strictly identical for both specimens. In situ X-ray diffraction reveals a marked influence of the reactive element on the composition of the oxide scale. The oxide layer formed on the yttrium-coated specimen comprised, in addition to α-alumina which is the main oxide also identified on the bare specimen, the presence of yttrium aluminates (YAlO 3, Y 3Al 5O 12) located in the outermost part of the layer.

In situ X-ray diffraction contribution to the study of reactive element oxide coating effect on the high temperature oxidation behaviour of FeCrAl alloys

NASA Astrophysics Data System (ADS)

Cueff, R.; Buscail, H.; Caudron, E.; Riffard, F.; Issartel, C.; Perrier, S.; El Messki, S.

2004-11-01

The influence of yttrium oxide coating (processed by sol-gel method) on the oxidation behaviour of a commercial FeCrAl alloy (Kanthal A1) has been investigated during isothermal exposures in air at 1373K. The scale growth kinetic of the uncoated alloy obeys a parabolic rate law during the whole oxidation test whereas the kinetic curve of the Y-coated specimen exhibits an initial transient stage during the first hours, followed by a parabolic regime. The yttrium sol-gel coating deposited on the bare alloy does not conduct to the beneficial effect usually ascribed to the reactive elements. No oxidation rate improvement of the coated alloy is observed, the parabolic rate constants values are strictly identical for the both specimens. In situ X-ray diffraction reveals a marked influence of the reactive element on the composition of the oxide scale. The oxide layer formed on the yttrium-coated specimen revealed, in addition to α-alumina which is the main oxide also identified on the bare specimen, the presence of yttrium aluminates (YAlO{3}, Y{3}Al{5}O{12}) located in the outermost part of the layer.

Effect of Al and Cr Content on Air and Steam Oxidation of FeCrAl Alloys and Commercial APMT Alloy

DOE PAGES

Unocic, Kinga A.; Yamamoto, Yukinori; Pint, Bruce A.

2017-03-09

To develop the next generation of accident-tolerant fuel cladding for light-water nuclear reactors, wrought FeCrAlY alloys with varying amounts of Cr and Al and commercial Kanthal APMT alloy were evaluated for short-term (4 h) oxidation resistance in steam and air at 1200–1475 °C. Model alloys with lower Cr contents and higher Al contents were evaluated in this paper as lower Cr contents are desirable for radiation damage resistance during operation. As expected, a synergistic effect was found between the Cr and Al contents to enable protective Al 2O 3 formation under these conditions. Characterization of the alumina scales formed inmore » steam found that the scale morphology was affected by the alloy Y content and detailed scanning transmission electron microscopy (STEM) detected Y segregation along scale grain boundaries at 1200 °C. However, after 4 h at 1475 °C, Y and Hf were not segregated to the oxide grain boundaries formed on APMT and the scale had a single layer structure. Finally, compared to oxidation in air, STEM characterization of the outer scale showed differences in the Fe and Cr distributions in steam.« less

2D-COS of in situ μ-Raman and in situ IR spectra for structure evolution characterisation of NEP-deposited cobalt oxide catalyst during n-nonane combustion

NASA Astrophysics Data System (ADS)

Chlebda, Damian K.; Jodłowski, Przemysław J.; Jędrzejczyk, Roman J.; Łojewska, Joanna

2017-11-01

New catalytic systems are still in development to meet the challenge of regulations concerning the emission of volatile organic compounds (VOCs). This is because such compounds have a significant impact on air quality and some of them are toxic to the environment and human beings. The catalytic combustion process of VOCs over non-noble metal catalysts is of great interest to researchers. The high conversion parameters and cost effective preparation makes them a valuable alternative to monoliths and noble metal catalysts. In this study, the cobalt catalyst was prepared by non-equilibrium plasma deposition of organic precursor on calcined kanthal steel. Thus prepared, cobalt oxide based microstructural short-channel reactors were tested for n-nonane combustion and the catalyst surfaces were examined by in situ μ-Raman spectroscopy and in situ infrared spectroscopy. The spectra collected at various temperatures were used in generalised two-dimensional correlation analysis to establish the sequential order of spectral intensity changes and correlate the simultaneous changes in bands selectively coupled by different interaction mechanisms. The 2D synchronous and asynchronous contour maps were proved to be a valuable extension to the standard analysis of the temperature dependent 1D spectra.

