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1

Direct morphological comparison of vacuum plasma sprayed and detonation gun sprayed hydroxyapatite coatings for orthopaedic applications.  

PubMed

Hydroxyapatite coatings on titanium substrates were produced using two thermal spray techniques vacuum plasma spraying and detonation gun spraying. X-ray diffraction was used to compare crystallinity and residual stresses in the coatings. Porosity was measured using optical microscopy in conjunction with an image analysis system. Scanning electron microscopy and surface roughness measurements were used to characterise the surface morphologies of the coatings. The vacuum plasma sprayed coatings were found to have a lower residual stress, a higher crystallinity and a higher level of porosity than the detonation gun coatings. It is concluded that consideration needs to be given to the significance of such variations within the clinical context. PMID:10048403

Gledhill, H C; Turner, I G; Doyle, C

1999-02-01

2

Vacuum Plasma Spray (VPS) Forming of Solar Thermal Propulsion Components Using Refractory Metals.  

National Technical Information Service (NTIS)

The Thermal Spray Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using Vacuum Plasma Spray (VPS) to form structural components from a tungsten/rhenium alloy. The components were assembled into an a...

F. R. Zimmerman D. A. Hissam H. P. Gerrish W. M. Davis

1999-01-01

3

Microstructure and Properties Characterization of Silicon Coatings Prepared by Vacuum Plasma Spraying Technology  

Microsoft Academic Search

Silicon coatings were fabricated by vacuum plasma spraying technology. The morphology, composition, and microstructure of\\u000a the coatings were investigated by FESEM, XRD, WDX, and TEM. The physical, mechanical, and thermal properties of the coatings\\u000a were characterized. The results showed that vacuum plasma sprayed silicon coatings were compact and consisted of well-molten\\u000a silicon splats. The oxidation introduced by the spraying process

Yaran Niu; Xuanyong Liu; Xuebin Zheng; Heng Ji; Chuanxian Ding

2009-01-01

4

Modelling and experimental analysis of vacuum plasma spraying. Part I: prediction of initial plasma properties at plasma gun exit  

Microsoft Academic Search

The plasma energy input rate of a dc Ar + H2 plasma jet has been measured experimentally under a series of vacuum plasma spraying (VPS) processing conditions. The plasma energy input rate increased approximately linearly with increasing plasma current and Ar flow rate, increased approximately parabolically with increasing H2 flow rate, but did not vary measurably with changes in VPS

Y. Y. Zhao; P. S. Grant; B. Cantor

2000-01-01

5

Ductility degradation of vacuum-plasma-sprayed NARloy-Z at elevated temperatures  

Microsoft Academic Search

Vacuum plasma spray forming is being used in the near-net fabrication of aerospace components at the Marshall Space Flight Center (MSFC), Alabama. For example, vacuum-plasma-sprayed (VPS) NARloy-Z (a copper-based alloy with high thermal conductivity) is used to form the combustion chamber liner of liquid rocket engines. VPS NARloy-Z possesses properties comparable with the wrought alloy at temperatures ranging from ?259

P. S. Chen; J. H. Sanders; Y. K. Liaw; F. Zimmermann

1995-01-01

6

Structure and property evaluation of a vacuum plasma sprayed nanostructured tungstenhafnium carbide bulk composite  

Microsoft Academic Search

Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured thermo-mechanical components. Spray drying of powder feedstock appears to have a significant effect on the improved mechanical properties of the bulk nanocomposite. The reported elastic modulus of the nanocomposite nearly doubles

K. E. Rea; V. Viswanathan; A. Kruize; J. Th. M. De Hosson; S. ODell; T. McKechnie; S. Rajagopalan; R. Vaidyanathan; S. Seal

2008-01-01

7

Optimizing the vacuum plasma spray deposition of metal, ceramic, and cermet coatings using designed experiments  

Microsoft Academic Search

The vacuum plasma spray (VPS) deposition of metal, ceramic, and cermet coatings has been investigated using designed statistical\\u000a experiments. Processing conditions that were considered likely to have a significant influence on the melting characteristics\\u000a of the precursor powders and hence deposition efficiency were incorporated into full and fractional factorial experimental\\u000a designs. The processing of an alumina powder was very sensitive

R. Kingswell; K. T. Scott; L. L. Wassell

1993-01-01

8

Optimizing the vacuum plasma spray deposition of metal, ceramic, and cermet coatings using designed experiments  

NASA Astrophysics Data System (ADS)

The vacuum plasma spray (VPS) deposition of metal, ceramic, and cermet coatings has been investigated using designed statistical experiments. Processing conditions that were considered likely to have a significant influence on the melting characteristics of the precursor powders and hence deposition efficiency were incorporated into full and fractional factorial experimental designs. The processing of an alumina powder was very sensitive to variations in the deposition conditions, particularly the injection velocity of the powder into the plasma flame, the plasma gas composition, and the power supplied to the gun. Using a combination of full and fractional factorial experimental designs, it was possible to rapidly identify the important spraying variables and adjust these to produce a deposition efficiency approaching 80 percent. The deposition of a nickel-base alloy metal powder was less sensitive to processing conditions. Generally, however, a high degree of particle melting was achieved for a wide range of spray conditions. Preliminary experiments performed using a tungsten carbide/cobalt cermet powder indicated that spray efficiency was not sensitive to deposition conditions. However, microstructural analysis revealed considerable variations in the degree of tungsten carbide dissolution. The structure and properties of the optimized coatings produced in the factorial experiments are also discussed.

Kingswell, R.; Scott, K. T.; Wassell, L. L.

1993-06-01

9

Thermoelectric properties of magnesium silicide fabricated using vacuum plasma thermal spray  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of magnesium silicide samples prepared by Vacuum Plasma Spray (VPS) are compared with those made from the conventional hot press method using the same feedstock powder. Thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit are characterized from room temperature to 700 K. X-ray diffraction and scanning electron microscopy of the samples are obtained to assess how phase and microstructure influence the thermoelectric properties. Carrier concentration and Hall mobility are obtained from Hall Effect measurements, which provide further insight into the electrical conductivity and Seebeck coefficient mechanisms. Low-temperature electrical conductivity measurements suggest a 3D variable range hopping effect in the samples. VPS samples achieved a maximum ZT = 0.16 at 700 K, which is around 30% of the hot press sample ZT = 0.55 at 700 K using the same raw powder. The results suggest that thermal spray is a potential deposition technique for thermoelectric materials.

Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Gambino, Richard

2013-10-01

10

Improvement of Ceramic Coatings for Electrostatic Adsorption Force Using Vacuum Plasma Spraying  

NASA Astrophysics Data System (ADS)

The purpose of this study is to improve ceramic coatings having a high stable electrostatic adsorption force. The use of the coating is for the Johnsen-Rahbek force type electrostatic chucks used to fix silicon wafers inside vacuum chambers for processes such as Etch, CVD and PVD for semiconductor manufacturers. Previously the authors developed a dielectric substance ceramic coating for electrostatic chucks using Atmospheric Plasma Spraying (APS). This ceramic coating was not suitable because of its unstable electrostatic adsorption force. In a subsequent study, Vacuum Plasma Sprayed (VPS) Al2O3-7.5mass%TiO2 coating was investigated. As a result, it was found that the VPS coating has stable electrical resistivity and adsorption force. The dielectric constant of VPS Al2O3-TiO2 coating was sufficient for application to electrostatic chuck. On the other hand, it was suggested from results with respect to residual adsorption force and duration time after power off that the residual adsorption characteristic was not adequate.

Takeuchi, Jun-Ichi; Yamasaki, Ryo; Tani, Kazumi; Takahashi, Yasuo

11

Vacuum arc velocity and erosion rate measurements on nanostructured plasma and HVOF spray coatings  

NASA Astrophysics Data System (ADS)

Arc velocity and erosion rate measurements were performed on nanostructured pure Cu cathodes in 10-5 Torr vacuum (1.3324 m Pa), in an external magnetic field of 0.04 T. Five different kinds of nanostructured cathodes were produced by spraying pure Cu powders of three different sizes, on Cu coupons by atmospheric pressure plasma spraying and high velocity oxygen fuel spraying techniques. The erosion rates of these electrodes were obtained by measuring the weight loss of the electrode after igniting as many as 135 arc pulses, each of which was 500 s long at an arc current of 125 A. The arc erosion values measured on three kinds of nanostructured coatings were 50% lower than the conventional pure massive Cu cathodes. Microscopic analyses of the arc traces on these nanostructured coatings show that the craters formed on these coatings were smaller than those formed on conventional Cu (<1 m in diameter compared with 7-12 m diameter on conventional Cu). It was concluded that nanostructured cathodes had lower erosion rates than conventional pure Cu cathodes.

Rao, Lakshminarayana; Munz, Richard J.; Meunier, Jean-Luc

2007-07-01

12

Reaction diffusion behaviors for interface between Ni-based super alloys and vacuum plasma sprayed MCrAlY coatings  

Microsoft Academic Search

The object of this study is overlay coatings of MCrAlY alloy sprayed by a vacuum plasma spray (VPS) process for the protection against high-temperature corrosion and oxidation in the field of gas turbine components. Reaction diffusion behaviors at the interface between the MCrAlY coatings and the substrate, which have an important effect on coating degradation, have not always been clarified.

Y. Itoh; M. Tamura

1999-01-01

13

A comparative study of high velocity oxygen fuel, vacuum plasma spray, and axial plasma spray for the deposition of CoNiCrAlY bond coat alloy  

NASA Astrophysics Data System (ADS)

In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.

Scrivani, A.; Bardi, U.; Carrafiello, L.; Lavacchi, A.; Niccolai, F.; Rizzi, G.

2003-12-01

14

Characteristics of TiNi shape memory alloy processed by vacuum plasma spray  

NASA Astrophysics Data System (ADS)

TiNi shape memory alloy has been used in many application fields due to its excellent shape memory effect (SME) and superelasticity (SE). However, it is difficult and costly to machine TiNi alloy into complex shapes due to its low ductility. To address this problem, one approach is near-net shape processing by vacuum plasma spraying (VPS). In this study, the transformation behavior, mechanical properties and microstructure of TiNi alloy processed by VPS method are studied. The as-sprayed and homogenized TiNi alloy exhibited compositional variations in the sample, though both samples exhibited a single TiNi phase with low transformation temperatures, below 170 K Aging the homogenized sample at 773 K for 18 ks led to an increase in the transformation temperature, resulting in good transformation behavior. Specifically, DSC measurement revealed clear transformation peaks due to Martensite, austenite and R-phase transitions. Compression testing of a sample aged at 773 K for 18 ks exhibited a good SME below Mf and superelasticity (SE) above Af. The recoverable strain due to SME and SE were more than 2.4 % and 5.0 %, respectively. TEM studies confirmed that aTi3Ni4 precipitate was formed by aging at 773 K for 18 ks.

Nakayama, Hiroyuki; Taya, Minoru; Smith, Ronald W.; Nelson, Travis; Yu, Michael; Rosenzweig, Edwin

2006-04-01

15

Microstructure Characteristics and Oxidation Behavior of Molybdenum Disilicide Coatings Prepared by Vacuum Plasma Spraying  

NASA Astrophysics Data System (ADS)

In this study, molybdenum disilicide (MoSi2) coatings were fabricated by vacuum plasma spraying technology. Their morphology, composition, and microstructure characteristics were intensively investigated. The oxidation behavior of MoSi2 coatings was also explored. The results show that the MoSi2 coatings are compact with porosity less than 5%. Their microstructure exhibits typical lamellar character and is mainly composed of tetragonal and hexagonal MoSi2 phases. A small amount of tetragonal Mo5Si3 phase is randomly distributed in the MoSi2 matrix. A rapid weight gain is found between 300 and 800 C. The MoSi2 coatings exhibit excellent oxidation-resistant properties at temperatures between 1300 and 1500 C, which results from the continuous dense glassy SiO2 film formed on their surface. A thick layer composed of Mo5Si3 is found to be present under the SiO2 film for the MoSi2 coatings treated at 1700 C, suggesting that the phenomenon of continuous oxidation took place.

Niu, Yaran; Fei, Xiaoai; Wang, Hongyan; Zheng, Xuebin; Ding, Chuanxian

2013-03-01

16

Fabrication and Tribological Evaluation of Vacuum Plasma-Sprayed B4C Coating  

NASA Astrophysics Data System (ADS)

B4C coating was fabricated by vacuum plasma spraying and the tribological properties of the coating against WC-Co alloy were evaluated by sliding wear tests. Al2O3 coating, one of the most commonly used wear-resistant coatings, was employed as comparison in the tribological evaluation. The results obtained show that, the B4C coating is composed of a large amount of nanostructured particles along with some amorphous phases. Both of the friction coefficient and wear rate of the B4C coating are much lower than those of the Al2O3 coating, and the tribological evaluation reveals a decreasing trend for the B4C coating in friction coefficient as well as wear rate with increasing normal load, which is explained in terms of the formation of a protective transfer layer on its worn surface. Tribofilm wear is found to be the dominant wear mechanism involved in the B4C/WC-Co alloy friction pair.

Zhu, Huiying; Niu, Yaran; Lin, Chucheng; Huang, Liping; Ji, Heng; Zheng, Xuebin

2012-12-01

17

High heat loading properties of vacuum plasma spray tungsten coatings on reduced activation ferritic/martensitic steel  

NASA Astrophysics Data System (ADS)

High density W coatings on reduced activation ferritic martensitic steel (RAF/M) have been produced by Vacuum Plasma Spraying technique (VPS) and heat flux experiments on them have been carried out to evaluate their possibility as a plasma-facing armor in a fusion device. In addition, quantitative analyses of temperature profile and thermal stress have been carried out using the finite element analysis (FEA) to evaluate its thermal properties. No cracks or exfoliation has been formed by steady state and cyclic heat loading experiments under heat loading at 700 C of surface temperature. In addition, stress distribution and maximum stress between interface of VPS-W and RAF/M have been obtained by FEA. On the other hand, exfoliation has occurred at interlayer of VPS-W coatings near the interface between VPS-W and RAF/M at 1300 C of surface temperature by cyclic heat loading.

Tokunaga, K.; Hotta, T.; Araki, K.; Miyamoto, Y.; Fujiwara, T.; Hasegawa, M.; Nakamura, K.; Ezato, K.; Suzuki, S.; Enoeda, M.; Akiba, M.; Nagasaka, T.; Kasada, R.; Kimura, A.

2013-07-01

18

Nd-Fe-B permanent magnets (thick films) produced by a vacuum-plasma-spraying process  

NASA Astrophysics Data System (ADS)

Thick, hard-magnetic Nd-Fe-B films (~1 mm) were deposited on different substrates (Cu, steel) by a low-pressure plasma-spraying process. The properties of the applied Nd-Fe-B powders (e.g., grain size, composition) and the conditions of the spraying process were optimized with respect to the mechanical and magnetic properties of the films. Film thicknesses up to 1.2 mm were achieved with good adhesive properties (bond strength>40 MPa). Cracks at the interface or within the films during the deposition process could be suppressed by adjusting the temperature profile of the substrate and controlling the deposition rate. Depending on the maximum temperature of the substrate and the thickness of the Nd-Fe-B films, either amorphous or microcrystalline structures were obtained. In general, the magnetic properties were improved by a postdeposition annealing treatment. Coercivities HcJ up to 16 kA/cm and isotropic remanences of about 0.6 T were achieved.

Rieger, G.; Wecker, J.; Rodewald, W.; Sattler, W.; Bach, Fr.-W.; Duda, T.; Unterberg, W.

2000-05-01

19

Porous tantalum coatings prepared by vacuum plasma spraying enhance bmscs osteogenic differentiation and bone regeneration in vitro and in vivo.  

PubMed

Tantalum, as a potential metallic implant biomaterial, is attracting more and more attention because of its excellent anticorrosion and biocompatibility. However, its significantly high elastic modulus and large mechanical incompatibility with bone tissue make it unsuitable for load-bearing implants. In this study, porous tantalum coatings were first successfully fabricated on titanium substrates by vacuum plasma spraying (VPS), which would exert the excellent biocompatibility of tantalum and alleviate the elastic modulus of tantalum for bone tissue. We evaluated cytocompatibility and osteogenesis activity of the porous tantalum coatings using human bone marrow stromal cells (hBMSCs) and its ability to repair rabbit femur bone defects. The morphology and actin cytoskeletons of hBMSCs were observed via electron microscopy and confocal, and the cell viability, proliferation and osteogenic differentiation potential of hBMSCs were examined quantitatively by PrestoBlue assay, Ki67 immunofluorescence assay, real-time PCR technology and ALP staining. For in vivo detection, the repaired femur were evaluated by histomorphology and double fluorescence labeling 3 months postoperation. Porous tantalum coating surfaces promoted hBMSCs adhesion, proliferation, osteogenesis activity and had better osseointegration and faster new bone formation rate than titanium coating control. Our observation suggested that the porous tantalum coatings had good biocompatibility and could enhance osseoinductivity in vitro and promote new bone formation in vivo. The porous tantalum coatings prepared by VPS is a promising strategy for bone regeneration. PMID:23776648

Tang, Ze; Xie, Youtao; Yang, Fei; Huang, Yan; Wang, Chuandong; Dai, Kerong; Zheng, Xuebin; Zhang, Xiaoling

2013-06-11

20

Effect of Vacuum Annealing on the Characteristics of Plasma Sprayed Al2O3-13wt.%TiO2 Coatings  

NASA Astrophysics Data System (ADS)

Adhesion strength is one of the critical properties for plasma-sprayed coating. In this study, the plasma-sprayed Al2O3-13wt.%TiO2/NiCrAl coatings were annealed at 300-900 C for 6 h in vacuum. The tensile bond strength and porosity of the coatings were investigated. The microstructure and the fracture were studied using optical microscopy, scanning electron spectroscopy, and x-ray diffraction. It was found that the tensile bond strength of coatings increased with the increase of annealing temperature until 500 C, reaching the maximum value of 41.2 MPa, and then decreased as the annealing temperature continues to increase. All coatings presented a brittle fracture and the fracture occurred inside the ceramic coatings except for the coating annealed at 500 C, which had a brittle-ductile mixed fracture and the fracture occurred at the interface of bond coating and the substrate.

Jingjing, Zhang; Zehua, Wang; Pinghua, Lin; Hongbin, Yuan; Zehua, Zhou; Shaoqun, Jiang

2012-09-01

21

Functionally graded vacuum plasma sprayed and magnetron sputtered tungsten/EUROFER97 interlayers for joints in helium-cooled divertor components  

NASA Astrophysics Data System (ADS)

Two coating technologies, magnetron sputtering and vacuum plasma spraying, have been investigated for their capability in producing functionally graded tungsten/EUROFER97 layers. In a first step, non-graded layers with different mixing ratios were deposited on tungsten substrates and characterized by nanoindentation, macroindentation, X-ray diffraction, transmission, Auger and scanning electron microscopy. The thermal stability of the sprayed layers against heat treatments at 800-1100 C for 60 min was further analyzed. In a second step, the produced functionally graded layers deposited on tungsten substrates were joined to EUROFER97 bulk-material by diffusion bonding. The bonding and the graded joints were microscopically characterized and exposed to thermal cycles between 20 C and 650 C. Results from this study show that both coating technologies are ideal for the synthesis of functionally graded tungsten/EUROFER97 coatings. This is important in providing insights for future development of joints with functionally graded interlayers.

Weber, T.; Stber, M.; Ulrich, S.; Vaen, R.; Basuki, W. W.; Lohmiller, J.; Sittel, W.; Aktaa, J.

2013-05-01

22

Thermographic Look at Plasma Spraying.  

National Technical Information Service (NTIS)

Plasma spray systems are used to deposit high temperature materials on substrates to form coatings. Thermal analysis of these systems will assist in determining spray parameters for different materials. Infrared videothermography was used to measure tempe...

M. D. Kelly L. D. Abney

1985-01-01

23

Plasma-sprayed materials for magnetic fusion energy devices  

Microsoft Academic Search

Plasma spray technology is being evaluated as a means to address important fabrication and maintenance problems associated with plasma-interactive components in magnetic fusion devices (e.g., limiters, divertors, and some first wall surfaces). Low-oxygen vacuum plasma sprayed copper has been tested as a ductile, high thermal conductivity interlayer to limit thermal stress and prevent cracking when brazing pyrolytic graphite (PG) tiles

M. F. Smith; C. D. Croessmann; F. M. Hosking; R. D. Watson; J. A. Koski

1991-01-01

24

Characterization of plasma sprayed nano-titania coatings by impedance spectroscopy  

Microsoft Academic Search

Nano-titania coatings were deposited via vacuum plasma spraying. The microstructure and chemical state of the coatings were investigated with SEM, TEM, XRD and XPS, respectively. The results showed that the vacuum plasma sprayed titanium oxide coatings possessed porous structure with small pores and agglomerated nanosized grains. The ac electrical data were measured in the frequency range 1 ? f ?

Yingchun Zhu; Chuanxian Ding

2000-01-01

25

Plasma-sprayed aluminium coating  

Microsoft Academic Search

Figure I Schematic diagram of the plasma-spraying. particles were caught by a special instrument at a distance of 3 m from the nozzle. Details of the experimental procedure are given elsewhere (3). Since it is generally believed (see, for instance (4)) that oxygen contained in the water-stabilized system must cause strongly oxidizing properties of the flame, a detailed X-ray phase

J. Ilavsky; J. Forman; P. Chraska

1992-01-01

26

Recent Developments in the Field of Plasma-Sprayed Thermal Barrier Coatings  

Microsoft Academic Search

Thermal barrier coating (TBC) systems are widely used in gas turbines on thermally highly loaded parts as blades, vanes or combustion chamber to improve the performance of the engines. The standard plasma-sprayed systems consist of a vacuum plasma-sprayed (VPS) MCrAlY (M = Ni or Co) and an atmospherically plasma sprayed (APS) ceramic top layer made of yttria partially stabilised zirconia

R. Vaen; J.-E. Dring; M. Dietrich; H. Lehmann; D. Stver

27

Metallurgy and properties of plasma spray formed materials  

SciTech Connect

Understanding the fundamental metallurgy of vacuum plasma spray formed materials is the key to enhancing and developing full material properties. Investigations have shown that the microstructure of plasma sprayed materials must evolve from a powder splat morphology to a recrystallized grain structure to assure high strength and ductility. A fully, or near fully, dense material that exhibits a powder splat morphology will perform as a brittle material compared to a recrystallized grain structure for the same amount of porosity. Metallurgy and material properties of nickel, iron, and copper base alloys will be presented and correlated to microstructure.

Mckechnie, T.N.; Liaw, Y.K.; Zimmerman, F.R.; Poorman, R.M.

1992-01-01

28

The effect of heat treatment on the stiffness of zirconia top coats in plasma-sprayed TBCs  

Microsoft Academic Search

Thermal barrier coating (TBC) specimens have been prepared by plasma spraying. A vacuum plasma spray (VPS) MCrAlY bond coat and atmospheric plasma spray (APS) zirconia top coat were deposited onto a nickel superalloy substrate. The stiffness of detached top coats was measured by cantilever bending and also by nanoindentation procedures. Measurements were made on specimens in the as-sprayed state and

J. A. Thompson; T. W. Clyne

2001-01-01

29

Developments in direct current plasma spraying  

Microsoft Academic Search

Thermal spray processing is used to confer specific in-service properties to components via the production of a coating between 50?m (minimum value) to a few millimeters thick. Thermal spray represents a global market of about 4.8Billion Euros (i.e., ?US$5 billion) in 2004; 30% of which is European based. 50% of this activity is devoted to plasma spray processing with about

Pierre Fauchais; Ghislain Montavon; Michel Vardelle; Julie Cedelle

2006-01-01

30

Plasma-Sprayed Tantalum/Alumina Cermets.  

National Technical Information Service (NTIS)

Cermets of tantalum and alumina were fabricated by plasma spraying, with the amount of alumina varied from 0 to 65 percent (by volume). Each of four compositions was then measured for tensile strength, elastic modulus, and coefficient of thermal expansion...

C. M. Kramer

1977-01-01

31

Characterization of Plasma Sprayed Beryllium ITER First Wall Mockups  

SciTech Connect

ITER first wall beryllium mockups, which were fabricated by vacuum plasma spraying the beryllium armor, have survived 3000 thermal fatigue cycles at 1 MW/sq m without damage during high heat flux testing at the Plasma Materials Test Facility at Sandia National Laboratory in New Mexico. The thermal and mechanical properties of the plasma sprayed beryllium armor have been characterized. Results are reported on the chemical composition of the beryllium armor in the as-deposited condition, the through thickness and normal to the through thickness thermal conductivity and thermal expansion, the four-point bend flexure strength and edge-notch fracture toughness of the beryllium armor, the bond strength between the beryllium armor and the underlying heat sink material, and ultrasonic C-scans of the Be/heat sink interface.

Castro, Richard G.; Vaidya, Rajendra U.; Hollis, Kendall J.

1997-12-31

32

Plasma Sprayed Hydroxyapatite Coatings: Influence of Spraying Power on Microstructure  

SciTech Connect

The plasma sprayed hydroxyapatite (HA) coatings are used on metallic implants to enhance the bonding between the implant and bone in human body. The coating process was implemented at different spraying power for each spraying condition. The coatings formed from a rapid solidification of molten and partly molten particles that impact on the surface of substrate at high velocity and high temperature. The study was concentrated on different spraying power that is between 23 to 31 kW. The effect of different power on the coatings microstructure was investigated using scanning electron microscope (SEM) and phase composition was evaluated using X-ray diffraction (XRD) analysis. The coatings surface morphology showed distribution of molten, partially melted particles and some micro-cracks. The produced coatings were found to be porous as observed from the cross-sectional morphology. The coatings XRD results indicated the presence of crystalline phase of HA and each of the patterns was similar to the initial powder. Regardless of different spraying power, all the coatings were having similar XRD patterns.

Mohd, S. M.; Abd, M. Z.; Abd, A. N. [Advanced Material Centre (AMREC), SIRIM Bhd, Lot 34, Jalan Hi-Tech 2/4, Kulim Hi-Tech Park, 09000 Kulim (Malaysia)

2010-03-11

33

Plasma Sprayed Hydroxyapatite Coatings: Influence of Spraying Power on Microstructure  

NASA Astrophysics Data System (ADS)

The plasma sprayed hydroxyapatite (HA) coatings are used on metallic implants to enhance the bonding between the implant and bone in human body. The coating process was implemented at different spraying power for each spraying condition. The coatings formed from a rapid solidification of molten and partly molten particles that impact on the surface of substrate at high velocity and high temperature. The study was concentrated on different spraying power that is between 23 to 31 kW. The effect of different power on the coatings microstructure was investigated using scanning electron microscope (SEM) and phase composition was evaluated using X-ray diffraction (XRD) analysis. The coatings surface morphology showed distribution of molten, partially melted particles and some micro-cracks. The produced coatings were found to be porous as observed from the cross-sectional morphology. The coatings XRD results indicated the presence of crystalline phase of HA and each of the patterns was similar to the initial powder. Regardless of different spraying power, all the coatings were having similar XRD patterns.

Mohd, S. M.; Abd, M. Z.; Abd, A. N.

2010-03-01

34

Thermal response of plasma sprayed tungsten coating to high heat flux  

Microsoft Academic Search

In order to investigate the thermal response of tungsten coating on carbon and copper substrates by vacuum plasma spray (VPS) or inert gas plasma spray (IPS), annealing and cyclic heat load experiments of these coatings were conducted. It is indicated that the multi-layered tungsten and rhenium interface of VPS-W\\/CFC failed to act as a diffusion barrier at elevated temperature and

X. Liu; L. Yang; S. Tamura; K. Tokunaga; N. Yoshida; N. Noda; Z. Xu

2004-01-01

35

Status of vacuum and plasma technology  

Microsoft Academic Search

Vacuum and surface technology have significantly contributed to the rapid progress in microelectronics, data storage, displays, photonics, aerospace, automotive, architectural glass and other industries. One of the key elements in the impressive development of vacuum and surface technology is the increased use of plasma processes. Plasma can be used as a tool for heating, evaporation, sputtering, etching and ionization as

Horst Heidsieck

1999-01-01

36

Automatic targeting of plasma spray gun  

DOEpatents

A means for monitoring the material portion in the flame of a plasma spray gun during spraying operations is provided. A collimated detector, sensitive to certain wavelengths of light emission, is used to locate the centroid of the material with each pass of the gun. The response from the detector is then relayed to the gun controller to be used to automatically realign the gun.

Abbatiello, Leonard A. (Oak Ridge, TN); Neal, Richard E. (Heiskell, TN)

1978-01-01

37

Current problems in plasma spray processing  

SciTech Connect

This detailed report summarizes 8 contributions from a thermal spray conference that was held in late 1991 at Brookhaven National Laboratory (Upton, Long Island, NY, USA). The subject of ``Plasma Spray Processing`` is presented under subject headings of Plasma-particle interactions, Deposit formation dynamics, Thermal properties of thermal barrier coatings, Mechanical properties of coatings, Feed stock materials, Porosity: An integrated approach, Manufacture of intermetallic coatings, and Synchrotron x-ray microtomographic methods for thermal spray materials. Each section is intended to present a concise statement of a specific practical and/or scientific problem, then describe current work that is being performed to investigate this area, and finally to suggest areas of research that may be fertile for future activity.

Berndt, C.C.; Brindley, W.; Goland, A.N.; Herman, H.; Houck, D.L.; Jones, K.; Miller, R.A.; Neiser, R.; Riggs, W.; Sampath, S.; Smith, M.; Spanne, P. [State Univ. of New York, Stony Brook, NY (United States). Thermal Spray Lab.

1991-12-31

38

Current problems in plasma spray processing  

SciTech Connect

This detailed report summarizes 8 contributions from a thermal spray conference that was held in late 1991 at Brookhaven National Laboratory (Upton, Long Island, NY, USA). The subject of Plasma Spray Processing'' is presented under subject headings of Plasma-particle interactions, Deposit formation dynamics, Thermal properties of thermal barrier coatings, Mechanical properties of coatings, Feed stock materials, Porosity: An integrated approach, Manufacture of intermetallic coatings, and Synchrotron x-ray microtomographic methods for thermal spray materials. Each section is intended to present a concise statement of a specific practical and/or scientific problem, then describe current work that is being performed to investigate this area, and finally to suggest areas of research that may be fertile for future activity.

Berndt, C.C.; Brindley, W.; Goland, A.N.; Herman, H.; Houck, D.L.; Jones, K.; Miller, R.A.; Neiser, R.; Riggs, W.; Sampath, S.; Smith, M.; Spanne, P. (State Univ. of New York, Stony Brook, NY (United States). Thermal Spray Lab.)

1991-01-01

39

Plasma Window as a Fast Vacuum Valve  

NASA Astrophysics Data System (ADS)

Plasma Window as a Fast Vacuum Valve. A. Hershcovitch, E. Johnson, Brookhaven National Laboratory, J. Noonan, E. Rotela, S. Sharma, A. Khounsary, Argonne National Laboratory-- Fast igniting plasma windows are being considered for use as emergency valves in case of vacuum breach in a beamline. Plasmas can be ignited faster than mechanical valves can close without causing damage to beamlines (unlike, presently used, msec spring loaded shutters). And, plasma windows have proven capability to separate between vacuum and atmosphere. In all existing vacuum valves, motion of solid objects is required. Consequently, the fastest valves or shutters are limited to a closing time of 7x10-3 sec. or longer (and a much longer opening time). But, intense discharges can be established within a few nanoseconds (10-9 sec.). Establishment of the plasma vacuum separator is determined by the motion of fast charged particles (as compared to solid objects in existing valves). Recently, an already established plasma window withstood vacuum breach tests. These experiments and fast igniting plasma configurations will be discussed.

Hershcovitch, Ady; Johnson, Erik; Noonan, John; Rotela, Elbio; Sharma, Sushil; Khounsary, Ali

1999-11-01

40

Effects of Surface Chemistry on Splat Formation During Plasma Spraying  

NASA Astrophysics Data System (ADS)

Ni-Cr single splats were plasma-sprayed at room temperature onto aluminum and stainless steel substrates, which were modified by thermal and hydrothermal treatments to control the oxide surface chemistry. The proportions of the different splat types were found to vary as a function of substrate pretreatment, especially when the pretreatment involved heating. It was observed that surface roughness did not correlate with changes in splat morphology. Substrate surfaces were characterized by X-ray photoelectron spectroscopy using in situ heating in vacuum to determine the effect of thermal pretreatment on substrate surface chemistry. It was found that the surface layers were composed primarily of oxyhydroxides. When the substrates were heated to 350 C, water vapor was released from the dehydration of oxyhydroxide. Preheating the substrate can remove the water prior to spraying: preheated substrates had improved the physical contact between the splat and substrate, which enhanced the formation of disk splats and increased the number of splats.

Tran, A. T. T.; Hyland, M. M.; Qiu, T.; Withy, B.; James, B. J.

2008-12-01

41

Process diagnostics in suspension plasma spraying  

Microsoft Academic Search

Benefits and limitations of process diagnostics are investigated for the suspension plasma spraying of yttria-stabilized zirconia thermal barrier coatings. The methods applied were enthalpy probe measurements, optical emission spectroscopy, and in-flight particle diagnostic.It was proved that the plasma characteristics are not affected negatively by the injection of the ethanol based suspension since the combustion of species resulting from ethanol decomposition

Georg Mauer; Alexandre Guignard; Robert Vaen; Detlev Stver

2010-01-01

42

Suspension Plasma Spraying: Process Characteristics and Applications  

Microsoft Academic Search

Suspension plasma spraying (SPS) offers the manufacture of unique microstructures which are not possible with conventional\\u000a powdery feedstock. Due to the considerably smaller size of the droplets and also the further fragmentation of these in the\\u000a plasma jet, the attainable microstructural features like splat and pore sizes can be downsized to the nanometer range. Our\\u000a present understanding of the deposition

Robert Vaen; Holger Kaner; Georg Mauer; Detlev Stver

2010-01-01

43

Present knowledge in suspension plasma spraying  

Microsoft Academic Search

Suspension plasma spraying (SPS) consists in injecting a non-Newtonian liquid in a d.c. plasma jet where it is fragmented and then vaporized. The sub-micrometric or nanometric particles contained in the suspension are then accelerated, heated, partially or totally melted before flattening onto the substrate to form the coating. Such coatings are finely structured and present better thermo-mechanical properties than conventionally

P. Fauchais; G. Montavon; A. Denoirjean; V. Rat; J.-F. Coudert; H. Ageorges; A. Bacciochini; E. Brousse; G. Darut; N. Caron; K. Wittmann-Teneze

2008-01-01

44

The thermal plasma near-net-shape spray forming of Al composites  

NASA Astrophysics Data System (ADS)

The vacuum-plasma-spraying technique presented in this article is suited to produce aluminum-matrix composites with a low coefficient of thermal expansion reinforced with fine ceramic particles, resulting in a uniform particle dispersion and bulk porosity of less than 1.5% in the as-sprayed condition. Plastic deformation of the plates followed by annealing resulted in significant increases in ultimate tensile strength, hardness, and elongation.

Smagorinski, M.; Tsantrizos, P.; Grenier, S.; Entezarian, M.; Ajersch, F.

1996-06-01

45

Porosity in plasma sprayed alumina coatings  

SciTech Connect

Small-angle neutron scattering (SANS) was used to study the porosity of plasma sprayed deposits of alumina in as-sprayed and heat-treated conditions. SANS results were compared with mercury intrusion porosimetry (MIP) and water immersion techniques. Multiple small-angle neutron scattering yields a volume-weighted effective pore radius (R{sub eff}), for pores with sizes between 0.08 and 10{mu}m, the pore volume in this size region, and from the Porod region, the surface area of pores of all sizes.

Ilavsky, J.; Herman, H.; Berndt, C.C. [State Univ. of New York, Stony Brook, NY (United States); Goland, A.N. [Brookhaven National Lab., Upton, NY (United States); Long, G.G.; Krueger, S.; Allen, A.J. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1994-03-01

46

Use of aqueous suspensions in plasma spraying of alumina coatings  

Microsoft Academic Search

The paper examines and compares the properties of Al2O3 coatings sprayed using two methods: arc plasma spraying (APS) of micron powders (average particle size is 45 ?m) and suspension\\u000a plasma spraying (SPS) (average particle size is 2.9 ?m). A system for feeding suspension into plasma spray is developed and\\u000a fabricated. It is established that SPS coatings contain finer structural components

V. E. Oliker; A. E. Terentev; L. K. Shvedova; I. S. Martsenyuk

2009-01-01

47

Suspension plasma spraying for hydroxyapatite powder preparation by RF plasma  

Microsoft Academic Search

Numerous techniques have been developed to synthesize ceramic powders with improved physical and chemical characteristics. This paper describes a new process called suspension plasma spraying (SPS), based on the use of radio frequency (RF) plasma technology. The objective of SPS is to prepare dense and spherical powders from a suspension of fine (<10 pm) or even ultrafine (<100 nm) powders.

Etienne Bouyer; F. Gitzhofer; M. I. Boulos

1997-01-01

48

Influence of the Spray Angle on the Characteristics of Atmospheric Plasma Sprayed Hard Material Based Coatings  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90 and 20 by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. Every spray bead was characterized by a Gaussian fit. This opens the opportunity to analyze the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, porosity, hardness, and morphology were carried out and the deposition efficiency as well as the tensile strength was measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, width, and form of the spray beads. The coatings become rougher and their quality decreases.

Tillmann, Wolfgang; Vogli, Evelina; Krebs, Benjamin

2008-12-01

49

Arc plasma sprayed C-band lithium ferrite phase shifters  

Microsoft Academic Search

The arc plasma spraying (APS) technology has demonstrated the capability of being economical in the fabrication of non-reciprocal ferrite phase shifter elements. It has been possible to arc plasma spray a C-band element in less than 10 minutes using a commercial spray dried lithium ferrite powder. This paper discusses the material properties (coercive force, remanence, and microwave loss) of the

Richard W. Babbitt

1975-01-01

50

Influence of Plasma Instabilities in Ceramic Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Direct current Suspension Plasma Spraying (SPS) allows depositing finely structured coatings. This article presents an analysis of the influence of plasma instabilities on the yttria-stabilized suspension drops fragmentation. A particular attention is paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of the arc root) and depending on the different spray parameters such as the plasma forming gas mixture composition and mass flow rate and the suspension momentum. By observing the suspension drops injection with a fast shutter camera and a laser flash sheet triggered by a defined transient voltage level of the plasma torch, the influence of plasma fluctuations on jet or drops fragmentation is studied through the deviation and dispersion trajectories of droplets within the plasma jet.

Etchart-Salas, R.; Rat, V.; Coudert, J. F.; Fauchais, P.; Caron, N.; Wittman, K.; Alexandre, S.

2007-12-01

51

Infrared Radiation Coatings Fabricated by Plasma Spray  

NASA Astrophysics Data System (ADS)

Infrared radiation coatings were prepared by plasma spray on the copper sheet. The structure and emissivity were examined by x-ray diffraction and infrared radiant instrument, respectively. The results show that an appropriate addition of TiO2 (5-15 wt.%) to NiO and Cr2O3 leads to high emissivity of coating with (Cr0.88Ti0.12)2O3 and NiCr2O4 phase. However, more (20-30 wt.%) will frustrate the formation of NiCr2O4 and ultimately decrease the emissivity. Moreover, the coating prepared by plasma spray endures a long working time without emissivity decrease.

Cheng, Xudong; Duan, Wei; Chen, Wu; Ye, Weiping; Mao, Fang; Ye, Fei; Zhang, Qi

2009-09-01

52

Spraying TiN by a Combined laser and low-pressure plasma spray system  

Microsoft Academic Search

The formation of a TiN-Ti composite coating by thermal spraying of titanium powder with laser processing of the subsequent\\u000a coating in a low-pressure N2 atmosphere was examined. A low-pressure plasma spray system was used in combination with a CO2 laser. First, the coating was plasma sprayed onto a mild steel substrate using a N2 plasma jet and titanium powder in

A. Ohmori; S. Hirano; K. Kamacta

1993-01-01

53

Plasma spray processing of TiC-based coatings for sliding wear resistance  

NASA Astrophysics Data System (ADS)

Titanium carbide-reinforced metallic coatings, produced by plasma spraying, can be used for sliding wear resistant applications. The sliding wear properties of such coatings are governed to a large extent by the strength, structure and stability of the bond interface between the carbide and the metallic phases. In the present investigation, the microstructure and sliding wear properties of plasma sprayed metal-bonded TiC coatings containing up to 90 v/o carbide have been studied. It was shown that alloying of the metallic phase improved carbide retention in TiC cermets due to better interface bonding, and increased wear resistance and lowered sliding coefficient of friction. TiC-based coatings were produced from both physically blended and synthesized feed powders. It was observed that the precursor TiC-based powder morphology and structure greatly affected the plasma sprayed coating microstructures and the resultant physical and mechanical characteristics. Physical blending of powders induced segregation during spraying, leading to somewhat lower deposit efficiencies and coating uniformity, while synthesized and alloyed titanium carbide/metal composite powders reduced problems of segregation and reactions associated with plasma spraying of physically blended powders where the TiC was in direct contact with the plasma jet. To understand oxidation effects of the environment, Ti and TiC-based coatings were produced under low pressure (VPS), air plasma (APS) and shrouded plasma sprayed conditions. APS Ti and TiC-based powders with reactive matrices suffered severe oxidation decomposition during flight, leading to poor deposition efficiencies and oxidized microstructures. High particle temperatures and cold air plasma spraying. Coating oxidation due to reactions of the particles with the surrounding air during spraying reduced coating hardness and wear resistance. TiC-with Ti or Ti-alloy matrix coatings with the highest hardness, density and wear resistance was achieved by spraying under vacuum plasma spray conditions. VPS coating microstructures of synthesized 40, 60 and 80 v/o TiC in Ti10Ni10Cr5Al and 80 v/o TiC in Fe30Cr alloy matrices exhibited fine and uniform distributions of spheroidal carbides. High volume fraction carbides were also obtained with no segregation effects. It was also shown that coatings produced from mechanically blended powders of 50, 70 and 90 vol. % TiC and commercially pure (C.P.) Ti, using low pressure plasma spray process (VPS), had densities >98% and were well bonded to steel, aluminum alloy or titanium alloy substrates. Reductions in jet oxygen contents by the use of an inert gas shroud enabled Ti and TiC-based coatings to be produced which were cleaner and denser than air plasma sprayed and comparable to vacuum plasma sprayed coatings. Direct oxygen concentration measurements in shrouded plasma jets made using an enthalpy probe and a gas analyzer also showed significant reductions in the entrainment of atmospheric oxygen. VPS and shrouded plasma spraying minimized carbide-matrix interface oxidation and improved coating wear resistance. The sliding wear resistance of synthesized coatings was very high and comparable with standard HVOF sprayed WC/Co and Crsb3Csb2/NiCr coatings. Shrouded plasma spray deposits of Crsb3Csb2/NiCr also performed much better than similar air plasma sprayed coatings, as result of reduced oxidation.