Advanced high temperature static strain sensor development

NASA Technical Reports Server (NTRS)

Hulse, C. O.; Stetson, K. A.; Grant, H. P.; Jameikis, S. M.; Morey, W. W.; Raymondo, P.; Grudkowski, T. W.; Bailey, R. S.

1986-01-01

An examination was made into various techniques to be used to measure static strain in gas turbine liners at temperatures up to 1150 K (1600 F). The methods evaluated included thin film and wire resistive devices, optical fibers, surface acoustic waves, the laser speckle technique with a heterodyne readout, optical surface image and reflective approaches and capacitive devices. A preliminary experimental program to develop a thin film capacitive device was dropped because calculations showed that it would be too sensitive to thermal gradients. In a final evaluation program, the laser speckle technique appeared to work well up to 1150 K when it was used through a relatively stagnant air path. The surface guided acoustic wave approach appeared to be interesting but to require too much development effort for the funds available. Efforts to develop a FeCrAl resistive strain gage system were only partially successful and this part of the effort was finally reduced to a characterization study of the properties of the 25 micron diameter FeCrAl (Kanthal A-1) wire. It was concluded that this particular alloy was not suitable for use as the resistive element in a strain gage above about 1000 K.

Advanced high temperature static strain sensor development

NASA Astrophysics Data System (ADS)

Hulse, C. O.; Stetson, K. A.; Grant, H. P.; Jameikis, S. M.; Morey, W. W.; Raymondo, P.; Grudkowski, T. W.; Bailey, R. S.

1986-08-01

An examination was made into various techniques to be used to measure static strain in gas turbine liners at temperatures up to 1150 K (1600 F). The methods evaluated included thin film and wire resistive devices, optical fibers, surface acoustic waves, the laser speckle technique with a heterodyne readout, optical surface image and reflective approaches and capacitive devices. A preliminary experimental program to develop a thin film capacitive device was dropped because calculations showed that it would be too sensitive to thermal gradients. In a final evaluation program, the laser speckle technique appeared to work well up to 1150 K when it was used through a relatively stagnant air path. The surface guided acoustic wave approach appeared to be interesting but to require too much development effort for the funds available. Efforts to develop a FeCrAl resistive strain gage system were only partially successful and this part of the effort was finally reduced to a characterization study of the properties of the 25 micron diameter FeCrAl (Kanthal A-1) wire. It was concluded that this particular alloy was not suitable for use as the resistive element in a strain gage above about 1000 K.

High-temperature Strain Sensor and Mounting Development

NASA Technical Reports Server (NTRS)

Williams, W. Dan; Lei, Jih-Fen; Reardon, Lawrence F.; Krake, Keith; Lemcoe, M. M.; Holmes, Harlan K.; Moore, Thomas C., Sr.

1996-01-01

This report describes Government Work Package Task 29 (GWP29), whose purpose was to develop advanced strain gage technology in support of the National Aerospace Plane (NASP) Program. The focus was on advanced resistance strain gages with a temperature range from room temperature to 2000 F (1095 C) and on methods for reliably attaching these gages to the various materials anticipated for use in the NASP program. Because the NASP program required first-cycle data, the installed gages were not prestabilized or heat treated on the test coupons before first-cycle data were recorded. NASA Lewis Research Center, the lead center for GWP29, continued its development of the palladium-chromium gage; NASA Langley Research Center investigated a new concept gage using Kanthal A1; and the NASA Dryden Flight Research Center chose the well-known BCL-3 iron-chromium-aluminum gage. Each center then tested all three gages. The parameters investigated were apparent strain, drift strain, and gage factor as a function of temperature, plus gage size and survival rate over the test period. Although a significant effort was made to minimize the differences in test equipment between the three test sites (e.g., the same hardware and software were used for final data processing), the center employed different data acquisition systems and furnace configurations so that some inherent differences may be evident in the final results.