Mohanty, Mahesh

54

Microstructure modifications and phase transformation in plasma-sprayed WCCo coatings following post-spray spark plasma sintering  

Microsoft Academic Search

Thermal sprayed tungsten carbide (WC)cobalt (Co) coatings have been extensively employed as abrasion\\/wear protective layers. However, carbon loss (decarburization) of WCCo powders during thermal spraying reduces the efficiency of the coatings against abrasive wear. Post-spray treatment with spark plasma sintering (SPS) technique was conducted on plasma-sprayed WCCo coatings in the present study with the aim to compensate the lost carbon

H. Li; K. A. Khor; L. G. Yu; P. Cheang

2005-01-01

55

Vacuum energy of a spherical plasma shell  

SciTech Connect

We consider the vacuum energy of the electromagnetic field interacting with a spherical plasma shell together with a model for the classical motion of the shell. We calculate the heat kernel coefficients, especially that for the TM mode, and carry out the renormalization by redefining the parameters of the classical model. It turns out that this is possible and results in a model which, in the limit of the plasma shell becoming an ideal conductor, reproduces the vacuum energy found by Boyer in 1968.

Bordag, M. [Institute for Theoretical Physics, Leipzig University, Vor dem Hospitaltore 1, D-04103 Leipzig (Germany); Khusnutdinov, N. [Department of Physics, Kazan State University, Kremlevskaya 18, Kazan 420008 (Russian Federation) and Department of Physics, Tatar State University of Humanity and Education, Tatarstan 2, Kazan 420021 (Russian Federation)

2008-04-15

56

Suspension plasma spraying: Process parameters and resulting coating architecture  

Microsoft Academic Search

Due to the large volume fraction of the internal interfaces, finely structured coatings (nano- or submicronsized) should exhibit better properties than the ones structured at a microscale. Suspension plasma spraying (SPS) appears as a technology permitting to manufacture such coatings and consisting in injecting within a plasma jet a liquid suspension of solid particles. Compared to plasma spraying of micron-sized

J.-F. Coudert; V. Rat; H. Ageorges; A. Denoirjean; P. Fauchais; G. Montavon; N. Caron; S. Alexandre

2007-01-01

57

Nanostructured photocatalytic titania coatings formed by suspension plasma spraying  

Microsoft Academic Search

This paper describes formation of titanium dioxide coatings designed for photocatalytic applications, obtained by suspension\\u000a plasma spraying (SPS), an alternative of the atmospheric plasma spraying (APS) technique in which the material feedstock is\\u000a a suspension of the material to be sprayed. Two different TiO2 powders were dispersed in distilled water and ethanol and injected in Ar-H2 or Ar-H2-He plasma under

Filofteia-Laura Toma; Ghislaine Bertrand; Didier Klein; Christian Coddet; Cathy Meunier

2006-01-01

58

Study of Multi-Function MicroPlasma Spraying Technology  

Microsoft Academic Search

A multi-functional micro-arc plasma spraying system was developed according to aerodynamics and plasma spray theory. The soft switch IGBT (Insulated Gate Bipolar Transistor) invert technique, micro-computer control technique, convergent-divergent nozzle structure and axial powder feeding techniques have been adopted in the design of the micro-arc plasma spraying system. It is not only characterized by a small volume, a light weight,

Liuying Wang; Hangong Wang; Shaochun Hua; Xiaoping Cao

2007-01-01

59

Influence of Plasma Instabilities in Ceramic Suspension Plasma Spraying  

Microsoft Academic Search

Direct current Suspension Plasma Spraying (SPS) allows depositing finely structured coatings. This article presents an analysis\\u000a of the influence of plasma instabilities on the yttria-stabilized suspension drops fragmentation. A particular attention is\\u000a paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of the\\u000a arc root) and depending on the different

R. Etchart-Salas; V. Rat; J. F. Coudert; P. Fauchais; N. Caron; K. Wittman; S. Alexandre

2007-01-01

60

Physicochemical differences after densifying radio frequency plasma sprayed hydroxyapatite powders using spark plasma and conventional sintering techniques  

Microsoft Academic Search

The aim of this comparative study was to elucidate the characterization of spherical radio frequency (RF) plasma sprayed hydroxyapatite (HA) powder consolidated by spark plasma sintering (SPS) and conventional sintering methods. SPS processing took place under low vacuum of 4.5Pa at the temperature of 9001200C for 3min with a heating rate of 100C\\/min. The conventional processing was conducted at the

J. L. Xu; K. A. Khor; R. Kumar

2007-01-01

61

Oxidation and degradation of a plasma-sprayed thermal barrier coating system  

SciTech Connect

The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni-22Cr-10Al-1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia top coatings was evaluated by thermogravimetric analysis at 1150{degrees}C for up to 200 hours. Coating durability was assessed by furnace cycling at 1150{degrees}C. Coatings and reaction products were identified by x-ray diffraction, field-emission scanning electron microscopy and energy dispersive spectroscopy.

Haynes, J.A. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering; Ferber, M.K.; Porter, W.D. [Oak Ridge National Lab., TN (United States)

1996-04-01

62

Measurement of the Vacuum Arc Plasma Force  

Microsoft Academic Search

The axial force carried by the expanding plasma plume from 50-250-A copper and aluminum vacuum arcs was measured using a pendulum whose axle was equipped with a rotary optical encoder. It was found that the force was a linear function of current. The electrode geometry was varied to find the maximum force. At maximum, the average forces per unit current

Harry S. Marks; Isak I. Beilis; Raymond L. Boxman

2009-01-01

63

Adhesion properties of plasma sprayed hydroxylapatite coatings for orthopaedic prostheses.  

PubMed

Using Air Plasma Spraying (APS) and Vacuum Plasma Spraying (VPS) techniques, hydroxylapatite (HA) and mixtures of HA and titanium (Ti) were deposited on a Ti6A14V alloy (and on an AISI 316L steel) subjected to different surface treatments. The deposits were investigated for their crystallinity, thickness, and adhesion properties. Higher adhesion values were obtained with VPS rather than with APS. By utilising VPS, the deposition conditions were selected in order to achieve crystallinity values between 70 and 90%. The adhesion results depend on the crystallinity (increasing with its decrease), on the thickness (decreasing slightly with its increase) and especially on the surface finish of the metallic substrate. A porous Ti precoat was more effective than either chemical etching in HCl or sandblasting; sandblasting being the least effective. In particular, the double deposits consisting of a porous Ti precoat and a successive layer of HA proved to be most interesting for their higher adhesion properties and for their capability of providing primary stability due to the presence of the HA and secondary stability, in the case of its reabsorption, due to the porous metal. PMID:8193564

Brossa, F; Cigada, A; Chiesa, R; Paracchini, L; Consonni, C

1993-01-01

64

Characteristic of a triple-cathode vacuum arc plasma source  

SciTech Connect

In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper.

Xiang, W.; Li, M.; Chen, L. [Institute of Electric Engineering, China Academy of Engineering Physics, P.O. Box 919-518, Mianyang 621900 (China)

2012-02-15

65

Characteristic of a triple-cathode vacuum arc plasma source.  

PubMed

In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper. PMID:22380209

Xiang, W; Li, M; Chen, L

2012-02-01

66

Manufacturing Process of Nanostructured Alumina Coatings by Suspension Plasma Spraying  

Microsoft Academic Search

This paper describes the formation process of nanostructured alumina coatings and the injection system obtained by suspension\\u000a plasma spraying (SPS), an alternative to the atmospheric plasma spraying technique in which the material feedstock is a suspension\\u000a of the nanopowder to be sprayed. The nanoscale alumina powders (d?20nm) were dispersed in distilled water or ethanol and injected by a peristaltic pump

Changjun Qiu; Yong Chen

2009-01-01

67

High heat load testing of plasma sprayed W coatings  

Microsoft Academic Search

The influence of five spraying parameters on the thermal shockresistance of plasma sprayed tungsten coatings was evaluated with a pulsed electron beam gun. The pulse duration was 0.2 s and the absorbed power density 60 MW\\/m2. Two series of samples were tested. Both were plasma sprayed in controlled inert atmosphere, one at atmospheric pressure (AP) and the other at low

M. Urquiaga Valdes; R. G. Saint-Jacques; J.-F. Ct; C. Moreau

1997-01-01

68

Molybdenum disilicide composites produced by plasma spraying  

SciTech Connect

The intermetallic compound, molybdenum disilicide (MoSi{sub 2}) is being considered for high temperature structural applications because of its high melting point and superior oxidation resistance at elevated temperatures. The lack of high temperature strength, creep resistance and low temperature ductility has hindered its progress for structural applications. Plasma spraying of coatings and structural components of MoSi{sub 2}-based composites offers an exciting processing alternative to conventional powder processing methods due to superior flexibility and the ability to tailor properties. Laminate, discontinuous and in situ reinforced composites have been produced with secondary reinforcements of Ta, Al{sub 2}O{sub 3}, SiC, Si{sub 3}N{sub 4} and Mo{sub 5}Si{sub 3}. Laminate composites, in particular, have been shown to improve the damage tolerance of MoSi{sub 2} during high temperature melting operations. A review of research which as been performed at Los Alamos National Laboratory on plasma spraying of MoSi{sub 2}-based composites to improve low temperature fracture toughness, thermal shock resistance, high temperature strength and creep resistance will be discussed.

Castro, R.G.; Hollis, K.J.; Kung, H.H.; Bartlett, A.H.

1998-05-25

69

Rolling contact fatigue performance of plasma sprayed coatings  

Microsoft Academic Search

This experimental study describes the Rolling Contact Fatigue (RCF) performance and the failure mechanisms of plasma sprayed tungsten carbide cobalt (WC-15%Co) coatings. The advancements of plasma spray coatings due to higher velocity and temperature of the impacting lamella call for investigations into new applications. One possible application is the rolling element bearing. A modified four ball machine which models the

R. Ahmed; M. Hadfield

1998-01-01

70

Solid oxide fuel cell processing using plasma arc spray deposition techniques  

SciTech Connect

The Westinghouse Electric Corporation, in conjunction with the Thermal Spray Laboratory of the State University of New York, Stony Brook, investigated the fabrication of a gas-tight interconnect layer on a tubular solid oxide fuel cell with plasma arc spray deposition. The principal objective was to determine the process variables for the plasma spray deposition of an interconnect with adequate electrical conductivity and other desired properties. Plasma arc spray deposition is a process where the coating material in powder form is heated to or above its melting temperature, while being accelerated by a carrier gas stream through a high power electric arc. The molten powder particles are directed at the substrate, and on impact, form a coating consisting of many layers of overlapping, thin, lenticular particles or splats. The variables investigated were gun power, spray distance, powder feed rate, plasma gas flow rates, number of gun passes, powder size distribution, injection angle of powder into the plasma plume, vacuum or atmospheric plasma spraying, and substrate heating. Typically, coatings produced by both systems showed bands of lanthanum rich material and cracking with the coating. Preheating the substrate reduced but did not eliminate internal coating cracking. A uniformly thick, dense, adherent interconnect of the desired chemistry was finally achieved with sufficient gas- tightness to allow fabrication of cells and samples for measurement of physical and electrical properties. A cell was tested successfully at 1000{degree}C for over 1,000 hours demonstrating the mechanical, electrical, and chemical stability of a plasma-arc sprayed interconnect layer.

Ray, E.R.; Spengler, C.J.; Herman, H.

1991-07-01

71

Solid oxide fuel cell processing using plasma arc spray deposition techniques. Final report  

SciTech Connect

The Westinghouse Electric Corporation, in conjunction with the Thermal Spray Laboratory of the State University of New York, Stony Brook, investigated the fabrication of a gas-tight interconnect layer on a tubular solid oxide fuel cell with plasma arc spray deposition. The principal objective was to determine the process variables for the plasma spray deposition of an interconnect with adequate electrical conductivity and other desired properties. Plasma arc spray deposition is a process where the coating material in powder form is heated to or above its melting temperature, while being accelerated by a carrier gas stream through a high power electric arc. The molten powder particles are directed at the substrate, and on impact, form a coating consisting of many layers of overlapping, thin, lenticular particles or splats. The variables investigated were gun power, spray distance, powder feed rate, plasma gas flow rates, number of gun passes, powder size distribution, injection angle of powder into the plasma plume, vacuum or atmospheric plasma spraying, and substrate heating. Typically, coatings produced by both systems showed bands of lanthanum rich material and cracking with the coating. Preheating the substrate reduced but did not eliminate internal coating cracking. A uniformly thick, dense, adherent interconnect of the desired chemistry was finally achieved with sufficient gas- tightness to allow fabrication of cells and samples for measurement of physical and electrical properties. A cell was tested successfully at 1000{degree}C for over 1,000 hours demonstrating the mechanical, electrical, and chemical stability of a plasma-arc sprayed interconnect layer.

Ray, E.R.; Spengler, C.J.; Herman, H.

1991-07-01

72

Spray-drying of ceramics for plasma-spray coating  

Microsoft Academic Search

The spray-drying process of ceramics which are candidate materials for thermal barrier coatings (TBCs), i.e. 3YSZ+0, 2, 4, 6 wt.% Al2O3, is discussed in this paper. The two most important properties of spray-dried powders to determine the coating quality are density and particle size. Polyethyleneimine (PEI) acts as both an organic binder and a dispersant giving low viscosity in the

X. Q Cao; R Vassen; S Schwartz; W Jungen; F Tietz; D Stever

2000-01-01

73

Solid oxide fuel cell electrolytes produced by a combination of suspension plasma spray and very low pressure plasma spray  

Microsoft Academic Search

Plasma spray coating techniques allow unique control of electrolyte microstructures and properties as well as facilitating deposition on complex surfaces. This can enable significantly improved solid oxide fuel cells (SOFCs), including non-planar designs. SOFCs are promising because they directly convert the oxidization of fuel into electrical energy. However, electrolytes deposited using conventional plasma spray are porous and often greater than

Elliot Slamovich; James Fleetwood; James F. McCloskey; Aaron Christopher Hall; Rodney Wayne Trice

2010-01-01

74

Aluminum composite reinforced with multiwalled carbon nanotubes from plasma spraying of spray dried powders  

Microsoft Academic Search

Homogenous dispersion of carbon nanotubes (CNTs) in micron sized aluminum silicon alloy powders was achieved by spray drying. Excellent flowability of the powders allowed fabrication of thick composite coatings and hollow cylinders (5mm thick) containing 5wt.% and 10wt.% CNT by plasma spraying. Two phase microstructure with matrix having good distribution of CNT and CNT rich clusters was observed. Microstructural evolution

Srinivasa R. Bakshi; Virendra Singh; Sudipta Seal; Arvind Agarwal

2009-01-01

75

Plasma plume characterization of a vacuum arc thruster  

Microsoft Academic Search

A Vacuum Arc Thruster (VAT) is a thruster that uses the plasma created in a vacuum arc, an electrical discharge in a vacuum that creates high velocity and highly ionized plasmas, as the propellant without additional acceleration. A VAT would be a small and inexpensive low thrust ion thruster, ideal for small satellites and formation flying spacecraft. The purpose of

Michael James Sekerak

2005-01-01

76

Process for producing plasma sprayed carbide-based coatings with minimal decarburization and near theoretical density.  

National Technical Information Service (NTIS)

Plasma spray deposition of carbide/metal hardcoatings is difficult because complex chemical transformations can occur while spraying, especially in the presence of oxygen. A commercial plasma spray torch has been modified to simultaneously inject carbide ...

W. J. Lenling M. F. Smith J. A. Henfling

1990-01-01

77

Liquid-Mn sintering of plasma-sprayed zirconia-yttria coatings  

Microsoft Academic Search

The penetration phenomena of liquid Mn into porous ZrO2-8 wt.% Y2O3 coating, plasma sprayed on JIS SS400 steel substrate was studied by heating at 1573 K in a vacuum atmosphere, and the possibility of improving the mechanical properties of the coating by heat treatment with liquid Mn was examined. It was found that liquid Mn rapidly penetrated the coating and

A. Ohmori; Z. Zhou; K. Inoue

1994-01-01

78

Plasma Electrolytic Oxidation of Arc-Sprayed Aluminum Coatings  

Microsoft Academic Search

Different posttreatment methods, such as heat treatment, mechanical processing, sealing, etc., are known to be capable to\\u000a improve microstructure and exploitation properties of thermal spray coatings. In this work, a plasma electrolytic oxidation\\u000a of aluminum coatings obtained by arc spraying on aluminum and carbon steel substrates is carried out. Microstructure and properties\\u000a of oxidized layers formed on sprayed coating as

Vasyl Pokhmurskii; Hrygorij Nykyforchyn; Mykhajlo Student; Mykhajlo Klapkiv; Hanna Pokhmurska; Bernhard Wielage; Thomas Grund; Andreas Wank

2007-01-01

79

Advanced microstructural study of suspension plasma sprayed titanium oxide coatings  

Microsoft Academic Search

Suspension plasma sprayed titanium oxide coatings were analyzed using transmission electron microscope (TEM) and using Raman spectroscopy. The suspensions used to spray were formulated using fine rutile pigment, water, alcohol or their mixtures, and a small quantity of dispersant. TEM study realized using a face-to-face preparation technique enabled to visualize a lamellar shape of grains and their columnar growth. The

Harry Podlesak; Lech Pawlowski; Jacky Laureyns; Roman Jaworski; Thomas Lampke

2008-01-01

80

Suspension plasma sprayed composite coating using amorphous powder feedstock  

Microsoft Academic Search

Al2O3ZrO2 composite coatings were deposited by the suspension plasma spray process using molecularly mixed amorphous powders. X-ray diffraction (XRD) analysis shows that the as-sprayed coating is composed of ?-Al2O3 and tetragonal ZrO2 phases with grain sizes of 26nm and 18nm, respectively. The as-sprayed coating has 93% density with a hardness of 9.9GPa. Heat treatment of the as-sprayed coating reveals that

Dianying Chen; Eric H. Jordan; Maurice Gell

2009-01-01

81

Solid oxide fuel cell electrolytes produced by a combination of suspension plasma spray and very low pressure plasma spray.  

SciTech Connect

Plasma spray coating techniques allow unique control of electrolyte microstructures and properties as well as facilitating deposition on complex surfaces. This can enable significantly improved solid oxide fuel cells (SOFCs), including non-planar designs. SOFCs are promising because they directly convert the oxidization of fuel into electrical energy. However, electrolytes deposited using conventional plasma spray are porous and often greater than 50 microns thick. One solution to form dense, thin electrolytes of ideal composition for SOFCs is to combine suspension plasma spray (SPS) with very low pressure plasma spray (VLPPS). Increased compositional control is achieved due to dissolved dopant compounds in the suspension that are incorporated into the coating during plasma spraying. Thus, it is possible to change the chemistry of the feed stock during deposition. In the work reported, suspensions of sub-micron diameter 8 mol.% Y2O3-ZrO2 (YSZ) powders were sprayed on NiO-YSZ anodes at Sandia National Laboratories (SNL) Thermal Spray Research Laboratory (TSRL). These coatings were compared to the same suspensions doped with scandium nitrate at 3 to 8 mol%. The pressure in the chamber was 2.4 torr and the plasma was formed from a combination of argon and hydrogen gases. The resultant electrolytes were well adhered to the anode substrates and were approximately 10 microns thick. The microstructure of the resultant electrolytes will be reported as well as the electrolyte performance as part of a SOFC system via potentiodynamic testing and impedance spectroscopy.

Slamovich, Elliot (Purdue University, West Lafayette, IN); Fleetwood, James (Purdue University, West Lafayette, IN); McCloskey, James F.; Hall, Aaron Christopher; Trice, Rodney Wayne (Purdue University, West Lafayette, IN)

2010-07-01

82

Fabrication of NiTi intermetallic compound coating made by laser plasma hybrid spraying of mechanically alloyed powders  

Microsoft Academic Search

NiTi intermetallic compounds not only have shape memory effects but also high erosion resistance. Therefore, applying this material as a coating is an effective method for preventing erosion. In this study, a mixture of Ti and Ni powders was subjected to a mechanical alloying process. Then, the mechanical and structural properties of the coating fabricated by vacuum plasma spraying and

Hitoshi Hiraga; Takashi Inoue; Shigeharu Kamado; Yo Kojima; Akira Matsunawa; Hirofumi Shimura

2001-01-01

83

Producing titanium aluminide foil from plasma-sprayed preforms  

NASA Astrophysics Data System (ADS)

High-strength titanium alloy and titanium aluminide foils are required for fabricating composite structures and honeycombs for advanced aircraft engines and airframes. Titanium aluminide alloys possess limited workability, which results in significant yield loss when these materials are produced by the conventional ingot metallurgy route. This article describes the use of induction plasma spray technology to fabricate foil preforms of a titanium alloy and a titanium aluminide. These plasma-sprayed preforms were converted into 100% dense wrought titanium aluminide foil by a roll-consolidation process. The microstructure and mechanical properties of titanium aluminide foil produced from plasma-sprayed preforms were virtually identical to those of conventional ingot metallurgy foil. The plasma-spray plus roll-consolidation route may lead to the production of titanium aluminide foil as continuous coil, which would improve process efficiency and yield high-quality titanium aluminide foil at low cost.

Jha, Sunil C.; Forster, James A.

1993-07-01

84

Induction Plasma Synthesis of Nano-Structured SOFCs Electrolyte Using Solution and Suspension Plasma Spraying: A Comparative Study  

Microsoft Academic Search

In this paper, two plasma spraying technologies: solution plasma spraying (SolPS) and suspension plasma spraying (SPS) were\\u000a used to produce nano-structured solid oxide fuel cells (SOFCs) electrolytes. Both plasma spraying processes were optimized\\u000a in order to achieve the thin gas-tight electrolytes. The comparison of the two plasma spraying processes is based on electrolyte\\u000a phase, microstructure, morphology, as well as on

Lu Jia; Franois Gitzhofer

2010-01-01

85

Onion-like carbon deposition by plasma spraying of nanodiamonds  

Microsoft Academic Search

A deposit of carbon nanoparticles based on an onion-like structure was fabricated from detonation nanodiamond powders by a novel plasma spraying process, electromagnetically accelerated plasma spraying (EMAPS). EMAPS was able to transform nanodiamonds to onion-like structured carbon within 300 ?s through a thermal graphitization process in which the temperature of the particles would be in the range of 27004500 K.

Anna Valeryevna Gubarevich; Junya Kitamura; Shu Usuba; Hiroyuki Yokoi; Yozo Kakudate; Osamu Odawara

2003-01-01

86

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings  

Microsoft Academic Search

Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma\\u000a spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2\\u000a n\\u000a experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine\\u000a quantitatively the phase composition of obtained deposits.

Harry Podlesak; Lech Pawlowski; Romain dHaese; Jacky Laureyns; Thomas Lampke; Severine Bellayer

2010-01-01

87

Operating parameters for suspension and solution plasma-spray coatings  

Microsoft Academic Search

The interest to manufacture on large surfaces thick (i.e., 10 to 20?m, average thickness) finely structured or nano-structured layers is increasingly growing since about 10years. This explains the interest for suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS), both allowing manufacturing finely structured layers of thicknesses varying between a few micrometers up to a few hundred of micrometers.

P. Fauchais; V. Rat; J.-F. Coudert; R. Etchart-Salas; G. Montavon

2008-01-01

88

Suspension plasma spraying of nanostructured WC-12Co coatings  

Microsoft Academic Search

Nanostructured WC-12% Co coatings were deposited by suspension plasma spraying of submicron feedstock powders, using an internal\\u000a injection plasma torch. The liquid carrier used in this approach allows for controlled injection of much finer particles than\\u000a in conventional thermal spraying, leading to thin coatings with a fine surface finish. A polyethylene-imine (PEI) dispersant\\u000a was used to stabilize the colloidal suspension

J. Oberste Berghaus; B. Marple; C. Moreau

2006-01-01

89

Suspension Plasma Spraying of YPSZ Coatings: Suspension Atomization and Injection  

Microsoft Academic Search

Among processes evaluated to produce some parts of or the whole solid-oxide fuel cell, Suspension Plasma Spraying (SPS) is\\u000a of prime interest. Aqueous suspensions of yttria partially stabilized zirconia atomized into a spray by an internal-mixing\\u000a co-axial twin-fluid atomizer were injected into a DC plasma jet. The dispersion and stability of the suspensions were enhanced\\u000a by adjusting the amount of

Rgine Rampon; Claudine Filiatre; Ghislaine Bertrand

2008-01-01

90

Enhancement of vacuum polarization effects in a plasma  

SciTech Connect

The dispersive effects of vacuum polarization on the propagation of a strong circularly polarized electromagnetic wave through a cold collisional plasma are studied analytically. It is found that, due to the singular dielectric features of the plasma, the vacuum effects on the wave propagation in a plasma are qualitatively different and much larger than those in pure vacuum in the regime when the frequency of the propagating wave approaches the plasma frequency. A possible experimental setup to detect these effects in plasma is described.

Di Piazza, A.; Hatsagortsyan, K. Z.; Keitel, C. H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2007-03-15

91

Microstructure of plasma-sprayed titania coatings deposited from spray-dried powder  

Microsoft Academic Search

TiO2 coatings were prepared by plasma spraying using a spray-dried powder as feedstock material. A systematic study has been performed to determine how the titania slurry formulation (e.g. dispersant level, pH, binder addition) affects the granule characteristics. Aqueous slurries consisting of 50 wt.% of TiO2 particles, 01.2 wt.% ammonium polyacrylate as a dispersant and up to 15 wt.% styreneester acrylic

N. Berger-Keller; G. Bertrand; C. Filiatre; C. Meunier; C. Coddet

2003-01-01

92

Modeling of non-Newtonian suspension plasma spraying in an inductively coupled plasma torch  

Microsoft Academic Search

Suspension plasma spray (SPS) is a promising technique for nano-structured coatings and nano-powder synthesis where nano-particles are injected into the plasma jet with the help of liquid precursors. Most of the suspensions used in plasma spraying have the non-Newtonian behavior (viscoelastic or thixotropic). After injection into the plasma, the suspension is firstly atomized by the plasma jet before the droplets

Lijuan Qian; Jianzhong Lin; Hongbing Xiong

2011-01-01

93

Boron carbide coating by electromagnetically accelerated plasma spraying  

Microsoft Academic Search

A new system of electromagnetically accelerated plasma spraying (EMAPS) consisting of a pulsed high-current arc-plasma gun\\u000a and a large flow rate pulsed powder injector has been developed to synthesize a hard and dense coating of boron carbide (B4C) with a high adhesion. The plasma gun with a co-axial cylindrical electrode configuration generates electromagnetically\\u000a accelerated arc plasma with a typical velocity

J. Kitamura; S. Usuba; Y. Kakudate; H. Yokoi; K. Yamamoto; A. Tanaka; S. Fujiwara

2003-01-01

94

Plasma Buildup and Breakdown Delay in a Triggered Vacuum Gap  

Microsoft Academic Search

The phenomena leading to the surface flashover across solid insulators in vacuum and the subsequent spread of the trigger plasma thus formed to bridge the main gap in a triggered vacuum switch are investigated experimentally. The results show that the breakdown proceeds in two stages. In the first stage a plasma is formed by electrons releasing and ionizing absorbed gases.

A. J. Green; C. Christopoulos

1979-01-01

95

Characterization of microstructure of Nano-TiO 2 coating deposited by vacuum cold spraying  

Microsoft Academic Search

Control of the microstructure of TiO2 coatings through preparation methods significantly influences the coating performance. In this study, a vacuum cold-spray\\u000a process, as a new coating technology, is used to deposit nanocrystalline TiO2 coatings on conducting glass and stainless steel substrates. TiO2 deposits were formed using two types of nanocrystalline TiO2 powders with mean particle diameters of 200 and 25

S.-Q. Fan; G.-J. Yang; C.-J. Li; G.-J. Liu; C.-X. Li; L.-Z. Zhang

2006-01-01

96

Thermal plasma spraying for SOFCs: Applications, potential advantages, and challenges  

Microsoft Academic Search

In this article, the applications, potential advantages, and challenges of thermal plasma spray (PS) processing for nanopowder production and cell fabrication of solid oxide fuel cells (SOFCs) are reviewed. PS processing creates sufficiently high temperatures to melt all materials fed into the plasma. The heated material can either be quenched into oxide powders or deposited as coatings. This technique has

Rob Hui; Zhenwei Wang; Olivera Kesler; Lars Rose; Jasna Jankovic; Sing Yick; Radenka Maric; Dave Ghosh

2007-01-01

97

Development of porous anode layers for the solid oxide fuel cell by plasma spraying  

NASA Astrophysics Data System (ADS)

This article focuses on the development of the anode layer for solid oxide fuel cells by plasma spraying. The composite (cermet) anode, developed by thermal spraying, consisted of nickel and yttria-stabilized zirconia (YSZ). The effect of different plasma-spraying technologies on the microstructure characteristics and the electrochemical behavior of the anode layer were investigated. Coatings were fabricated by spraying nickel-coated graphite or nickel oxide with YSZ using a Triplex II plasma torch under atmospheric conditions as well as a standard F4 torch under atmospheric or soft-vacuum conditions. The investigations were directed to have an open microporous structure, higher electrical conductivity, and catalytic activity of anode deposits. Porosity was investigated by measuring the gas permeability. Scanning electron microscopy and x-ray diffraction technologies were applied to examine the morphology, microstructure, and composition of the layers. Electrical conductivity measurements were carried out to determine the ohmic losses within the anode layer. The most promising layers were analyzed by measuring the electrochemical behavior to obtain information about catalytic activity and performance.

Weckmann, H.; Syed, A.; Ilhan, Z.; Arnold, J.

2006-12-01

98

Occurrence of tungsten plasma in plasma spraying of WC/Co  

NASA Astrophysics Data System (ADS)

The conditions under which tungsten is vaporized and ionized during plasma spraying of WC/Co powders are investigated spectroscopically. Overheating of the powder results in less cobalt and decarburization of WC in the sprayed coating. The plasma is dominated by ionized tungsten and the resulting coating has a substantial amount of tungsten metal.

Detering, B. A.; Knibloe, J. R.; Eddy, T. L.

99

From DC Time-Dependent Thermal Plasma Generation to Suspension Plasma-Spraying Interactions  

Microsoft Academic Search

This paper proposes an original route for modeling the time-dependent behavior of a plasma jet issued from a DC plasma-spraying\\u000a torch operating with various kinds of gas mixtures. The hydrodynamic interactions between this jet and a liquid jet for suspension\\u000a plasma-spraying or a classical particle injection for the deposition of coatings are studied. In a first step, the classical plasma

Erick Meillot; S. Vincent; C. Caruyer; J. P. Caltagirone; D. Damiani

2009-01-01

100

Induction plasma-sprayed photocatalytically active titania coatings and their characterisation by micro-Raman spectroscopy  

Microsoft Academic Search

Undoped TiO2 (anatase) powder was deposited by induction plasma spraying (IPS) varying the plasma power, the carrier gas (argon) flow rate and the powder feed rate according to statistical design of experiments (SDE) methodology. In addition, anatase powders doped with varying amounts of V, Nb or Ta oxides were deposited by suspension plasma spraying (SPS) using reactive induction plasma spray

I. Burlacov; J. Jirkovsk; M. Mller; R. B. Heimann

2006-01-01

101

Modeling of Oxidation of Molybdenum Particles during Plasma Spray Deposition  

SciTech Connect

An oxidation model for molybdenum particles during the plasma spray deposition process is presented. Based on a well-verified model for plasma chemistry and the heating and phase change of particles in a plasma plume, this model accounts for the oxidant diffusion around the surface of particles or splats, oxidation on the surface, as well as oxygen diffusion in molten molybdenum. Calculations are performed for a single molybdenum particle sprayed under Metco-9MB spraying conditions. The oxidation features of particles during the flight are compared with those during the deposition. The result shows the dominance of oxidation of a molybdenum particle during the flight, as well as during deposition when the substrate temperature is high (above 400 C).

Fincke, James Russell; Wan, Y. P.; Jiang, X. Y.; Sampath, S.; Prasad, V.; Herman, H.

2001-06-01

102

Characterization of plasma sprayed and explosively consolidated simulated lunar soil  

SciTech Connect

Two methods for the use of lunar materials for the construction of shelters on the Moon are being proposed: explosive consolidation of the soil into structural components and plasma spraying of the soil to join components. The plasma-sprayed coating would also provide protection from the intense radiation. In this work, a mare simulant was plasma-sprayed onto a stainless steel substrate. Deposition of a 0.020 inch coating using power inputs of 23, 25, 27 and 29 kW were compared. Hardness of the coatings increased with each increase of power to the system, while porosity at the interface decreased. All coatings exhibited good adhesion. Simultaneously, an explosively consolidated sample was similarly characterized to afford a comparison of structural features associated with each mode of proposed use.

Powell, S.J.; Inal, O.T. [New Mexico Tech, Socorro, NM (United States); Smith, M.F. [Sandia National Labs., Albuquerque, NM (United States)

1997-06-01

103

The Role of Spraying Parameters and Inert Gas Shrouding in Hybrid Water-Argon Plasma Spraying of Tungsten and Copper for Nuclear Fusion Applications  

NASA Astrophysics Data System (ADS)

Tungsten-based coatings have potential application in the plasma-facing components in future nuclear fusion reactors. By the combination of refractory tungsten with highly thermal conducting copper, or steel as a construction material, functionally graded coatings can be easily obtained by plasma spraying, and may result in the development of a material with favorable properties. During plasma spraying of these materials in the open atmosphere, oxidation is an important issue, which could have adverse effects on their properties. Among the means to control it is the application of inert gas shrouding, which forms the subject of this study and represents a lower-cost alternative to vacuum or low-pressure plasma spraying, potentially applicable also for spraying of large surfaces or spacious components. It is a continuation of recent studies focused on the effects of various parameters of the hybrid water-argon torch on the in-flight behavior of copper and tungsten powders and the resultant coatings. In the current study, argon shrouding with various configurations of the shroud was applied. The effects of torch parameters, such as power and argon flow rate, and powder morphology were also investigated. Their influence on the particle in-flight behavior as well as the structure, composition and properties of the coatings were quantified. With the help of auxiliary calculations, the mass changes of the powder particles, associated with oxidation and evaporation, were assessed.

Mat?j?ek, J.; Kavka, T.; Bertolissi, G.; Ctibor, P.; Vilmov, M.; Mulek, R.; Nevrl, B.

2013-06-01

104

Suspension and Solution Plasma or HVOF Spraying  

Microsoft Academic Search

Nanostructured materials offer significant improvements in engineering properties because their grain sizes are smaller than those of conventionally processed materials by a factor of almost 2 orders of magnitude (Ref 1). Since the mid1990s, research has been conducted using thermal spray technology for the deposition of finely structured or nanostructured coatings (Ref 2, 3). To produce finely structured coatings by

Pierre Fauchais

2008-01-01

105

Microstructure of Suspension Plasma Spray and Air Plasma Spray Al 2 O 3 -ZrO 2 Composite Coatings  

Microsoft Academic Search

Al2O3-ZrO2 coatings were deposited by the suspension plasma spray (SPS) molecularly mixed amorphous powder and the conventional air\\u000a plasma spray (APS) Al2O3-ZrO2 crystalline powder. The amorphous powder was produced by heat treatment of molecularly mixed chemical solution precursors\\u000a below their crystallization temperatures. Phase composition and microstructure of the as-synthesized and heat-treated SPS\\u000a and APS coatings were characterized by XRD and

Dianying Chen; Eric H. Jordan; Maurice Gell

2009-01-01

106

Vacuum arc ion sources with gaseous plasma trigger systems  

Microsoft Academic Search

Triggering systems for vacuum arc plasma sources and ion sources have been developed that make use of a gaseous trigger discharge in a strong magnetic field. Two kinds of trigger discharge configurations have been explored, a Penning discharge and a magnetron discharge. The approach works reliably for low gas pressure in the vacuum arc environment and for long periods of

A. G. Nikolaev; G. Y. Yushkov; E. M. Oks; I. G. Brown; R. A. MacGill; M. R. Dickinson

1996-01-01

107

Modeling of formation of deposited layer by plasma spray process  

NASA Astrophysics Data System (ADS)

An analytical model is developed to describe the plasma deposition process in which average solidified thickness and coating and substrate temperatures are obtained. During the deposition process, the solidification rate is periodically varied, due to the impingement of liquid splats, and the amount of liquid in the coating layer increases. Periodical variation of the solidification rate causes temperature fluctuation in coating and substrate. The nature of interfacial structure of plasma-sprayed NiCrBSi MA powder is compared with the result predicted using the model, which indicates that the liquid deposited at the coating surface during deposition causes discontinuous boundaries within the coating. The spraying rate and the solidification rate reverse periodically with spraying process.

Lee, Joo-Dong; Ra, Hyung-Yong; Hong, Kyung-Tae; Hur, Sung-Kang

1992-03-01

108

Parameters Controlling Liquid Plasma Spraying: Solutions, Sols, or Suspensions  

NASA Astrophysics Data System (ADS)

This article presents what is our present knowledge in plasma spraying of suspension, sol, and solution in order to achieve finely or nano-structured coatings. First, it describes the different plasma torches used, the way liquid jet is injected, and the different measurements techniques. Then, drops or jet fragmentation is discussed with especially the influence of arc root fluctuations for direct current plasma jets. The heat treatment of drops and droplets is described successively for suspensions, sols, and solutions both in direct current or radio-frequency plasmas, with a special emphasize on the heat treatment, during spraying, of beads and passes deposited. The resulting coating morphologies are commented and finally examples of applications presented: Solid Oxide Fuel Cells, Thermal Barrier coatings, photocatalytic titania, hydroxyapatite, WC-Co, complex oxides or metastable phases, and functional materials coatings.

Fauchais, P.; Etchart-Salas, R.; Rat, V.; Coudert, J. F.; Caron, N.; Wittmann-Tnze, K.

2008-03-01

109

Mechanical and physical properties of plasma-sprayed stabilized zirconia  

SciTech Connect

Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

Siemers, P.A.; Mehan, R.L.

1983-09-01

110

Effects of Plasma Spray Parameters on Two Layer Thermal Barrier.  

National Technical Information Service (NTIS)

The power level and the type of arc gas used during plasma spraying of a two layer thermal barrier system (TBS) were found to affect the life of the system. Life at 1095 C in a cyclic furnace test was improved by about 140 percent by increasing the power ...

S. Stecura

1981-01-01

111

Influence of Glass Content on Damping Properties of Plasma-Sprayed Mixtures of Zirconia and Glass  

NASA Astrophysics Data System (ADS)

The addition by vacuum infiltration of small quantities of a polymer has been found to increase significantly the ability of a plasma-sprayed coating to dissipate vibratory energy at temperatures in the glassy-rubbery transition range of the polymer. As vitreous enamels and glasses undergo a glassy transition, but at much higher temperatures, the addition of a small amount of glass to a ceramic has the potential of providing high damping at such temperatures. Mixtures of yttria-stabilized zirconia (YSZ) and a glass frit were plasma sprayed on specimens with bond coats. Measures of system response (resonant frequencies and loss factors) were extracted from frequency responses to excitations of cantilever beam specimens over a range of excitation amplitudes. Comparisons of values determined before and after coating were used to determine the damping properties of the coatings alone as functions of strain, at temperatures of special interest. Emphasis was given to identifying the lowest level of glass giving significantly more damping than that of the plasma-sprayed ceramic alone. Coatings with weight fractions of 5, 2, 1, , and 0% glass were tested. The inclusion of glass at all weight fractions considered was found to yield significant increases in both the stiffness and dissipation of the coatings.