Verification of Experimental Techniques for Flow Surface Determination

NASA Technical Reports Server (NTRS)

Lissenden, Cliff J.; Lerch, Bradley A.; Ellis, John R.; Robinson, David N.

1996-01-01

The concept of a yield surface is central to the mathematical formulation of a classical plasticity theory. However, at elevated temperatures, material response can be highly time-dependent, which is beyond the realm of classical plasticity. Viscoplastic theories have been developed for just such conditions. In viscoplastic theories, the flow law is given in terms of inelastic strain rate rather than the inelastic strain increment used in time-independent plasticity. Thus, surfaces of constant inelastic strain rate or flow surfaces are to viscoplastic theories what yield surfaces are to classical plasticity. The purpose of the work reported herein was to validate experimental procedures for determining flow surfaces at elevated temperatures. Since experimental procedures for determining yield surfaces in axial/torsional stress space are well established, they were employed -- except inelastic strain rates were used rather than total inelastic strains. In yield-surface determinations, the use of small-offset definitions of yield minimizes the change of material state and allows multiple loadings to be applied to a single specimen. The key to the experiments reported here was precise, decoupled measurement of axial and torsional strain. With this requirement in mind, the performance of a high-temperature multi-axial extensometer was evaluated by comparing its results with strain gauge results at room temperature. Both the extensometer and strain gauges gave nearly identical yield surfaces (both initial and subsequent) for type 316 stainless steel (316 SS). The extensometer also successfully determined flow surfaces for 316 SS at 650 C. Furthermore, to judge the applicability of the technique for composite materials, yield surfaces were determined for unidirectional tungsten/Kanthal (Fe-Cr-Al).

Corrosion resistance of alumina-forming alloys against molten chlorides for energy production. I: Pre-oxidation treatment and isothermal corrosion tests

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

Gomez-Vidal, J. C.; Fernandez, A. G.; Tirawat, R.

Advanced components in next-generation concentrating solar power (CSP) applications will require advanced heat-transfer fluids and thermal-storage materials that work from about 550 °C to at least 720 °C, for integration with advanced power-conversion systems. To reach the cost target, less-expensive salts such as molten chlorides have been identified as high-temperature fluid candidates. High-strength alloys need to be identified and their mechanical and chemical degradation must be minimized to be used in CSP applications. Approaches for corrosion mitigation need to be investigated and optimized to drive down corrosion rates to acceptable levels—in the order of tens of micrometers per year—for achievingmore » a long system lifetime of at least 30 years. Surface passivation is a good corrosion mitigation approach because the alloy could then be exposed to both the liquid and the vapor phases of the salt mixture. In this investigation, we pre-oxidized the alumina-forming alloys Inconel 702, Haynes 224, and Kanthal APMT at different temperatures, dwelling times, and atmospheres to produce the passivation by forming protective oxides at the surface. The pretreated alloys were later corroded in molten MgCl2 – 64.41 wt% KCl at 700 °C in a flowing Ar atmosphere. We performed electrochemical techniques such as open-circuit potential followed by a potentiodynamic polarization sweep and conventional long-term weight-change tests to down-select the best-performing alloy and pre-oxidation conditions. The best corrosion results were obtained for In702 pre-oxidized in zero air at 1050 °C for 4 h. Finally, metallographic characterization of the pre-oxidized alloys and of the corroded surfaces showed that the formation of dense and uniform alumina scale during the pre-oxidation appears to protect the alloy from attack by molten chloride.« less

Corrosion resistance of alumina-forming alloys against molten chlorides for energy production. I: Pre-oxidation treatment and isothermal corrosion tests

DOE PAGES

Gomez-Vidal, J. C.; Fernandez, A. G.; Tirawat, R.; ...