Torvik, P. J.; Henderson, J. P.

2012-07-01

112

Formation of boron carbide coating by electromagnetically accelerated plasma spraying  

Microsoft Academic Search

Boron carbide (B4C) coating formation is investigated using an electromagnetically accelerated plasma spraying, which can generate a dense and a high velocity plasma jet of 1 MPa and 2.02.5 km\\/s by applying a pulsed high-current arc-discharge to accelerate and heat powders. Highly crystalline B4C coatings with roughened coating-substrate interfaces were formed on mirror-polished stainless (SUS304) substrates without a binder material.

J. Kitamura; S. Usuba; Y. Kakudate; H. Yokoi; K. Yamamoto; A. Tanaka; S. Fujiwara

2003-01-01

113

Parameters Controlling Liquid Plasma Spraying: Solutions, Sols, or Suspensions  

Microsoft Academic Search

This article presents what is our present knowledge in plasma spraying of suspension, sol, and solution in order to achieve\\u000a finely or nano-structured coatings. First, it describes the different plasma torches used, the way liquid jet is injected,\\u000a and the different measurements techniques. Then, drops or jet fragmentation is discussed with especially the influence of\\u000a arc root fluctuations for direct

P. Fauchais; R. Etchart-Salas; V. Rat; J. F. Coudert; N. Caron; K. Wittmann-Tnze

2008-01-01

114

Laser acceleration in vacuum, gases, and plasmas withcapillary waveguide  

SciTech Connect

I propose a new method for laser acceleration of relativistic electrons using the leaky modes of a hollow dielectric waveguide. The hollow core of the waveguide can be either in vacuum or filled with uniform gases or plasmas. In case of vacuum and gases, TM01 mode is used for direct acceleration. In case of plasmas, EH11 mode is used to drive longitudinal plasma wave for acceleration. Structure damage due to high power laser can be avoided by choosing a core radius sufficiently larger than laser wavelength. Effect of nonuniform plasma density on waveguide performance is also analyzed.

Xie, Ming

1998-07-01

115

Investigations of plasma instabilities in a spray torch  

NASA Astrophysics Data System (ADS)

Plasma spray technology has been widely applied in industry. Unfortunately, the sprayed coating quality is not always perfect and predictable. Plasma jet instability is one of major causes for the inconsistent coating quality. This research has focused on investigating the causes of plasma jet instability, especially the arc instability in a spray torch. With combinations of electrical measurements, optical measurements and acoustic measurements, this research is designed to provide a complete picture of this arc instability. The approach has been to determine the effects of the instability on the in-flight particle properties and the coating quality. The arc instability has been characterized by the arc voltage waveform. High-speed video imaging has been used to capture the arc dynamical behavior. A simple analytical model has been developed to quantitatively estimate the arc column diameter. The velocity of the plasma jet has been measured based on the arc fluctuation propagation. The anode deterioration has been found having strong influences on the arc instability. These influences have been quantitatively described in terms of the boundary layer thickness and the arc operation mode. Fuzzy logic models have been used to diagnose the anode condition on-line and provide control strategies for constant particle heating. Effects of anode erosion on the jet turbulence have also been observed with a heating helium gas that simulates the jet. The heating and cooling processes of a substrate exposed to a plasma jet have been measured, and the influence of the substrate temperature on the coating porosity has been investigated. The results of this research contribute to the understanding of the details of the plasma spray process and help to lay a solid foundation for process optimization and development of feedback control yielding a consistent coating quality.

Duan, Zheng

2000-11-01

116

New technique deducing plasma potential by a capacitive coupling method in spraying dielectric barrier discharge plasmas  

SciTech Connect

A new method to measure the plasma potential in an atmospheric dielectric barrier discharge (DBD) plasmas is developed for a new spraying DBD plasma source, which is sustained by electric fields generated by flowing plasmas at the outer region of the electrodes, since conventional electric probe can not be applied due to arcing. The new technique is to measure the spatially averaged plasma potential by using a capacitive coupling method with calculation of collisional sheath thickness.

Choi, Yong-Sup; Chung, Kyu-Sun; Jung, Yong Ho; You, Hyun-Jong; Lee, Myoung-Jae [Electric Probe Applications Laboratory (ePAL), Hanyang University, Seoul 133-791 (Korea, Republic of)

2005-01-01

117

Capillary waveguide for laser acceleration in vacuum, gases and plasmas  

SciTech Connect

The authors propose a new method for laser acceleration of relativistic electrons using the leaky modes of a hollow dielectric waveguide. The hollow core of the waveguide can be either in vacuum or filled with uniform gases or plasmas. In of vacuum and gases, TM{sub 01} mode is used for direct acceleration. In case of plasmas, EH{sub 11} mode is used to drive longitudinal plasma wave for acceleration. Structure damage by high power laser is avoided by choosing a core radius much larger than laser wavelength.

Xie, Ming

1998-06-01

118

Manufacturing Solid Oxide Fuel Cells with an Axial-injection Plasma Spray System  

Microsoft Academic Search

Atmospheric plasma spraying has emerged as a cost-effective alternative to traditional sintering processes for solid oxide fuel cell (SOFC) manufacturing. However, the use of plasma spraying for SOFCs presents unique challenges, mainly due to the high porosity required for the electrodes and fully dense coatings required for the electrolytes. By using optimized spray conditions combined with appropriate feedstocks, SOFC electrolytes

Z. Tang; A. Burgess; O. Kesler

119

Phase evolution of hydroxapatite coatings suspension plasma sprayed using variable parameters in simulated body fluid  

Microsoft Academic Search

Fine, hydroxyapatite (HA) powder, synthesized using calcium nitrate and diammonium nitrate was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto titanium substrates. The deposition process was optimized using statistical design of 2n experiments with two variables: spray distance and electric power input to arc plasma. The sprayed coatings were soaked in simulated body

Romain d'Haese; Lech Pawlowski; Muriel Bigan; Roman Jaworski; Marc Martel

2010-01-01

120

Rheological properties of suspensions containing cross-linked starch nanoparticles prepared by spray and vacuum freeze drying methods.  

PubMed

The rheological behavior of suspensions containing vacuum freeze dried and spray dried starch nanoparticles was investigated to explore the effect of these two drying methods in producing starch nanoparticles which were synthesized using high pressure homogenization and mini-emulsion cross-linking technique. Suspensions containing 10% (w/w) spray dried and vacuum freeze dried nanoparticles were prepared. The continuous shear viscosity tests, temperature sweep tests, the frequency sweep and creep-recovery tests were carried out, respectively. The suspensions containing vacuum freeze dried nanoparticles showed higher apparent viscosity within shear rate range (0.1-100 s(-1)) and temperature range (25-90 C). The suspensions containing vacuum freeze dried nanoparticles were found to have more shear thinning and less thixotropic behavior compared to those containing spray dried nanoparticles. In addition, the suspensions containing vacuum freeze dried particles had stronger elastic structure. However, the suspensions containing spray dried nanoparticles had more stiffness and greater tendency to recover from the deformation. PMID:22944440

Shi, Ai-min; Li, Dong; Wang, Li-jun; Adhikari, Benu

2012-07-31

121

Plasma-sprayed ceramic coatings for molten metal environments.  

SciTech Connect

Coating porosity is an important parameter to optimize for plasma-sprayed ceramics which are intended for service in molten metal environments. Too much porosity and the coatings may be infiltrated by the molten metal causing corrosive attack of the substrate or destruction of the coating upon solidification of the metal. Too little porosity and the coating may fail due to its inability to absorb thermal strains. This study describes the testing and analysis of tungsten rods coated with aluminum oxide, yttria-stabilized zirconia, yttrium oxide, and erbium oxide deposited by atmospheric plasma spraying. The samples were immersed in molten aluminum and analyzed after immersion. One of the ceramic materials used, yttrium oxide, was heat treated at 1000 C and 2000 C and analyzed by X-ray diffractography and mercury intrusion porosimetry. Slight changes in crysl nl structure and significant changes in porosity were observed after heat treatments.

Hollis, K. J. (Kendall J.); Peters, M. I. (Maria I.); Bartram, B. D. (Brian D.)

2002-01-01

122

Identification of Desirable Precursor Properties for Solution Precursor Plasma Spray  

NASA Astrophysics Data System (ADS)

In solution precursor plasma spray chemical precursor solutions are injected into a standard plasma torch and the final material is formed and deposited in a single step. This process has several attractive features, including the ability to rapidly explore new compositions and to form amorphous and metastable phases from molecularly mixed precursors. Challenges include: (a) moderate deposition rates due to the need to evaporate the precursor solvent, (b) dealing on a case by case basis with precursor characteristics that influence the spray process (viscosity, endothermic and exothermic reactions, the sequence of physical states through which the precursor passes before attaining the final state, etc.). Desirable precursor properties were identified by comparing an effective precursor for yttria-stabilized zirconia with four less effective candidate precursors for MgO:Y2O3. The critical parameters identified were a lack of major endothermic events during precursor decomposition and highly dense resultant particles.

Muoto, Chigozie K.; Jordan, Eric H.; Gell, Maurice; Aindow, Mark

2011-06-01

123

Grinding induced effects in plasma sprayed zirconia coatings  

NASA Astrophysics Data System (ADS)

The effect of grinding on the surface layer properties of ceria and yttria partially stabilized zirconia plasma-sprayed coatings (CePSZ, YPSZ, respectively) has been studied by X-ray diffraction methods. For this purpose, the modified model of line broadening analysis has been derived. The model considers elastic anisotropic properties along with more random paracrystal imperfections, both affecting X-ray line broadening. Grinding-induced microstructural changes were also studied using an estimation from the quantitative Orientation Distribution Function (ODF) texture. It was concluded, based on this work, that CePSZ ceramic is less mechanically stable compared to YPSZ. Consequently, more beneficial mechanical properties of a ground surface layer can be expected for CePSZ plasma-sprayed coatings.

Zeman, J.; Cepera, M.; Musil, J.; Filipensky, J.

1993-12-01

124

Electrochemical Evaluation of Pyrite Films Prepared by Plasma Spraying  

SciTech Connect

Thermally activated batteries use electrodes that are typically fabricated by cold pressing of powder. In the LiSi/FeS2 system, natural (mineral) pyrite is used for the cathode. In an effort to increase the energy density and specific energy of these batteries, flame and plasma spraying to form thin films of pyrite cathodes were evaluated. The films were deposited on a 304 stainless steel substrate (current collector) and were characterized by scanning electron microscopy and x-ray dlfllaction. The films were electrochemically tested in single cells at 5000C and the petiormance compared to that of standard cells made with cold-pressed powders. The best results were obtained with material deposited by de-arc plasma spraying with a proprietq additive to suppress thermal decomposion of the pyrite.

Guidotti, R.A.; Reinhardt, F.W.

1998-10-30

125

Response surface methodology for optimization of plasma spraying  

NASA Astrophysics Data System (ADS)

Response surface methodology was used to describe empirical relationships among three principal independent variables that control the plasma spraying process. The torch-substrate distance, the amount of hydrogen in the primary gas (argon), and the powder feed rate were studied. A number of dependent variables (responses) were determined, including the deposited layer roughness, density, hardness, chemical composition, and erosion rate. The technique facilitates mapping of the responses within a limited experimental region without much prior knowledge of the process mechanisms. The maps allow process optimization and selection of operating conditions to achieve the desired specifications of the plasma sprayed coating. To illustrate the approach, a simple system of WC-12%Co was deposited on a mild steel substrate. The resulting response surfaces were used to define optimum, or robust, deposition parameters.

Troczynski, T.; Plamondon, M.

1992-12-01

126

Laser remelting of plasma-sprayed coatings on nuclear valves  

NASA Astrophysics Data System (ADS)

Three kinds of plasma sprayed coatings on nuclear valves of FRAMATOME, which are the cobalt-based Stellite, the nickel-based Eutroloy, and the iron-based Cenium, were remelted with a 5 kW CO2 laser. The aim is to build-up a fine homogeneous metallurgical structure onto the hardface, with a uniform thickness and free of cracks in order to improve the wear and galling properties of the coatings. It was concluded from the experimental results that for plasma sprayed Stellite coating, satisfactory results can be obtained by carefully selecting the process parameters, preheating of the substrate is not needed; and for the Eutroloy coating, preheating of the substrate is necessary to get rid of cracking during laser remelting. Laser remelting is not an adequate process for Cerium coating because it is very difficult to avoid cracks on the remelted layer.

Li, Yanxiang; Steen, William M.; Sharkey, Sarah J.

1993-05-01

127

Influence of a thermal treatment on the mechanical properties of plasma sprayed elaborated zirconia.  

National Technical Information Service (NTIS)

Plasma spraying allows making ceramic massive pieces. Nevertheless, a rough-sprayed piece is porous and has poor mechanical properties until it is processed by thermal treatment. It then acquires high thermomechanical properties, including high wearing pr...

E. Rigal T. Priem E. Vray

1995-01-01

128

Plasma-sprayed coatings for fusion reactor applications  

Microsoft Academic Search

A series of plasma-sprayed coatings has been given a preliminary evaluation to assess the potential of this class of materials in fusion reactor applications. TiC, TiB, Be and VBe coatings on copper and stainless steel were tested for coating adherence, ion erosion resistance and susceptability to arc erosion. The coatings, in general, display a good resistance to thermal shock failure.

A. W. Mullendore; D. M. Mattox; J. B. Whitley; D. J. Sharp

1979-01-01

129

Grinding induced effects in plasma sprayed zirconia coatings  

Microsoft Academic Search

The effect of grinding on the surface layer properties of ceria and yttria partially stabilized zirconia plasma-sprayed coatings\\u000a (CePSZ, YPSZ, respectively) has been studied by X-ray diffraction methods. For this purpose, the modified model of line broadening\\u000a analysis has been derived. The model considers elastic anisotropic properties along with more random paracrystal imperfections,\\u000a both affecting X-ray line broadening. Grinding-induced microstructural

J. Zeman; M. Cepera; J. Musil; J. Filipensky

1993-01-01

130

Microlaminate composite structures by low pressure plasma spray deposition  

Microsoft Academic Search

The low pressure plasma spray (LPPS) process has been utilized in the development and fabrication of metal\\/metal, metal\\/carbide, and metal\\/oxide composite structures; including particulate dispersion and both continuous and discontinuous laminates. This report describes the LPPS process and the development of copper\\/tungsten microlaminate structures utilizing this processing method. Microstructures and mechanical properties of the Cu\\/W composites are compared to conventionally

R. G. Castro; P. W. Stanek

1988-01-01

131

Two zones microstructure of suspension plasma sprayed hydroxyapatite coatings  

Microsoft Academic Search

The plasma spraying process of hydroxyapatite (HA) suspension was optimized in order to obtain possibly dense and well adherent coatings onto aluminum and titanium alloy substrates. The process variables included the suspension liquid (water, ethanol or their mixture), the pneumatic pressure applied to inject the suspension (0.2 to 0.8bar), type of injection (nozzle or atomizer), geometry of suspension injection to

Stefan Kozerski; Lech Pawlowski; Roman Jaworski; Francine Roudet; Fabrice Petit

2010-01-01

132

The solution precursor plasma spray processing of nanomaterials  

Microsoft Academic Search

Solution precursor plasma spray (SPPS) synthesis is a simple, single-step, and rapid technique for synthesizing nano-ceramic\\u000a materials from solution precursors. This innovative method uses molecularly mixed precursors as liquids, avoiding a separate\\u000a processing method for the preparation of powders and enabling the synthesis of a wide range of metal oxide powders and coatings.\\u000a Also, this technique is considered to be

E. Brinley; K. S. Babu; S. Seal

2007-01-01

133

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings  

NASA Astrophysics Data System (ADS)

Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2 n experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine quantitatively the phase composition of obtained deposits. Raman microscopy and electron probe microanalysis (EPMA) enabled localization of the phases in different positions of the coating cross sections. Transmission electron microscopic (TEM) study associated with energy-dispersive x-ray spectroscopy (EDS) enabled visualization and analysis of a two-zone microstructure. One zone contained crystals of hydroxyapatite, tetracalcium phosphate, and a phase rich in calcium oxide. This zone included lamellas, usually observed in thermally sprayed coatings. The other zone contained fine hydroxyapatite grains that correspond to nanometric and submicrometric solids from the suspension that were agglomerated and sintered in the cold regions of plasma jet and on the substrate.

Podlesak, Harry; Pawlowski, Lech; D'Haese, Romain; Laureyns, Jacky; Lampke, Thomas; Bellayer, Severine

2010-03-01

134

A 5-year comparison of hydroxyapatite-coated titanium plasmasprayed and titanium plasmasprayed cylinder dental implants  

Microsoft Academic Search

Objective. A preliminary report from this study showed that hydroxyapatite-coated (HA) titanium plasmasprayed (TPS) cylinder implants had fewer failures than TPS cylinder implants before prosthetic loading. The purpose of this article is to report the long-term success associated with the 2 systems. In addition, local and systemic factors that may influence the success or failure of the implants were analyzed.

John D. Jones; John Lupori; Joseph E. Van Sickels; Wayne Gardner

1999-01-01

135

Addressing processing problems associated with plasma spraying of hydroxyapatite coatings.  

PubMed

Biomedical coatings generally have to satisfy specific requirements such as a high degree of crystallinity (for positive biological responses), good coating adhesion and optimal porosity. These are necessary to enhance biocompatibility, accelerate post-operative healing and improved fixation. Thermal spray processes have been frequently used to deposit functionally active biomedical coatings, such as hydroxyapatite (HA), onto prosthetic implants. The benefits of HA materials in coated implants have been widely acknowledged, but the occurrence of several poor performances has generated concerns over the consistency and reliability of thermally sprayed HA coatings. Recent investigations using HA coatings have shown that process related variability has significant influence on coating characteristics such as phase composition, structure and chemical composition and performance such as bioresorption, degradation and bone apposition. Variation in process parameters such as powder morphology can induce microstructural and mechanical inconsistencies that have an effect on the service performance of the coating. In order to reach some acceptable level of reliability, it may be necessary to control existing variability in commercially available HA feedstock. In addition, certain opposing factors severely constrain the means to achieve the necessary coating conditions via thermal spraying alone; therefore, creating the need to introduce other innovative or secondary treatment stages to attain the desired results. This paper highlights some of the problems associated with plasma spray coating of HA and suggests that tailoring the powder feedstock morphology and properties through suitable conditioning processes can aid the deposition efficiency and produce an acceptable coating structure. PMID:8991486

Cheang, P; Khor, K A

1996-03-01

136

Deposition Behavior and Microstructural Features of Vacuum Kinetic Sprayed Aluminum Nitride  

NASA Astrophysics Data System (ADS)

The vacuum kinetic spray (VKS) method is a relatively advanced technology by which thin and dense ceramic coatings can be fabricated via the high-speed impact of submicron-sized particles at room temperature. However, the actual bonding mechanism associated with the VKS process has not yet been elucidated. In this study, AlN powders were pretreated through ball-milling and heat-treatment processes in order to investigate the effects of microstructural changes on the deposition behavior. It was found that ball-milled and heat-treated powder with polycrystals formed by partially aligned dislocations showed considerably higher deposition rates when compared to only ball-milled powder with tangled dislocations. Therefore, in the VKS process, the deposition behavior is shown to be affected by not only the particle size and defect density, but also the microstructure of the feedstock powder.

Park, Hyungkwon; Heo, Jeeae; Cao, Fei; Kwon, Juhyuk; Kang, Kicheol; Bae, Gyuyeol; Lee, Changhee

2013-04-01

137

Plasma sprayed magnetic composites process, microstructure and properties  

NASA Astrophysics Data System (ADS)

The dissertation presents research results from integrated studies of process, structure and magnetic properties of plasma-sprayed ferrite-metal composites. These magnetic composites are considered as the core materials for miniaturized high frequency planar inductors, thick film magnetoresistive sensors and potentially as magnetostrictive sensors. Offering the advantages of low substrate temperature during processing, high throughput production capability, cost efficiency and minimizing the interfacial reaction between the ferrite and metal phases, plasma spraying can be considered as a promising route for fabricating magnetic composites with industrial applications. A multitude of experimental techniques, including phase analysis, microstructure observation, magnetic property and electrical property measurements and numerical modeling have been applied for this investigation. A number of fundamental attributes in terms of process-microstructure-property relationships have been investigated by a systematic processing approach through the frame work of process maps. Such studies can provide insight into process control and optimization. Three types of magnetic composites have been fabricated using plasma spraying. Rocksalt structured monoxides form in the as-sprayed coatings due to deoxidation of ferrite as well as the oxidation of metallic particles. Random cation distribution and the presence of monoxides and microstructural defects, degrade the magnetic and electrical properties of the composites. Low temperature air annealing can improve these properties by means of forming insulating trivalent oxides (Hematite) and ordering the cations. Functional properties such as magnetoresistance and magnetostriction of comparable value to bulk materials can be obtained after annealing. A salient finding is the transition form a giant magnetoresistance (GMR) to anisotropic magnetoresistance (AMR) at the percolation threshold which has been reported for the first time in magnetic composites. Thermally sprayed composites coatings are found to have a much smaller percolation threshold due to the anisotropy of splats. Using the effective medium approximation, the relationship between the percolation threshold and aspect ratio has been derived. The experimental results are in good agreement with simulation results. This is the first time that the percolation phenomenon in thermally sprayed composites has been studied quantitatively and compared with theory.

Liang, Shanshan

138

Plasma spraying induced changes of calcium phosphate ceramic characteristics and the effect on in vitro stability  

Microsoft Academic Search

Plasma spraying is a commonly used technique to apply thin calcium phosphate ceramic coatings. Special consideration is given to retaining the original structure of CPC particles. However, changes are possible. Thus this study focused on plasma spraying induced changes in material characteristics of commercial coatings and their influence onin vitro dissolution. All analysed coatings were found to undergo significant plasma

S. R. Radin; P. Ducheyne

1992-01-01

139

Innovative and emerging processes in plasma spraying: from micro- to nano-structured coatings  

Microsoft Academic Search

In the context of nanometre-sized structured materials and the perspectives of their technological applications, plasma spray technology is developing to master the coating microstructure at a nanometre scale level. This paper is an attempt to describe (i) the latest advances in the control of the conventional plasma spray process that requires the monitoring of both the plasma jet fluctuation level

P. Fauchais; A. Vardelle

2011-01-01

140

High temperature in-situ XRD of plasma sprayed HA coatings  

Microsoft Academic Search

The control of phase transformations in plasma sprayed hydroxyapatite (HA) coatings are critical to the clinical performance of the material. This paper reports the use of high temperature X-ray diffraction (HT-XRD) to study, in-situ, the phase transformations occurring in plasma sprayed HA coatings. The coatings were prepared using different spray power levels (net plasma power of 12 and 15kW) and

S. W. K. Kweh; K. A. Khor; P. Cheang

2002-01-01

141

Residual stress in plasma sprayed ceramic turbine tip and gas path seal specimens  

NASA Astrophysics Data System (ADS)

The residual stresses in a ceramic sheet material used for turbine blade tip gas path seals, were estimated. These stresses result from the plasma spraying process which leaves the surface of the sheet in tension. To determine the properties of plasma sprayed ZrO2-Y2O3 sheet material, its load deflection characteristics were measured. Estimates of the mechanical properties for sheet materials were found to differ from those reported for plasma sprayed bulk materials.

Hendricks, R. C.; McDonald, G.; Mullen, R. L.

1983-02-01

142

Process for producing plasma sprayed carbide-based coatings with minimal decarburization and near theoretical density  

Microsoft Academic Search

Plasma spray deposition of carbide\\/metal hardcoatings is difficult because complex chemical transformations can occur while spraying, especially in the presence of oxygen. A commercial plasma spray torch has been modified to simultaneously inject carbide powder and a metal alloy powder at two different locations in the plasma stream. Composite hardcoatings of tungsten carbide\\/cobalt with a nickel-base alloy matrix have been

W. J. Lenling; M. F. Smith; J. A. Henfling

1990-01-01

143

Oxidation of nickel during plasma spraying and some properties of nickel oxide  

Microsoft Academic Search

The techniques of plasma spraying are suitable for deposition of metals, ceramics or composites. Atmospheric plasma spraying\\u000a of metals is accompanied by their oxidation. The oxidation of nickel during its spraying gives rise to NiO. During the flight\\u000a of molten nickel particles in the plasma plume, the first stage of the oxidation reaction takes place. To determine the amount\\u000a of

K. Volenk; P. Ctibor; J. Dubsk; P. Chrska; J. Hork

2004-01-01

144

Improvement of plasma-sprayed YSZ electrolytes for solid oxide fuel cells by alumina addition  

Microsoft Academic Search

Atmospheric plasma spray is a fast and economical process for deposition of yttria-stabilized zirconia (YSZ) electrolyte for\\u000a solid oxide fuel cells. YSZ powders have been used to prepare plasma-sprayed thin ceramic films on the metallic substrate\\u000a employing plasma spray technology at atmospheric pressure. Alumina doping was employed to improve the structural characteristics\\u000a and electrical properties of YSZ. The effect of

Amin Mirahmadi; Mohammad Pourmalek

2010-01-01

145

Caracterisation of Titanium Nitride Layers Deposited by Reactive Plasma Spraying  

NASA Astrophysics Data System (ADS)

Forming and cutting tools are subjected to the intense wear solicitations. Usually, they are either subject to superficial heat treatments or are covered with various materials with high mechanical properties. In recent years, thermal spraying is used increasingly in engineering area because of the large range of materials that can be used for the coatings. Titanium nitride is a ceramic material with high hardness which is used to cover the cutting tools increasing their lifetime. The paper presents the results obtained after deposition of titanium nitride layers by reactive plasma spraying (RPS). As deposition material was used titanium powder and as substratum was used titanium alloy (Ti6Al4V). Macroscopic and microscopic (scanning electron microscopy) images of the deposited layers and the X ray diffraction of the coatings are presented. Demonstration program with layers deposited with thickness between 68,5 and 81,4 ?m has been achieved and presented.

Ro?u, Radu Alexandru; ?erban, Viorel-Aurel; Bucur, Alexandra Ioana; Popescu, Mihaela; U?u, Drago?

2011-01-01

146

Plasma-sprayed ceramic coatings for protection against molten metal.  

SciTech Connect

Molten metal environments pose a special demand on materials due to the high temperature corrosion effects and thermal expansion mismatch induced stress effects. A solution that has been successfully employed is the use of a base material for the mechanical strength and a coating material for the chemical compatibility with the molten metal. The work described here used such an approach coating tungsten rods with aluminum oxide, yttria-stabilized zirconia, yttrium oxide, and erbium oxide deposited by atmospheric plasma spraying. The ceramic materials were deposited under varying conditions to produce different structures. Measurement of particle characteristics was performed to correlate to material properties. The coatings were tested in a thermal cycling environment to simulate the metal melting cycle expected in service. Results of the testing indicate the effect of material composition and spray conditions on the thermal cycle crack resistance of the coatings.

Hollis, K. J. (Kendall J.); Peters, M. I. (Maria I.); Bartram, B. D. (Brian D.)

2002-01-01

147

Plasma spraying of Wc-Co part I: Theoretical investigation of particle heating and acceleration during spraying  

NASA Astrophysics Data System (ADS)

Plasma-sprayed WC-Co coatings are used extensively in a variety of wear-resistant applications. The quality of these sprayed coatings depends greatly on the temperature and velocity of the powder particles impacting the substrate. Because it is both expensive and difficult to experimentally determine these particle parameters, the present study deals with a theoretical investigation of particle heatup and acceleration during plasma spraying of WC-Co based on a recently developed model. The effect of WC-Co particle size on the evolution of particle temperature and velocity is examined through calculations performed under typical spraying conditions. The implications of the powder particles, assuming an off-axis trajectory during their traverse through the plasma flame, are also discussed.

Joshi, S. V.

1993-06-01

148

New plasma concepts for enhanced microwave vacuum electronics  

Microsoft Academic Search

Summary form only given. Recently, new concepts in the field of microwave radiation generation have led to the possibly of major advances on the frontier of microwave vacuum devices. These concepts include the emerging technology of DC to AC radiation converters, or DARC sources, ionization fronts for frequency upshifting and conversion of extremely large plasma wakes into a Cherenkov radiation

J. R. Hoffman; P. Muggli; M. A. Gundersen; W. B. Mori; C. Joshi; T. Katsouleas

1999-01-01

149

Testing program for Burning Plasma Experiment vacuum vessel bolted joint  

Microsoft Academic Search

As presently designed, the Burning Plasma Experiment vacuum vessel will be segmentally fabricated and assembled by bolted joints in the field. Due to geometry constraints, most of the bolted joints have significant eccentricity, which causes the joint behavior to be sensitive to joint clamping forces. Experience indicates that, as a result of this eccentricity, the joint will tend to open

P. K. Hsueh; M. Z. Khan; J. Swanson; T. Feng; S. Dinkevich; J. Warren

1991-01-01

150

Evaluation of corrosion on plasma sprayed and anodized titanium implants, both with and without bone cement.  

PubMed

The corrosion behavior of titanium with vacuum plasma sprayed titanium coatings and with anodized surfaces, both with and without polymeric bone cement were evaluated. Electrochemical extraction tests were carried out with subsequent analysis of the electrolyte by ICP-MS in order to verify our hypothesis of the ionic permeability of the polymer cement. The complexity of the situation resides in the existence of two interfaces: electrolyte-polymer and polymer-metal. The surface preparation (treatment of the surface) plays an important role in the corrosion resistance of titanium. The electrochemical magnitudes that were examined reveal that the plasma spray surfaces have the lowest corrosion resistance. The cement, in spite of having reduced electrical conductivity in comparison to metal, is an ionic transporter, and therefore capable of participating in the corrosion process. In the present study, we observed in fact crevice corrosion at the metal-cement interface. In the case of plasma spray surfaces, a process of diffusion of titanium particles in the electrolyte could accompany the crevice corrosion. In this study, we have shown that there is a corrosion process at the surface of the titanium through the cement which has as a consequence on the one hand the formation of titanium cations and on the other hand the growth of a passive layer on the titanium. In conclusion, we identified two principal factors that influence the corrosion process: [1] the type of surface treatment for the titanium, and [2] the ionic conductivity of the cement. There is indeed ionic transport through the cement; as evidenced by the presence of titanium in the electrolyte solution (ICP-MS analysis) and chloride at the surface of the titanium sample (EDX analysis). We show that the polymer cement is an ionic conductor and participates in the corrosion of the embedded titanium. We cannot deduce from our results, however, whether the polymer itself possesses corrosive properties. Long-term experiments will be necessary to study the degradation behavior of the polymer cement. PMID:12895575

Reclaru, L; Lerf, R; Eschler, P-Y; Blatter, A; Meyer, J-M

2003-08-01

151

Amorphous and crystalline phase formation during suspension plasma spraying of the aluminazirconia composite  

Microsoft Academic Search

The focus of this study is the amorphous phase formation in the aluminayttria stabilized zirconia composite coatings during thermal spray deposition. The investigated processes include conventional and suspension plasma spraying. The focus of this paper is on suspension spraying, while making a comparison of the two processes. Through the study of the in-flight collected particles and coatings produced from the

F. Tarasi; M. Medraj; A. Dolatabadi; J. Oberste-Berghaus; C. Moreau

2011-01-01

152

Effect of Chamber Pressure on Particle Velocities in Low-Pressure Plasma Spray Deposition.  

National Technical Information Service (NTIS)

A laser velocimeter has been used to measure spray particle velocities in a low-pressure plasma spray system at chamber pressures ranging from 6.7 to 80 kPa (50 to 600 Torr). For Al sub 2 O sub 3 spray powder with a mean diameter of 44 mu m, peak particle...

M. F. Smith R. C. Dykhuizen

1987-01-01

153

Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming.  

PubMed

Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites. PMID:17450788

Laha, T; Liu, Y; Agarwal, A

2007-02-01

154

The measurement of single particle temperature in plasma sprays  

SciTech Connect

A measurement technique for simultaneously obtaining the size, velocity, temperature, and relative number density of particles entrained in high temperature flow fields is described. In determining the particle temperature from a two-color pyrometery technique, assumptions about the relative spectral emissivity of the particle are required. For situations in which the particle surface undergoes chemical reactions the assumption of grey body behavior is shown to introduce large Temperature measurement uncertainties. Results from isolated, laser heated, single particle measurements and in-flight data from the plasma spraying of WC-Co are presented. 10 refs., 5 figs.

Fincke, J.R.; Swank, W.D. (EG and G Idaho, Inc., Idaho Falls, ID (USA)); Bolsaitis, P.P.; Elliott, J.F. (Massachusetts Inst. of Tech., Cambridge, MA (USA))

1990-01-01

155

Titanium Carbonitride Coatings Prepared by Reactive Plasma Spraying ti Powders  

NASA Astrophysics Data System (ADS)

Titanium Carbonitride (TiCN), a new high hardness and wear-resistant material, has been applied widely in many fields. TiCN coating was first fabricated using reactive plasma spraying (RPS) technology in the reactive chamber that was filled with nitrogen and acetylene (N2 and C2H2) in this study. The microstructure and the phase composition of the coatings were analyzed by SEM and XRD. More chemical information of surface was analyzed by XPS. The Vickers microhardness of TiCN coating is 1659.11 HV100g, and the cross-section of the coating shows a conspicuous phenomenon of indentation size effect.

Zhu, Lin; He, Jining; Yan, Dianran; Dong, Yanchun; Xiao, Lisong

156

Study of plasma- and detonation gun-sprayed alumina coatings using taguchi experimental design  

Microsoft Academic Search

Atmospheric plasma spraying (APS) is a most versatile thermal spray method for depositing alumina (Al2O3) coatings, and detonation gun (D-gun) spraying is an alternative thermal spray technology for depositing such coatings with\\u000a extremely good wear characteristics. The present study is aimed at comparing the characteristics of Al2O3 coatings deposited using the above techniques by using Taguchi experimental design.\\u000a \\u000a Alumina coating

P. Saravanan; V. Selvarajan; M. P. Srivastava; D. S. Rao; S. V. Joshi; G. Sundararajan

2000-01-01

157

Adhesion of plasma sprayed zirconia splats on stainless steel  

NASA Astrophysics Data System (ADS)

Thermal spray technology is an alternative material fabrication technique to the traditional solidification and powder processing methods for producing thick coatings and bulk free-forms. Extensive research has enabled the extension of this technique to a wider range of material classes including polymers, bioceramics and functionally gradient materials. A key area of application of thermal spraying is the formation of thermal barrier coatings for turbine components used in power generation and propulsion. Continuing research intends to improve the quality of coatings produced by this technique to compete with other technologies like physical vapor deposition to make use of some of the advantages like higher throughput that thermal spraying affords. Understanding the adhesion of plasma sprayed coatings is essential to improving the service life of coated components. Progressively research has focussed on the nature of the unique building blocks of plasma sprayed coatings called splats. The current research intends to characterize the microadhesion at the splat substrate interface using nondestructive methods based on the analysis of images obtained using the scanning electron microscope (SEM). A model system of yttria stabilized zirconia, a traditional thermal barrier material, on steel substrate is chosen for the study. Two techniques are developed based on the analysis of through thickness crack distribution and fragmentation of thin brittle films on ductile substrates and that based on the analysis of interface cracking. A novel imaging technique is used to determine the extent of interface cracking from the contrast observed in SEM images. Based on the understanding of ceramic splat formation on metal substrates a shear lag theory of tensile residual stress generation is used to explain the fragmentation observed in splats. An earlier analysis of cracking in brittle films due to uniaxial stress is extended to the present case of equibiaxial thermal residual stress. Three geometric features are identified to analyze the observed fragment geometries and correlated with local interfacial adhesion in splats. The measurements are extracted from secondary and back-scattered electron images using image segmentation software. Measurement of cracked interfacial areas was accomplished using charging contrast in the secondary and specimen current images of splats. Based on these measurements it was found that micro adhesion decreases within splats from center to the periphery. This variation in adhesion was attributed to the temperature and pressure distribution in the splat-substrate interface during formation.

Rangarajan, Srinivasan

2000-10-01

158

Microstructure Changes of Plasma Spraying Tungsten Coatings on Cfc after Different Temperature Annealing  

NASA Astrophysics Data System (ADS)

Thermal behaviors of tungsten coating of 0.5 mm thick with multi-layers interface of tungsten (W) and rhenium (Re) coated on CFC (CX-2002U) substrate by vacuum plasma spraying (VPS) technique were examined by annealing with an electron beam thermal load facility between 1200 C and 2000 C. Change of the microstructure was observed and its chemical composition was analyzed by EDS after annealing. It was observed that remarkable recrystallization of VPS-W occurred above 1400 C. The structure of the multi-layers of W and Re become obscure by the mutual diffusion of W, Re and C above 1600C and finally disappeared after annealing at 2000 C for one hour. Very hard tungsten carbides are formed at the interface above 1600 C and they were broadening with increasing annealing temperature and time.

Liu, X.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.

2003-06-01

159

Improving the erosion resistance of plasma-sprayed zirconia thermal barrier coatings by laser glazing  

Microsoft Academic Search

In this study under review, substrates of 100mm25mm2mm SUS 420 stainless steel coupons were first sprayed with a Ni22Cr10Al1Y bond coat and then with a 19.5wt.% yttria-stabilized zirconia (YSZ) top coat using an air-plasma spray system. After that, the plasma-sprayed yttria-stabilized zirconia thermal barrier coatings (TBCs) were glazed using a pulsed CO2 laser. The subsequent effects of laser glazing on

Pi-Chuen Tsai; Jiing-Herng Lee; Chi-Lung Chang

2007-01-01

160

Point load-induced fracture behavior in zirconia plasma spray coating  

Microsoft Academic Search

Heat-resistant coatings prepared by two different spraying methods: atmospheric pressure plasma spraying (APS) and high-pressure plasma spraying (HPPS), were tested using tungsten carbide indenters of different diameters, for the purpose of proposing the best suited method of indentation testing. It was found that with the APS method, the indentation loaddepth curve gave the indentation depth and the residual depth smaller

Yoshio Akimune; Kazuo Matsuo; Satoshi Sodeoka; Tatsuo Sugiyama; Satoshi Shimizu

2004-01-01

161

Effective Parameters in Axial Injection Suspension Plasma Spray Process of Alumina-Zirconia Ceramics  

Microsoft Academic Search

Suspension plasma spray (SPS) is a novel process for producing nano-structured coatings with metastable phases using significantly\\u000a smaller particles as compared to conventional thermal spraying. Considering the complexity of the system there is an extensive\\u000a need to better understand the relationship between plasma spray conditions and resulting coating microstructure and defects.\\u000a In this study, an alumina\\/8wt.% yttria-stabilized zirconia was deposited

F. Tarasi; M. Medraj; A. Dolatabadi; J. Oberste-Berghaus; C. Moreau

2008-01-01

162

Application of Suspension Plasma Spraying (SPS) for Manufacture of Ceramic Coatings  

Microsoft Academic Search

Conventional thermal spray processes as atmospheric plasma spraying (APS) have to use easily flowable powders with a size\\u000a up to 100?m. This leads to certain limitations in the achievable microstructural features. Suspension plasma spraying (SPS)\\u000a is a new promising processing method which employs suspensions of sub-micrometer particles as feedstock. Therefore much finer\\u000a grain and pore sizes as well as dense

Holger Kassner; Roberto Siegert; Dag Hathiramani; Robert Vassen; Detlev Stoever

2008-01-01

163

Influence of Suspension Plasma Spraying Process Parameters on TiO 2 Coatings Microstructure  

Microsoft Academic Search

The study aimed at optimizing the suspension plasma spraying of TiO2 coatings obtained using different suspensions of fine rutile particles in water solution onto aluminum substrates. The experiments\\u000a of spraying were designed using a 23 full factorial plan. The plan enabled to find the effects of three principal parameters, i.e. electric power input to plasma,\\u000a spray distance, and suspension feed

Roman Jaworski; Lech Pawlowski; Francine Roudet; Stefan Kozerski; Agns Le Maguer

2008-01-01

164

Bioactive Glass-Ceramic Coatings Synthesized by the Liquid Precursor Plasma Spraying Process  

Microsoft Academic Search

In this study, the liquid precursor plasma spraying process was used to manufacture P2O5-Na2O-CaO-SiO2 bioactive glass-ceramic coatings (BGCCs), where sol and suspension were used as feedstocks for plasma spraying. The effect\\u000a of precursor and spray parameters on the formation and crystallinity of BGCCs was systematically studied. The results indicated\\u000a that coatings with higher crystallinity were obtained using the sol precursor,

Yanfeng Xiao; Lei Song; Xiaoguang Liu; Yi Huang; Tao Huang; Jiyong Chen; Yao Wu; Fang Wu

2011-01-01

165

New generation of plasma-sprayed mullite coatings on silicon carbide  

Microsoft Academic Search

Mullite is promising as a protective coating for silicon-based aggressive high-temperature environments. Conventionally plasma-sprayed mullite on SiC tends to crack and debond on thermal cycling. It is shown that this behavior is due to the presence of amorphous mullite in the conventionally sprayed mullite. Heating the SiC substrate during the plasma spraying eliminated the amorphous phase and produced coatings with

Kang N. Lee; Robert A. Miller; Nathan S. Jacobson

1995-01-01

166

Influence of suspension characteristics on coatings microstructure obtained by suspension plasma spraying  

Microsoft Academic Search

The growing interest for SOFC leads research towards new materials but also towards processes which could be more effective and less expensive to produce fuel cells. Plasma spraying is one of these interesting processes due to its ability to manufacture the whole cell with the same process. The present study uses suspension plasma spraying (SPS) process which consists in injecting

R. Rampon; O. Marchand; C. Filiatre; G. Bertrand

2008-01-01

167

Effect of suspension plasma spraying process parameters on YSZ coating microstructure and permeability  

Microsoft Academic Search

Suspension plasma spraying (SPS) is a modification of plasma spray processes that uses small feedstock powders suspended in a liquid to rapidly produce fully sintered, thin ceramic coatings with good microstructural control and no need for post-deposition heat treatments. This technique has been proposed as a potential next generation manufacturing method to fabricate metal supported solid oxide fuel cells (SOFC).

D. Waldbillig; O. Kesler

2011-01-01

168

Characterization of suspension plasma-sprayed solid oxide fuel cell electrodes  

Microsoft Academic Search

Suspension plasma spray is a promising technique that uses fine particles dispersed in a liquid as feedstock material instead of dry powder as in conventional plasma spraying and has been implemented here to produce layers with appropriate morphologies and microstructures for SOFC applications.This study uses a pressurized gas delivery system to feed the slurry through a homemade two-fluid atomizing nozzle

O. Marchand; P. Bertrand; J. Mougin; C. Comminges; M.-P. Planche; G. Bertrand

2010-01-01

169

In Situ Monitoring of Plasma Spraying Process by Laser Acoustic Emission Method  

Microsoft Academic Search

Estimation of microfractures in ceramic coating layer during plasma spraying process is critical for its reliability. Acoustic emission (AE) method enables in-process monitoring of such microfractures. Laser AE method was adopted to realize the monitoring of plasma spraying process by non-contact detection of AE with laser interferometer. Also a high performance method for noise reduction of laser AE waveform was

Kaita Ito; Manabu Enoki; Makoto Watanabe; Seiji Kuroda

2008-01-01

170

Characteristics of a Plasma Torch Designed for Very Low Pressure Plasma Spraying  

NASA Astrophysics Data System (ADS)

Unlike atmosphere plasma spraying (APS), very low pressure plasma spraying (VLPPS) can only weakly heat the feed materials at the plasma-free region exit of the nozzle. Most current VLPPS methods have adopted a high power plasma gun, which operates at high arc currents up to 2500 A to remedy the lower heating ability, causing a series of problems for both the plasma torch and the associated facility. According to the Kundsen number and pressures distribution inside of the nozzle in a low-pressure environment, a plasma torch was designed with a separated anode and nozzle, and with the powder feed to the plasma jets inside the nozzle intake. In this study, the pressures in the plasma gas intake, in the nozzle intake and outside the plasma torch were measured using an enthalpy probe. For practice, SUS 316 stainless steel coatings were prepared at the plasma currents of 500-600 A, an arc voltage of 50 V and a chamber pressure of 1000 Pa; the results indicated that coatings with an equiaxed microstructure could be deposited in proper conditions.

Gao, Yang; Yang, De Ming; Gao, Jianyi

2012-06-01

171

Improvement of Plasma Spray Torch Stability by Controlling Pressure and Voltage Dynamic Coupling  

Microsoft Academic Search

The development of coating formation processes involving electric arcs depends on process stability and the capacity to ensure\\u000a a constant reproducibility of coating properties. This is particularly important when considering suspension plasma spraying\\u000a or solution precursor plasma spraying. Submicron particles closely follow plasma instabilities and have nonhomogeneous plasma\\u000a treatment. Recently, it has been shown that arc voltage fluctuations in direct-current

V. Rat; J. F. Coudert

2011-01-01

172

PLASMA WINDOW FOR VACUUM - ATMOSPHERE INTERFACE AND FOCUSING LENS OF SOURCES FOR NON-VACUUM MATERIAL MODIFICATION.  

SciTech Connect

Material modifications by ion implantation, dry etching, and micro-fabrication are widely used technologies, all of which are performed in vacuum, since ion beams at energies used in these applications are completely attenuated by foils or by long differentially pumped sections, which ate currently used to interface between vacuum and atmosphere. A novel plasma window, which utilizes a short arc for vacuum-atmosphere interface has been developed. This window provides for sufficient vacuum atmosphere separation, as well as for ion beam propagation through it, thus facilitating non-vacuum ion material modification.

HERSHCOVITCH,A.

1997-09-07

173

Calcium phosphate coating on titanium using laser and plasma spray  

NASA Astrophysics Data System (ADS)

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.

Roy, Mangal

174

Phase transformation and wear studies of plasma sprayed yttria stabilized zirconia coatings containing various mol% of yttria  

SciTech Connect

Plasma sprayable grade zirconia powders doped with various mol% of yttria (0, 2, 3, 4, 6, 8 and 12 mol%) were synthesized by a chemical co-precipitation route. The coprecipitation conditions were adjusted such that the powders possessed good flowability in the as calcined condition and thus avoiding the agglomeration step like spray drying. Identical plasma spray parameters were used for plasma spraying all the powders on stainless steel plates. The powders and plasma sprayed coatings were characterized by X-ray diffractometry, Scanning Electron Microscopy and Raman spectroscopy. Zirconia powders are susceptible to phase transformations when subjected to very high temperatures during plasma spraying and XRD is insensitive to the presence of some non crystalline phases and hence Raman spectroscopy was used as an important tool. The microstructure of the plasma sprayed coatings showed a bimodal distribution containing fully melted and unmelted zones. The microhardness and wear resistance of the plasma sprayed coatings were determined. Among the plasma sprayed coatings, 3 mol% yttria stabilized zirconia coating containing pure tetragonal zirconia showed the highest wear resistance. - Research Highlights: {yields} Preparation plasma sprayable YSZ powders without any agglomeration process and plasma spraying {yields} Phase transformation studies of plasma sprayed YSZ coatings by XRD and Raman spectroscopy {yields} Microstructure of the plasma sprayed coatings exhibited bimodal distribution {yields} Plasma sprayed 3 mol% YSZ coating exhibited the highest wear resistance {yields} Higher wear resistance is due to the higher fracture toughness of tetragonal 3 mol% YSZ phase.

Aruna, S.T., E-mail: aruna_reddy@nal.res.in; Balaji, N.; Rajam, K.S.

2011-07-15

175

Analytical and mechanical testing of high velocity oxy-fuel thermal sprayed and plasma sprayed calcium phosphate coatings.  

PubMed

Plasma spraying (PS) is the most frequently used coating technique for implants; however, in other industries a cheaper, more efficient process, high-velocity oxy-fuel thermal spraying (HVOF), is in use. This process provides higher purity, denser, more adherent coatings than plasma spraying. The primary objective of this work was to determine if the use of HVOF could improve the mechanical properties of calcium phosphate coatings. Previous studies have shown that HVOF calcium phosphate coatings are more crystalline than plasma sprayed coatings. In addition, because the coatings are exposed to more complex loading profiles in vivo than standard ASTM tensile tests provide, a secondary objective of this study was to determine the applicability of four-point bend testing for these coatings. Coatings produced by HVOF and PS were analyzed by profilometry, diffuse reflectance Fourier transform infrared spectroscopy, X-ray diffraction, four-point bend, and ASTM C633 tensile testing. HVOF coatings were found to have lower amorphous calcium phosphate content, higher roughness values, and lower ASTM C633 bond strengths than PS coatings; however, both coatings had similar crystal unit cell sizes, phases present (including hydroxyapatite, beta-tricalcium phosphate, and tetracalcium phosphate), and four-point bend bond strengths. Thus, the chemical, structural, and mechanical results of this study, in general, indicate that the use of HVOF to produce calcium phosphate coatings is equivalent to those produced by plasma spraying. PMID:10556851

Haman, J D; Chittur, K K; Crawmer, D E; Lucas, L C

1999-01-01

176

Predicting ion charge state distributions of vacuum arc plasmas  

SciTech Connect

Multiply charged ions are present in vacuum arc plasmas. The ions are produced at cathode spots, and their charge state distributions (CSDs) depend on the cathode material but only little on the arc current or other parameters as long as the current is relatively low and the anode is not actively involved in the plasma production. There are experimental data of ion CSDs available in the literature for 50 different cathode materials. The CSDs can be calculated based on the assumption that thermodynamic equilibrium is valid in the vicinity of the cathode spot, and the equilibrium CSDs `freeze` at a certain distance from the cathode spot (transition to a non-equilibrium plasma). Plasma temperatures and densities at the `freezing points` have been calculated, and, based on the existence of characteristic groups of elements in the Periodic Table, predictions of CSDs can be made for metallic elements which have not yet been used as cathode materials.

Anders, A. [Lawrence Berkeley Lab., CA (United States); Schulke, T. [Fraunhofer-Einrichtung fuer Werkstoffphysik und Schichttechnologie (IWS), Dresden (Germany)

1996-04-01

177

Study of Al 2O 3 coatings on AISI 316 stainless steel obtained by controlled atmosphere plasma spraying (CAPS)  

Microsoft Academic Search

The tribological behaviour of Al2O3 coatings on AISI 316 stainless steel, obtained by the process of controlled atmosphere plasma spraying (CAPS), is studied in this work. Atmospheric plasma spraying (APS) and high pressure plasma spraying (HPPS) were applied in order to produce these coatings. The APS coatings exhibited lower microhardness values compared to the values of HPPS coatings. Regarding the

Ch. I. Sarafoglou; D. I. Pantelis; S. Beauvais; M. Jeandin

2007-01-01

178

Liquid-Mn sintering of plasma-sprayed zirconia-yttria coatings  

NASA Astrophysics Data System (ADS)

The penetration phenomena of liquid Mn into porous ZrO2-8 wt.% Y2O3 coating, plasma sprayed on JIS SS400 steel substrate was studied by heating at 1573 K in a vacuum atmosphere, and the possibility of improving the mechanical properties of the coating by heat treatment with liquid Mn was examined. It was found that liquid Mn rapidly penetrated the coating and formed an interface between the coating and the substrate. The densification of the coating occurred when ZrO2 particles were sintered with liquid Mn that penetrated the porous ZrO2 coating. It was revealed that the dense coating was free of porosities and that its hardness increased greatly after heat treatment with Mn, compared with as-sprayed ZrO2 coating. Moreover the modulus of elasticity and the fracture toughness of the coating reached the same levels as those of sintered partially stabilized ZrO2 (Y2O3).

Ohmori, A.; Zhou, Z.; Inoue, K.

1994-11-01

179

Effects of the spray angle on splat morphology during thermal spraying  

Microsoft Academic Search

The effects of spray angle on the morphology of thermally sprayed particles impinging on polished substrates have been studied by implementing several statistical tools (i.e., Gaussian analysis, Weibull distribution and the t-test). Nickel-based alloy (Astroloy) particles were vacuum plasma-sprayed onto copper plates at normal (i.e., 90 ) and several off-normal spray angles (i.e., 75, 60, 45 and 30 ). Different

G. Montavon; S. Sampath; C. C. Berndt; H. Herman; C. Coddet

1997-01-01

180

Numerical simulation of alumina spraying in argon-helium plasma jet  

SciTech Connect

A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of alumina spraying in a turbulent argon-helium plasma jet in air environment, including torch geometry, substrate, and multiple species with chemical reactions. Particle-plasma interactions including turbulent dispersion have been modeled in a fully self-consistent manner. Interactions between the plasma and the torch and substrate walls are modeled using wall functions. (15 refs.)

Chang, C.H.

1992-01-01

181

Numerical simulation of alumina spraying in argon-helium plasma jet  

SciTech Connect

A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of alumina spraying in a turbulent argon-helium plasma jet in air environment, including torch geometry, substrate, and multiple species with chemical reactions. Particle-plasma interactions including turbulent dispersion have been modeled in a fully self-consistent manner. Interactions between the plasma and the torch and substrate walls are modeled using wall functions. (15 refs.)

Chang, C.H.

1992-08-01

182

In situ characterization of small-particle plasma sprayed powders  

NASA Astrophysics Data System (ADS)

The effect of various small-particle plasma spray powder injection parameters on the in situ particle position, velocity, and temperature is measured for yttria-stabilized zirconia and yttrium-aluminum-garnet powder. Using full-factorial experiments and multiple regression analysis, carrier gas flow, injector angle, and powder feeder disc speed were found to significantly affect the particle properties. Temperature and velocity were inversely related; on average, the cooler particles traveled faster. These properties also correlated to the particle position in the flame, where particles above the centerline of the flame traveled faster. The trends are discussed on the basis of residence time in the flame, as well as in terms of particle size segregation effects. Coating density and splat geometry reflect the temperature and velocity differences between the runs. Slower, hotter particles possessed more intrasplat and intersplat porosity and less splat-substrate contact area, leading to lower overall coating density.

Su, Y. J.; Faber, K. T.; Bernecki, T. F.

2002-03-01

183

Electron beam melting at high pressures with a vacuum separator/plasma lens  

SciTech Connect

Plasmas can be used to provide a vacuum-atmosphere interface or separation between vacua regions as an alternative to differential pumping. Vacuum-atmosphere interface utilizing a cascade arc discharge was successfully demonstrated and a 175 keV electron beam was successfully propagated from vacuum through such a plasma interface and out into atmospheric pressure. This plasma device also functions as an effective plasma tens. Such a device can be adopted for use in electron beam melting.

Hershcovitch, A.

1995-12-31

184

Models of low-beta plasma expansion across magnetized vacuum  

NASA Astrophysics Data System (ADS)

Detailed understanding of the microphysics associated with dynamic penetration of low-beta plasmas across magnetic fields has important implications for a number of applications including magnetic-fusion-energy (MFE), high-power transmission-lines, and charged-particle-beam diodes. Analytic models providing linear growth rates and characteristic wavelengths and frequencies for unstable modes at the interface between plasma and vacuum regions are presented and compared with detailed particle-in-cell simulations. The simulations treat both collisionless and collisional plasma regimes in a variety of configurations. Results of this combined theoretical analysis are compared with measurements from several experiments including magnetized electron-beam-diodes and high-power, magnetically-insulated transmission-lines. Potential applications of this modeling to MFE are discussed.

Rose, D. V.; Welch, D. R.; Genoni, T. C.

2007-11-01

185

Suspension Plasma-Sprayed Alumina Coating Structures: Operating Parameters Versus Coating Architecture  

Microsoft Academic Search

Suspension plasma spraying (SPS) is able to process sub-micrometric-sized feedstock particles and permits the deposition of\\u000a layers thinner (from 5 to 50?m) than those resulting from conventional atmospheric plasma spraying (APS). SPS consists in\\u000a mechanically injecting within the plasma flow a liquid suspension of particles of average diameter varying between 0.02 and\\u000a 1?m, average values. Upon penetration within the DC

O. Tingaud; A. Grimaud; A. Denoirjean; G. Montavon; V. Rat; J. F. Coudert; P. Fauchais; T. Chartier

2008-01-01

186

Preparation of perovskite powders and coatings by radio frequency suspension plasma spraying  

Microsoft Academic Search

Perovskite-type LaMnO3 powders and coatings have been prepared by a novel technique: reactive suspension plasma spraying (SPS) using an inductively\\u000a coupled plasma of approximately 40 kW plate power and an oxygen plasma sheath gas. Suitable precursor mixtures were found\\u000a on the basis of solid state reactions, solubility, and the phases obtained during the spray process. Best results were achieved\\u000a by

G. Schiller; M. Mller; F. Gitzhofer

1999-01-01

187

Surface modification of polymer surfaces: atmospheric plasma versus vacuum plasma treatments  

NASA Astrophysics Data System (ADS)

An atmospheric pressure non-equilibrium plasma (APNEP) has been developed in the UK by EA Technology Ltd and is currently being investigated in collaboration with the University of Surrey. The main focus is the use of atmospheric pressure plasmas to modify the surfaces of commercially important polymers including polyolefins, poly(ethylene terephthalate) and poly(methyl methacrylate). These surface modifications include surface cleaning and degreasing, oxidation, reduction, grafting, cross-linking (carbonization), etching and deposition. When trying to achieve targeted surface engineering, it is vital to gain an understanding of the mechanisms that cause these effects, for example, surface functionalization, adhesion promotion or multi-layer deposition. Hence comparisons between vacuum plasma treated surfaces have also been sought with a view to using the extensive vacuum plasma literature to gain further insight. In this paper, we will introduce the APNEP and compare the key characteristics of the plasma with those of traditional vacuum plasma systems before highlighting some of the surface modifications that can be achieved by using atmospheric plasma. Data from the analysis of treated polymers (by spectroscopy, microscopy and surface energy studies) and from direct measurements of the plasma and afterglow will be presented. Finally, our current understanding of the processes involved will be given, particularly those that are important in downstream surface treatments which take place remote from the plasma source.

Shenton, M. J.; Stevens, G. C.

2001-09-01

188

Effect of rolling on the thermo-physical properties of SiCp\\/Al composites fabricated by plasma spraying  

Microsoft Academic Search

Aluminum (Al) matrix composites reinforced by SiC particulates (SiCp\\/Al) were fabricated by the atmospheric plasma spraying. The composite powder, as a feedstock for plasma spraying, was prepared by ball milling of pure Al powders with 55 vol.% SiC particles. The feedstock was deposited into a freestanding bulk composite sheet on a graphite substrate by atmospheric plasma spraying. As-sprayed composites had

Kwangjun Euh; Suk Bong Kang

2005-01-01

189

The abrasive wear of plasma sprayed nanoscale tungsten carbide-cobalt (WC-Co)  

Microsoft Academic Search

Thermal spray coatings composed of a variety of carbide sizes and cobalt contents were sprayed with a high energy plasma spray system. The size of the carbides used fell into three rough groupings, micrometer scale carbides (1--2 mum), submicrometer (700--300 nm), and nanoscale (≈100 nm). The feedstock powder was evaluated in terms of their size distribution, external morphology, internal morphology,

Graham Alfred Tewksbury

2002-01-01

190

Expert system for process optimization of atmospheric plasma spraying of high performance ceramics  

Microsoft Academic Search

This paper deals with an experimental investigation on the process of atmospheric plasma spraying of high performance ceramics such as Al2O3, Al2O3TiO2, and PSZ on a steel substrate. The ceramic coatings were deposited under different spray conditions and optimal spray parameters were evaluated based on the quality of the coating judged in terms of bond strength and porosity. An expert

S. Gowri; G. Uma Shankar; K. Narayanasamy; R. Krishnamurthy

1997-01-01

191

Quenching stress in plasma sprayed coatings and its correlation with the deposit microstructure  

Microsoft Academic Search

Quenching stress arises within a thermally sprayed splat as its thermal contraction after solidification is constrained by\\u000a the underlying solid. Dependence of the quenching stress in plasma-sprayed deposits of Ni-20Cr alloy and alumina on the substrate\\u000a temperature during spraying was discussed in conjunction with the change in the nature of the interlamellar contact between\\u000a splats. It was found by mercury

S. Kuroda; T. Dendo; S. Kitahara

1995-01-01

192

Tokamak plasma response to droplet spraying from melted plasma-facing components  

NASA Astrophysics Data System (ADS)

High-Z materials such as tungsten are currently the potentially best candidates for plasma-facing components (PFCs) in future fusion devices. However, the threat of melting under uncontrolled conditions and the associated material redistribution and loss can place strict limits on the lifetime of PFCs and plasma operation conditions. In particular, material losses in the form of fine sprayed droplets can provide a very intensive source of impurities in the plasma core. In this paper, the plasma response to radiation losses from impurity particles produced by droplet evaporation is modelled for the conditions found in the tokamak TEXTOR. The interplay between tungsten spraying and plasma behaviour, resulting in the reduction of power transferred to the limiter and diminution of droplet production, is taken into account. Calculations predict, in agreement with experimental observations, that this evolution results in a new steady state with significantly reduced central temperature and peaked impurity radiation profile. The efficiency of melt conversion into droplets, estimated by comparing experimental and computed plasma temperatures, is in reasonable agreement with the predictions from models for droplet generation.

Tokar, M. Z.; Coenen, J. W.; Philipps, V.; Ueda, Y.; TEXTOR Team

2012-01-01

193

Visual and Electrical Evidence Supporting a Two-Plasma Mechanism of Vacuum Breakdown Initiation  

SciTech Connect

The energy available during vacuum breakdown between copper electrodes at high vacuum was limited using resistors in series with the vacuum gap and arresting diodes. Surviving features observed with SEM in postmortem samples were tentatively correlated with electrical signals captured during breakdown using a Rogowski coil and a high-voltage probe. The visual and electrical evidence is consistent with the qualitative model of vacuum breakdown by unipolar arc formation by Schwirzke [1, 2]. The evidence paints a picture of two plasmas of different composition and scale being created during vacuum breakdown: an initial plasma made of degassed material from the metal surface, ignites a plasma made up of the electrode material.

Castano-Giraldo, C. [University of Illinois, Urbana-Champaign; Aghazarian, Maro [ORNL; Caughman, John B [ORNL; Ruzic, D. N. [University of Illinois, Urbana-Champaign

2012-01-01

194

Phenomena Involved in Suspension Plasma Spraying Part 1: Suspension Injection and Behavior  

Microsoft Academic Search

Suspension Plasma Spraying (SPS) is a relatively new deposition process which enables to spray micron and submicron particles. It offers the possibility to form finely structured coatings with intermediate thicknesses of a few tens of microns. In order to have a better understanding in SPS, the two parts of this paper are devoted to the description of the phenomena involved

J. Fazilleau; C. Delbos; V. Rat; J. F. Coudert; P. Fauchais; B. Pateyron

2006-01-01

195

Evaporated-gas-induced splashing model for splat formation during plasma spraying  

Microsoft Academic Search

The effect of surface adsorbates on splat formation during thermal spraying is examined by controlling substrate adsorption. Splats are formed on a polished flat stainless steel substrate surface by plasma spraying. The adsorption state of the substrate is controlled with different organic substances of different boiling points and different preheating temperatures. The droplet materials used are aluminum, nickel, and Al2O3.

Chang-Jiu Li; Jing-Long Li

2004-01-01

196

Ion charge state distributions of vacuum arc plasmas: The origin of species  

Microsoft Academic Search

Vacuum arc plasmas are produced at micrometer-size, nonstationary cathode spots. Ion charge state distributions (CSD's) are experimentally known for 50 elements, but the theoretical understanding is unsatisfactory. In this paper, CSD's of vacuum arc plasmas are calculated under the assumption that the spot plasma experiences an instantaneous transition from equilibrium to nonequilibrium while expanding. Observable charge state distributions are the

Andr Anders

1997-01-01

197

Tantalum oxide-based plasma-sprayed environmental barrier coatings  

NASA Astrophysics Data System (ADS)

Energy efficiency in gas turbine engines is linked to the high temperature capabilities of materials used in the hot section of the engine. To facilitate a significant increase in engine efficiency, tough structural ceramics have been developed that can handle the thermo-mechanical stresses that gas turbine components experience. Unfortunately, the high-temperature, high-pressure, and high-velocity combustion gases in a gas turbine contain water vapor and/or hydrogen which have been shown to volatilize the protective silica layer on silicon-based ceramics. This degradation leads to significant surface recession in ceramic gas turbine components. In order to maintain their structural integrity, an environmental barrier coating (EBC) could be used to protect ceramics from the harsh gas turbine environment. Due to its coefficient of thermal expansion and phase stability at elevated temperatures, tantalum oxide (Ta2O5) was examined as the base material for an air plasma-sprayed EBC on Si3N 4 ceramics. As-sprayed pure Ta2O5 was comprised of both low-temperature beta-Ta2O5 and high-temperature alpha-Ta 2O5 that was quenched into the structure. Residual stress measurements via X-ray diffraction determined the as-sprayed coating to be in tension and extensive vertical macrocracks were observed in the coating. Heat treatments of the pure coating led to conversion of alpha-Ta2 O5 to beta-Ta2O5, conversion of tensile stresses to compressive, localized buckling of the coating, and significant grain growth which caused microcracking in the coating. The pure coating was found to be an inadequate EBC. Al2O3 was investigated as a solid solution alloying addition designed to enhance the stability of beta-Ta2O 5, and reduce grain growth by slowing grain boundary diffusion. La 2O3 was investigated as an alloying addition designed to form second phase particles which would reduce grain growth through pinning. Al2O3 was successful at both stabilizing beta-Ta 2O5 and reducing grain growth, though AlTaO4 was found to form in the coatings. La2O3 additions led to the formation of LaTa7O19 which also contributed to grain growth reduction. Residual stresses in the alloyed coatings were generally found to be tensile. Microcracks were not observed in coatings that were alloyed with both Al2O3 and La2O3 with the most promising alloy being Ta2O5 + 1.5 wt.% Al 2O3 + 1.5 wt.% La2O3.

Weyant, Christopher M.

198

Effect of Microstructure on the Electrical Properties of Nano-Structured TiN Coatings Deposited by Vacuum Cold Spray  

NASA Astrophysics Data System (ADS)

TiN coatings on Al2O3 substrates were fabricated by vacuum cold spray (VCS) process using ultrafine starting ceramic powders of 20 nm in size at room temperature (RT). Microstructure analysis of the samples was carried out by scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. Sheet resistance of the VCS TiN coatings was measured with a four-point probe. The effects of microstructure on the electrical properties of the coatings were investigated. It was found that the sheet resistance and electrical resistivity of TiN coatings were significantly associating with the spray distance, nozzle traversal speed, and deposition chamber pressure. A minimum sheet resistance of 127 ? was achieved. The microstructural changes can be correlated to the electrical resistivity of TiN coatings.

Wang, Y.-Y.; Liu, Y.; Yang, G.-J.; Feng, J.-J.; Kusumoto, K.

2010-12-01

199

Plasma plume characterization of a vacuum arc thruster  

NASA Astrophysics Data System (ADS)

A Vacuum Arc Thruster (VAT) is a thruster that uses the plasma created in a vacuum arc, an electrical discharge in a vacuum that creates high velocity and highly ionized plasmas, as the propellant without additional acceleration. A VAT would be a small and inexpensive low thrust ion thruster, ideal for small satellites and formation flying spacecraft. The purpose of this thesis was to quantitatively and qualitatively examine the VAT plasma plume to determine operating characteristics and limitations. A VAT with a titanium cathode was operated in two regimes: (A) single 100mus pulse, discharge current JD=510A, and (B) multiple 1500mus pulses at f=40.8Hz, JD=14A. The cathode was 3.18mm diameter Ti rod, surrounded by a 0.80mm thick alumina insulator, set in a molybdenum anode. Three Configurations were tested: Cfg1 (Regime A, cathode recessed 3.00mm from anode), Cfg2 (Regime A, cathode and anode flush), Cfg3 (Regime B, cathode recessed 3.00mm). A semi-empirical model was derived for VAT performance based on the MHD equation of motion using data for ion velocity, ion charge state distribution, ion current fraction (F), and ion current density distribution (ICDD). Additional performance parameters were a2, the peak ion current density angular offset from the cathode normal, and a3, the width of the ion current distribution. Measurements were taken at 162 points on a plane in the plasma plume using a custom faraday probe, and the ICDD empirical form was determined to be a Gaussian. The discharge voltage (VD) and F were Cfg1: VD=25.5V, F=0.025-0.035; Cfg2: VD=40.7V, F=0.08-0.10; Cfg3: VD=14.9V, F=0.006-0.021. For Cfg1, a2 started 15 off-axis while a20 for Cfg2 and 3. In Cfg1, a 3=0.7-0.6, and in Cfg2 a3=1.0-1.1, so the recessed cathode focused the plasma more. However, F is more important for VAT performance because upper and lower bounds for thrust, specific impulse, thrust-to-power, and efficiency were calculated and Cfg2 had the highest performance. High-speed videos captured cathode spot motion showing that the cathode spot had preferred attachment points at the cathode edge. Photographs show uneven cathode erosion at the edge, a deposited layer of cathode material on the anode and insulator, and large macroparticles.

Sekerak, Michael James

200

The development of beryllium plasma spray technology for the International Thermonuclear Experimental Reactor (ITER)  

SciTech Connect

Over the past five years, four international parties, which include the European Communities, Japan, the Russian Federation and the United States, have been collaborating on the design and development of the International Thermonuclear Experimental Reactor (ITER), the next generation magnetic fusion energy device. During the ITER Engineering Design Activity (EDA), beryllium plasma spray technology was investigated by Los Alamos National Laboratory as a method for fabricating and repairing and the beryllium first wall surface of the ITER tokamak. Significant progress has been made in developing beryllium plasma spraying technology for this application. Information will be presented on the research performed to improve the thermal properties of plasma sprayed beryllium coatings and a method that was developed for cleaning and preparing the surface of beryllium prior to depositing plasma sprayed beryllium coatings. Results of high heat flux testing of the beryllium coatings using electron beam simulated ITER conditions will also be presented.

Castro, R.G.; Elliott, K.E.; Hollis, K.J. [Los Alamos National Lab., NM (United States). Material Science and Technology Div.; Bartlett, A.H. [Norsam Technologies Inc., Los Alamos, NM (United States); Watson, R.D. [Sandia National Lab., Albuquerque, NM (United States). Fusion Technology Dept.

1999-02-01

201

Sintering and Creep Behavior of Plasma-Sprayed Zirconia and Hafnia Based Thermal Barrier Coatings.  

National Technical Information Service (NTIS)

The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result o...

D. Zhu R. A. Miller

1998-01-01

202

Bearing Structures Fabricated from Arc Plasma Sprayed Layers Coated with Solid Film Lubricants.  

National Technical Information Service (NTIS)

Multilayer bearing structures were fabricated by arc plasma spraying of selected metallic alloy powders of mild and hardened steel test blocks which were then coated with a dry film lubricant. Five different alloys were investigated, and the quality and a...

B. Roessler M. C. Narasiman

1982-01-01

203

Investigation of particle trajectories and melting in an air plasma sprayed zirconia.  

National Technical Information Service (NTIS)

The partially stabilized zirconia powders used to plasma spray thermal barrier coatings typically exhibit broad particle-size distributions. There are conflicting reports in the literature about the extent of injection-induced particle-sizing effects in a...

R. A. Neiser T. J. Roemer

1996-01-01

204

Ceramic plasma-sprayed coating of melting crucibles for casting metal fuel slugs  

NASA Astrophysics Data System (ADS)

Thermal cycling and melt reaction studies of ceramic coatings plasma-sprayed on Nb substrates were carried out to evaluate the performance of barrier coatings for metallic fuel casting applications. Thermal cycling tests of the ceramic plasma-sprayed coatings to 1450 C showed that HfN, TiC, ZrC, and Y2O3 coating had good cycling characteristics with few interconnected cracks even after 20 cycles. Interaction studies by 1550 C melt dipping tests of the plasma-sprayed coatings also indicated that HfN and Y2O3 do not form significant reaction layer between U-20 wt.% Zr melt and the coating layer. Plasma-sprayed Y2O3 coating exhibited the most promising characteristics among HfN, TiC, ZrC, and Y2O3 coating.

Kim, Ki Hwan; Lee, Chong Tak; Lee, Chan Bock; Fielding, R. S.; Kennedy, J. R.

2013-10-01

205

Effect of Microstructure on the Electrical Properties of Nano-Structured TiN Coatings Deposited by Vacuum Cold Spray  

Microsoft Academic Search

TiN coatings on Al2O3 substrates were fabricated by vacuum cold spray (VCS) process using ultrafine starting ceramic powders of 20nm in size at\\u000a room temperature (RT). Microstructure analysis of the samples was carried out by scanning electron microscopy, transmission\\u000a electron microscopy, and x-ray diffraction. Sheet resistance of the VCS TiN coatings was measured with a four-point probe.\\u000a The effects of

Y.-Y. Wang; Y. Liu; G.-J. Yang; J.-J. Feng; K. Kusumoto

2010-01-01

206

Understanding of suspension DC plasma spraying of finely structured coatings for SOFC  

Microsoft Academic Search

Suspension plasma spraying was used to achieve a dense and thin (?30 ?m) yttria stabilized zirconia (YSZ) coating for the electrolyte of solid oxide fuel cells (SOFCs). A suspension of YSZ powder (d50?1 ?m) was mechanically injected in direct current (dc) plasma jets. The plasma jet acted as an atomizer and the suspension drops (d?200 ?m) were sheared, long before

Pierre Fauchais; Vincent Rat; Cdric Delbos; Jean Franois Coudert; Thierry Chartier; Luc Bianchi

2005-01-01

207

Electrocatalytically Active Nickel-Based Electrode Coatings Formed by Atmospheric and Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Ni-based electrode coatings with enhanced surface areas, for hydrogen production, were developed using atmospheric plasma spray (APS) and suspension plasma spray (SPS) processes. The results revealed a larger electrochemical active surface area for the coatings produced by SPS compared to those produced by APS process. SEM micrographs showed that the surface microstructure of the sample with the largest surface area was composed of a large number of small cauliflower-like aggregates with an average diameter of 10 ?m.

Aghasibeig, M.; Mousavi, M.; Ben Ettouill, F.; Moreau, C.; Wuthrich, R.; Dolatabadi, A.

2013-10-01

208

Laser-induced surface acoustic waves for evaluation of elastic stiffness of plasma sprayed materials  

Microsoft Academic Search

The elastic properties of plasma sprayed deposits have been evaluated using a laser-excited surface acoustic wave (SAW) technique and an inversion processing analysis. The SAWs including Lamb and Rayleigh waves were generated in plasma sprayed NiCoCrAlY and ZrO2, respectively, and their group velocity dispersions were used to determine the elastic properties (i.e.Young's modulus, Poison's ratio and density) of the deposits.

X. Q. Ma; Y. Mizutani; M. Takemoto

2001-01-01

209

Low-thermal-conductivity plasma-sprayed thermal barrier coatings with engineered microstructures  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process has been used to deposit ZrO27wt.% Y2O3 thermal barrier coatings (TBCs) that contain alternate layers of low and high porosities (layered-SPPS). The thermal conductivity of the layered-SPPS coating is found to be lower than those of both a SPPS coating with distributed porosity and an air-plasma-sprayed coating of the same composition, in the

Amol D. Jadhav; Nitin P. Padture; Eric H. Jordan; Maurice Gell; Pilar Miranzo; Edwin R. Fuller

2006-01-01

210

Nanoparticles Modeling in Axially Injection Suspension Plasma Spray of Zirconia and Alumina Ceramics  

Microsoft Academic Search

Suspension plasma spray (SPS) is a thermal spray method in which nanoparticles are injected into the plasma jet with the help\\u000a of suspension droplets to achieve thin and finely structured nanocoatings. The nanoparticles experience three in-flight stages:\\u000a injection within the suspension droplets, discharge of the nanoparticle agglomerates after the evaporation of the suspension\\u000a solvent, and tracking of the nanoparticle or

Hong-Bing Xiong; Jian-Zhong Lin

2009-01-01

211

Effect of the Structural Scale of Plasma-Sprayed Alumina Coatings on Their Friction Coefficients  

Microsoft Academic Search

The objective of this study is to compare the tribological properties of alumina coatings with two different structural scales,\\u000a a micrometer-sized one manufactured by atmospheric plasma spraying and a sub-micrometer-sized one manufactured by suspension\\u000a plasma spraying. Coating architectures were analyzed and their friction coefficients in dry sliding mode measured. Sub-micrometer-sized\\u000a structured coatings present a lower friction coefficient than micrometer ones,

G. Darut; H. Ageorges; A. Denoirjean; G. Montavon; P. Fauchais

2008-01-01

212

Column Formation in Suspension Plasma-Sprayed Coatings and Resultant Thermal Properties  

Microsoft Academic Search

The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with\\u000a median diameters of 15?m and 80nm. The powder-ethanol suspensions made with 15-?m diameter YSZ particles formed coatings\\u000a with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder\\u000a yielded a coarse columnar microstructure not observed in

Kent Vanevery; Matthew J. M. Krane; Rodney W. Trice; Hsin Wang; Wallace D Porter; Matthew Besser; Daniel Sordelet; Jan Ilavsky; Jonathan Almer

2011-01-01

213

Al 2 O 3 -ZrO 2 Finely Structured Multilayer Architectures from Suspension Plasma Spraying  

Microsoft Academic Search

Suspension plasma spraying (SPS) is an alternative to conventional atmospheric plasma spraying (APS) aiming at manufacturing\\u000a thinner layers (i.e., 10-100?m) due to the specific size of the feedstock particles, from a few tens of nanometers to a few\\u000a micrometers. The staking of lamellae and particles, which present a diameter ranging from 0.1 to 2.0?m and an average thickness\\u000a from 20

Olivier Tingaud; Ghislain Montavon; Alain Denoirjean; Jean-Franois Coudert; Vincent Rat; Pierre Fauchais

2010-01-01

214

Suspension plasma sprayed TiO 2 coatings using different injectors and their photocatalytic properties  

Microsoft Academic Search

Stable water- and water\\/ethanol suspensions of TiO2 were plasma sprayed on stainless steel substrates. The suspensions were injected using two different systems: external, using an atomizing injector, and internal, performed with a continuous-stream injector inside the plasma torch anode. In order to find the optimal spray parameters, seven experimental runs were performed and the resulted deposits were mainly characterized by

Stefan Kozerski; Filofteia-Laura Toma; Lech Pawlowski; Beate Leupolt; Leszek Latka; Lutz-Michael Berger

2010-01-01

215

Phase transformation of ultrafine rare earth oxide powders synthesized by radio frequency plasma spraying  

Microsoft Academic Search

Inductively coupled radio frequency plasma spraying was used to prepare ultrafine powders of Sm2O3, Dy2O3, and Lu2O3. These three materials were studied because they are effective dopants in multi-layer ceramic capacitors (MLCC) to improve lifetime. The as-sprayed powders consist of both micron-sized mono-dispersed spherical particles and nano-sized particles in various shapes. In addition to the spheroidization effect, plasma treatment leads

X. L. Sun; A. I. Y. Tok; R. Huebner; F. Y. C. Boey

2007-01-01

216

Influence of heat treatment on nanocrystalline zirconia powder and plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Nanostructured zirconia top coat was deposited by air plasma spray and NiCoCrAlTaY bond coat was deposited on Ni substrate by low pressure plasma spray. Nanostructured and conventional thermal barrier coatings were heat-treated at temperature varying from 1050 to 1 250 C for 2-20 h. The results show that obvious grain growth was found in both nanostructured and conventional thermal barrier

Xian-liang JIANG; Chun-bo LIU; Min LIU; Hui-zhao ZHU

2010-01-01

217

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

Microsoft Academic Search

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered\\u000a to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock\\u000a powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still\\u000a unclear. This study, investigated the influence of feedstock particle size in

Mohammed Shahien; Motohiro Yamada; Toshiaki Yasui; Masahiro Fukumoto

2011-01-01

218

Low-pressure plasma-sprayed (LPPS) bioceramic coatings with improved adhesion strength and resorption resistance  

NASA Astrophysics Data System (ADS)

Prespray annealing of commercially available hydroxyapatite (HAp) plasma-spray powder at 1300 C for 1 h in air leads to substantial densification without noticeable thermal decomposition. The resulting HAp coatings, low-pressure plasma sprayed onto Ti-6A1-4V substrates, show a dense microstructure, im-proved adhesion strength, and higher rsorption resistance when treated for 7 days in simulated body fluid (Hanks balanced salt solution).

Heimann, R. B.; Vu, T. A.

1997-06-01

219

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

NASA Astrophysics Data System (ADS)

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still unclear. This study, investigated the influence of feedstock particle size in RPS of aluminum nitride (AlN) coatings, through plasma nitriding of aluminum (Al) feedstock powders. It was possible to fabricate AlN-based coatings through plasma nitriding of all kinds of Al powders in atmospheric plasma spray (APS) process. The nitriding ratio was improved with decreasing the particle size of feedstock powder, due to improving the nitriding reaction during flight. However, decreasing the particle size of feedstock powder suppressed the coatings thickness. Due to the loss of the powder during the injection, the excessive vaporization of fine Al particles and the completing nitriding reaction of some fine Al particles during flight. The feedstock particle size directly affects on the nitriding, melting, flowability, and the vaporization behaviors of Al powders during spraying. It concluded that using smaller particle size powders is useful for improving the nitriding ratio and not suitable for fabrication thick AlN coatings in reactive plasma spray process. To fabricate thick AlN coatings through RPS, enhancing the nitriding reaction of Al powders with large particle size during spraying is required.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2011-03-01

220

Plasma-Enhanced Surface Modification of Sprayed Carbon Nanotube Electrodes for Lithographically Integrated Biosensing System  

NASA Astrophysics Data System (ADS)

A sprayed carbon nanotube (CNT)-modified working electrode was successfully integrated into an electrochemical three-electrode system based on a glass substrate. The integrated biosensing system was fabricated through a series of photolithographic patterning and plasma etching processes. A CNT-dispersed solution was sprayed on the three-electrode system, and the CNT-modified surface was treated with O2 plasma to pattern, clean, and activate the CNT layer. The optimized plasma treatment conditions were verified in terms of plasma power and treatment time by scanning electron microscopy (SEM), cyclic voltammetry (CV), and X-ray photoelectron spectroscopy (XPS).