2017-02-24

Advanced components in next-generation concentrating solar power (CSP) applications will require advanced heat-transfer fluids and thermal-storage materials that work from about 550 °C to at least 720 °C, for integration with advanced power-conversion systems. To reach the cost target, less-expensive salts such as molten chlorides have been identified as high-temperature fluid candidates. High-strength alloys need to be identified and their mechanical and chemical degradation must be minimized to be used in CSP applications. Approaches for corrosion mitigation need to be investigated and optimized to drive down corrosion rates to acceptable levels—in the order of tens of micrometers per year—for achievingmore » a long system lifetime of at least 30 years. Surface passivation is a good corrosion mitigation approach because the alloy could then be exposed to both the liquid and the vapor phases of the salt mixture. In this investigation, we pre-oxidized the alumina-forming alloys Inconel 702, Haynes 224, and Kanthal APMT at different temperatures, dwelling times, and atmospheres to produce the passivation by forming protective oxides at the surface. The pretreated alloys were later corroded in molten MgCl2 – 64.41 wt% KCl at 700 °C in a flowing Ar atmosphere. We performed electrochemical techniques such as open-circuit potential followed by a potentiodynamic polarization sweep and conventional long-term weight-change tests to down-select the best-performing alloy and pre-oxidation conditions. The best corrosion results were obtained for In702 pre-oxidized in zero air at 1050 °C for 4 h. Finally, metallographic characterization of the pre-oxidized alloys and of the corroded surfaces showed that the formation of dense and uniform alumina scale during the pre-oxidation appears to protect the alloy from attack by molten chloride.« less

Corrosion resistance of alumina forming alloys against molten chlorides for energy production. II: Electrochemical impedance spectroscopy under thermal cycling conditions

DOE PAGES

Gomez-Vidal, Judith C.; Fernandez, A. G.; Tirawat, R.; ...

2017-04-01

Next-generation power systems require higher temperatures to increase the efficiency of electricity production in the power block. Concentrating solar power (CSP) technology is looking for high temperature thermal fluids able to work in the range of 550–750 °C. Molten chlorides containing NaCl, KCl, MgCl 2, and/or ZnCl 2 are being considered for solar receivers and/or sensible- or latent- thermal energy storage systems. Vapor pressures of chlorides are high enough that in combination with oxygen gaseous compounds will produce a harsh atmosphere that is generally very aggressive to common chromia forming alloys. Corrosion mitigations must consider a solution in which bothmore » zones (immersed in fluid and exposed to vapor phase) will be protected. This could easily be obtained using alloy surface modification approaches. Surface passivation, produced after pre-oxidation treatments, of alumina forming alloys (Inconel 702, Haynes 224 and Kanthal APMT) was evaluated in molten 35.59 wt% MgCl2 – 64.41 wt% KCl thermally cycled from 550 °C to 700 °C in flowing Ar and static zero air (ZA) atmospheres. Electrochemical impedance spectroscopy tests and metallographic characterization showed that the best performing alloy was pre-oxidized In702 in ZA at 1050 °C for 4 h due to the formation of protective, dense and continuous alumina layers. The alumina layers were unstable when flowing Ar was used as the inert atmosphere during corrosion evaluations. Corrosion results in static ZA are promising for next-generation CSP applications using molten chlorides because alumina scales were stable after 185 h of immersion in the oxygen-containing atmosphere. Alumina layers in pre-oxidized Al-FA In702 grew from 5 µm (before immersion) to 13 µm (after 185 h of immersion). As a result, the use of these alloys could be commercial feasibility and cost-effective because of the possibility of using oxygen-containing atmospheres instead of keeping enclosed systems with inert

Corrosion resistance of alumina forming alloys against molten chlorides for energy production. II: Electrochemical impedance spectroscopy under thermal cycling conditions

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

Gomez-Vidal, Judith C.; Fernandez, A. G.; Tirawat, R.