Jin, Joon-Hyung; Kim, Joon Hyub; Lee, Jun-Yong; Lee, Cheol Jin; Min, Nam Ki

2012-01-01

221

Microstructural and in vitro chemical investigations into plasma-sprayed bioceramic coatings.  

PubMed

Hydroxyapatite (HA) coatings plasma sprayed without and with bond coats (titania, zirconia) onto titanium alloy (Ti6A14V) substrates under both atmospheric and low pressure plasma spray conditions were investigated in terms of their microstructure and their resorption resistance during immersion in simulated body fluid (Hank's balanced salt solution). The microstructures of test samples were characterized using SEM on as-sprayed and leached surfaces and on the corresponding cross sections. Selected coating systems were studied by 2-dimensional secondary ion mass spectroscopy imaging to obtain information on plasma spray induced diffusional processes at the coating interfaces, as well as the spatial distribution of minor and trace elements. Coatings consisting of thin (10-15 microm) titania/zirconia (eutectic ratio) and titania bond coats, combined with a 150- to 180-microm thick HA top coat, yielded peel strengths in excess of 32 N/m, as well as sufficient resorption resistance. PMID:9855203

Heimann, R B; Kurzweg, H; Ivey, D G; Wayman, M L

1998-01-01

222

Plasma spraying of Wc-Co part II: Experimental study of particle deposition and coating microstructure  

NASA Astrophysics Data System (ADS)

WC-Co base wear-resistant coatings deposited by plasma spraying are widely used to enhance component longevity in a variety of wear environments. During spraying of WC-Co, ideally only the cobalt phase should melt and act as a binder for the WC particles. Although it is undesirable to fully melt WC because it can cause decarburization, complete melting of the cobalt phase and its satisfactory flattening on impacting the substrate is necessary to minimize porosity and achieve good substrate/coating adhesion. In this article, the influence of the primary plasma spray variables on the melting characteristics of WC-Co powders is investigated with respect to the microstructure of these coatings. This experimental work complements an analytical study on plasma spraying of WC-Co, and thus, observations are presented to support the predictions of the modeling effort.

Joshiand, S. V.; Srivastava, M. P.

1993-06-01

223

Integrity and thermal decomposition of apatite in coatings influenced by underlying titanium during plasma spraying and post-heat-treatment.  

PubMed

The integrity and thermal decomposition of calcium apatite are influenced by the underlying titanium during plasma-spraying deposition, especially at the apatite/titanium interface. The destruction of apatite at the interface is governed by substrate temperature, titanium catalysis, and its reaction with titanium dioxide produced from oxidation of titanium in the plasma gas. The apatite in the outer layer of coatings is affected mainly by the substrate temperature and can keep its integrity with a suitable plasma-spraying procedure to minimize the increase of substrate temperature. The heat treatment of the coatings in vacuum results in the decomposition of apatite to alpha-tricalcium phosphate (alpha-TCP) and tetracalcium phosphate monoxide (TCPM) with the increase of intensity approaching the interface, which roughens the surface of the coatings. In the air-heat treatment, oxidation of titanium produces a thickened, dense rutile layer at the interface which prevents titanium atoms from diffusing into the coatings and inhibits the titanium-catalyzed decomposition of apatite. The apatite adjacent to the rutile layer reacts moderately with rutile to produce calcium titanate (CaTiO3), alpha- and beta-TCP, while the apatite in the outer layer, separated from the rutile layer, maintains its integrity without decomposition even in a prolonged air-heat treatment. The retention of apatite integrity leads to a decreased surface roughness of the coating. PMID:8788100

Weng, J; Liu, X; Zhang, X; de Groot, K

1996-01-01

224

Clogging and Lump Formation During Atmospheric Plasma Spraying with Powder Injection Downstream the Plasma Gun  

NASA Astrophysics Data System (ADS)

This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder injector. A new geometry of the powder port ring holder was designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This solution was successfully tested for applications with Ni-5wt.%Al and ZrO2-7wt.%Y2O3 powders used in production. The possible secondary effect of plasma jet shrouding by the gas screen, and its consequence on powder particles prior to impact was also studied.

Choquet, Isabelle; Bjrklund, Stefan; Johansson, Jimmy; Wigren, Jan

2007-12-01

225

Influence of injection mode on properties of DC plasma jets for thermal plasma spraying  

NASA Astrophysics Data System (ADS)

In plasma spraying powder particles are transported to the plasma jet with the help of a carrier gas. The influence of this gas was investigated by means of an enthalpy probe system with a mass spectrometer for measuring plasma temperature, velocity and plasma gas composition, and visualized by means of Schlieren optics. The enthalpy probe system does not allow measurements of the plasma flow containing solid particles. Therefore, to establish changes of the jet characteristics the carrier gas was supplied through different ports without addition of any powders. Nitrogen and helium were used as carrier gases. They were supplied into the jet with flow rates from 5 to 20 slpm either directly into the plasma beam through a hole in the nozzle or with help of an external injector positioned at a distance of several millimeters from the exit nozzle. Injection of the carrier gas led to high jet perturbations. Values of the centerline temperature and the velocity were reduced. The higher the carrier gas flow rate the stronger the changes of the jet properties. Nitrogen carrier gas perturbed plasma jet flow more than helium.

Kavka, T.; Maslani, A.; Arnold, J.; Henne, R.

2004-03-01

226

Reactive Plasma Nitriding of AL2O3 Powder in Thermal Spray  

NASA Astrophysics Data System (ADS)

Among advanced ceramics, aluminum nitride (AlN) had attracted much attention in the field of electrical and structural applications due to its outstanding properties. However, it is difficult to fabricate AlN coating by conventional thermal spray processes directly. Due to the thermal decomposition of feedstock AlN powder during spraying without a stable melting phase (which is required for deposition in thermal spray). Reactive plasma spraying (RPS) has been considered as a promising technology for in-situ formation of AlN thermally sprayed coatings. In this study the possibility of fabrication of AlN coating by reactive plasma nitriding of alumina (Al2O3) powder using N2/H2 plasma was investigated. It was possible to fabricate a cubic-AlN (c-AlN) based coating and the fabricated coating consists of c-AlN, ?-Al2O3, Al5O6N and ?-Al2O3. It was difficult to understand the nitriding process from the fabricated coatings. Therefore, the Al2O3 powders were sprayed and collected in water. The microstructure observation of the collected powder and its cross section indicate that the reaction started from the surface. Thus, the sprayed particles were melted and reacted in high temperature reactive plasma and formed aluminum oxynitride which has cubic structure and easily nitride to c-AlN. During the coatings process the particles collide, flatten, and rapidly solidified on a substrate surface. The rapid solidification on the substrate surface due to the high quenching rate of the plasma flame prevents AlN crystal growth to form the hexagonal phase. Therefore, it was possible to fabricate c-AlN/Al2O3 based coatings through reactive plasma nitriding reaction of Al2O3 powder in thermal spray.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

227

Modeling of evaporation and oxidation phenomena in plasma spraying of metal powders  

NASA Astrophysics Data System (ADS)

Plasma spraying of metals in air is usually accompanied by evaporation and oxidation of the sprayed material. Optimization of the spraying process must ensure that the particles are fully molten during their short residence time in the plasma jet and prior to hitting the substrate, but not overheated to minimize evaporation losses. In atmospheric plasma spraying (ASP), it is also clearly desirable to be able to control the extent of oxide formation. The objective of this work to develop an overall mathematical model of the oxidization and volatilization phenomena involved in the plasma-spraying of metallic particles in air atmosphere. Four models were developed to simulate the following aspects of the atmospheric plasma spraying (APS) process: (a) the particle trajectories and the velocity and temperature profiles in an Ar-H 2 plasma jet, (b) the heat and mass transfer between particles and plasma jet, (c) the interaction between the evaporation and oxidation phenomena, and (d) the oxidation of liquid metal droplets. The resulting overall model was generated by adapting the computational fluid dynamics code FIDAP and was validated by experimental measurements carried out at the collaborating plasma laboratory of the University of Limoges. The thesis also examined the environmental implications of the oxidization and volatilization phenomena in the plasma spraying of metals. The modeling results showed that the combination of the standard k-s model of turbulence and the Boussinesq eddy-viscosity model provided a more accurate prediction of plasma gas behavior. The estimated NOx generation levels from APS were lower than the U.S.E.P.A. emission standard. Either enhanced evaporation or oxidation can occur on the surface of the metal particles and the relative extent is determined by the process parameters. Comparatively, the particle size has the greatest impact on both evaporation and oxidation. The extent of particle oxidation depends principally on gas-liquid oxidation. The convection due to recirculating flow of liquid within the metal droplet (Hill's vortex) dominates the mass transfer of oxygen after the metal particles become molten. This study showed that the behavior of evaporation and oxidation of metal particles in atmospheric plasma spraying can be predicted and the process parameters can be optimized to reduce the evaporation and/or oxidation of metal particles in industrial applications of plasma spraying.

Zhang, Hanwei

228

Plasma expansion into vacuum assuming a steplike electron energy distribution.  

PubMed

The expansion of a semi-infinite plasma slab into vacuum is analyzed with a hydrodynamic model implying a steplike electron energy distribution function. Analytic expressions for the maximum ion energy and the related ion distribution function are derived and compared with one-dimensional numerical simulations. The choice of the specific non-Maxwellian initial electron energy distribution automatically ensures the conservation of the total energy of the system. The estimated ion energies may differ by an order of magnitude from the values obtained with an adiabatic expansion model supposing a Maxwellian electron distribution. Furthermore, good agreement with data from experiments using laser pulses of ultrashort durations ?(L)

Kiefer, Thomas; Schlegel, Theodor; Kaluza, Malte C

2013-04-22

229

Effect of powder loading on the excitation temperature of a plasma jet in DC thermal plasma spray torch  

Microsoft Academic Search

A DC non-transferred mode plasma spray torch was fabricated for plasma spheroidization. The effect of powder-carrier gas and powder loading on the temperature of the plasma jet generated by the torch has been studied. The experiment was done at different input power levels; the temperature of the jet was within 50007000K argon was used as plasma gas and powder-carrier gas.

G. Shanmugavelayutham; V. Selvarajan; P. V. A. Padmanabhan; K. P. Sreekumar; N. K. Joshi

2007-01-01

230

Outgassing tests on thick plasma-sprayed TiC coatings for fusion applications  

SciTech Connect

TiC coatings of 300-..mu..m thickness produced by plasma spraying have been tested for their outgassing properties from room temperature to 1000 /sup 0/C, to assess their suitability as high-heat/particle flux protective surfaces in tokamaks. The coatings were found to contain the following approximate amounts of gas (in mol %): H/sub 2/, 0.9; H/sub 2/O, 0.7; CO, 0.05; Ar, 0.01; CO/sub 2/, 0.03, and lesser amounts of N/sub 2/ and hydrocarbons. The experimental uncertainties are estimated to be +- 25%. Whereas argon outgasses totally at room temperature and water vapor mostly below 100 /sup 0/C, the other gases require much higher temperatures. This material, baked only at less than or equal to100 /sup 0/C, would be acceptable with respect to the base vacuum of a tokamak; however high-temperature baking is recommended from the viewpoint of recycling and impurity control.

Terreault, B.; Boucher, C.; Andrew, P.L.; Haasz, A.A.; Brunet, C.; Dallaire, S.

1987-11-01

231

Three-dimensional simulation of thermal plasma spraying of partially molten ceramic agglomerates  

Microsoft Academic Search

Thermal plasma spraying of agglomerated nanostructured ceramic particles has been studied using computational fluid dynamics.\\u000a The plasma jet is modeled as a mixture of Ar-H2 plasmas issuing into a quiescent atmosphere. The particles, modeled as micron-sized spheres, are introduced into the jet\\u000a outside the plasma gun exit with radial injection. The existence of a simple target in front of the

I. Ahmed; T. L. Bergman

2000-01-01

232

Induction Plasma Synthesis of Nano-Structured SOFCs Electrolyte Using Solution and Suspension Plasma Spraying: A Comparative Study  

NASA Astrophysics Data System (ADS)

In this paper, two plasma spraying technologies: solution plasma spraying (SolPS) and suspension plasma spraying (SPS) were used to produce nano-structured solid oxide fuel cells (SOFCs) electrolytes. Both plasma spraying processes were optimized in order to achieve the thin gas-tight electrolytes. The comparison of the two plasma spraying processes is based on electrolyte phase, microstructure, morphology, as well as on plasma deposition rate. The results show that nano-structured thin electrolytes (~5 ?m thick) have been successfully SPS deposited on porous anodes with a high deposition rate. Compared to the electrolytes produced by SolPS, the SPS-deposited electrolyte layer is much denser. During the SPS process, fine droplets of 0.5-1 ?m in diameter impact on the surface of the coating and penetrate into the pores of the anode. As the stresses are reduced on the resulting 0.5-2 ?m splats, there is no apparent microcracks network on the splats, this resulting in highly gas-tight coatings. It is demonstrated that the SPS process is beneficial for the improvement of the performance of the films to be used as SOFC electrolytes.

Jia, Lu; Gitzhofer, Franois

2010-03-01

233

Effect of gun current on the microstructure and crystallinity of plasma sprayed hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) is a bioactive material because its chemical structure is close to the natural bone. Its bioactive properties make it attractive material in biomedical applications. Gas tunnel type plasma spraying (GTPS) technique was employed in the present study to deposit HA coatings on SUS 304 stainless steel substrate. GTPS is composed of two plasma sources: gun which produces internal low power plasma (1.3-8 kW) and vortex which produces the main plasma with high power level (10-40 kW). Controlling the spraying parameters is the key role for spraying high crystalline HA coatings on the metallic implants. In this study, the arc gun current was changed while the vortex arc current was kept constant at 450 A during the spraying process of HA coatings. The objective of this study is to investigate the influence of gun current on the microstructure, phase crystallinity and hardness properties of HA coatings. The surface morphology and microstructure of as-sprayed coatings were examined by scanning electron microscope. The phase structure of HA coatings was investigated by X-ray diffraction analysis. HA coatings sprayed at high gun current (100 A) are dense, and have high hardness. The crystallinity of HA coatings was decreased with the increasing in the gun current. On the other hand, the hardness was slightly decreased and the coatings suffer from some porosity at gun currents 0, 30 and 50 A.

Morks, M. F.; Kobayashi, A.

2007-06-01

234

A fabrication process for vacuum-deposited strain gauges on thermally sprayed Al2O3  

NASA Astrophysics Data System (ADS)

Electrically insulating films of Al2O3 were deposited using thermal spray technology followed by the sputter deposition of a strain gauge pattern using shadow masking techniques. For the first time, a thin film strain gauge of chromium was successfully fabricated on thermally sprayed Al2O3 insulation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and profilometer characterization techniques were used to examine structure and surface morphologies of the Al2O3 coatings. A gauge factor of around 2 was found for chromium film as well as hysteresis and creep for loads exceeding 1700 micro strain. The results are discussed.

Djugum, R.; Jolic, K. I.

2006-02-01

235

Mullite coatings on ceramic substrates: Stabilisation of Al 2O 3SiO 2 suspensions for spray drying of composite granules suitable for reactive plasma spraying  

Microsoft Academic Search

The present work deals with the preparation of stable alumina+silica suspensions with high solid loading for the production of spray-dried composite powders. These composite powders are to be used for reactive plasma spraying whereby the formation of mullite and the coating on a ceramic substrate are achieved in a single step process. Electrostatic stabilisation of alumina and silica suspensions has

A. Schrijnemakers; S. Andr; G. Lumay; N. Vandewalle; F. Boschini; R. Cloots; B. Vertruyen

2009-01-01

236

Optimisation and Reproducibility of Plasma Sprayed Tungsten Carbide Coatings.  

National Technical Information Service (NTIS)

Work relating to the optimization of a tungsten carbide coating to meet a particular industrial specification is presented. Having established the working point spraying conditions a series of repeat test are carried out in order to demonstrate the repeat...

C. E. Grinnell

1988-01-01

237

Innovative and emerging processes in plasma spraying: from micro- to nano-structured coatings  

NASA Astrophysics Data System (ADS)

In the context of nanometre-sized structured materials and the perspectives of their technological applications, plasma spray technology is developing to master the coating microstructure at a nanometre scale level. This paper is an attempt to describe (i) the latest advances in the control of the conventional plasma spray process that requires the monitoring of both the plasma jet fluctuation level and particle processing and (ii) the innovative plasma spray processes that have recently emerged. The latter can be ranked in two classes: the processes that use a liquid feedstock where coatings are essentially formed by the impact of molten particles and droplets; and the processes that generally use a powder feedstock where coatings are generated by the condensation of a vapour with possible inclusion of nanometre-sized particles. Their potential applications are briefly presented and it is concluded that they should develop into viable technologies in the near future.

Fauchais, P.; Vardelle, A.

2011-05-01

238

Vacuum arc plasma transport through a magnetic duct with a biased electrode at the outer wall  

Microsoft Academic Search

Metal plasma formed by a vacuum arc plasma source can be passed through a toroidal-section magnetic duct for the filtering of macroparticles from the plasma stream. In order to maximize the plasma transport efficiency of the filter the duct wall should be biased, typically to a positive voltage of about 10-20 V. In some cases it is not convenient to

T. Zhang; B. Y. Tang; Q. C. Chen; Z. M. Zeng; P. K. Chu; M. M. M. Bilek; I. G. Brown

1999-01-01

239

Vacuum arc plasma transport through a magnetic duct with a biased electrode at the outer wall  

Microsoft Academic Search

Metal plasma formed by a vacuum arc plasma source can be passed through a toroidal-section magnetic duct for the filtering of macroparticles from the plasma stream. In order to maximize the plasma transport efficiency of the filter the duct wall should be biased, typically to a positive voltage of about 1020 V. In some cases it is not convenient to

T. Zhang; B. Y. Tang; Q. C. Chen; Z. M. Zeng; P. K. Chu; M. M. M. Bilek; I. G. Brown

1999-01-01

240

Multi-scale Phenomena and Structures Observed in Fabrication of Thermal Barrier Coatings by Using Plasma Spraying  

Microsoft Academic Search

Thermal barrier coatings (TBC) fabricated by plasma spray can exhibit a wide range of microstructures due to differences in feedstock powders and spraying conditions. Since different microstructures naturally result in different thermal and mechanical properties and service life as thermal barrier coatings, it is of great importance to understand the relationship among the feedstock characteristics, spray conditions and the coating

Seiji Kuroda; Hideyuki Murakami; Makoto Watanabe; Kaita Itoh; Kentaro Shinoda; Xiancheng Zhang

2010-01-01

241

Suspension and solution plasma spraying of finely structured layers: potential application to SOFCs  

Microsoft Academic Search

Suspension direct current plasma spraying allows achieving finely structured coatings whose thickness is between few tens and few hundreds of micrometres. Drops (200-300 m in diameter) or liquid jets are mechanically injected in the plasma jet. With radial injection they are rapidly (a few s) fragmented into droplets (a few m in diameter). The latter are vaporized (in a few

P. Fauchais; R. Etchart-Salas; C. Delbos; M. Tognonvi; V. Rat; J. F. Coudert; T. Chartier

2007-01-01

242

Induction plasma sprayed nano hydroxyapatite coatings on titanium for orthopaedic and dental implants  

Microsoft Academic Search

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared

Mangal Roy; Amit Bandyopadhyay; Susmita Bose

2011-01-01

243

Study of atmospheric plasma spray process with the emphasis on gas-shrouded nozzles  

Microsoft Academic Search

An atmospheric plasma spraying process is investigated in this work by using experimental approach and mathematical modelling. Emphasis was put on the gas shrouded nozzles, their design, and the protection against the mixing with the surrounding air, which they give to the plasma jet. First part of the thesis is dedicated to the analysis of enthalpy probe method, as a

Miodrag M. Jankovic

1997-01-01

244

Tribological properties of TiC-Fe coatings obtained by plasma spraying reactive powders  

NASA Astrophysics Data System (ADS)

Titanium carbide-based coatings have been considered for use in sliding wear resistance applications. Carbides embedded in a metal matrix would improve wear properties, providing a noncontinuous ceramic surface. TiC-Fe coatings obtained by plasma spraying of spray-dried TiC-Fe composite powders containing large and angular TiC particles are not expected to be as resistant as those containing TiC particles formed upon spraying. Coatings containing 60 vol% TiC dispersed in a steel matrix deposited by plasma spraying reactive micropellets, sintered reactive micropellets, and spray-dried TiC-Fe composite powders are compared. The sliding wear resistance of these coatings against steel was measured following the test procedure recommended by the Versailles Advanced Materials and Standards (VAMAS) program, and the inherent surface porosity was evaluated by image analysis. Results show that, after a 1-km sliding distance, TiC-Fe coatings obtained after spraying sintered reactive powders exhibit scar ring three times less deep than sprayed coatings using spray-dried TiC-Fe composite powders. For all coatings considered, porosity is detrimental to wear performance, because it generally lowers the coating strength and provides cavities that favor the adhesion of metal. However, porosity can have a beneficial effect by entrapping debris, thus reducing friction. The good wear behavior of TiC-Fe coatings manufactured by plasma spraying of sintered reactive powders is related to their low coefficient of friction against steel. This is due to the microstructure of these coatings, which consists of 0.3 to 1 ?m TiC rounded particles embedded in a steel matrix.

Dallaire, S.; Cliche, G.

1993-03-01

245

Plasma and Particle Temperature Measurements in Thermal Spray: Approaches and Applications  

NASA Astrophysics Data System (ADS)

Growing demands on the quality of thermally sprayed coatings require reliable methods to monitor and optimize the spraying processes. Thus, the importance of diagnostic methods is increasing. A critical requirement of diagnostic methods in thermal spray is the accurate measurement of temperatures. This refers to the hot working gases as well as to the in-flight temperature of the particles. This article gives a review of plasma and particle temperature measurements in thermal spray. The enthalpy probe, optical emission spectroscopy, and computer tomography are introduced for plasma measurements. To determine the in-flight particle temperatures mainly multicolor pyrometry is applied and is hence described in detail. The theoretical background, operation principles and setups are given for each technique. Special interest is attached to calibration methods, application limits, and sources of errors. Furthermore, examples of fields of application are given in the form of results of current research work.

Mauer, Georg; Vaen, Robert; Stver, Detlev

2010-11-01

246

Plasma and Particle Temperature Measurements in Thermal Spray: Approaches and Applications  

NASA Astrophysics Data System (ADS)

Growing demands on the quality of thermally sprayed coatings require reliable methods to monitor and optimize the spraying processes. Thus, the importance of diagnostic methods is increasing. A critical requirement of diagnostic methods in thermal spray is the accurate measurement of temperatures. This refers to the hot working gases as well as to the in-flight temperature of the particles. This article gives a review of plasma and particle temperature measurements in thermal spray. The enthalpy probe, optical emission spectroscopy, and computer tomography are introduced for plasma measurements. To determine the in-flight particle temperatures mainly multicolor pyrometry is applied and is hence described in detail. The theoretical background, operation principles and setups are given for each technique. Special interest is attached to calibration methods, application limits, and sources of errors. Furthermore, examples of fields of application are given in the form of results of current research work.

Mauer, Georg; Vaen, Robert; Stver, Detlev

2011-03-01

247

Effective Parameters in Axial Injection Suspension Plasma Spray Process of Alumina-Zirconia Ceramics  

NASA Astrophysics Data System (ADS)

Suspension plasma spray (SPS) is a novel process for producing nano-structured coatings with metastable phases using significantly smaller particles as compared to conventional thermal spraying. Considering the complexity of the system there is an extensive need to better understand the relationship between plasma spray conditions and resulting coating microstructure and defects. In this study, an alumina/8 wt.% yttria-stabilized zirconia was deposited by axial injection SPS process. The effects of principal deposition parameters on the microstructural features are evaluated using the Taguchi design of experiment. The microstructural features include microcracks, porosities, and deposition rate. To better understand the role of the spray parameters, in-flight particle characteristics, i.e., temperature and velocity were also measured. The role of the porosity in this multicomponent structure is studied as well. The results indicate that thermal diffusivity of the coatings, an important property for potential thermal barrier applications, is barely affected by the changes in porosity content.

Tarasi, F.; Medraj, M.; Dolatabadi, A.; Oberste-Berghaus, J.; Moreau, C.

2008-12-01

248

The evolution of ion charge states in cathodic vacuum arc plasmas: a review  

SciTech Connect

Cathodic vacuum arc plasmas are known to contain multiply charged ions. 20 years after Pressure Ionization: its role in metal vapour vacuum arc plasmas and ion sources appeared in vol. 1 of Plasma Sources Science and Technology, it is a great opportunity to re-visit the issue of pressure ionization, a non-ideal plasma effect, and put it in perspective to the many other factors that influence observable charge state distributions, such as the role of the cathode material, the path in the density-temperature phase diagram, the noise in vacuum arc plasma as described by a fractal model approach, the effects of external magnetic fields and charge exchange collisions with neutrals. A much more complex image of the vacuum arc plasma emerges putting decades of experimentation and modeling in perspective.

Anders, Andre

2011-12-18

249

Tribological properties of TiC-Fe coatings obtained by plasma spraying reactive powders  

Microsoft Academic Search

Titanium carbide-based coatings have been considered for use in sliding wear resistance applications. Carbides embedded in\\u000a a metal matrix would improve wear properties, providing a noncontinuous ceramic surface. TiC-Fe coatings obtained by plasma\\u000a spraying of spray-dried TiC-Fe composite powders containing large and angular TiC particles are not expected to be as resistant\\u000a as those containing TiC particles formed upon spraying.

S. Dallaire; G. Cliche

1993-01-01

250

Effect of substrate temperature on adhesion strength of plasma-sprayed nickel coatings  

Microsoft Academic Search

We plasma-sprayed nickel coatings on stainless steel and cobalt alloy coupons heated to temperatures ranging from room temperature\\u000a to 650 C. Temperatures, velocities, and sizes of spray particles were recorded while in-flight and held constant during experiments.\\u000a We measured coating adhesion strength and porosity, photographed coating microstructure, and determined thickness and composition\\u000a of surface oxide layers on heated substrates. Coating

V. Pershin; M. Lufitha; S. Chandra; J. Mostaghimi

2003-01-01

251

Atmospheric Plasma Spraying Low-Temperature Cathode Materials for Solid Oxide Fuel Cells  

Microsoft Academic Search

Atmospheric plasma spraying (APS) is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional\\u000a layers to be built rapidly with controlled microstructures. The technique allows SOFCs that operate at low temperatures (500-700C)\\u000a to be fabricated by spraying directly onto robust and inexpensive metallic supports. However, standard cathode materials used\\u000a in commercial SOFCs exhibit high polarization resistances at

J. Harris; O. Kesler

2010-01-01

252

Tensile strength of plasma-sprayed alumina and\\/or zirconia coatings on titanium  

Microsoft Academic Search

The heat treatment effect on the characteristics and tensile strength of plasma-sprayed alumina, yttria-stabilized zirconia\\u000a (YSZ), and mixtures of alumina and YSZ coatings on titanium was investigated. The as-sprayed structures of alumina and YSZ\\u000a coatings consists of a and y alumina phases, and cubic and tetragonal zirconia phases, respectively. The tensile strength\\u000a of the coatings containing a large amount of

K. Kishitake; H. Era; S. Baba

1995-01-01

253

Direct measurement of strain behavior of compression loaded plasma-sprayed yttria-stabilized zirconia  

Microsoft Academic Search

Direct measurement of the stressstrain behavior of stand-alone plasma-sprayed 7wt.% Y2O3ZrO2 (YSZ) coatings was made at room temperature. YSZ coatings were evaluated in the as-sprayed condition, and after heat-treatments for 10, 50, and 100h at 1200C using both monotonic and two different cyclic uniaxial compression loading profiles. Heat-treatments were used to change the primarily mechanically interlocked system of lamella to

Christopher Petorak; Rodney W. Trice

2011-01-01

254

Plasma spray forming: An alternate route for manufacturing free-standing components  

Microsoft Academic Search

The present study uses plasma spray technology as a production process for the fabrication of free- stand-ing, near- net-\\u000a shaped NiAl components. Attention is especially focused on the in situ synthesis of NiAl. A new internal, dual powder injector\\u000a blade has been designed to improve the gun performance as well as the spray efficiency of the feedstock powder. The specific

A. Geibel; L. Froyen; L. Delaey; K. U. Leuven

1996-01-01

255

In Situ Particle Behavior of Cast Iron Powder by Suspension Plasma Spraying  

Microsoft Academic Search

An important issue for atmospheric plasma sprayed metal coatings is the oxidation involved during processing that significantly\\u000a affects its phase composition and microstructure and thus the overall coating properties. In this study, suspension thermal\\u000a spraying was used to manufacture cast iron coatings with high amounts of graphite carbon as solid-lubricant, because graphite\\u000a structure is considerably diminished in molten droplets of

C. Tekmen; K. Iwata; Y. Tsunekawa; M. Okumiya

2010-01-01

256

Plasma sprayed composite coatings obtained by liquid injection of secondary phases  

Microsoft Academic Search

A secondary suspension injection system was designed, manufactured and tested, with the aim of depositing composite coatings formed by a conventional air plasma sprayed matrix embedding heat-sensitive phases sprayed and protected in a liquid suspension flow.The system is composed of two main sections: a pressurized vessel, equipped with regulation and recirculation sub-systems, and an adjustable nozzle holder.Preliminary experimental activities were

F. Cipri; F. Marra; G. Pulci; J. Tirill; C. Bartuli; T. Valente

2009-01-01

257

Microstructure and Thermal Properties of Plasma Sprayed Thermal Barrier Coatings from Nanostructured YSZ  

Microsoft Academic Search

Nanostructured yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were produced by atmospheric plasma spraying.\\u000a The microstructure of the sprayed coating was characterized by transmission electron microscope (TEM) and scanning electron\\u000a microscope (SEM). The nano-coating had a higher porosity of ~25% than the conventional coating, which is mainly attributed\\u000a to the large amount of intersplat gaps in the nano-coating. The thermal

Jing Wu; Hong-Bo Guo; Le Zhou; Lu Wang; Sheng-Kai Gong

2010-01-01

258

Corrosion performance of plasma-sprayed cast iron coatings on aluminum alloy for automotive components  

Microsoft Academic Search

Corrosion behaviour of coatings sprayed with water-atomized (WA), cast iron powder were investigated by surface analyses and electrochemical methods, such as potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in deaerated 0.5 M H2SO4 solution. WA cast iron powders of Fe3.75C3.60Si3.93Al (wt.%) were deposited onto an aluminum alloy (AA383 alloy) substrate by atmospheric DC plasma spraying. Four types of samples

W. J. Kim; S. H. Ahn; H. G. Kim; J. G. Kim; Ismail Ozdemir; Y. Tsunekawa

2005-01-01

259

Electrochemical Evaluation of Thin-Film Li-Si Anodes Prepared by Plasma Spraying  

SciTech Connect

Thin-film electrodes of a plasma-sprayed Li-Si alloy were evaluated for use as anodes in high-temperature thermally activated (thermal) batteries. These anodes were prepared using 44% Li/56% Si (w/w) material as feed material in a special plasma-spray apparatus under helium or hydrogen, to protect this air- and moisture-sensitive material during deposition. Anodes were tested in single cells using conventional pressed-powder separators and lithiated pyrite cathodes at temperatures of 400 to 550 C at several different current densities. A limited number of 5-cell battery tests were also conducted. The data for the plasma-sprayed anodes was compared to that for conventional pressed-powder anodes. The performance of the plasma-sprayed anodes was inferior to that of conventional pressed-powder anodes, in that the cell emfs were lower (due to the lack of formation of the desired alloy phases) and the small porosity of these materials severely limited their rate capability. Consequently, plasma-sprayed Li-Si anodes would not be practical for use in thermal batteries.

GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; SCHARRER,GREGORY L.

1999-09-08

260

Probe Measurement of Residual Plasma of a Magnetically Stabilized High-Current Vacuum Arc  

Microsoft Academic Search

A glow-to-arc transition of rarefied plasma that controls the ultimate performance of a vacuum interrupter depends on the state of remaining plasma in the contact gap after current zero. In this study, the electron temperature and the ion density of residual plasma of a magnetically stabilized high-current vacuum arc were measured by the electrostatic (Langumuir) probe method. As a result

Kazuyoshi Arai; Shinji Takahashi; Osami Morimiya; Yosimitu Niwa

2003-01-01

261

Microstructure and photocatalytic activity of suspension plasma sprayed TiO 2 coatings on steel and glass substrates  

Microsoft Academic Search

In this study, TiO2 coatings were deposited by suspension plasma spraying (SPS) from a commercial TiO2 nanoparticle suspension on two different substrates: a standard stainless steel and a Pyrex glass. Coatings were sprayed on both substrates with an F4-MB monocathode torch; a Triplex Pro tricathode torch was also used to spray coatings just on the stainless steel substrates. Spraying distance

E. Bannier; G. Darut; E. Snchez; A. Denoirjean; M. C. Bordes; M. D. Salvador; E. Rayn; H. Ageorges

2011-01-01

262

Photo-Catalytic Activity and Photo-Absorption of Plasma-Sprayed Nano-Structured TiO2 Coatings  

Microsoft Academic Search

Titanium dioxide coatings were deposited by utilizing atmospheric plasma-spraying system. The agglomerated P25\\/20 nano-powder and different spraying parameters (e.g., Argon flow rate and spray distance) were used to determine their influences on the microstructure, crystalline structure, photo-absorption, and photo-catalytic performance of the coatings. The microstructure and phases of as-sprayed TiO2 coatings were characterized by scanning electron microscope SEM and X-ray

Maryamossadat Bozorgtabar; Mehdi Salehi; Mohammadreza Rahimipour; Mohammadreza Jafarpour

2010-01-01

263

Effects of Anode Arc Root Fluctuation on Coating Quality During Plasma Spraying  

NASA Astrophysics Data System (ADS)

To obtain a coating of high quality, a new type of plasma torch was designed and constructed to increase the stability of the plasma arc and reduce the air entrainment into the plasma jet. The torch, called bi-anode torch, generates an elongated arc with comparatively high arc voltage and low arc fluctuation. Spraying experiments were carried out to compare the quality of coatings deposited by a conventional torch and a bi-anode torch. Alumina coatings and tungsten carbide coatings were prepared to appraise the heating of the sprayed particles in the plasma jets and the entrainment of the surrounding air into the plasma jets, respectively. The results show that anode arc root fluctuation has only a small effect on the melting rate of alumina particles. On the other hand, reduced air entrainment into the plasma jet of the bi-anode torch will drastically reduce the decarbonization of tungsten carbide coatings.

An, Lian-Tong; Gao, Yang; Sun, Chengqi

2011-06-01

264

Relativistic laser pulse focusing and self-compression in stratified plasma-vacuum systems  

SciTech Connect

Laser pulse compression in plasma-vacuum systems is investigated in the weakly relativistic regime. First, within one-dimensional hydrodynamic models, the basic features of propagation in plasmas, like width and amplitude changes, are demonstrated. The numerical findings can be interpreted, in part, a by simplified model based on the variation of action method. Since transverse effects like filamentation do play a significant role, the numerical evaluations are then generalized to two-dimensional situations. An approximate analytical criterion for the dominating transverse wave number during laser propagation in plasmas is presented. Finite plasma-vacuum systems show in addition to the filamentation instability the so-called plasma lens effect. The latter is first demonstrated for a single plasma layer. It is then discussed how (i) longitudinal and transversal self-compression in plasmas, (ii) focusing by a plasma layer, and (iii) cleaning of unstable modes compete with each other in layered plasma-vacuum systems. Depending on the available parameters, optimized plasma-vacuum systems are proposed for pulse compression. Such systems can be used as a substitute for hollow fibers which are in use to shorten a pulse. Pulse lengths of one or two cycles can be reached by optimized plasma-vacuum systems, while attaining ultrarelativistic intensities in the focal spot behind the system of layers.

Karle, Ch.; Spatschek, K. H. [Institut fuer Theoretische Physik, Heinrich-Heine-Universitaet Duesseldorf, D-40225 Duesseldorf (Germany)

2008-12-15

265

Interelectrode plasma parameters and plasma deposition in a hot refractory anode vacuum arc  

NASA Astrophysics Data System (ADS)

The new mode of Vacuum arc-Hot Refractory Anode Vacuum Arc-was studied experimentally using a Langmuir probe, two types of thermal probes, and film collection substrates. The plasma density, electron temperature, plasma energy flux, cathode erosion, mass deposition rate on a substrate, and macroparticle contamination in the deposited films were measured. The arc initially operated as a usual vacuum arc sustained by cathode spots, i.e., and the vapor and plasma source located at the cathode spot. At a later stage the anode heated up and metal vapor originating at the cathode was re-evaporated from the nonconsumable hot graphite anode. Initially, plasma density was about (3-4).1020 m-3 but it increased with time, reaching about 2.1021 m-3 after 60 s in a 340 A arc. The electron temperature initially was about 1.6 eV and decreased with time to a steady-state value of about 1.1 eV after 20 s. The radial plasma energy flux generated by 175 and 340 A arcs was about 1 and 2 MW/m2, respectively, at 1.6 cm from the electrode axis. The deposition rate on substrates placed 110-120 mm from the electrode axis reached about 2 ?m/min. The density of macroparticles found on substrates exposed during the first 60 s of arcing was ~103 macroparticles per mm2, however, this density was reduced to about 1 macroparticle per mm2 on substrates exposed to only the second 30 s period.

Beilis, I. I.; Keidar, M.; Boxman, R. L.; Goldsmith, S.

2000-07-01

266

Structural, Mechanical and Erosion Properties of Yttrium Oxide Coatings by Axial Suspension Plasma Spraying for Electronics Applications  

NASA Astrophysics Data System (ADS)

Yttrium oxide (Y2O3) coatings have been prepared by axial suspension plasma spraying with fine powders. It is clarified that the coatings have high hardness, low porosity, high erosion resistance against CF4 -containing plasma and retention of smooth eroded surface. This suggests that the axial suspension plasma spraying of Y2O3 is applicable to fabricating equipment for electronic devices, such as dry etching. Surface morphologies of the slurry coatings with splats are similar to conventional plasma-sprayed Y2O3 coatings, identified from microstructural analysis. Dense coating structures with no lamellar boundaries have been seen, which is apparently different from the conventional coatings. It has also been found that crystal structure of the suspension coatings mainly composed of metastable monoclinic phase, whereas the powders and the conventional plasma spray coatings have stable cubic phase. Mechanism of coating formation by plasma spraying with fine powder slurries is discussed based on the results.

Kitamura, Junya; Tang, Zhaolin; Mizuno, Hiroaki; Sato, Kazuto; Burgess, Alan

2011-01-01

267

Mechanical Properties and Microstructure of Plasma Sprayed Ni-Based Metallic Glass Coating  

NASA Astrophysics Data System (ADS)

Various developmental research works on the metallic glass have been conducted in order to broaden its application field. Thermal spraying method is one of the potential techniques to enhance the excellent properties such as high toughness and corrosion resistance of the metallic glass material. The gas tunnel type plasma spraying is useful to obtain high quality ceramic coatings such as Al2O3 and ZrO2 coatings. In this study, the Ni-based metallic glass coatings were produced by the gas tunnel type plasma spraying under various experimental conditions, and their microstructure and mechanical properties were investigated. At the plasma current of 200-300 A, the Ni-based metallic glass coatings of more than 200 ?m in thickness were formed densely with Vickers hardness of about Hv = 600.

Kobayashi, Akira; Kuroda, Toshio; Kimura, Hisamichi; Inoue, Akihisa

2010-10-01

268

Mechanical Properties and Microstructure of Plasma Sprayed Ni-Based Metallic Glass Coating  

SciTech Connect

Various developmental research works on the metallic glass have been conducted in order to broaden its application field. Thermal spraying method is one of the potential techniques to enhance the excellent properties such as high toughness and corrosion resistance of the metallic glass material. The gas tunnel type plasma spraying is useful to obtain high quality ceramic coatings such as Al{sub 2}O{sub 3} and ZrO{sub 2} coatings. In this study, the Ni-based metallic glass coatings were produced by the gas tunnel type plasma spraying under various experimental conditions, and their microstructure and mechanical properties were investigated. At the plasma current of 200-300 A, the Ni-based metallic glass coatings of more than 200 {mu}m in thickness were formed densely with Vickers hardness of about Hv = 600.

Kobayashi, Akira; Kuroda, Toshio [Joining and Welding Res. Inst., Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Kimura, Hisamichi; Inoue, Akihisa [Inst. for Materials Res., Tohoku University, Katahira, Sendai 980-8577 (Japan)

2010-10-13

269

Pressure-Based Liquid Feed System for Suspension Plasma Spray Coatings  

NASA Astrophysics Data System (ADS)

Thermal spraying with liquid-based feedstocks demonstrated a potential to produce coatings with new and enhanced characteristics. A liquid delivery system prototype was developed and tested in this study. The feeder is based on the 5MPE platform and uses a pressure setup to optimally inject and atomize liquid feedstock into a plasma plume. A novel self-cleaning apparatus is incorporated into the system to greatly reduce problems associated with clogging and agglomeration of liquid suspensions. This approach also allows the liquid feedstock line to the gun to remain charged for quick on-off operation. Experiments on aqueous and ethanol-based suspensions of titania, alumina, and YSZ were performed through this liquid delivery system using a 9MB plasma gun. Coatings with ultrafine splat microstructures were obtained by plasma spraying of those suspensions. Phase composition and microstructure of the as-sprayed coatings were investigated.