Next-generation power systems require higher temperatures to increase the efficiency of electricity production in the power block. Concentrating solar power (CSP) technology is looking for high temperature thermal fluids able to work in the range of 550–750 °C. Molten chlorides containing NaCl, KCl, MgCl 2, and/or ZnCl 2 are being considered for solar receivers and/or sensible- or latent- thermal energy storage systems. Vapor pressures of chlorides are high enough that in combination with oxygen gaseous compounds will produce a harsh atmosphere that is generally very aggressive to common chromia forming alloys. Corrosion mitigations must consider a solution in which bothmore » zones (immersed in fluid and exposed to vapor phase) will be protected. This could easily be obtained using alloy surface modification approaches. Surface passivation, produced after pre-oxidation treatments, of alumina forming alloys (Inconel 702, Haynes 224 and Kanthal APMT) was evaluated in molten 35.59 wt% MgCl2 – 64.41 wt% KCl thermally cycled from 550 °C to 700 °C in flowing Ar and static zero air (ZA) atmospheres. Electrochemical impedance spectroscopy tests and metallographic characterization showed that the best performing alloy was pre-oxidized In702 in ZA at 1050 °C for 4 h due to the formation of protective, dense and continuous alumina layers. The alumina layers were unstable when flowing Ar was used as the inert atmosphere during corrosion evaluations. Corrosion results in static ZA are promising for next-generation CSP applications using molten chlorides because alumina scales were stable after 185 h of immersion in the oxygen-containing atmosphere. Alumina layers in pre-oxidized Al-FA In702 grew from 5 µm (before immersion) to 13 µm (after 185 h of immersion). As a result, the use of these alloys could be commercial feasibility and cost-effective because of the possibility of using oxygen-containing atmospheres instead of keeping enclosed systems with inert

Preparation and Testing of Corrosion and Spallation-Resistant Coatings

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

Hurley, John

2015-11-01

This Energy & Environmental Research Center (EERC) project is designed to determine if plating APMT®, a specific highly oxidation-resistant oxide dispersion-strengthened FeCrAl alloy made by Kanthal, onto nickel-based superalloy turbine parts is a viable method for substantially improving the lifetimes and maximum use temperatures of the parts. The method for joining the APMT plate to the superalloys is called evaporative metal bonding and involves placing a thin foil of zinc between the plate and the superalloy, clamping them together, and heating in an atmosphere-controlled furnace. Upon heating, the zinc melts and dissolves the oxide skins of the alloys at themore » bond line, allowing the two alloys to diffuse into each other. The zinc then diffuses through the alloys and evaporates from their surfaces. During this annual reporting period, the finite element model was completed and used to design clamping jigs to hold the APMT plate to the larger blocks of superalloys during the bonding process. The clamping system was machined from titanium–zirconium–molybdenum and used to bond the APMT plate to the superalloy blocks. The bond between the APMT plate was weak for one of each of the superalloy blocks. We believe that this occurred because enough oxidation had occurred on the surface of the parts as a result of a 1-month time period between sandblasting to prepare the parts and the actual bonding process. The other blocks were, therefore, bonded within 1 day of preparing the parts for bonding, and their joints appear strong. Scanning electron microscopy analyses of representative joints showed that no zinc remained in the alloys after bonding. Also, phases rich in hafnium and tantalum had precipitated near the bond line in the APMT. Iron from the APMT had diffused into the superalloys during bonding, more extensively in the CM247LC than in the Rene 80. Nickel from the superalloys had diffused into the APMT, again more extensively in the joint with the CM

Effects of gravitational acceleration on high pressure combustion of methanol droplets

NASA Astrophysics Data System (ADS)

Chauveau, C.; Vieille, B.; Gökalp, I.; Segawa, D.; Kadota, T.; Nakainkyo, A.