Cotler, Elliot M.; Chen, Dianying; Molz, Ronald J.

2011-06-01

270

Wear resistance of laser cladding and plasma spray welding layer on stainless steel surface  

NASA Astrophysics Data System (ADS)

The effect of coatings, which are formed with laser cladding and plasma spray welding on 1Cr18Ni9Ti base metal, on wear resistance is studied, A 5-kW transverse flowing CO2 laser is used for cladding Co base alloy powder pre-placed on the substrate. Comparing with the plasma spray coatings, the spoiled rate of products with laser clad layers was lower and the rate of finished products was higher. Their microstructure is extremely fine. They have close texture and small size grain. Their dilution resulting from the compositions of the base metal and thermal effect on base metal are less. The hardness, toughness, and strength of the laser cladding layers are higher. Wear tests show that the laser layers have higher properties of anti-friction, anti-scour and high-temperature sliding strike. The wear resistance of laser clad layers are about one time higher than that of plasma spray welding layer.

Wang, Xinlin; Shi, Shihong; Zheng, Qiguang

2004-03-01

271

Microstructures and bond strengths of plasma-sprayed hydroxyapatite coatings on porous titanium substrates.  

PubMed

Hydroxyapatite (HA) coating was carried out by plasma spraying on bulk Ti substrates and porous Ti substrates having a Young's modulus similar to that of human bone. The microstructures and bond strengths of HA coatings were investigated in this study. The HA coatings with thickness of 200-250 microm were free from cracks at interfaces between the coating and Ti substrates. XRD analysis revealed that the HA powder used for plasma spraying had a highly crystallized apatite structure, while the HA coating contained several phases other than HA. The bond strength between the HA coating and the Ti substrates evaluated by standard bonding test (ASTM C633-01) were strongly affected by the failure behavior of the HA coating. A mechanism to explain the failure is discussed in terms of surface roughness of the plasma-sprayed HA coatings on the bulk and porous Ti substrates. PMID:15965595

Oh, Ik-Hyun; Nomura, N; Chiba, A; Murayama, Y; Masahashi, N; Lee, Byong-Taek; Hanada, S

2005-07-01

272

Plasma-sprayed calcium phosphate particles with high bioactivity and their use in bioactive scaffolds.  

PubMed

Highly crystalline feedstock hydroxyapatite (HA) particles with irregular shapes were spheroidized by plasma spraying them onto the surface of ice blocks or into water. The spherical Ca-P particles thus produced contained various amounts of the amorphous phase which were controlled by the stand-off distance between the spray nozzle and the surface of ice blocks or waiter. The smooth surface morphology without cracks of spherical Ca-P particles indicated that there were very low thermal stresses in these particles. Plasma-sprayed Ca-P particles were highly bioactive due to their amorphous component and hence quickly induced the formation of bone-like apatite on their surfaces after they were immersed in an acellular simulated body fluid at 36.5 C. Bone-like apatite nucleated on dissolved surface (due to the amorphous phase) of individual Ca-P particles and grew to coalesce between neighboring Ca-P particles thus forming an integrated apatite plate. Bioactive and biodegradable composite scaffolds were produced by incorporating plasma-spray ed Ca-P particles into a degradable polymer. In vitro experiments showed that plasma-sprayed Ca-P particles enhanced the formation of bone-like apatite on the pore surface of Ca-P/PLLA composite scaffolds. PMID:12059011

Weng, Jie; Wang, Min; Chen, Jiyong

2002-07-01

273

The corrosion behaviour of a plasma spraying Al 2O 3 ceramic coating in dilute HC1 solution  

Microsoft Academic Search

Al2O3 ceramic coatings plasma sprayed on the surface of metals change greatly the corrosion law of metals in strong acid solutions and enhance effectively their corrosion resistance property. In this paper, the corrosion behaviour of a Q235 steel with plasma sprayed Al2O3 coatings in a boiling 5% HCl solution is investigated. The corrosion rate of the Al2O3 coating sprayed on

Yan Dianran; He Jining; Wu Jianjun; Qiu Wanqi; Ma Jing

1997-01-01

274

Researching for Corrosion-Resistance Performance of Laser-Hybrid Plasma Spraying NiCr-Cr3C2 Coating  

Microsoft Academic Search

In this paper, the NiCr-Cr3C2 coating was prepared by laser-hybrid plasma spraying (LHPS)technology, the NSS (Neutral Salt Spraying) test results showed that the LHPS NiCr-Cr3C2 coating had good corrosion-resistance performance comparing with the base material and the APS (air plasma spraying) coating. A SEM (scanning electron microscope) was used to analyze corrosion morphology of the samples, The LHPS coating overcame

Shu-qing Li; Qi-lian Li; Shui-li Gong; Chun Wang

2011-01-01

275

A Study on Microstructure and Dielectric Performances of Alumina/Copper Composites by Plasma Spray Coating  

NASA Astrophysics Data System (ADS)

In this study, surfaces of copper plates were coated with a thick alumina layer by the plasma spray coating to fabricate a composite with a dielectric performance that made them suitable as substrates in electronic devices with high thermal dissipation. The performance of alumina dielectric layer fabricated by the plasma spray coating and traditional screen-printing process was compared, respectively. Effects of the spraying parameters and size of alumina particles on the microstructure, thickness, and the surface roughness of the coated layer were explored. In addition, the thermal resistance perpendicular to the interface of copper and alumina and the breakdown voltage across the alumina layer of the composite were also investigated. Experimental results indicated that alumina particles with 5-22 ?m in diameter tended to form a thicker layer with a poorer surface roughness than that of the particles with 22-45 ?m in diameter. The thermal resistance increased with the surface roughness of the alumina layer, and the breakdown voltage was affected by the ambient moisture, the microstructure and the thickness of the layer. The optimal parameters for plasma spray coating were an alumina powder of particles size between 22 and 45 ?m, a plasma power of 40 kW, a spraying velocity of 750 m/s, an argon flow rate of 45 L/min, a spraying distance of 140 mm, and a spraying angle of 90. It can be concluded that an alumina layer thickness of 20 ?m provided a low surface roughness, low thermal resistance, and highly reliable breakdown voltage (38 V/?m).

Lin, Kuan Hong; Xu, Zi Hao; Lin, Shun Tian

2011-03-01

276

Capillary Plasma Electrode Discharge as an Intense and Efficient Source of Vacuum Ultraviolet Radiation for Plasma Display  

Microsoft Academic Search

The characteristic properties of microscale capillary plasma electrode structures were experimentally investigated and compared to the dielectric barrier discharge (DBD) structure. The vacuum ultraviolet (VUV) emission from the capillary plasma electrode discharges (CPEDs) was more intense and more efficient than the one from the DBD. Based on VUV emission characteristics, it is confirmed that the CPED-based plasma display could be

Soo-Ho Park; Tae-Seung Cho; Kurt H. Becker; Erich E. Kunhardt

2009-01-01

277

Atmosphere corrosion behavior of plasma sprayed and laser remelted coatings on copper  

NASA Astrophysics Data System (ADS)

Nickel and chromium coatings were produced using plasma spraying and laser remelting on the copper sheet. The corrosion test was carried out in an acidic atmosphere, and the corrosive behaviors of both coatings and original copper samples were investigated by using an impedance comparison method. Experimental results show that nickel and chromium coatings display better corrosion resistance properties relative to the original pure copper sample. The corrosion rate of chromium coating is less than that of nickel coating, and corrosion resistances of laser remelted nickel and chromium samples are better than those of plasma sprayed samples. The corrosion deposit film of copper is loose compared with nickel and chromium.

Liang, Gongying; Wong, T. T.; An, Geng; MacAlpine, J. M. K.

2006-01-01

278

Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating  

SciTech Connect

The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value. 9 references.

Miller, R.A.; Argarwal, P.; Duderstadt, E.C.

1984-07-01

279

Plasma sprayed cast iron coatings containing solid lubricant graphite and h-BN structure  

Microsoft Academic Search

Water-atomized cast iron powder of Fe-2.17 at.%C-9.93at.%Si-3.75at.%Al were deposited onto an aluminum alloy substrate by\\u000a atmospheric direct current plasma spraying to improve its tribological properties. Preannealing of the cast iron powder allows\\u000a the precipitation of considerable amounts of graphite structure in the powder. However, significant reduction in graphitized\\u000a carbon in cast iron coatings is inevitable after plasma spraying in air

Y. Tsunekawa; I. Ozdemir; M. Okumiya

2006-01-01

280

Tribological behavior of plasma spray coatings for marine diesel engine piston ring and cylinder liner  

Microsoft Academic Search

High-temperature wear characteristics between plasma spray coated piston rings and cylinder liners were investigated to find\\u000a the optimum combination of coating materials using the disc-on-plate reciprocating wear test in dry conditions. The disc and\\u000a plate represented the piston ring and the cylinder liner, respectively. Coating materials studied were Cr2O3-NiCr, Cr2O3-NiCr-Mo, and Cr3C2-NiCr-Mo. Plasma spray conditions for the coating materials were

Jong-Hyun Hwang; Myoung-Seoup Han; Dae-Young Kim; Joong-Geun Youn

2006-01-01

281

Microstructure and tribological behavior of suspension plasma sprayed Al 2O 3 and Al 2O 3YSZ composite coatings  

Microsoft Academic Search

Several alumina and aluminazirconia composite coatings were manufactured by suspension plasma spraying (SPS), implementing different operating conditions in order to achieve dense and cohesive structures. Temperatures and velocities of the in flight particles were measured with a commercial diagnostic system (Accuraspray) at the spray distance as a function of the plasma operating parameters. Temperatures around 2000C and velocities as high

O. Tingaud; P. Bertrand; G. Bertrand

2010-01-01

282

The effect of solids and dispersant loadings on the suspension viscosities and deposition rates of suspension plasma sprayed YSZ coatings  

Microsoft Academic Search

Suspension plasma spraying (SPS) is a promising modification of traditional plasma spraying techniques that uses small (?2?m) particles suspended in a liquid to fabricate coatings with fine microstructures and controlled porosity rapidly and without the need for post-deposition heat treatments. These qualities make SPS an interesting new technique to manufacture solid oxide fuel cell (SOFC) active layers. However, in order

D. Waldbillig; O. Kesler

2009-01-01

283

Ductile phase toughening of molybdenum disilicide by low pressure plasma spraying  

SciTech Connect

The low fracture toughness of MoSi{sub 2} at ambient temperature has prompted investigations into new processing methods in order to impart some degree of fracture toughness into this inherently brittle material. In the following investigation, low pressure plasma spraying was employed as a fabricating technique to produce spray-formed deposits of MoSi{sub 2} and ductile reinforced MoSi{sub 2} composites containing approximately 10 and 20 volume percent of a discontinuous tantalum lamelli reinforcement. Fracture toughness (K{sub 1C}) measurements of MoSi{sub 2} and the MoSi{sub 2}/Ta composites were done using a chevron notched 4-point bend fracture toughness test in both the as-sprayed condition and after hot isostatic pressing at 1200{degrees}C/206 MPa for 1 hour. Results from the ductile reinforced MoSi{sub 2}/Ta composites have shown fracture toughness increases on the order of 200% over the as-sprayed MoSi{sub 2}. In addition, a marked anisotropy in fracture toughness was observed in the spray-formed deposits due to the layered splat structure produced by the low pressure plasma spray process.

Castro, R.G.; Rollett, A.D.; Stanek, P.W. [Los Alamos National Lab., NM (United States); Smith, R.W. [Drexel Univ., Philadelphia, PA (United States). Dept. of Materials Engineering

1992-02-01

284

Ductile phase toughening of molybdenum disilicide by low pressure plasma spraying  

SciTech Connect

The low fracture toughness of MoSi{sub 2} at ambient temperature has prompted investigations into new processing methods in order to impart some degree of fracture toughness into this inherently brittle material. In the following investigation, low pressure plasma spraying was employed as a fabricating technique to produce spray-formed deposits of MoSi{sub 2} and ductile reinforced MoSi{sub 2} composites containing approximately 10 and 20 volume percent of a discontinuous tantalum lamelli reinforcement. Fracture toughness (K{sub 1C}) measurements of MoSi{sub 2} and the MoSi{sub 2}/Ta composites were done using a chevron notched 4-point bend fracture toughness test in both the as-sprayed condition and after hot isostatic pressing at 1200{degrees}C/206 MPa for 1 hour. Results from the ductile reinforced MoSi{sub 2}/Ta composites have shown fracture toughness increases on the order of 200% over the as-sprayed MoSi{sub 2}. In addition, a marked anisotropy in fracture toughness was observed in the spray-formed deposits due to the layered splat structure produced by the low pressure plasma spray process.

Castro, R.G.; Rollett, A.D.; Stanek, P.W. (Los Alamos National Lab., NM (United States)); Smith, R.W. (Drexel Univ., Philadelphia, PA (United States). Dept. of Materials Engineering)

1992-01-01

285

Microstructural inhomogeneity in plasma-sprayed hydroxyapatite coatings and effect of post-heat treatment  

NASA Astrophysics Data System (ADS)

The microstructural inhomogeneity in the plasma-sprayed hydroxyapatite (HA) coatings was characterized by using electron probe microanalyser (EPMA). A simple and artful method was developed to detect the interface characteristics. All the samples for observation were ground and polished along the direction parallel to the coating surfaces. The BSE images directly and clearly showed the inhomogeneity in the as-sprayed coatings with the amorphous regions being bright gray and crystalline regions being dark gray. X-ray diffractometer (XRD) patterns indicated that after immersion in deionized water for 20 days, bone-like apatite and ?-Ca2P2O7 precipitated on the polished surfaces of the as-sprayed HA coatings. The post-heat treatment could eliminate the microstructural inhomogeneity in the coatings. Only ?-Ca2P2O7 precipitated on the surfaces of the heat-treated HA coatings. The immersed samples were re-polished till tiny substrate was bared to investigate the effect of immersion on interface. It was shown that the immersion decreased the cohesive strength of the as-sprayed coatings. There were more and broader cracks in the splats that came into contact with the substrate and amorphous phase increased toward the coating substrate interface. Post-heat treatment was proved to reduce the peeling off of coating during re-polishing operation. It was proposed that the distributions of amorphous phase and cracks in as-sprayed coatings are detrimental to coating properties and should be modified through improving the plasma spraying processing.

Lu, Yu-Peng; Xiao, Gui-Yong; Li, Shi-Tong; Sun, Rui-Xue; Li, Mu-Sen

2006-01-01

286

The abrasive wear of plasma sprayed nanoscale tungsten carbide-cobalt (WC-Co)  

NASA Astrophysics Data System (ADS)

Thermal spray coatings composed of a variety of carbide sizes and cobalt contents were sprayed with a high energy plasma spray system. The size of the carbides used fell into three rough groupings, micrometer scale carbides (1--2 mum), submicrometer (700--300 nm), and nanoscale (?100 nm). The feedstock powder was evaluated in terms of their size distribution, external morphology, internal morphology, and initial carbide size. Two different fixtures were used in spraying to evaluate the effect of cooling rate on the wear resistance of the coatings. The microstructures of the sprayed coatings were examined using optical metallography, SEM, FESEM, TEM, XRD and chemical analysis. The coatings were evaluated in low stress abrasive wear by the ASTM G-65 Dry Sand Rubber Wheel test. Furthermore, the porosity and hardness of the coatings were evaluated. The cobalt content was found to be the predominant influence on the wear rate of the coatings. The decrease in the carbide size was not found to effect the wear rate of the coatings. Coatings sprayed on the 'hot' fixture were found to have slightly improved wear resistance as compared to coatings sprayed on the 'cold' fixture. The wear rates of the coatings were found to be a function of the WC/Co volume ratio.

Tewksbury, Graham Alfred

287

Cavitation-Erosion of Plasma-Sprayed Alloys.  

National Technical Information Service (NTIS)

Very limited research has been carried out on the cavitation-erosion (CE) resistance of thermal sprayed protective coatings. In the work that has been carried out to date, there appears to be a relation between the nature of the particle-particle cohesive...

M. F. Smith H. Bhat H. Herman

1984-01-01

288

Spraying Powder Materials by the High-Enthalpy Laminar Plasma Flow  

SciTech Connect

One of the most promising engineering solutions of the problem of spraying powder materials is the proposed method of plasma spraying by the laminar plasma jet. Laminar plasma flow is characterized by small jet angle divergence; the powder particles are penetrated and accelerated mainly in the axial direction. The molten powder particles are transported almost to the surface of a treated work-piece inside the laminar plasma flow in an atmosphere of the plasma-forming gas with the acceleration on the entire transfer area, which leads to an increase in the particles velocity, a decrease of their oxidability, an increase in the powder deposition efficiency, density, adhesion strength with the surface to be coated.

Khutsishvili, M.; Kikvadze, L. [Plasma Spray Laboratory, Georgian Technical University, M. Kostava street 77, Tbilisi 0175 (Georgia)

2008-03-19

289

Simulation studies to optimize the process of plasma spray deposition of yttrium oxide  

NASA Astrophysics Data System (ADS)

Simulation studies on the thermal behaviour of yttrium oxide particles in a thermal plasma jet was carried out with the objective of controlling and optimization of the plasma spray process. The 'in-flight' behaviour of yttrium oxide particles in the plasma jet was studied by solving the heat transfer and momentum transfer equations using the velocity and temperature distribution in the plasma jet obtained from a two-dimensional model. In particular, the effect of particle size, thermal power of the torch and the torch operating parameters like gas flow rates were considered to calculate the heat transfer and momentum transfer to the particle. Results of simulation studies agree quite well with the experimental results on variation of deposition efficiency with power and particle size. The complete description of the model with the results obtained for the typical operating parameters of our plasma spray torch is presented in the paper.

Thiyagarajan, T. K.; Sreekumar, K. P.; Selvan, V.; Ramachandran, K.; Ananthapadmanabhan, P. V.

2010-02-01

290

Spraying Powder Materials by the High-Enthalpy Laminar Plasma Flow  

NASA Astrophysics Data System (ADS)

One of the most promising engineering solutions of the problem of spraying powder materials is the proposed method of plasma spraying by the laminar plasma jet. Laminar plasma flow is characterized by small jet angle divergence; the powder particles are penetrated and accelerated mainly in the axial direction. The molten powder particles are transported almost to the surface of a treated work-piece inside the laminar plasma flow in an atmosphere of the plasma-forming gas with the acceleration on the entire transfer area, which leads to an increase in the particles velocity, a decrease of their oxidability, an increase in the powder deposition efficiency, density, adhesion strength with the surface to be coated.

Khutsishvili, M.; Kikvadze, L.

2008-03-01

291

Ion mean charge state in a biased vacuum arc plasma duct  

Microsoft Academic Search

Vacuum arc or cathodic arc metal plasma sources are attractive and convenient for depositing high-quality thin metal films and metallurgical coatings. It is a common practice to use a curved magnetic filter duct to eliminate macroparticle contamination and to bias the duct wall with a positive voltage to enhance the throughput of the metal plasma. The metal plasma usually consists

Dixon Tat-Kun Kwok; Paul K. Chu; M. M. M. Bilek; Ian G. Brown; Alexey Vizir

2000-01-01

292

Mechanical, In Vitro Antimicrobial and Biological Properties of Plasma Sprayed Silver-Doped Hydroxyapatite Coating  

PubMed Central

Implant related infection is one of the key concerns in total joint hip arthroplasties. In order to reduce bacterial adhesion, silver (Ag) / silver oxide (Ag2O) doping was used in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0 and 6.0 wt% Ag, heat treated at 800 C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas Aeruginosa (PAO1). Live/Dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Present results suggest that the plasma sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag doped HA coatings.

Roy, Mangal; Fielding, Gary A.; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

2012-01-01

293

Vacuum arc ion source with filtered plasma for macroparticle-free implantation  

Microsoft Academic Search

An inherent feature of the vacuum arc discharge is that small droplets of micrometer size (macroparticles) are produced along with the plasma in the cathode spots. Droplet contamination of the substrate can occur when implanting metal ions using a vacuum arc ion source. The contamination can be significant for some cathode materials such as lead and other low melting point

Simone Anders; Andre Anders; Ian G. Brown; Robert A. MacGill; Michael R. Dickinson

1994-01-01

294

Electron beam extraction from a broad-beam vacuum-arc metal plasma source  

Microsoft Academic Search

We describe experiments demonstrating the formation of a high current electron beam from a vacuum arc plasma. A preexisting vacuum arc ion source was used, with the extraction voltage reversed in polarity so as to form an electron beam rather than an ion beam; no other changes were required. The beam formed was of energy up to 33 keV, beam

Efim M. Oks; Ian G. Brown

1998-01-01

295

Development of a Plasma Source for a Vacuum Arc Thruster Controlled by a Microcontroller  

Microsoft Academic Search

A plasma source for vacuum arc thruster was developed. Electrical energy stored in two resonators is delivered to a vacuum gap and metal ions are emitted from the electrodes. The ions obtain momentum and the thruster obtains thrust power from reaction of ions. A high frequency (HF) current was used to generate energetic ions in spark phase, and a low

S. Shibata; T. Yanagidaira; K. Tsuruta

2006-01-01

296

Improvement in mechanical properties of plasma sprayed hydroxyapatite coatings by Al2O3 reinforcement.  

PubMed

Thermal sprayed hydroxyapatite coatings suffer from poor mechanical properties like tensile strength, wear resistance, hardness, toughness and fatigue. The mechanical properties of hydroxyapatite coatings can be enhanced via incorporation of secondary bioinert reinforcement material. In this study an attempt has been made to improve the mechanical properties of plasma sprayed hydroxyapatite by reinforcing it with 10, 20 and 30% Al2O3. The plasma sprayed coatings have been characterized using FE-SEM/EDAX, XRD, AFM and FTIR spectroscopy. Corrosion studies have been done in simulated body fluid and abrasive wear studies have been performed on flat specimens on a disk wear tester. Microhardness, tensile strength and wear resistance are found to be increased with increasing Al2O3 content. All types of coatings show superior resistance against corrosion in simulated body fluid. PMID:23623104

Mittal, Manoj; Nath, S K; Prakash, Satya

2013-03-14

297

Effect of Gun Current on Electrical Properties of Atmospheric Plasma-Sprayed Lanthanum Silicate Coatings  

NASA Astrophysics Data System (ADS)

Apatite-type lanthanum silicate (ATLS) electrolyte coatings for use in intermediate-temperature solid oxide fuel cells were deposited by atmospheric plasma spraying (APS). Plasma-sprayed coatings with typical composition La10(SiO4)6O3 exhibiting good densification and high oxide ionic conductivity were obtained by properly adjusting the spraying parameters, particularly the gun current. The highest obtained ionic conductivity value of 3.3 mS/cm at 1,173 K in air is comparable to other ATLS conductors. This work demonstrated empirically that utilization of the APS technique is feasible to synthesize dense La10(SiO4)6O3 electrolyte coatings using gun currents within an unusually broad range.

Gao, Wei; Liao, Han-Lin; Coddet, Christian

2013-10-01

298

Application of Suspension Plasma Spraying (SPS) for Manufacture of Ceramic Coatings  

NASA Astrophysics Data System (ADS)

Conventional thermal spray processes as atmospheric plasma spraying (APS) have to use easily flowable powders with a size up to 100 ?m. This leads to certain limitations in the achievable microstructural features. Suspension plasma spraying (SPS) is a new promising processing method which employs suspensions of sub-micrometer particles as feedstock. Therefore much finer grain and pore sizes as well as dense and also thin ceramic coatings can be achieved. Highly porous coatings with fine pore sizes are needed as electrodes in solid-oxide fuel cells. Cathodes made of LaSrMn perovskites have been produced by the SPS process. Their microstructural and electrochemical properties will be presented. Another interesting application is thermal barrier coating (TBC). SPS allows the manufacture of high-segmented TBCs with still relatively high porosity levels. In addition to these specific applications also the manufactures of new microstructures like nano-multilayers and columnar structures are presented.

Kassner, Holger; Siegert, Roberto; Hathiramani, Dag; Vassen, Robert; Stoever, Detlev

2008-03-01

299

Synthesis and Preliminary Tests of Suspension Plasma Spraying of Fine Hydroxyapatite Powder  

NASA Astrophysics Data System (ADS)

The synthetic hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a very useful biomaterial for numerous applications in medicine, such as e.g., fine powder for suspension plasma spraying. The powder was synthesized using aqueous solution of ammonium phosphate (H2(PO4)NH4) and calcium nitrate (Ca(NO3) 4H2O) in the carefully controlled experiments. The synthesized fine powder was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The powder was formulated into water and alcohol based suspension and used to carry out the initial tests of plasma spraying onto titanium substrate. The phase analysis of sprayed coating was made with the XRD.

Jaworski, Roman; Pierlot, Christel; Pawlowski, Lech; Bigan, Muriel; Quivrin, Maxime

2008-12-01

300

Process Conditions and Microstructures of Ceramic Coatings by Gas Phase Deposition Based on Plasma Spraying  

NASA Astrophysics Data System (ADS)

Plasma spraying at very low pressure (50-200 Pa) is significantly different from atmospheric plasma conditions (APS). By applying powder feedstock, it is possible to fragment the particles into very small clusters or even to evaporate the material. As a consequence, the deposition mechanisms and the resulting coating microstructures could be quite different compared to conventional APS liquid splat deposition. Thin and dense ceramic coatings as well as columnar-structured strain-tolerant coatings with low thermal conductivity can be achieved offering new possibilities for application in energy systems. To exploit the potential of such a gas phase deposition from plasma spray-based processes, the deposition mechanisms and their dependency on process conditions must be better understood. Thus, plasma conditions were investigated by optical emission spectroscopy. Coating experiments were performed, partially at extreme conditions. Based on the observed microstructures, a phenomenological model is developed to identify basic growth mechanisms.

Mauer, G.; Hospach, A.; Zotov, N.; Vaen, R.

2013-03-01

301

Measurement of the elastic modulus of a plasma-sprayed thermal barrier coating using spherical indentation  

Microsoft Academic Search

Failure in plasma-sprayed thermal barrier coatings systems mostly takes place in the ceramic topcoat or at the interface between the topcoat and the bondcoat. The failure normally occurs by spallation of the topcoat at shutdown operations from high temperatures where compressive thermal mismatch stresses are induced in the topcoat. In order to analyse the residual stresses, knowledge about the elastic

Mats Eskner; Rolf Sandstrm

2004-01-01

302

Effect of Sintering on Mechanical and Physical Properties of Plasma-Sprayed Thermal Barrier Coatings.  

National Technical Information Service (NTIS)

The effect of sintering on mechanical and physical properties of free-standing plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings (TBCs) was determined by annealing them at 1316 C in air. Mechanical and physical properties of the TBCs, including stre...

S. R. Choi D. M. Zhu R. A. Miller

2004-01-01

303

Structure and mechanical properties of boron carbide coatings formed by electromagnetically accelerated plasma spraying  

Microsoft Academic Search

Structural and mechanical properties are investigated on thick boron carbide (B4C) coatings, which are formed onto stainless steel substrates by using an electromagnetically accelerated plasma spraying. Hardness, porosity and surface roughness of the coatings show dependences on both the size of raw powder and the substrates distance. Within the coating conditions using two different sized raw powders; 3010 ?m and

J. Kitamura; S. Usuba; Y. Kakudate; H. Yokoi; K. Yamamoto; A. Tanaka; S. Fujiwara

2003-01-01

304

Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical properties  

Microsoft Academic Search

Flame-spheroidized feedstock, with excellent known heat transfer and consistent melting capabilities, were used to produce hydroxyapatite (HA) coatings via plasma spraying. The characteristics and inherent mechanical properties of the coatings have been investigated and were found to have direct and impacting relationship with the feedstock characteristics, processing parameters as well as microstructural deformities. Processing parameters such as particle sizes (SHA:

S. W. K Kweh; K. A Khor; P Cheang

2000-01-01

305

Mechanical properties of suspension plasma sprayed hydroxyapatite coatings submitted to simulated body fluid  

Microsoft Academic Search

Home synthesized (HA) powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto titanium substrate. The deposition process was optimized and the resulting coatings were soaked in simulated body fluid (SBF) for the periods of 3, 7, 14, 28, and 60days at controlled temperature of 37C. The microstructural research enabled to find in

Leszek ?atka; Lech Pawlowski; Didier Chicot; Christel Pierlot; Fabrice Petit

2010-01-01

306

Comment on ''High coercivity, isotropic plasma sprayed samarium-cobalt magnets''  

Microsoft Academic Search

It is shown that the experimental results obtained by Kumar et al. on plasma-sprayed Sm-Co alloys, which seem to refute the existence of a eutectoid decomposition of SmCo5, can actually be taken as further experimental evidence in favor of the presence of the decomposition reaction.

K. H. J. Buschow; F. J. A. den Broeder

1980-01-01

307

Comment on High coercivity, isotropic plasma sprayed samarium-cobalt magnets  

Microsoft Academic Search

It is shown that the experimental results obtained by Kumar etal. on plasma-sprayed Sm-Co alloys, which seem to refute the existence of a eutectoid decomposition of SmCo5, can actually be taken as further experimental evidence in favor of the presence of the decomposition reaction.

K. H. J. Buschow; F. J. A. den Broeder

1980-01-01

308

Development of a Plasma Sprayed Ceramic Gas Path Seal for High Pressure Turbine Applications.  

National Technical Information Service (NTIS)

The plasma sprayed graded layered yittria stabilized zirconia (ZrO2)/metal(CoCrAlY) seal system for gas turbine blade tip applications up to 1589 K (2400 F) seal temperatures was studied. Abradability, erosion, and thermal fatigue characteristics of the g...

L. T. Shiembob

1977-01-01

309

Axial variation of electron number density in thermal plasma spray jets  

Microsoft Academic Search

The electron number density has been measured in a plasma spray torch using Stark broadening of H $_{\\\\beta}$ and Ar-I (430 nm) line. A small amount of hydrogen (1% by volume in argon gas) was introduced to study the H $_{\\\\beta}$ line profile. Axial variation of electron number density has been determined up to a distance of 20 mm from

N. K. Joshi; S. N. Sahasrabudhe; K. P. Sreekumar; N. Venkatramani

2003-01-01

310

Size sensitivity to thermal shock of plasma-sprayed ceramics and factors affecting the size effect  

Microsoft Academic Search

The influence of specimen size on thermal shock resistance is investigated for relatively large plasma-sprayed alumina tubes of varying diameter, length, and wall thickness. The observations suggest that an increasing wall thickness has a significant effect on the critical temperature difference for the onset of fracture, {Tc}, compared to the relatively weak effect of tube diameter and length. A plot

Ekkehard H. Lutz

1995-01-01

311

Tensile properties of carbon nanotube reinforced aluminum nanocomposite fabricated by plasma spray forming  

Microsoft Academic Search

Uniaxial tensile tests were performed on plasma spray formed (PSF) AlSi alloy reinforced with multiwalled carbon nanotubes (MWCNTs). The addition of CNTs leads to 78% increase in the elastic modulus of the composite. There was a marginal increase in the tensile strength of CNT reinforced composite with degradation in strain to failure by 46%. The computed critical pullout length of

T. Laha; Y. Chen; D. Lahiri; A. Agarwal

2009-01-01

312

An Insight into Suspension Plasma Spray: Injection of the Suspension and Its Interaction with the Plasma Flow  

Microsoft Academic Search

Yttria Stabilized Zirconia (YSZ) suspensions were injected in an atmospheric plasma jet using two designs of a home-made two-fluid\\u000a atomizing nozzle. The sprays of drops were visualized and the behavior of the suspension in the plasma jet was investigated\\u000a by implementing the Particle Image Velocimetry (PIV) method. The effects of the suspension formulation (surface tension, liquid\\u000a viscosity, and relative gas-to-liquid

O. Marchand; L. Girardot; M. P. Planche; P. Bertrand; Y. Bailly; G. Bertrand

313

Experimental design of plasma spraying and laser treatment of hydroxyapatite coatings  

Microsoft Academic Search

Plasma spray process of hydroxyapatite (Ca10(PO4)6(OH)2, HA) followed by laser treatment of obtained coatings were optimized by an advanced statistical planning of experiments. The full factorial design of 24 experiments was used to find effects of four principal parameters, i.e. electric power, plasma forming gas composition, carrier gas flow rate and laser power density onto microstructure of hydroxyapatite (HA) coatings

S. Dyshlovenko; C. Pierlot; L. Pawlowski; R. Tomaszek; P. Chagnon

2006-01-01

314

A Computational Examination of the Sources of Statistical Variance in Particle Parameters During Thermal Plasma Spraying  

Microsoft Academic Search

Computational modeling is used to systematically examine many of the sources of statistical variance in particle parameters during thermal plasma spraying. Using the computer program LAVA, a steady-state plasma jet typical of a commercial torch at normal operating conditions, is first developed. Then, assuming a single particle composition(ZrO2) and injection location, real world complexity (e.g., turbulent dispersion, particle size and

R. L. Williamson; J. R. Fincke; C. H. Chang

2000-01-01

315

Phase Formation and Transformation in Alumina\\/YSZ Nanocomposite Coating Deposited by Suspension Plasma Spray Process  

Microsoft Academic Search

Suspension Plasma Spray process was used for deposition of pseudo-eutectic composition of alumina- yttria-stabilized zirconia as a potential thermal barrier coating using Mettech axial III torch. Process variables including feed and plasma parameters were altered to find their effects on the formation of phases in the composite coating. The in-flight particle velocity was found to be the crucial parameter on

F. Tarasi; M. Medraj; A. Dolatabadi; J. Oberste-Berghaus; C. Moreau

2009-01-01

316

Phase Formation and Transformation in Alumina\\/YSZ Nanocomposite Coating Deposited by Suspension Plasma Spray Process  

Microsoft Academic Search

Suspension Plasma Spray process was used for deposition of pseudo-eutectic composition of alumina-yttria-stabilized zirconia\\u000a as a potential thermal barrier coating using Mettech axial III torch. Process variables including feed and plasma parameters\\u000a were altered to find their effects on the formation of phases in the composite coating. The in-flight particle velocity was\\u000a found to be the crucial parameter on phase

F. Tarasi; M. Medraj; A. Dolatabadi; J. Oberste-Berghaus; C. Moreau

2010-01-01

317

Numerical Modeling in Radio Frequency Suspension Plasma Spray of Zirconia Powders  

Microsoft Academic Search

A comprehensive model was developed to investigate the suspension spraying for a radio frequency (RF) inductively coupled\\u000a plasma torch. Firstly, the electromagnetic field is solved with the Maxwell equations and validated by the analytical solutions.\\u000a Secondly, the plasma field with different power inputs is simulated by solving the governing equations of the fluid flow coupled\\u000a with the RF heating. Then,

Lijuan Qian; Jianzhong Lin; Hongbin Xiong

2010-01-01

318

Radio frequency (RF) suspension plasma sprayed ultra-fine hydroxyapatite (HA)\\/zirconia composite powders  

Microsoft Academic Search

Ultra-fine hydroxyapatite (HA)\\/ZrO2 composite powders was synthesised by radio frequency (RF) induction suspension plasma spray. A wet suspension of HA\\/ZrO2 was employed as feedstock. The suspension was injected axially into the RF plasma to produce the nano-composite powders, which were subsequently accumulated in cyclone collectors. The particle size and morphology was resolved by using the Zeta potential nano-particle size analyser,

Rajendra Kumar; P. Cheang; K. A. Khor

2003-01-01

319

Some Observations on Particle Size and Velocity Measurements Using Phase Doppler Anemometry in Plasma Spray  

Microsoft Academic Search

Applications of Phase-Doppler anemometry to the measurements of metal (nickel) particle size and velocity in the plasma spray process have been studied and analyzed with the aid of Mie scattering theory. The optimum optical settings used in two PDA systems were determined and tested experimentally. Measurements at cross-sectional planes 5 and 10 cm below the SG-100 (Miller) plasma gun were

J. Ma; S. C. M. Yu; H. W. Ng; Y. C. Lam

2004-01-01

320

A sputtered zirconia primer for improved thermal shock resistance of plasma-sprayed ceramic turbine seals  

Microsoft Academic Search

The development of plasma-sprayed yttria stabilized zirconia (YSZ) ceramic turbine blade tip seal components is discussed. The YSZ layers are quite thick (0.040 to 0.090 in.). The service potential of seal components with such thick ceramic layers is cyclic thermal shock limited. The most usual failure mode is ceramic layer delamination at or very near the interface between the plasma

R. C. Bill; J. Sovey; G. P. Allen

1981-01-01

321

Deposition of nanostructured photocatalytic zinc ferrite films using solution precursor plasma spraying  

Microsoft Academic Search

Deposition of pure spinet phase, photocatalytic zinc ferrite films on SS-304 substrates by solution precursor plasma spraying (SPPS) has been demonstrated for the first time. Deposition parameters such as precursor solution pH, concentration, film thickness, plasma power and gun-substrate distance were found to control physico-chemical properties of the film, with respect to their crystallinity, phase purity, and morphology. Alkaline precursor

Rekha Dom; G. Sivakumar; Neha Y. Hebalkar; Shrikant V. Joshi; Pramod H. Borse

2012-01-01

322

Biaxial residual stress states of plasma-sprayed hydroxyapatite coatings on titanium alloy substrate  

Microsoft Academic Search

Biaxial residual stress states of plasma-sprayed hydroxyapatite coatings (HACs) on titanium alloy substrate as a function of plasma power, powder feed rate and coating thickness were studied by X-ray `sin2? method. The Young's modulus of hydroxyapatite (HA), required for the stress analysis, was measured from the separated free coating by three-point bending test method. It was found that the directions

Y. C Yang; Edward Chang; B. H Hwang; S. Y Lee

2000-01-01

323

Sliding wear resistance of reactive plasma sprayed TiTiN coatings  

Microsoft Academic Search

The reactive plasma spraying (RPS) of titanium powders in a nitrogen containing plasma gas produces thick coatings characterised by microdispersed titanium nitride phases in a titanium matrix. In this paper, the wear resistance properties of TiTiN coatings deposited on carbon steel substrates by means of RPS technique are studied. Wear tests were performed in block-on-ring configuration and dry sliding conditions,

F. Borgioli; E. Galvanetto; F. P. Galliano; T. Bacci

2006-01-01

324

Improvement of wear resistance of plasma-sprayed molybdenum blend coatings  

NASA Astrophysics Data System (ADS)

The wear resistance of plasma sprayed molybdenum blend coatings applicable to synchronizer rings or piston rings was investigated in this study. Four spray powders, one of which was pure molybdenum and the others blended powders of bronze and aluminum-silicon alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that the phases formed during spraying were relatively homogeneously distributed in the molybdenum matrix. The wear test results revealed that the wear rate of all the coatings increased with increasing wear load and that the blended coatings exhibited better wear resistance than the pure molybdenum coating, although the hardness was lower. In the pure molybdenum coatings, splats were readily fractured, or cracks were initiated between splats under high wear loads, thereby leading to the decrease in wear resistance. On the other hand, the molybdenum coating blended with bronze and aluminum-silicon alloy powders exhibited excellent wear resistance because hard phases such as CuAl2 and Cu9Al4 formed inside the coating.

Ahn, Jeehoon; Hwang, Byoungchul; Lee, Sunghak

2005-06-01

325

Optimization of Atmospheric Plasma Spray Process Parameters using a Design of Experiment for Alloy 625 coatings  

NASA Astrophysics Data System (ADS)

Alloy 625 is a Ni-based superalloy which is often a good solution to surface engineering problems involving high temperature corrosion, wear, and thermal degradation. Coatings of alloy 625 can be efficiently deposited by thermal spray methods such as Air Plasma Spraying. As in all thermal spray processes, the final properties of the coatings are determined by the spraying parameters. In the present study, a D-optimal experimental design was used to characterize the effects of the APS process parameters on in-flight particle temperature and velocity, and on the oxide content and porosity in the coatings. These results were used to create an empirical model to predict the optimum deposition conditions. A second set of coatings was then deposited to test the model predictions. The optimum spraying conditions produced a coating with less than 4% oxide and less than 2.5% porosity. The process parameters which exhibited the most important effects directly on the oxide content in the coating were particle size, spray distance, and Ar flow rate. The parameters with the largest effects directly on porosity were spray distance, particle size, and current. The particle size, current, and Ar flow rate have an influence on particle velocity and temperature but spray distance did not have a significant effect on either of those characteristics. Thus, knowledge of the in-flight particle characteristics alone was not sufficient to control the final microstructure. The oxidation index and the melting index incorporate all the parameters that were found to be significant in the statistical analyses and correlate well with the measured oxide content and porosity in the coatings.

Azarmi, F.; Coyle, T. W.; Mostaghimi, J.