1999-06-01

A Franco-Japanese cooperative research program on microgravity combustion has been initiated. One of the studies is devoted to the experimental investigation of high pressure combustion of methanol droplets, under normal and reduced gravity conditions, which are obtained in a drop tower and during the parabolic flight of an airplane. A methanol droplet is suspended at the center of a high-pressure combustion chamber, and is ignited with an electrically heated kanthal wire. A high-speed video camera is used to obtain the time histories of the squared droplet diameter, which are used to determine the droplet burning rate. The results show that the d-square law is valid for all the conditions of the present experiments. The droplet burning rate increases with ambient pressure and does not show a maximum around the critical pressure of methanol. Experiments also show that the droplet burning rate decreases with the reduction of gravitational acceleration. Un programme de collaboration franco-japonais sur la combustion en microgravité a été initié. Une des études est consacrée à l'investigation expérimentale de la combustion de gouttelettes de métha nol sous haute pression, dans des conditions de gravité terrestre et aussi de gravité réduite obtenues par l'utilisation d'une tour de chute libre et par les vols paraboliques d'un avion-laboratoire. Une goutte de méthanol est suspendue au centre d'une chambre à haute pression et est enflammée par un filament électrique porté à haute température. Une caméra vidéo rapide permet le suivi temporel de l'évolution du diamètre de la goutte qui est utilisé pour déterminer le taux de combustion. Les résultats montrent que la loi en D2 est valide pour toutes les conditions explorées dans la présente étude. Le taux de combustion augmente avec l'augmentation de la pression ambiante et ne démontre pas l'existence d'un maximum à la pression critique du méthanol. Le taux de combustion décroît de mani

Hydromagmatic and peperitic interactions: A new experimental approach.

NASA Astrophysics Data System (ADS)

Downey, W. S.; Spieler, O.; Kunzmann, T.; Mastin, L.; Dingwell, D. B.; Shaw, C. J.

2007-12-01

Hydromagmatic interactions in general and the formation of peperites in particular, are poorly understood. We have designed and tested a new series of experiments to analyze the formation of fine hydromagmatic basaltic ash, and the processes occurring during magma/wet-sediment interaction. This study evaluates the mechanism of "turbulent shedding", (Mastin, 2007) where fine hydromagmatic ash is produced by the removal of quenched glassy rinds on clast surfaces that are rapidly deforming within turbulent transport. During magma/wet-sediment interactions the rapid heat transfer rate can lead to oscillations in the vapor film, and its possible collapse to generate a vapor explosion, between the two media producing either fluidal or brecciated textures of the silicate. In these experiment 0.5 kg of basaltic melt is generated in an internally heated autoclave at temperatures of up to 1300 (º)C and ejected via gas pressure into a low pressure tank. The autoclave can be pressurized to 50 MPa and is designed to eject the melt directly into water, wet sediments or water spray. The later technique is commonly used by powder metallurgists to produce micron-sized fragments of metallic glass, and is the desired technique to aid in the production of fine-ash via "turbulent shedding". Two molybdenum wound furnaces are used to produce the melt while a third Kanthal-wound furnace is used to control the temperature at the ejection orifice. Six thermocouples are used to control the furnaces and to record the thermal gradient throughout the setup. Pressure transducers in the high and low pressure section record the expansion volume due thermal interaction. The autoclave is separated from the low pressure tank with a diaphragm to prevent water from entering the high temperature zone. The goal of these experiments is to give insight into the role of hydrodynamic process during magma/water interaction and in the generation of peperites. The first experiments have resulted in the

Preparation and testing of corrosion and spallation-resistant coatings

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

Hurley, John P.; Cavalli, Matthew N.

2016-06-30

The goal of this project was to take a recently developed method of bonding oxide dispersion-strengthened (ODS) FeCrAl plating to nickel superalloys closer to commercial use in syngas-fired turbines. The project was designed to better understand and develop the bonding process and to determine if plating APMT®, a specific highly oxidation-resistant ODS FeCrAl alloy made by Kanthal, onto nickel-based superalloy turbine parts is a viable method for substantially improving the lifetimes and maximum use temperatures of the parts. The superalloys investigated for protection were CM247LC and Rene® 80, both alumina scale-forming alloys. The method for bonding the APMT plate tomore » the superalloys is called evaporative metal bonding, which involves placing a thin foil of zinc between the plate and the superalloy, clamping them together, and heating in an atmosphere-controlled furnace. Upon heating, the zinc melts and dissolves the oxide skins of the alloys at the bond line, allowing the two alloys to diffuse into each other. The zinc then diffuses through the alloys and evaporates from their surfaces, creating a bond between the APMT and the superalloy that is stronger than the APMT itself. Testing showed that the diffusivity of zinc in both APMT and CM247LC is quite similar at 700°C but 15 times higher in the APMT at 1214°C. Coefficients of thermal expansion were determined for each of the alloys as a function of temperature. This information was entered into a finite-element model using ANSYS, which was used to design a clamping jig for pressing the APMT to the superalloys at the bonding temperature. Scanning electron microscopy analyses of representative joints showed that no zinc remained in the alloys after bonding Unfortunately, the analyses also showed some small pieces of broken aluminum oxide scale near the bond lines, indicating that its scale was not sufficiently removed during prebonding cleaning. Samples from each of the bonded blocks were sent to