2008-03-01

326

Plasma density decay of vacuum discharges after current zero  

Microsoft Academic Search

In vacuum circuit breakers the post-arc current caused by the remaining ions and electrons in the contact gap is an indication of the residual ionization and its decay. It coincides with the formation of a positive space charge sheath in front of the new cathode, which grows toward the new anode. In a vacuum test chamber an arc (1.5-15 kA

G. Duning; Manfred Lindmayer

1999-01-01

327

Structural, Mechanical and Erosion Properties of Yttrium Oxide Coatings by Axial Suspension Plasma Spraying for Electronics Applications  

Microsoft Academic Search

Yttrium oxide (Y2O3) coatings have been prepared by axial suspension plasma spraying with fine powders. It is clarified that the coatings have\\u000a high hardness, low porosity, high erosion resistance against CF4 -containing plasma and retention of smooth eroded surface. This suggests that the axial suspension plasma spraying of Y2O3 is applicable to fabricating equipment for electronic devices, such as dry

Junya Kitamura; Zhaolin Tang; Hiroaki Mizuno; Kazuto Sato; Alan Burgess

2011-01-01

328

Changes in plasma composition during the expansion into the first vacuum stage of an inductively coupled plasma mass spectrometer  

Microsoft Academic Search

The effects of collisions on the composition of the plasma passing through the first vacuum stage of an inductively coupled plasma mass spectrometer were monitored in three sets of experiments. Rates of collisional quenching of an excited state in the neutral calcium atom were estimated from changes in experimental fluorescence lifetimes. Intensities from collisionally-assisted fluorescence provided evidence of energy transfer

Jeffrey H. Macedone; Paul B. Farnsworth

2006-01-01

329

Phase transformation and bond coat oxidation behavior of plasma-sprayed zirconia thermal barrier coating  

Microsoft Academic Search

ZrO2CeO2Y2O3 and ZrO2Y2O3 thermal barrier coatings were prepared using the air plasma spray process. Phase transformation in the ceramic top coating, bond coat oxidation and thermal barrier properties were investigated to compare ZrO2CeO2Y2O3 with ZrO2Y2O3 at 1300C under high temperature thermal cycles. In the as-sprayed condition, both coatings showed a 7?11% porosity fraction and typical lamellar structures formed by continuous

C. H. Lee; H. K. Kim; H. S. Choi; H. S. Ahn

2000-01-01

330

Abrasive wear behavior of cast iron coatings plasma-sprayed at different mild steel substrate temperatures  

NASA Astrophysics Data System (ADS)

Three kinds of cast iron coatings were prepared by atmospheric plasma spraying. During the spraying, the mild steel substrate temperature was controlled to be averagely 50, 180, and 240C, respectively. Abrasive wear tests were conducted on the coatings under a dry friction condition. It is found that the abrasive wear resistance is enhanced with the substrate temperature increasing. SEM observations show that the wear losses of the coatings during the wear tests mainly result from the spalling of the splats. Furthermore, the improved wear resistance of the coatings mainly owes to the formation of oxides and the enhancement in the mechanical properties with the substrate temperature increasing.

Xing, Ya-zhe; Wei, Qiu-lan; Jiang, Chao-ping; Hao, Jian-min

2012-08-01

331

High temperature in-situ XRD of plasma sprayed HA coatings.  

PubMed

The control of phase transformations in plasma sprayed hydroxyapatite (HA) coatings are critical to the clinical performance of the material. This paper reports the use of high temperature X-ray diffraction (HT-XRD) to study, in-situ, the phase transformations occurring in plasma sprayed HA coatings. The coatings were prepared using different spray power levels (net plasma power of 12 and 15 kW) and different starting powder size ranges (20-45; 45-75 microm). The temperature range employed was room temperature (approximately 26 degrees C) to 900 degrees C in normal atmosphere and pressure. High temperature differential scanning calorimetry (DSC) was also employed to investigate and determine the precise onset temperature of phase transformations during the recrystallization process. Results showed that actual onset of thermal degradation in the coating into other metastable phases like TTCP, beta-TCP and CaO occurred at 638 degrees C. The aforementioned phase transitions were independent of the selected spraying parameters. The degree of melting and thermal dissociation of HA actually determines the amount of calcium phosphate phases that are formed. A high power level of 15 kW produced a greater degree of melting, resulting in more CaO, TTCP and beta-TCP being formed as a result. PMID:11762329

Kweh, S W K; Khor, K A; Cheang, P

2002-01-01

332

Oxidation and particle deposition modeling in plasma spraying of Ti6Al4V\\/SiC fiber composites  

Microsoft Academic Search

Plasma spraying is known to be a promising process for the manufacturing of Ti\\/SiC long-fiber composites. However, some improvements\\u000a remain for this process to be applied in an industrial route. These include: oxygen contamination of the sprayed material\\u000a through that of titanium particles before and during spraying, damage to fibers due to a high level of thermal stresses induced\\u000a at

E. Cochelin; F. Borit; G. Frot; M. Jeandin; L. Decker; D. Jeulin; B. Al Taweel; V. Michaud; P. Nol

1999-01-01

333

Suspension Plasma Spraying of Alumina Coatings: Process and Coating Structure  

Microsoft Academic Search

Summary form only given. Due to the large volume fraction of the internal interfaces, coatings structured at the nanoscale should exhibit better properties than conventional coatings structured at the microscale. However, when processing by thermal plasmas such feedstock, several questions arise: (i) how feeding the plasma jet with nanosized powders? (ii) how keeping their nanostructured structures when melting them? (iii)

J.-F. Coudert; V. Rat; H. Ageorges; A. Denoirjean; P. Fauchais; G. Montavon

2007-01-01

334

Oxidation and ablation of polymers by vacuum-UV radiation from low pressure plasmas  

Microsoft Academic Search

Low-pressure glow discharge plasmas are increasingly used as an effective method for the surface modification of polymers; they can also serve in the laboratory to simulate low Earth orbital environment (LEO). Although Vacuum-Ultraviolet (VUV, ? < 200 nm) is an important component of plasma environment, only few studies have focused on its effects so far. The emission from low-pressure microwave

A. C. Fozza; J. Roch; J. E. Klemberg-Sapieha; A. Kruse; A. Hollnder; M. R. Wertheimer

1997-01-01

335

Multiple Ionization Of Metal Ions By ECR Heating Of Electrons In Vacuum Arc Plasmas  

SciTech Connect

A joint research and development effort has been initiated, whose ultimate goal is the enhancement the mean ion charge states in vacuum arc metal plasmas by a combination of a vacuum arc discharge and an electron cyclotron resonance (ECR) heating. Metal plasma was generated by a special vacuum arc mini-gun and injected into mirror magnetic trap. Plasma was pumped by high frequency gyrotron-generated microwave radiation (frequency 37.5 GHz, max power 100 kW, pulse duration 1.5 ms). Using of powerful microwaves makes it possible to sustain sufficient temperature of electrons needed for multiple ionizations at high plasma density (more then 1013 cm-3). Parameter of multiple ionization efficiency Ne{tau}i, where Ne is plasma density, {tau}i, is ion lifetime, in such a case could reach rather high value {approx}109 cm-3-s. In our situation {tau}i = Ltrap/Vi, where Ltrap is trap length, Vi is plasma gun flow velocity. The results have demonstrated substantial multiple ionization of metal ions (including metals with high melting temperature). For a metal (lead, platinum) plasma, ECR heating shifted the average ion charge up to 5+. Further increase of the ion charge states will be attained by increasing the vacuum arc plasma density and optimizing the ECR heating conditions.

Vodopyanov, A.V.; Golubev, S.V.; Mansfeld, D.A.; Razin, S.V. [Institute of Applied Physics (IAP RAS), Nizhny Novgorod (Russian Federation); Nikolaev, A.G.; Oks, E.M.; Savkin, K.P. [High Current Electronics Institute (HCEI RAS), Tomsk (Russian Federation)

2005-03-15

336

Fabrication of Nano-TiO 2 Coating for Dye-Sensitized Solar Cell by Vacuum Cold Spraying at Room Temperature  

Microsoft Academic Search

Deposition of nanocrystalline TiO2 coating at low temperature is becoming more attractive due to the possibility for continuous roll production of the coating\\u000a for assembly lines of dye-sensitized solar cell (DSC) at a low cost. In this study, porous nano-TiO2 coating was deposited by vacuum cold spraying (VCS) at room temperature on a conducting glass substrate using commercial\\u000a P25 nanocrystalline

Sheng-Qiang Fan; Chang-Jiu Li; Guan-Jun Yang; Ling-Zi Zhang; Jin-Cheng Gao; Ying-Xin Xi

2007-01-01

337

Processing-microstructure-properties relationships in small-particle plasma-sprayed ceramic coatings  

NASA Astrophysics Data System (ADS)

The objective of this study was to determine processing-microstructure-properties relationships for small-particle plasma-sprayed (SPPS) ceramic coatings. Plasma-sprayed yttria partially-stabilized zirconia (YSZ) coatings, which are used to protect superalloys from heat and the environment in turbine engines, and plasma-sprayed alumina coatings, which are being investigated as a potential replacement for chrome in corrosion protection applications, were fabricated using SPPS technology and their microstructure and pertinent properties were examined. The properties of plasma-sprayed YSZ and alumina coatings were investigated with designed experiments. The parameters varied include power, spray distance, total plasma gas flow, percent hydrogen in the plasma gas, injector angle, injector offset and carrier gas flow. The variations in thermal diffusivity, thermal conductivity, elastic modulus, and hardness for the YSZ SPPS coatings were found to correlate to the variations in density, which were related to the processing variables. It was found that surface roughness was related to the amount of splashing and debris associated with the single splats. In four-point bending strain tolerance and fatigue tests, the SPPS YSZ coatings showed very little acoustic emission activity, except in the case of tensile fatigue of a coating without network cracks. Small angle X-ray scattering experiments revealed that SPPS YSZ coatings have significantly less submicron intersplat porosity than conventional plasma-sprayed coatings, and that the pore and microcrack scattering area decreases with heat treatment due to the sintering of microcracks and small pores. The SPPS alumina coatings were optimized to produce a coating with excellent corrosion protection capabilities. It was found that the hardest SPPS alumina coatings did not provide the best corrosion protection due to unique porosity defect structures associated with surface bumps in the coatings. The surface bumps were associated with conditions that produced splats that had high amounts of splashing and debris. Significant improvements in properties, such as surface roughness, thermal conductivity, hardness, strain tolerance, fatigue resistance, and corrosion protection, were achieved for both the SPPS YSZ and SPPS alumina coatings compared to conventionally plasmasprayed YSZ and alumina coatings.

Mawdsley, Jennifer Renee

338

Effect of Deposition Rate on the Stress Evolution of Plasma-Sprayed Yttria-Stabilized Zirconia  

NASA Astrophysics Data System (ADS)

The deposition rate plays an important role in determining the thickness, stress state, and physical properties of plasma-sprayed coatings. In this article, the effect of the deposition rate on the stress evolution during the deposition (named evolving stress) of yttria-stabilized zirconia coatings was systematically studied by varying the powder feed rate and the robot-scanning speed. The evolving stress during the deposition tends to increase with the increased deposition rate, and this tendency was less significant at a longer spray distance. In some cases, the powder feed rate had more significant influence on the evolving stress than the robot speed. This tendency can be associated with a deviation of a local deposition temperature at a place where sprayed particles are deposited from an average substrate temperature. At a further higher deposition rate, the evolving stress was relieved by introduction of macroscopic vertical cracks as well as horizontal branching cracks.

Shinoda, Kentaro; Colmenares-Angulo, Jose; Valarezo, Alfredo; Sampath, Sanjay

2012-12-01

339

Deposition of titanium nitride and hydroxyapatite-based biocompatible composite by reactive plasma spraying  

NASA Astrophysics Data System (ADS)

Titanium nitride is a bioceramic material successfully used for covering medical implants due to the high hardness meaning good wear resistance. Hydroxyapatite is a bioactive ceramic that contributes to the restoration of bone tissue, which together with titanium nitride may contribute to obtaining a superior composite in terms of mechanical and bone tissue interaction matters. The paper presents the experimental results in obtaining composite layers of titanium nitride and hydroxyapatite by reactive plasma spraying in ambient atmosphere. X-ray diffraction analysis shows that in both cases of powders mixtures used (10% HA + 90% Ti; 25% HA + 75% Ti), hydroxyapatite decomposition occurred; in variant 1 the decomposition is higher compared with the second variant. Microstructure of the deposited layers was investigated using scanning electron microscope, the surfaces presenting a lamellar morphology without defects such as cracks or microcracks. Surface roughness values obtained vary as function of the spraying distance, presenting higher values at lower thermal spraying distances.

Ro?u, Radu Alexandru; ?erban, Viorel-Aurel; Bucur, Alexandra Ioana; Drago?, U?u

2012-02-01

340

Plasma processing and synthesis of materials  

SciTech Connect

These proceedings compile papers about plasma. Topics include: Plasma arc spraying, vacuum melting, plasma melters for nuclear waste vitrification, thermal degradation of metal oxides in plasma, electrohydrodynamics, laser-induced fluorescence, measurements of temperature in plasma, and modeling and diagnostics in plasma processing.

Apelian, D.; Szekely, J.

1987-01-01

341

High Charge State Ions Extracted from Metal Plasmas in the Transition Regime from Vacuum Spark to High Current Vacuum Arc  

SciTech Connect

Metal ions were extracted from pulsed discharge plasmas operating in the transition region between vacuum spark (transient high voltage of kV) and vacuum arc (arc voltage ~;; 20 V). At a peak current of about 4 kA, and with a pulse duration of 8 ?s, we observed mean ion charges states of about 6 for several cathode materials. In the case of platinum, the highest average charge state was 6.74 with ions of charge states as high as 10 present. For gold we found traces of charge state 11, with the highest average charge state of 7.25. At currents higher than 5 kA, non-metallic contaminations started to dominate the ion beam, preventing further enhancement of the metal charge states.

Yushkov, Georgy Yu.; Anders, A.

2008-06-19

342

The Effect of Spray-Dried Porcine Plasma on Growth Performance in the Early-Weaned Pig'f2  

Microsoft Academic Search

~ ~ ~ ~ ~ ~ ~~ ~ ABSTRACT: A total of 904 weanling pigs were used to investigate the effects of 1) spray-dried porcine plasma (SDPP), 2) blends of SDPP and spray-dried blood meal (SDBM), and 3) added dietary methionine in a SDPP-based diet on starter pig performance. In Exp. 1, 534 weanling pigs (initially 6.4 kg and 21

L. J. Kats; J. L. Nelssen; M. D. Tokach; R. D. Goodband; J. A. Hansen; J. L. Laurin

2009-01-01

343

Plasma Spray Synthesis Of Nanostructured V2O5 Films For Electrical Energy Storage  

SciTech Connect

We demonstrate for the first time, the synthesis of nanostructured vanadium pentoxide (V2O5) films and coatings using plasma spray technique. V2O5 has been used in several applications such as catalysts, super-capacitors and also as an electrode material in lithium ion batteries. In the present studies, V2O5 films were synthesized using liquid precursors (vanadium oxychloride and ammonium metavanadate) and powder suspension. In our approach, the precursors were atomized and injected radially into the plasma gun for deposition on the substrates. During the flight towards the substrate, the high temperature of the plasma plume pyrolyzes the precursor particles resulting into the desired film coatings. These coatings were then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Differential Scanning Calorimetry (DSC). Among the precursors, vanadium oxychloride gave the best results in terms of nanocrystalline and monophasic films. Spraying of commercial powder suspension yielded multi-phasic mixture in the films. Our approach enables deposition of large area coatings of high quality nanocrystalline films of V2O5 with controllable particle morphology. This has been optimized by means of control over precursor composition and plasma spray conditions. Initial electrochemical studies of V2O5 film electrodes show potential for energy storage studies.

Nanda, Jagjit [ORNL

2011-01-01

344

Transport of a vacuum arc plasma beam through the aperture of an annular anode  

Microsoft Academic Search

The plasma beam produced by a vacuum arc plasma source was injected into a cylindrical duct through an annular anode aperture. The plasma source consisted of a frustum cone-shaped Cu cathode, and either a 20-mm-thick annular Cu anode with aperture diameter D of 10, 17, 30, 40, or 50 mm, or 35 mm thick and D=40 or 50 mm. Magnetic

Vladimir N. Zhitomirsky; Raymond L. Boxman; Samuel Goldsmith

2005-01-01

345

Method and Process Development of Advanced Atmospheric Plasma Spraying for Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

Over the last few years, global economic growth has triggered a dramatic increase in the demand for resources, resulting in steady rise in prices for energy and raw materials. In the gas turbine manufacturing sector, process optimizations of cost-intensive production steps involve a heightened potential of savings and form the basis for securing future competitive advantages in the market. In this context, the atmospheric plasma spraying (APS) process for thermal barrier coatings (TBC) has been optimized. A constraint for the optimization of the APS coating process is the use of the existing coating equipment. Furthermore, the current coating quality and characteristics must not change so as to avoid new qualification and testing. Using experience in APS and empirically gained data, the process optimization plan included the variation of e.g. the plasma gas composition and flow-rate, the electrical power, the arrangement and angle of the powder injectors in relation to the plasma jet, the grain size distribution of the spray powder and the plasma torch movement procedures such as spray distance, offset and iteration. In particular, plasma properties (enthalpy, velocity and temperature), powder injection conditions (injection point, injection speed, grain size and distribution) and the coating lamination (coating pattern and spraying distance) are examined. The optimized process and resulting coating were compared to the current situation using several diagnostic methods. The improved process significantly reduces costs and achieves the requirement of comparable coating quality. Furthermore, a contribution was made towards better comprehension of the APS of ceramics and the definition of a better method for future process developments.

Mihm, Sebastian; Duda, Thomas; Gruner, Heiko; Thomas, Georg; Dzur, Birger

2012-06-01

346

Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers  

NASA Astrophysics Data System (ADS)

The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current commericial YSZ coatings generated using micron-sized powders. The coatings for this research were made via the recently developed suspension plasma spraying (SPS) process. With SPS, powders are suspended in a solvent containing dispersing agents; the suspension is then injected directly into a plasma flow that evaporates the solvent and melts the powder while transporting it to the substrate. Although related to the industrial TBC production method of air plasma spraying (APS), SPS has two important differences---the ability to spray sub-micron diameter ceramic particles, and the ability to alloy the particles with chemicals dissolved in the solvent. These aspects of SPS were employed to generate a series of coatings from suspensions containing 100 nm diameter YSZ powder particles, some of which were alloyed with neodymium and ytterbium ions from the solvent. The SPS coatings contained columnar structures not observed in APS TBCs; thus, a theory was developed to explain the formation of these features. The thermal conductivity of the coatings was tested to evaluate the effects of these unique microstructures and the effects of the alloying process. The results for samples in the as-sprayed and heat-treated conditions were compared to conventional YSZ TBCs. This comparison showed that, relative to APS YSZ coatings, the unalloyed SPS samples typically exhibited higher as-sprayed and lower heat-treated thermal conductivities. All thermal conductivity values for the alloyed samples were lower than conventional YSZ TBCs. The different thermal conduction behaviors were linked to the porosity and compositional properties of the coatings using immersion density, SEM, and synchrotron radiation characterization techniques.

van Every, Kent J.

347

Anisotropic electrical conduction from heterogeneous oxidation states in plasma sprayed TiO2 coatings  

NASA Astrophysics Data System (ADS)

Microstructural and electrical characterizations of air plasma sprayed TiO2 coatings were carried out to investigate the details of deoxidation during the spray process and the changes following air annealing. The coatings were found to behave as an n-type semiconductor indicating the presence of oxygen vacancies. Direct-current resistivity measurements in plane (?IP) and through thickness (?TT) of the coatings as a function of annealing time and temperature showed remarkably large anisotropies (=?TT/?IP) of up to 105. Impedance spectroscopy of the specimens coupled with microstructural analysis revealed that the origin of this anisotropy lies in the heterogeneous deoxidation and reoxidation behavior of the coatings. Due to rapid quenching, the high temperature deoxidation state is preserved in the splat boundaries making them more conductive than the bulk of the splat in the as-sprayed coating. Upon annealing in air, the splat boundaries get selectively oxidized due to faster surface diffusion of oxygen and become more insulating. This behavior, together with the layered morphology of plasma sprayed coatings, results in anisotropy.

Sharma, Atin; Gouldstone, Andrew; Sampath, Sanjay; Gambino, Richard J.

2006-12-01

348

Miniature pulsed vacuum arc plasma gun and apparatus for thin-film fabrication  

DOEpatents

A miniature (dime-size in cross-section) vapor vacuum arc plasma gun is described for use in an apparatus to produce thin films. Any conductive material can be layered as a film on virtually any substrate. Because the entire apparatus can easily be contained in a small vacuum chamber, multiple dissimilar layers can be applied without risk of additional contamination. The invention has special applications in semiconductor manufacturing. 8 figs.

Brown, I.G.; MacGill, R.A.; Galvin, J.E.; Ogletree, D.F.; Salmeron, M.

1998-11-24

349

Miniature pulsed vacuum arc plasma gun and apparatus for thin-film fabrication  

DOEpatents

A miniature (dime-size in cross-section) vapor vacuum arc plasma gun is described for use in an apparatus to produce thin films. Any conductive material can be layered as a film on virtually any substrate. Because the entire apparatus can easily be contained in a small vacuum chamber, multiple dissimilar layers can be applied without risk of additional contamination. The invention has special applications in semiconductor manufacturing.

Brown, Ian G. (Berkeley, CA); MacGill, Robert A. (Richmond, CA); Galvin, James E. (Emmeryville, CA); Ogletree, David F. (El Cerrito, CA); Salmeron, Miquel (El Cerrito, CA)

1998-01-01

350

Changes in plasma composition during the expansion into the first vacuum stage of an inductively coupled plasma mass spectrometer  

NASA Astrophysics Data System (ADS)

The effects of collisions on the composition of the plasma passing through the first vacuum stage of an inductively coupled plasma mass spectrometer were monitored in three sets of experiments. Rates of collisional quenching of an excited state in the neutral calcium atom were estimated from changes in experimental fluorescence lifetimes. Intensities from collisionally-assisted fluorescence provided evidence of energy transfer between excited states. Changes in analyte number density along the axis of the supersonic expansion in the first vacuum stage provided evidence that ion-electron recombination occurs to a significant extent during the expansion. Together, the experiments create a picture of the first vacuum stage in which collisions play an important role in shaping the composition of the plasma that is ultimately delivered to the mass analyzer.

Macedone, Jeffrey H.; Farnsworth, Paul B.

2006-09-01

351

The structure, properties and performance of plasma-sprayed beryllium for fusion applications  

SciTech Connect

Plasma-spray technology is under investigation as a method for producing high thermal conductivity beryllium coatings for use in magnetic fusion applications. Recent investigations have focused on optimizing the plasma-spray process for depositing beryllium coatings on damaged beryllium surfaces. Of particular interest has been optimizing the processing parameters to maximize the through-thickness thermal conductivity of the beryllium coatings. Experimental results will be reported on the use of secondary H{sub 2} gas additions to improve the melting of the beryllium powder and transferred-arc cleaning to improve the bonding between the beryllium coatings and the underlying surface. Information will also be presented on thermal fatigue tests which were done on beryllium coated ISX-B beryllium limiter tiles using 10 sec cycle times with 60 sec cooldowns and an International Thermonuclear Experimental Reactor (ITER) relevant divertor heat flux slightly in excess of 5 MW/m{sup 2}.

Castro, R.G.; Stanek, P.W.; Elliott, K.E. [and others

1995-09-01

352

Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation  

SciTech Connect

Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work. 13 references.

Berndt, C.C.; Miller, R.A.

1984-07-01

353

Preparation and in vitro evaluation of plasma-sprayed bioactive akermanite coatings.  

PubMed

Bioactive ceramic coatings on titanium (Ti) alloys play an important role in orthopedic applications. In this study, akermanite (Ca(2)MgSi(2)O(7)) bioactive coatings are prepared through a plasma spraying technique. The bonding strength between the coatings and Ti-6Al-4V substrates is around 38.7-42.2 MPa, which is higher than that of plasma sprayed hydroxyapatite (HA) coatings reported previously. The prepared akermanite coatings reveal a distinct apatite-mineralization ability in simulated body fluid. Furthermore, akermanite coatings support the attachment and proliferation of rabbit bone marrow mesenchymal stem cells (BMSCs). The proliferation rate of BMSCs on akermanite coatings is obviously higher than that on HA coatings. PMID:23159958

Yi, Deliang; Wu, Chengtie; Ma, Xubing; Ji, Heng; Zheng, Xuebin; Chang, Jiang

2012-11-16

354

Effects of humidity on the flow characteristics of a composite plasma spray powder  

NASA Astrophysics Data System (ADS)

The effects of environmental humidity on the flow characteristics of a multicomponent (composite) plasma spray powder have been investigated. Angular and spherical BaF2-CaF2 powder was fabricated by comminution and by atomization, respectively. The fluorides were blended with nichrome, chromia, and silver powders to produce a composite plasma spray feedstock. The tap density, apparent density, and angle of repose were measured at 50% relative humidity (RH). The flow of the powder was studied from 2 to 100% RH. The results suggest that the feedstock flow is only slightly degraded with increasing humidity below 66% RH and is more affected above 66% RH. There was no flow above 90% RH except with narrower particle size distributions of the angular fluorides, which allowed flow up to 95% RH. These results offer guidance that enhances the commercial potential for this material system.

Stanford, Malcolm K.; Dellacorte, Christopher

2006-03-01

355

Features of calcium phosphate plasma-sprayed coatings: an in vitro study.  

PubMed

Factors involved with the plasma-spray coating procedure, such as starting powder compound (fluorapatite, hydroxylapatite, magnesium-whitlockite, or tetra-calcium phosphate), powder particle distribution 1-45 or 1-125 microns), powder port gun (port 2 or 6), and post-heat treatment of 1 h at 600 degrees C, were examined for their effects on crystallinity and solubility/stability of the coating. From solubility tests, X-ray diffractometry, and scanning microscopy studies, the solubility and crystallinity were found to be dependent on Ca/P ratio, particle distribution, and post-heat treatment. The post-heat treatment influenced the degree of both crystallinity and solubility. The plasma-spray powder port factor for the hydroxylapatite coatings was not significant. Incubation in buffer of the coatings introduced precipitation at the surfaces of all non-heat-treated coatings except fluorapatite. No precipitation could be observed in any of the heat-treated coatings. PMID:7983094

Klein, C P; Wolke, J G; de Blieck-Hogervorst, J M; de Groot, K

1994-08-01

356

Analysis of powder particles of high carbon cast iron after air plasma spraying  

NASA Astrophysics Data System (ADS)

Structure and phase analysis of high carbon cast iron prepared by plasma spraying was performed using X-ray diffraction and Mssbauer spectroscopy. The sprayed powder particles were trapped in liquid nitrogen to fix their composition during the flight from the plasma torch. The results show decarburization and oxidation of the powder. The carbon content decrease is more pronounced on surfaces of the particles. The fresh powder exhibits an anomalous magnetic transition from ferromagnetic to paramagnetic state during the sample cooling from room temperature down to 28 K. This effect was explained as result of high concentration of defects and strains. The long time ageing at room temperature caused transition to more stable phase composition and diminishing of the anomalous magnetic transition.

Schneeweiss, O.; Volenk, K.

2009-02-01

357

A design of experiment study of plasma sprayed alumina-titania coatings  

SciTech Connect

An experimental study of the plasma spraying of alumina-titania powder is presented in this paper. This powder system is being used to fabricate heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. Coating experiments were conducted using a Taguchi fractional-factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments in order to display the range of plasma processing conditions and their effect on the resultant coating. The coatings were characterized by hardness and electrical tests, image analysis, and optical metallography. Coating qualities are discussed with respect to dielectric strength, hardness, porosity, surface roughness, deposition efficiency, and microstructure. The attributes of the coatings are correlated with the changes in operating parameters.

Steeper, T.J. [Du Pont de Nemours (E.I.) and Co., Aiken, SC (United States). Savannah River Lab.; Varacalle, D.J. Jr.; Wilson, G.C. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Riggs, W.L. II [Tubal Cain Co., Loveland, OH (United States); Rotolico, A.J.; Nerz, J.E. [Metco/Perkin-Elmer, Westbury, NY (United States)

1992-08-01

358

A design of experiment study of plasma sprayed alumina-titania coatings  

SciTech Connect

An experimental study of the plasma spraying of alumina-titania powder is presented in this paper. This powder system is being used to fabricate heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. Coating experiments were conducted using a Taguchi fractional-factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments in order to display the range of plasma processing conditions and their effect on the resultant coating. The coatings were characterized by hardness and electrical tests, image analysis, and optical metallography. Coating qualities are discussed with respect to dielectric strength, hardness, porosity, surface roughness, deposition efficiency, and microstructure. The attributes of the coatings are correlated with the changes in operating parameters.

Steeper, T.J. (Du Pont de Nemours (E.I.) and Co., Aiken, SC (United States). Savannah River Lab.); Varacalle, D.J. Jr.; Wilson, G.C. (EG and G Idaho, Inc., Idaho Falls, ID (United States)); Riggs, W.L. II (Tubal Cain Co., Loveland, OH (United States)); Rotolico, A.J.; Nerz, J.E. (Metco/Perkin-Elmer, Westbury, NY (United States))

1992-01-01

359

High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma  

SciTech Connect

A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 {mu}s, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed.

Vodopyanov, A. V.; Golubev, S. V.; Khizhnyak, V. I.; Mansfeld, D. A.; Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Vizir, A. V.; Yushkov, G. Yu. [Institute of Applied Physics, Russian Academy of Science, Nizhniy Novgorod 603950 (Russian Federation); High Current Electronics Institute, Siberian Division, Russian Academy Science, Tomsk 634055 (Russian Federation)

2008-02-15

360

High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma.  

PubMed

A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 micros, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed. PMID:18315170

Vodopyanov, A V; Golubev, S V; Khizhnyak, V I; Mansfeld, D A; Nikolaev, A G; Oks, E M; Savkin, K P; Vizir, A V; Yushkov, G Yu

2008-02-01

361

Eddy currents in a nonperiodic vacuum vessel induced by axisymmetric plasma motion  

SciTech Connect

A method is described for calculating the two-dimensional trajectory of a vertically or horizontally unstable axisymmetric tokamak plasma in the presence of a resistive vacuum vessel. The vessel is not assumed to have toroidal symmetry. The plasma is represented by a current-filament loop that is free to move vertically and to change its major radius. Its position is evolved in time self-consistently with the vacuum vessel eddy currents. The plasma current, internal inductance, and poloidal beta can be specified functions of time so that eddy currents resulting from a disruption can be modeled. The vacuum vessel is represented by a set of current-filaments whose positions and orientations are chosen to model the dominant eddy current paths. Although the specific application is to TFTR, the present model is of general applicability. 7 refs., 4 figs., 2 tabs.

DeLucia, J.

1985-12-01

362

Use of Polycarbonate Vacuum Vessels in High-Temperature Fusion-Plasma Research  

SciTech Connect

Magnetic fusion energy (MFE) research requires ultrahigh-vacuum (UHV) conditions, primarily to reduce plasma contamination by impurities. For radiofrequency (RF)-heated plasmas, a great benefit may accrue from a non-conducting vacuum vessel, allowing external RF antennas which avoids the complications and cost of internal antennas and high-voltage high-current feedthroughs. In this paper we describe these and other criteria, e.g., safety, availability, design flexibility, structural integrity, access, outgassing, transparency, and fabrication techniques that led to the selection and use of 25.4-cm OD, 1.6-cm wall polycarbonate pipe as the main vacuum vessel for an MFE research device whose plasmas are expected to reach keV energies for durations exceeding 0.1 s

B. Berlinger, A. Brooks, H. Feder, J. Gumbas, T. Franckowiak and S.A. Cohen

2012-09-27

363

COMPARISON OF THERMAL PROPERTIES OF THERMAL BARRIER COATING DEPOSITED ON IN738 USING STANDARD AIR PLASMA SPRAY WITH 100HE PLASMA SPRAY SYSTEM  

SciTech Connect

A typical blade material is made of Nickel super alloy and can bear temperatures up to 950C. But the operating temperature of a gas turbine is above the melting point of super alloy nearly at 1500C. This could lead to hot corrosions, high temperature oxidation, creep, thermal fatigue may takes place on the blade material. Though the turbine has an internal cooling system, the cooling is not adequate to reduce the temperature of the blade substrate. Therefore to protect the blade material as well as increase the efficiency of the turbine, thermal barrier coatings (TBCs) must be used. A TBC coating of 250 ?m thick can reduce the temperature by up to 200 C. Air Plasma Spray Process (APS) and High Enthalpy Plasma Spray Process (100HE) were the processes used for coating the blades with the TBCs. Because thermal conductivity increases with increase in temperature, it is desired that these processes yield very low thermal conductivities at high temperatures in order not to damage the blade. An experiment was carried out using Flash line 5000 apparatus to compare the thermal conductivity of both processes.The apparatus could also be used to determine the thermal diffusivity and specific heat of the TBCs. 75 to 2800 K was the temperature range used in the experimentation. It was found out that though 100HE has high deposition efficiency, the thermal conductivity increases with increase in temperatures whiles APS yielded low thermal conductivities.

Uppu, N.; Mensah, P.F.; Ofori, D.

2006-07-01

364

A study of wear resistance of plasma-sprayed and laser-remelted coatings on aluminium alloy  

Microsoft Academic Search

Two kinds of alloys NiCrBSi and NiCrBSi+WC were plasma sprayed onto aluminium alloy. The coatings were remelted successively with a CO2 laser. A comparison of the wear resistance properties of both laser-treated and plasma-sprayed samples with those of aluminium alloy was conducted. A scanning electron microscope (SEM) was used to analyse wear phenomena of samples. Experimental results showed that the

G. Y. Liang; T. T. Wong; J. M. K. MacAlpine; J. Y. Su

2000-01-01

365

Effects of Spray-Dried Animal Plasma in Calf Milk Replacer on Health and Growth of Dairy Calves1  

Microsoft Academic Search

Male Holstein calves (n = 120) purchased from local dairy farms were fed one of three calf milk replacers for 42 d. Experimental milk replacers were formulated to contain whey protein concentrate (WPC) as the pri- maryproteinsourceorWPCplus5%spray-driedbovine plasma (SDBP) or spray-dried porcine plasma (SDPP). The SDPP was heated to remove heat-insoluble materi- als and provide products with similar IgG content.

J. D. Quigley III; T. M. Wolfe

2003-01-01

366

Structure, mechanical performance and electrochemical characterization of plasma sprayed SiO 2\\/Ti-reinforced hydroxyapatite biomedical coatings  

Microsoft Academic Search

For achieving an excellent bioactivity and mechanical properties, silica and titanium-reinforced hydroxyapatite composite coatings were deposited onto 304 SUS substrate by using a gas-tunnel plasma spraying system. A commercial HA powder of average size 1045?m was blended with fused amorphous silica and titanium powders with HA:SiO2:Ti wt.% ratios of 75:15:10 respectively. The mixed powders have been plasma sprayed at various

M. F. Morks; N. F. Fahim; A. Kobayashi

2008-01-01

367

Plasma-Etching of Spray-Coated Single-Walled Carbon Nanotube Films for Biointerfaces  

NASA Astrophysics Data System (ADS)

We present an effective method for the batch fabrication of miniaturized single-walled carbon nanotube (SWCNT) film electrodes using oxygen plasma etching. We adopted the approach of spray-coating for good adhesion of the SWCNT film onto a pre-patterned Pt support and used O2 plasma patterning of the coated films to realize efficient biointerfaces between SWCNT surfaces and biomolecules. By these approaches, the SWCNT film can be easily integrated into miniaturized electrode systems. To demonstrate the effectiveness of plasma-etched SWCNT film electrodes as biointerfaces, Legionella antibody was selected as analysis model owing to its considerable importance to electrochemical biosensors and was detected using plasma-etched SWCNT film electrodes and a 3,3',5,5'-tetramethyl-benzidine dihydrochloride/horseradish peroxidase (TMB/HRP) catalytic system. The response currents increased with increasing concentration of Legionella antibody. This result indicates that antibodies were effectively immobilized on plasma-etched and activated SWCNT surfaces.

Kim, Joon Hyub; Lee, Jun-Yong; Min, Nam Ki

2012-08-01

368

Three-dimensional numerical simulation of splat formation on substrates in plasma spraying  

Microsoft Academic Search

Plasma sprayed coatings are built up by the accumulation of splats formed by the impacting, spreading and solidifying of molten\\u000a droplets on the substrate. A three-dimensional computational model including heat transfer and solidification is established\\u000a to simulate the formation process of a single splat using the computational fluid dynamics (CFD) software, FLUENT. The fluid\\u000a flow and energy equations are discretized

Chang-wen Cui; Qiang Li

2011-01-01

369

Adhesion strength of plasma-sprayed hydroxyapatite coatings on laser gas-nitrided pure titanium  

Microsoft Academic Search

A layer of bioceramic HA was coated on laser gas-nitrided pure titanium and grit-blasted pure titanium substrates using plasma-spraying technique, respectively. X-ray diffraction analysis showed that the microstructures of the coating were mainly composed of HA, amorphous calcium phosphate (ACP) and some minute phases of tricalcium phosphate (TCP, ?-TCP and ?-TCP), tetracalcium phosphate (TTCP) and calcium oxide (CaO). The experimental

Sen Yang; H. C. Man; Wen Xing; Xuebin Zheng

2009-01-01

370

Finite element analysis of residual stress in plasma-sprayed ceramic  

SciTech Connect

Residual stress in a ZrO2-Y2O3 ceramic coating resulting from the plasma spraying operation is calculated. The calculations were done using the finite element method. Both thermal and mechanical analysis were performed. The resulting residual stress field was compared to the measurements obtained by Hendricks and McDonald. Reasonable agreement between the predicted and measured moment occurred. However, the resulting stress field is not in pure bending. 14 references.

Mullen, R.L.; Hendricks, R.C.; Mcdonald, G.

1985-08-01

371

Plasma spray coating of fly ash pre-mixed with aluminium powder deposited on metal substrates  

Microsoft Academic Search

Plasma spray technology has the advantage of being able to process low-grade-ore minerals to produce value-added products, and also to deposit ceramics, metals and a combination of these, generating homogenous coatings with the desired microstructure on a range of substrate. The present work deals with the development of a ceramic composite coating on metal substrates using fly ash (the thermal

S. C Mishra; K. C Rout; P. V. A Padmanabhan; B Mills

2000-01-01

372

Influence of particle parameters at impact on splat formation and solidification in plasma spraying processes  

Microsoft Academic Search

A measurement system consisting of two high- speed two- color pyrometers was used to monitor the flattening degree and cooling\\u000a rate of zirconia particles on a smooth steel substrate at 75 or 150 C during plasma spray deposition. This instrument provided\\u000a data on the deformation behavior and freezing of a particle when it impinged on the surface, in connection with

M. Vardelle; A. Vardelle; A. C. Leger; P. Fauchais; D. Gobin

1995-01-01

373

Superconducting and structural properties of plasma sprayed YBaCuO layers deposited on metallic substrates  

Microsoft Academic Search

The properties of plasma sprayed Y-Ba-Cu-O coatings deposited on metallic substrates are studied. Stainless steel, nickel steels and pure nickel are used as substrate. Y-Ba-Cu-O deposited on stainless steel and nickel steel reacts with the substrate. This interaction can be suppressed by using an yttria-stabilized zirconia (YsZ) diffusion barrier. However, after heat treatment the Y-Ba-Cu-O layers on YsZ show cracks

H. Hemmes; D. Jger; M. Smithers; Veer van der J; D. Stover; H. Rogalla

1993-01-01

374

Plasma-sprayed glass-ceramic coatings on ceramic tiles: microstructure, chemical resistance and mechanical properties  

Microsoft Academic Search

This article reports the characterisation and optimisation of glass-ceramic coatings plasma-sprayed on traditional ceramic substrates, dealing with microstructures, chemical resistance, and superficial mechanical properties. A CaOZrO2SiO2 (CZS) frit, capable of complete crystallization after proper thermal treatment, has been employed: due to its refractory nature, its firing temperature in a traditional process would be unbearable for common substrates. The frit was

Giovanni Bolelli; Valeria Cannillo; Luca Lusvarghi; Tiziano Manfredini; Cristina Siligardi; Cecilia Bartuli; Alessio Loreto; Teodoro Valente

2005-01-01

375

Anisotropic thermal conductivities of plasma-sprayed thermal barrier coatings in relation to the microstructure  

Microsoft Academic Search

Anisotropic thermal conductivities of the plasma-sprayed ceramic coating are explicitly expressed in terms of the microstructural\\u000a parameters. The dominant features of the porous space are identified as strongly oblate (cracklike) pores that tend to be\\u000a either parallel or normal to the substrate. The scatter in pore orientations is shown to have a pronounced effect on the effective\\u000a conductivities. The established

Igor Sevostianov; Mark Kachanov

2000-01-01

376

Pyrometer system for monitoring the particle impact on a substrate during a plasma spray process  

Microsoft Academic Search

A measurement system consisting of two high-speed two-colour pyrometers is described; the system is suitable for monitoring the flattening and cooling of particles on a substrate during plasma spray deposition. The first double-wavelength optical fibre pyrometer is focused 2 mm before the substrate and the other is focused on the substrate surface. The present instrument provides data on the temperature,

M. Vardelle; A. Vardelle; P. Fauchais; C. Moreau

1994-01-01

377

Pulsed laser sealing of plasma-sprayed layers of 8 wt % yttria stabilized zirconia  

Microsoft Academic Search

Results are reported of the laser surface sealing of plasma-sprayed layers of 8 wt% yttria partially stabilized zirconia (YPSZ) using pulsed treatments with powers of 0.4 and 1 kW. The structural features of the processed material were examined for a range of laser processing parameters including preheating, processing temperature and power density. By controlling the processing parameters it was possible

K. Mohammed Jasim; R. D. Rawlings; D. R. F. West

1992-01-01

378

Thermophysical, mechanical and microstructural characterization of aged free-standing plasma-sprayed zirconia coatings  

Microsoft Academic Search

The effect of porosity on the thermal diffusivity and elastic modulus has been studied on artificially aged, free-standing thermal barrier coatings (TBCs) produced by air plasma spray (APS). The activation energy of the sintering phenomenon was estimated from the variation in diffusivity with time and temperature. X-ray diffraction was used to evaluate the phase stability of 7wt.% yttria partially stabilized

F. Cernuschi; P. G. Bison; S. Marinetti; P. Scardi

2008-01-01

379

In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components  

SciTech Connect

A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

380

Novel structured yttria-stabilized zirconia coatings fabricated by hybrid thermal plasma spraying  

Microsoft Academic Search

Yttria-stabilized ZrO2 powders with initial sizes of 522 ?m were chsosen as feedstock for hybrid thermal plasma deposition. At 100kW RF input power, the microstructures of the deposited coatings varied from mostly sprayed splats to physical-vapor-deposited nanostructures when the powder feeding rate was reduced from 4 to 1 g\\/min. At a powder feeding rate of 2 g\\/min, a peculiar layered

H. Huang; K. Eguchi; T. Yoshida

2003-01-01

381

Metallurgical characterization of plasma-sprayed tungsten carbide-cobalt coatings  

Microsoft Academic Search

Four commercial WC-Co powders prepared from different manufacturing techniques and having variations in binder metal content (11-20% wt), and WC grain size (1-15 ..mu.. m). Using identical process parameters, these powders were plasma sprayed, and the resulting coatings were characterized for changes in chemistry, phase content, and microstructural parameters. Finally, the coatings were evaluated for resistance to abrasion, sliding wear,

Rangaswamy

1987-01-01

382

Pressure-Based Liquid Feed System for Suspension Plasma Spray Coatings  

Microsoft Academic Search

Thermal spraying with liquid-based feedstocks demonstrated a potential to produce coatings with new and enhanced characteristics. A liquid delivery system prototype was developed and tested in this study. The feeder is based on the 5MPE platform and uses a pressure setup to optimally inject and atomize liquid feedstock into a plasma plume. A novel self-cleaning apparatus is incorporated into the

Elliot M. Cotler; Dianying Chen; Ronald J. Molz

2011-01-01

383

Plasma Spray Synthesis Of Nanostructured V2O5 Films For Electrical Energy Storage  

Microsoft Academic Search

We demonstrate for the first time, the synthesis of nanostructured vanadium pentoxide (V2O5) films and coatings using plasma spray technique. V2O5 has been used in several applications such as catalysts, super-capacitors and also as an electrode material in lithium ion batteries. In the present studies, V2O5 films were synthesized using liquid precursors (vanadium oxychloride and ammonium metavanadate) and powder suspension.