PREPARATION AND TESTING OF CORROSIONAND SPALLATION-RESISTANT COATINGS

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

Hurley, John

2014-11-01

This Energy & Environmental Research Center (EERC) project is designed to determine if plating APMT®, a specific highly oxidation-resistant oxide dispersion-strengthened FeCrAl alloy made by Kanthal, onto nickel-based superalloy turbine parts is a viable method for substantially improving the lifetimes and maximum use temperatures of the parts. The method for joining the APMT plate to the superalloys is called evaporative metal bonding and involves placing a thin foil of zinc (Zn) between the plate and the superalloy, clamping them together, and heating in an atmosphere-controlled furnace. Upon heating, the Zn melts and dissolves the oxide skins of the alloys atmore » the bond line, allowing the two alloys to diffuse into each other. The Zn then diffuses through the alloys and evaporates from their surfaces. Laboratory testing to determine the diffusion rate of Zn through the alloys has been completed. However, an analytical solution does not exist to model the diffusion of zinc through the alloys. For this reason, a finite difference algorithm using MATLAB was developed. It makes use of the hopscotch algorithm. The model allows the user to specify the dimensions of the metal parts, the Zn concentration at the bondline, the mesh size, time step, and Zn diffusivity. The experimentally measured values of diffusivity for Zn in APMT and Rene 80/CM 247LC are approximately 2.7 × 10-12 and 4 × 10-14 m2/s, respectively. While the qualitative behavior of the model appears correct, a comparison of the diffusion predictions with the experimental results from earlier in the project indicates that the expected Zn concentration is significantly higher than that measured experimentally. The difference depends on the assumed initial concentration, which is difficult to quantify exactly under experimental conditions for t = 0. In addition to the diffusion work, the coefficients of thermal expansions were determined for each of the alloys as a function of temperature. This

Preparation and Testing of Corrosion-and Spallation-Resistant Coatings

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

Hurley, John

2013-10-31

This Energy & Environmental Research Center (EERC) project is designed to determine if plating APMT®, a specific highly oxidation-resistant oxide dispersion-strengthened FeCrAl alloy made by Kanthal, onto nickel-based superalloy turbine parts is a viable method for substantially improving the lifetimes and maximum use temperatures of the parts. The method for joining the APMT plate to the superalloys is called evaporative metal bonding and involves placing a thin foil of zinc (Zn) between the plate and the superalloy, clamping them together, and heating in an atmosphere-controlled furnace. Upon heating, the Zn melts and dissolves the oxide skins of the alloys atmore » the bond line, allowing the two alloys to diffuse into each other. The Zn then diffuses through the alloys and evaporates from their surfaces. Laboratory testing to determine the diffusion rate of Zn through the alloys has been completed. We have found that we were not able to create joints when temperatures much lower than the original temperature of 1214°C are used. Therefore, we limited our diffusion rate measurements to the two hold temperatures used in the procedure: 700° and 1214°C. The diffusivity of zinc in both APMT and CM247LC is quite similar at 700°C. Diffusivity in the APMT appears to be slightly higher, but the midline composition after 30 minutes at this temperature is quite similar. At 1214°C, the situation is very different. The calculated diffusivity of zinc in APMT is approximately 15 times higher than in CM247LC or Rene® 80 (~120 vs. ~8 μm²/min) at that temperature. In addition to the diffusion work, the coefficients of thermal expansions were determined for each of the alloys as a function of temperature. This information has been entered into a finite element model using ANSYS so that appropriate force-applying structures can be designed for use in joining structures composed of APMT and the nickel alloys. Gasifier sampling activities continue to determine what types