Nanda; Jagjit

2011-01-01

384

Pressure-Based Liquid Feed System for Suspension Plasma Spray Coatings  

Microsoft Academic Search

Thermal spraying with liquid-based feedstocks demonstrated a potential to produce coatings with new and enhanced characteristics.\\u000a A liquid delivery system prototype was developed and tested in this study. The feeder is based on the 5MPE platform and uses\\u000a a pressure setup to optimally inject and atomize liquid feedstock into a plasma plume. A novel self-cleaning apparatus is\\u000a incorporated into the

Elliot M. Cotler; Dianying Chen; Ronald J. Molz

2011-01-01

385

Fabrication and electrochemical performance of solid oxide fuel cell components by atmospheric and suspension plasma spray  

Microsoft Academic Search

The theory of functionally graded material (FGM) was applied in the fabrication process of PEN (Positive-Electrolyte-Negative), the core component of solid oxide fuel cell (SOFC). To enhance its electrochemical performance, the functionally graded PEN of planar SOFC was prepared by atmospheric plasma spray (APS). The cross-sectional SEM micrograph and element energy spectrum of the resultant PEN were analyzed. Its interface

Wei-sheng XIA; Yun-zhen YANG; Hai-ou ZHANG; Gui-lan WANG

2009-01-01

386

Recent Developments in Suspension Plasma Sprayed Titanium Oxide and Hydroxyapatite Coatings  

Microsoft Academic Search

The paper aims at reviewing of the recent studies related to the development of suspension plasma sprayed TiO2 and Ca5(PO4)3OH (hydroxyapatite, HA) coatings as well as their multilayer composites obtained onto stainless steel, titanium and aluminum\\u000a substrates. The total thickness of the coatings was in the range 10 to 150?m. The suspensions on the base of distilled water,\\u000a ethanol and

R. Jaworski; L. Pawlowski; C. Pierlot; F. Roudet; S. Kozerski; F. Petit

2010-01-01

387

Liquid plasma sprayed coatings of yttria-stabilized zirconia for SOFC electrolytes  

Microsoft Academic Search

To achieve solid oxide fuel cells (SOFC) at reduced costs, the atmospheric plasma spray (APS) process could be an attractive\\u000a technique. However, to make dense and thin layers as needed for electrolytes, a suspension is preferably implemented as a\\u000a feedstock material instead of a conventional powder. Suspensions of yttria-stabilized zirconia particles in methanol have\\u000a been prepared with various solid loadings

R. Rampon; F.-L. Toma; G. Bertrand; C. Coddet

2006-01-01

388

Suspension plasma spraying of TiO 2 for the manufacture of photovoltaic cells  

Microsoft Academic Search

Highly porous TiO2 coatings have been produced by suspension plasma spraying on ITO coated glass substrates. The deposition process could be optimized so that fine\\/nano grained highly porous coatings were obtained. Mean crystallite sizes well below 50nm could be achieved in the coatings for the anatase phase.Special emphasis was on the establishment of a high volume fraction of the desired

Robert Vaen; Zeng Yi; Holger Kaner; Detlev Stver

2009-01-01

389

Preparation and antibacterial properties of plasma sprayed nano-titania\\/silver coatings  

Microsoft Academic Search

In this work, plasma sprayed nano-titania\\/silver coatings were deposited on titanium substrates to obtain an implant material having excellent antibacterial property. The surface characteristics of nano-titania\\/silver coatings were investigated by scanning electron microscopy, energy dispersive spectrometer, optical emission spectrometry and X-ray diffraction. The bioactivity of nano-titania\\/silver coatings was examined by simulated body fluid soaking test. The antibacterial activity against Escherichia

Baoe Li; Xuanyong Liu; Fanhao Meng; Jiang Chang; Chuanxian Ding

2009-01-01

390

In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components  

DOEpatents

A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

391

Mechanical properties of solution-precursor plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The microstructure of thermal barrier coatings (TBCs) of 7wt.% Y2O3 stabilized ZrO2 (7YSZ) deposited using the solution-precursor plasma spray (SPPS) method has: (i) controlled porosity, (ii) vertical cracks, and (iii) lack of large-scale splat boundaries. An unusual feature of such SPPS TBCs is that they are well-adherent in ultra-thick forms (~4mm thickness), where most other types of ultra-thick ceramic coatings

Amol D. Jadhav; Nitin P. Padture

2008-01-01

392

Axial variation of electron number density in thermal plasma spray jets  

Microsoft Academic Search

The electron number density has been measured in a plasma spray torch using Stark broadening of H{beta} and Ar-I (430 nm) line. A small amount of hydrogen (1% by volume in argon gas) was introduced to study the H{beta} line profile. Axial variation of electron number density has been determined up to a distance of 20 mm from the nozzle

N. K. Joshi; S. N. Sahasrabudhe; K. P. Sreekumar; N. Venkatramani

2003-01-01

393

Spinel oxides growing on Fe-Cr alloy particles during plasma spraying  

Microsoft Academic Search

Oxidation reactions during plasma spraying of metallic powders give rise to oxide crusts on powder particle surfaces. The\\u000a first oxidation stage occurs in flight of molten particles. It is usually followed by the second stage after hitting a substrate.\\u000a To investigate the oxidation products immediately after the first stage, abrupt stopping of in-flight oxidation is possible\\u000a by trapping and quenching

O. Schneeweiss; J. Dubsk; K. Volenk; J. Had; J. Leitner; M. Seberni

2001-01-01

394

S-Band Lithium Ferrite Phase Shifters by Arc Plasma Spraying  

Microsoft Academic Search

The arc plasma fabrication of ferrite phase shifters has been extended from C-band to S-band. Two S-band lithium ferrite compositions, Ampex 3-601 and Ampex 3-750, were sprayed around a dielectric for phase shifter applications in the 3 to 4 GHz range. The larger dielectric and greater ferrite wall thickness of the S-band phase shifter necessitated a moderation of the arc

V. Wade; R. Babbitt

1976-01-01

395

THE THERMAL SHOCK ENDURANCE OF A PLASMA SPRAYED ZrO2 COATING ON STEEL  

Microsoft Academic Search

By addition of a Ni-Cr undercoating to a steel substrate, a ZrO2; coating with high thermal shock endurance was produced. This coating resists to an initial quenching temperature gradient of 1000K. The plasma spray coating material is 7wt%-CaO stabilized ZrO2 powder. The chemical composition and the thermal expansion coefficient of the base steel, and also the Ni-Cr undercoating were evaluated

T. Kurushivna; K. Ishizaki

1993-01-01

396

Characterization of crystallographic texture in plasma-sprayed splats by electron-backscattered diffraction  

Microsoft Academic Search

The surface microtexture of splats deposited by atmospheric dc plasma spraying was studied by the electron-backscattered diffraction method. The examined splats were yttria-stabilized zirconia (YSZ) and nickel deposited onto a mirror-polished stainless steel substrate preheated to 500K. The YSZ splats exhibited a disk-shaped morphology and had a peculiar <111> fiber texture in their peripheral region; the fiber axes were perpendicular

Kentaro Shinoda; Masahiko Demura; Hideyuki Murakami; Seiji Kuroda; Sanjay Sampath

2010-01-01

397

Thermal conductivity and phase evolution of plasma-sprayed multilayer coatings  

Microsoft Academic Search

Multilayer coatings were prepared using small-particle plasma spray to investigate the effect of interfaces on thermal conductivity and phase stability. Monolithic and multilayer alumina and yttria partially-stabilized zirconia coatings, with 0, 3, 20, and 40 interfaces in 200380 m thick coatings were studied. Thermal conductivity was determined for the temperature range 25 C to 1200 C using the laser flash

Y. Jennifer Su; Hsin Wang; Wally D. Porter; A. R. De Arellano Lopez; K. T. Faber

2001-01-01

398

Apatite\\/titanium composite coatings on titanium or titanium alloy by RF plasma-spraying process  

Microsoft Academic Search

To improve adhesiveness of hydroxapatite (HA) coatings to the titanium substrates, a HA\\/Ti composite was formed on substrates using a radio-frequency (RF) plasma spraying process. This process would reduce the residual stress caused by the large difference between the linear thermal expansion coefficient of the substrate and of HA. The HA\\/Ti composites were prepared by controlled feeding ratio of HA

M. Inagaki; Y Yokogawa; T Kameyama

2001-01-01

399

Nitride formation in synthesis of titanium aluminide matrix composite coatings by reactive RF plasma spraying  

Microsoft Academic Search

This paper presents an in situ process to form intermetallic matrix composite coatings by reactive radio frequency (RF) plasma spraying with premixed elemental\\u000a powder. The typical splat morphology of impinged titanium droplets on a stainless steel substrate is a disk with an outer\\u000a peripheral fringe. If the supplied titanium powder size becomes finer or the nitrogen partial pressure in the

Yoshiki Tsunekawa; Makoto Hiromura; Masahiro Okumiya

2000-01-01

400

On characterisation of wire-arc-plasma-sprayed Ni on alumina substrate  

SciTech Connect

A study was carried out on metal-ceramic bonding produced by the technique of wire-arc-plasma spraying of Ni on Al{sub 2}O{sub 3} substrate. The Ni layer and the Ni/Al{sub 2}O{sub 3} interface were characterised using optical and electro-optic techniques. The plasma-deposited Ni layer shows a uniform lamellar microstructure throughout the cross-section. The metal-ceramic interface was found to be well bonded with no pores, flaws or cracks in the as-sprayed condition. The optical metallography and concentration profiles established with the help of an electron probe microanalyser confirmed the absence of any intermediate phase at the interface. An annealing treatment at 1273 K for 24 h on the plasma-coated samples did not result in formation of any intermetallic compound or spinel at the Ni/Al{sub 2}O{sub 3} interface. This indicates that the oxygen picked up by Ni during the spraying operation is less than the threshold value required to form the spinel NiAl{sub 2}O{sub 4}.

Laik, A. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Chakravarthy, D.P. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kale, G.B. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)]. E-mail: gbkale@apsara.barc.ernet.in

2005-08-15

401

Influence of impact parameters of zirconia droplets on splat formation and morphology in plasma spraying  

NASA Astrophysics Data System (ADS)

In this study, the effects of the impact parameters, namely, the diameter d0, velocity V0, and temperature T0, of an impacting droplet of yttria-stabilized zirconia (YSZ) on splat morphology have been investigated systematically under plasma spraying conditions. In particular, fully molten droplets of 30-90 ?m in d0 that impact on a preheated quartz glass substrate at V0 of 10-70 m/s have been examined via hybrid plasma spraying. The degree of flattening of final splat morphology, ?, was found to be predicted by the relationship ?=0.43Re1/3, where Re is the Reynolds number. The dimensionless spreading time of droplets, ts*=tsV0/d0, was distributed around 2.7, where ts is the spreading time of the droplet. The ideal maximum spread factor derived from the splat height was approximately proportional to Re1/4. The latter two findings suggest that the analytical model developed by Pasandideh-Fard et al. [Phys. Fluids 8, 650 (1996)] can be applied to the droplet impact in plasma spraying especially for the case of YSZ. In addition, the thermal contact resistance of disk shaped splats decreased with the increase of V0 within the range of 10-5-10-6 m2 K/W.

Shinoda, Kentaro; Koseki, Toshihiko; Yoshida, Toyonobu

2006-10-01

402

Evaluating microhardness of plasma sprayed Al2O3 coatings using Vickers indentation technique  

NASA Astrophysics Data System (ADS)

In this work, the microhardness of plasma sprayed Al2O3 coatings was evaluated using the Vickers indentation technique, and the effects of measurement direction, location and applied loads were investigated. The measured data sets were then statistically analysed employing the Weibull distribution to evaluate their variability within the coatings. It was found that the Vickers hardness (VHN) increases with decreasing applied indenter load, which can be explained in terms of Kick's law and the Meyer index k of 1.93, as well as relating to the microstructural characteristics of plasma sprayed coatings and the elastic recovery taking place during indentation. In addition, VHN, measured on the cross section of coatings, was obviously higher than that on its top surface. The obtained Weibull modulus and variation coefficient indicate that the VHN was less variable when measured at a higher applied load and on the cross section of coating. The obvious dependence of the VHN on the specific indentation location within through-thickness direction was also realized. These phenomena described above in this work were related to the special microstructure and high anisotropic behaviour of plasma sprayed coatings.

Yin, Zhijian; Tao, Shunyan; Zhou, Xiaming; Ding, Chuanxian

2007-11-01

403

Plasma sprayed cast iron coatings containing solid lubricant graphite and h-BN structure  

NASA Astrophysics Data System (ADS)

Water-atomized cast iron powder of Fe-2.17 at.%C-9.93at.%Si-3.75at.%Al were deposited onto an aluminum alloy substrate by atmospheric direct current plasma spraying to improve its tribological properties. Preannealing of the cast iron powder allows the precipitation of considerable amounts of graphite structure in the powder. However, significant reduction in graphitized carbon in cast iron coatings is inevitable after plasma spraying in air atmosphere due to the in-flight burning and dissolution into molten iron droplets. Hexagonal boron nitride (h-BN) powders, which have excellent lubricating properties like graphite, were incorporated into the cast iron powder as a solid lubricant by the sintering process (1300C) to obtain protective coatings with a low friction coefficient. The performance of each coating was evaluated using a ring-on-disk-type wear tester under a paraffin-based oil condition in an air atmosphere. A conventional cast iron liner, which had a flaky graphite embedded in the pearlitic matrix, was also tested under similar conditions for comparison. Sections of worn surfaces and debris were characterized, and the wear behavior of plasma-sprayed coatings was discussed.

Tsunekawa, Y.; Ozdemir, I.; Okumiya, M.

2006-06-01

404

The Performances of TiN-TiB2 Coating Prepared by Reactive Plasma Spraying  

NASA Astrophysics Data System (ADS)

Reactive plasma sprayed coatings were prepared on carbon steel substrates with Ti and B4C as starting materials. Two kinds of gases (Ar and N2) were used as feeding gases for powders, respectively. 10 wt.% Cr was added in the powders as binder to increase the bond strength of the coating. The phases, microstructure, micro-hardness and corrosion polarization behavior in 3.5 wt.% NaCl solution of the two coatings were studied. The results show that TiN-TiB2 coatings were prepared under both conditions. The two coatings have typically laminated structure. However, the coating prepared with Ar as feeding gas has higher porosity and some unmelted Cr particles. It also contains certain content of titanium oxides. The microhardness of coating prepared with Ar as feeding gas is lower due to its higher porosity, unmelted Cr particles and some amounts of TiO2. The corrosion resistance of TiN-TiB2 coating prepared with Ar as feeding gas in 3.5 wt.% NaCl solution is worse than that of the coating prepared with N2 as feeding gas. Yet the corrosion resistance of reactive plasma sprayed TiN-TiB2 coating is improved greatly compared with that of carbon steel. The thermodynamic analysis of reactive plasma spraying process is also discussed.

Ma, Jing; Hu, Jianwen; Yan, Dongqing; Mao, Zhengping

2012-06-01

405

Bond-coating in plasma-sprayed calcium-phosphate coatings.  

PubMed

The influence of bond-coating on the mechanical properties of plasma-spray coatings of hydroxyatite on Ti was investigated. Plasma-spray powder was produced from human teeth enamel and dentine. Before processing the main apatite coating, a very thin layer of Al2O3/TiO2 was applied on super clean and roughened, by Al2O3 blasting, Ti surface as bond-coating. The experimental results showed that bond-coating caused significant increase of the mechanical properties of the coating layer: In the case of the enamel powder from 6.66 MPa of the simple coating to 9.71 MPa for the bond-coating and in the case of the dentine powder from 6.27 MPa to 7.84 MPa, respectively. Both tooth derived powders feature high thermal stability likely due to their relatively high content of fluorine. Therefore, F-rich apatites, such those investigated in this study, emerge themselves as superior candidate materials for calcium phosphate coatings of producing medical devices. The methods of apatite powder production and shaping optimization of powder particles are both key factors of a successful coating. The methods used in this study can be adopted as handy, inexpensive and reliable ways to produce high quality of powders for plasma spray purposes. PMID:17122932

Oktar, F N; Yetmez, M; Agathopoulos, S; Lopez Goerne, T M; Goller, G; Peker, I; Ipeker, I; Ferreira, J M F

2006-11-22

406

New approach to enhance the photocatalytic activity of plasma sprayed TiO 2 coatings using p-n junctions  

Microsoft Academic Search

To investigate the original reasons of the remarkable difference of the photocatalytic activity of plasma sprayed TiO2 and TiO2Fe3O4 coatings, the photoelectrochemical characteristics of plasma sprayed TiO2 and TiO2Fe3O4 electrodes were examined. The photo-response of the sprayed TiO2 electrode was comparable to that of single crystal TiO2, but the breakdown voltage was approximately 0.5 V (vs. SCE). The short-circuit current

Fuxing Ye; Akira Ohmori; Changjiu Li

2004-01-01

407

Fabrication of a vacuum vessel for a cusp confinement plasma using cast Al  

NASA Astrophysics Data System (ADS)

The Madison Plasma Dynamo Experiment (MPDX) facility will create large, un-magnetized, fast flowing, hot plasma for investigating magnetic field self-generation and flow driven MHD instabilities. The scale of the experiment is important to do this science, and so bigger is better. The core infrastructure of MPDX is the matching pair of 3 meter diameter hemispheres. For MPDX the cost and complexity of the vacuum vessel built by traditional means challenged the budget. The path to making this high-vacuum vessel led the research team and collaborators to push the limit cast Al. The challenges and solutions of making the MPDX vessel will be discussed and illustrated today.

Clark, Mike; Collins, Cami; Katz, Noam; Weisberg, Dave; Wallace, John; Forest, Cary

2012-10-01

408

Redshift modification of pulsars and magnetars by relativistic plasmas and vacuum polarization  

NASA Astrophysics Data System (ADS)

The redshifts of emissions from pulsars and magnetars consist of two components: gravitational and non-gravitational redshifts. The latter results from the electromagnetic and kinetic effects of relativistic plasmas, characterized by refractive indices and streaming velocities of the media, respectively. The vacuum polarization effect induced by strong magnetic fields can modify the refractive indices of the media, and thus leads to a modification to the redshifts. The Gordon effective metric is introduced to study the redshifts of emissions. The modification of the gravitational redshift, caused by the effects of relativistic plasmas and vacuum polarization, is obtained.

Luo, Yuee; Bu, Zhigang; Chen, Wenbo; Li, Hehe; Ji, Peiyong

2013-11-01

409

Nitride formation in synthesis of titanium aluminide matrix composite coatings by reactive RF plasma spraying  

NASA Astrophysics Data System (ADS)

This paper presents an in situ process to form intermetallic matrix composite coatings by reactive radio frequency (RF) plasma spraying with premixed elemental powder. The typical splat morphology of impinged titanium droplets on a stainless steel substrate is a disk with an outer peripheral fringe. If the supplied titanium powder size becomes finer or the nitrogen partial pressure in the plasma gas increases, splats containing prominent asperities with a smaller flattening ratio appear along with the plain disk type. An increase in nitrogen content is detected in all the splats sprayed with finer titanium powder and/or higher nitrogen partial pressure. The splats containing prominent asperities, which correspond to TiN, are twice as high in nitrogen content than the plain disk type. Aluminum splats are also classified into two categories: a disk type with an irregular outer periphery and a seminodular type. Oxygen exists on the splat surfaces, on which there are nitrogen concentrated areas corresponding to AlN. Consequently, the nitride formation proceeds on titanium and aluminum droplets during the flight as well as on the substrate. If the substrate temperature is higher than 873 K just before spraying with premixed titanium and aluminum powder, the formation of TiAl and Ti2AlN proceeds on the substrate because of negligible mutual collisions during the flight. Titanium aluminide matrix in situ composites sprayed with premixed titanium and aluminum powder contain more nitrides than those sprayed with TiAl compound powder, because of the higher nitrogen absorption in titanium and aluminum droplets that results in an exothermic reaction.

Tsunekawa, Yoshiki; Hiromura, Makoto; Okumiya, Masahiro

2000-03-01

410

A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes  

NASA Astrophysics Data System (ADS)

In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12% Co, A12O3, and Cr3C2-MCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al2O3 shows least wear resistance to every wear mode.

Sundararajan, G.; Prasad, K. U. M.; Rao, D. S.; Joshi, S. V.

1998-06-01

411

Thin film synthesis using miniature pulsed metal vapor vacuum arc plasma guns  

SciTech Connect

Metallic coatings can be fabricated using the intense plasma generated by the metal vapor vacuum arc. We have made and tested an embodiment of vacuum arc plasma source that operates in a pulsed mode, thereby acquiring precise control over the plasma flux and so also over the deposition rate, and that is in the form of a miniature plasma gun, thereby allowing deposition of metallic thin films to be carried out in confined spaces and also allowing a number of such guns to be clustered together. The plasma is created at the cathode spots on the metallic cathode surface, and is highly ionized and of directed energy a few tens of electron volts. Adhesion of the film to the substrate is thus good. Virtually all of the solid metals of the Periodic Table can be used, including highly refractory metals like tantalum and tungsten. Films, including multilayer thin films, can be fabricated of thickness from Angstroms to microns. We have carried out preliminary experiments using several different versions of miniature, pulsed, metal vapor vacuum arc plasma guns to fabricate metallic thin films and multilayers. Here we describe the plasma guns and their operation in this application, and present examples of some of the thin film structures we have fabricated, including yttrium and platinum films of thicknesses from a few hundred Angstroms up to 1 micron and an yttrium-cobalt multilayer structure of layer thickness about 100 Angstroms. 33 refs., 5 figs.

Godechot, X.; Salmeron, M.B.; Ogletree, D.F.; Galvin, J.E.; MacGill, R.A.; Dickinson, M.R.; Yu, K.M.; Brown, I.G.

1990-04-01

412

Phase Formation and Transformation in Alumina/YSZ Nanocomposite Coating Deposited by Suspension Plasma Spray Process  

NASA Astrophysics Data System (ADS)

Suspension Plasma Spray process was used for deposition of pseudo-eutectic composition of alumina-yttria-stabilized zirconia as a potential thermal barrier coating using Mettech axial III torch. Process variables including feed and plasma parameters were altered to find their effects on the formation of phases in the composite coating. The in-flight particle velocity was found to be the crucial parameter on phase formation in the resulting coatings. Low particle velocities below 650 m/s result in the formation of stable phases i.e., ?-alumina and tetragonal zirconia. In contrast, high particle velocities more than 750 m/s favor the metastable ?-alumina and cubic zirconia phases as dominant structures in as-deposited coatings. Accordingly, the plasma auxiliary gas and plasma power as influential parameters on the particle velocity were found to be reliable tools in controlling the resulting coating structure thus, the consequent properties. The noncrystalline portion of the coatings was also studied. It was revealed that upon heating, the amorphous phase prefers to crystallize into pre-existing crystalline phases in the as-deposited coating. Thus, the ultimate crystalline structure can be designed using the parameters that control the particle velocity during plasma spray coating.

Tarasi, F.; Medraj, M.; Dolatabadi, A.; Oberste-Berghaus, J.; Moreau, C.

2010-06-01

413

Microstructure of a plasma-sprayed Mo-Si-B alloy  

NASA Astrophysics Data System (ADS)

Powders of Mo52Si38B10 were plasma sprayed under inert conditions onto stainless steel substrates to determine if high density free standing forms could be synthesized by this process. Thermal spray conditions were varied to minimize porosity and oxygen impurities while minimizing evaporative metal losses. The assprayed and sintered microstructures were characterized using scanning and transmission electron microscopy and quantitative x-ray diffraction (XRD). The as-sprayed microstructure consisted of elongated splats tens of microns in length and only one to three microns in thickness. The splats contained submicrometer grains of primarily MoB and Mo5Si3B x (T1) and minor amounts of MoSi2 and a glassy grain boundary phase. The interior of the splats typically consisted of a fine eutectic of MoB and T1. Small pieces were cut out of the cross section of the sample and pressureless sintered for 2, 6, and 10 h at 1800 C in flowing Ar. After sintering for 2 h at 1800 C, the samples exhibited a coarser but equiaxed microstructure (1 to 5 m grain size) containing 78 vol.% T1, 16 vol.% MoB, and 6 vol.% MoSi2 as determined by XRD. Approximately 8 at.% of the Si formed silica. The high-temperature anneal removed all vestiges of the layered structure observed in the as-sprayed samples.

Kramer, M. J.; Okumus, S. C.; Besser, M. F.; nal, .; Akinc, M.

2000-03-01

414

Low-Energy Plasma Spray (LEPS) Deposition of Hydroxyapatite/Poly-?-Caprolactone Biocomposite Coatings  

NASA Astrophysics Data System (ADS)

Thermal spraying is widely employed to deposit hydroxyapatite (HA) and HA-based biocomposites on hip and dental implants. For thick HA coatings (>150 ?m), problems are generally associated with the build-up of residual stresses and lack of control of coating crystallinity. HA/polymer composite coatings are especially interesting to improve the pure HA coatings' mechanical properties. For instance, the polymer may help in releasing the residual stresses in the thick HA coatings. In addition, the selection of a bioresorbable polymer may enhance the coatings' biological behavior. However, there are major challenges associated with spraying ceramic and polymeric materials together because of their very different thermal properties. In this study, pure HA and HA/poly-?-caprolactone (PCL) thick coatings were deposited without significant thermal degradation by low-energy plasma spraying (LEPS). PCL has never been processed by thermal spraying, and its processing is a major achievement of this study. The influence of selected process parameters on microstructure, composition, and mechanical properties of HA and HA/PCL coatings was studied using statistical design of experiments (DOE). The HA deposition rate was significantly increased by the addition of PCL. The average porosity of biocomposite coatings was slightly increased, while retaining or even improving in some cases their fracture toughness and microhardness. Surface roughness of biocomposites was enhanced compared with HA pure coatings. Cell culture experiments showed that murine osteoblast-like cells attach and proliferate well on HA/PCL biocomposite deposits.

Garcia-Alonso, Diana; Parco, Maria; Stokes, Joseph; Looney, Lisa

2012-01-01

415

Very low pressure plasma sprayed alumina and yttria-stabilized zirconia thin dense coatings using a modified transferred arc plasma torch  

Microsoft Academic Search

As a novel thermal spray process, very low pressure plasma spray (VLPPS) process has been significantly used to deposit thin, dense and homogenous ceramic coating materials for special application needs in recent years. In this study, in order to enhance low-energy plasma jet under very low pressure ambience, a home-made transferred arc nozzle was made and mounted on a low-power

Lin Zhu; Nannan Zhang; Baicheng Zhang; Fu Sun; Rodolphe Bolot; Marie-Pierre Planche; Hanlin Liao; Christian Coddet

416

Process maps for plasma spray. Part II: Deposition and properties  

SciTech Connect

This is the second paper of a two part series based on an integrated study carried out at the State University of New York at Stony Brook and Sandia National Laboratories. The goal of the study is the fundamental understanding of the plasma-particle interaction, droplet/substrate interaction, deposit formation dynamics and microstructure development as well as the deposit property. The outcome is science-based relationships, which can be used to link processing to performance. Molybdenum splats and coatings produced at 3 plasma conditions and three substrate temperatures were characterized. It was found that there is a strong mechanical/thermal interaction between droplet and substrate, which builds up the coatings/substrate adhesion. Hardness, thermal conductivity, and modulus increase, while oxygen content and porosity decrease with increasing particle velocity. Increasing deposition temperature resulted in dramatic improvement in coating thermal conductivity and hardness as well as increase in coating oxygen content. Indentation reveals improved fracture resistance for the coatings prepared at higher deposition temperature. Residual stress was significantly affected by deposition temperature, although not significant by particle energy within the investigated parameter range. Coatings prepared at high deposition temperature with high-energy particles suffered considerably less damage in wear tests. Possible mechanisms behind these changes are discussed within the context of relational maps which are under development.

XIANGYANG,JIANG; MATEJICEK,JIRI; KULKARNI,ANAND; HERMAN,HERBERT; SAMPATH,SANJAY; GILMORE,DELWYN L.; NEISER JR.,RICHARD A

2000-03-28

417

Effect of Zr on microstructure of metallic glass coatings prepared by gas tunnel type plasma spraying.  

PubMed

Metallic glass is one of the most attractive advanced materials, and many researchers have conducted various developmental research works. Metallic glass is expected to be used as a functional material because of its excellent physical and chemical functions such as high strength and high corrosion resistance. However, the application for small size parts has been carried out only in some industrial fields. In order to widen the industrial application fields, a composite material is preferred for the cost performance. In the coating processes of metallic glass with the conventional deposition techniques, there is a difficulty to form thick coatings due to their low deposition rate. Thermal spraying method is one of the potential candidates to produce metallic glass composites. Metallic glass coatings can be applied to the longer parts and therefore the application field can be widened. The gas tunnel plasma spraying is one of the most important technologies for high quality ceramic coating and synthesizing functional materials. As the gas tunnel type plasma jet is superior to the properties of other conventional type plasma jets, this plasma has great possibilities for various applications in thermal processing. In this study, the gas tunnel type plasma spraying was used to form the metallic glass coatings on the stainless-steel substrate. The microstructure and surface morphology of the metallic glass coatings were examined using Fe-based metallic glass powder and Zr-based metallic glass powder as coating material. For the mechanical properties the Vickers hardness was measured on the cross section of both the coatings and the difference between the powders was compared. PMID:22905546

Kobayashi, A; Kuroda, T; Kimura, H; Inoue, A

2012-06-01

418

Contamination due to memory effects in filtered vacuum arc plasma deposition systems  

SciTech Connect

Thin film synthesis by filtered vacuum arc plasma deposition is a widely used technique with a number of important emerging technological applications. A characteristic feature of the method is that during the deposition process not only is the substrate coated by the plasma, but the plasma gun itself and the magnetic field coil and/or vacuum vessel section constituting the macroparticle filter are also coated to some extent. If then the plasma gun cathode is changed to a new element, there can be a contamination of the subsequent film deposition by sputtering from various parts of the system of the previous coating species. We have experimentally explored this effect and compared our results with theoretical estimates of sputtering from the SRIM (Stopping and Range of Ions in Matter) code. We find film contamination of order 10-4 - 10-3, and the memory of the prior history of the deposition hardware can be relatively long-lasting.

Martins, D.R.; Salvadori, M.C.; Verdonck, P.; Brown, I.G.

2002-08-13

419

Electromagnetic loads and structural response of the CIT (Compact Ignition Tokamak) vacuum vessel to plasma disruptions  

SciTech Connect

Studies of the electromagnetic loads produced by a variety of plasma disruptions, and the resulting structural effects on the compact Ignition Tokamak (CIT) vacuum vessel (VV), have been performed to help optimize the VV design. A series of stationary and moving plasmas, with disruption rates from 0.7--10.0 MA/ms, have been analyzed using the EMPRES code to compute eddy currents and electromagnetic pressures, and the NASTRAN code to evaluate the structural response of the vacuum vessel. Key factors contributing to the magnitude of EM forces and resulting stresses on the vessel have been found to include disruption rate, and direction and synchronization of plasma motion with the onset of plasma current decay. As a result of these analyses, a number of design changes have been made, and design margins for the present 1.75 meter design have been improved over the original CIT configuration. 1 ref., 10 figs., 4 tabs.

Salem, S.L.; Listvinsky, G.; Lee, M.Y.; Bailey, C.

1987-01-01

420

Vacuum laser-initiated plasma shutters for retropulse isolation in Antares  

Microsoft Academic Search

We have demonstrated that sintered LiF spatial filters may be used in a 10⁻⁶-torr vacuum environment as laser-initiated plasma shutters for retropulse isolation in the Antares high-energy laser fusion system. In our experiments, a 1.1-ns pulsed CO laser, at a 10-..mu..m wavelength and an energy of up to 3.0 J, was used for plasma initiation; a chopped probe laser tuned

T. W. Sheheen; S. J. Czuchlewski; J. Hyde; R. L. Ainsworth

1983-01-01

421

Effect of substrate temperature on adhesion strength of plasma-sprayed nickel coatings  

NASA Astrophysics Data System (ADS)

We plasma-sprayed nickel coatings on stainless steel and cobalt alloy coupons heated to temperatures ranging from room temperature to 650 C. Temperatures, velocities, and sizes of spray particles were recorded while in-flight and held constant during experiments. We measured coating adhesion strength and porosity, photographed coating microstructure, and determined thickness and composition of surface oxide layers on heated substrates. Coating adhesion strength on stainless steel coupons increased from 10 74 MPa when substrate temperatures were raised from 25 650 C. Coating porosity was lower on high-temperature surfaces. Surface oxide layers grew thicker when substrates were heated, but oxidation alone could not account for the increase in coating adhesion strength. When a coupon was heated to 650 C and allowed to cool before plasma-spraying, its coating adhesion strength was much less than that of a coating deposited on a surface maintained at 650 C. Cobalt alloy coupons, which oxidize much less than stainless steel when heated, also showed improved coating adhesion when heated. Heating the substrate removes surface moisture and other volatile contaminants, delays solidification of droplets so that they can better penetrate surface cavities, and promotes diffusion between the coating and substrate. All of these mechanisms enhance coating adhesion.

Pershin, V.; Lufitha, M.; Chandra, S.; Mostaghimi, J.

2003-09-01

422

Column formation in suspension plasma-sprayed coatings and resultant thermal properties.  

SciTech Connect

The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with median diameters of 15 {micro}m and 80 nm. The powder-ethanol suspensions made with 15-{micro}m diameter YSZ particles formed coatings with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to variations in deposition behavior. The thermal conductivity (k th) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200 C heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.% exhibited significantly different k th values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension formulations. Heat treatment increased the k th of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k th increase was less than has been observed in APS coatings.

Van Every, K.; Krane, M. J. M.; Trice, R. W.; Wang, H.; Porter, W.; Besser, M.; Sordelet, D.; Ilavsky, J.; Almer, J. (Purdue Univ.); (ORNL); (Ames Lab.)

2011-06-01

423

Column Formation in Suspension Plasma-Sprayed Coatings and Resultant Thermal Properties  

SciTech Connect

The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with median diameters of 15 {micro}m and 80 nm. The powder-ethanol suspensions made with 15-{micro}m diameter YSZ particles formed coatings with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to variations in deposition behavior. The thermal conductivity (k{sub th}) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200 C heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.% exhibited significantly different k{sub th} values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension formulations. Heat treatment increased the k{sub th} of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k{sub th} increase was less than has been observed in APS coatings.

VanEvery, Kent; Krane, Matthew J.M.; Trice, Rodney W; Wang, Hsin; Porter, Wallace; Besser, Matthew; Sordelet, Daniel; Ilavsky, Jan; Almer, Jonathan

2012-03-19

424

An investigation of particle trajectories and melting in an air plasma sprayed zirconia  

SciTech Connect

The partially stabilized zirconia powders used to plasma spray thermal barrier coatings typically exhibit broad particle-size distributions. There are conflicting reports in the literature about the extent of injection-induced particle-sizing effects in air plasma-sprayed materials. If significant spatial separation of finer and coarser particles in the jet occurs, then one would expect it to play an important role in determining the microstructure and properties of deposits made from powders containing a wide range of particle sizes. This paper presents the results of a study in which a commercially available zirconia powder was fractionated into fine, medium, and coarse cuts and sprayed at the same torch conditions used for the ensemble powder. Diagnostic measurements of particle surface temperature, velocity, and number-density distributions in the plume for each size-cut and for the ensemble powder are reported. Deposits produced by traversing the torch back and forth to produce a raised bead were examined metallographically to study their shape and location with respect to the torch centerline and to look at their internal microstructure. The results show that, for the torch conditions used in this study, the fine, medium, and coarse size-cuts all followed the same mean trajectory. No measureable particle segregation effects were observed. Considerable differences in coatings microstructure were observed. These differences can be explained by the different particle properties measured in the plume.

Neiser, R.A. [Sandia National Labs., Albuquerque, NM (United States); Roemer, T.J. [Ktech Corp., Albuquerque, NM (United States)

1996-12-31

425

Vacuum-plasma technology for obtaining protective coatings from complex alloys  

Microsoft Academic Search

Abtract This work is devoted to obtaining coatings from M - Cr - Al - Y alloys by the vacuum-plasma method using 10 103 eV particle energies. In this energy range we can realize predominant precipitation (condensation) of the coating, ionic (dry) etching, or the formation of a diffuse layer on the surface depending on the particle type and the

S. A. Muboyadzhan; E. N. Kablov; S. A. Budinovskii

1995-01-01

426

Time and space resolved Langmuir probe measurements of a pulsed vacuum arc plasma  

Microsoft Academic Search

The time and space evolution of pulsed vacuum arc plasma parameters have been measured using a single cylindrical Langmuir probe in a free expansion cup. Electron density ne, effective electron temperature Teff and electron energy distribution function (EEDF) are derived from the IV curves using Druyvesteyn method. Results show that during the discharge time, the electron density ne is between

Lei Chen; Dazhi Jin; Xiaohua Tan; Jingyi Dai; Liang Cheng; Side Hu

427

CHF3 Plasma Treatment of Si Field Emitter Arrays For No Damage Vacuum Packaging  

Microsoft Academic Search

Si field emitter arrays (FEAs) are promising cold cathodes for field emission displays (FEDs). The emission current from the Si FEAs, however, is known to decrease significantly after the vacuum-packaging process based on the frit sealing technique. In this work, we have investigated the mechanism of the current decrease and found that CHF3 plasma treatment of the tip surface was

Masayoshi Nagao; Hisao Tanabe; Takashi Matsukawa; Seigo Kanemaru; Junji Itoh

2000-01-01

428

Optical Investigation of the Plasma Jet of Vacuum-Arc Cathode Spot  

Microsoft Academic Search

The results of the optical study of the plasma jet of the cathode spot of a freely burning vacuum arc with copper electrodes at a current of 60 A are given, as well as of the arc stabilized with a uniform axial magnetic field of induction up to 0.18 T. The axial and radial profiles of radiation intensity for different

Alexey M. Chaly; Alexander A. Logatchev; Roman A. Taktarov; Konstantin K. Zabello; Sergey M. Shkol'nik

2009-01-01

429

Oxidation of nickel during plasma spraying and some properties of nickel oxide  

NASA Astrophysics Data System (ADS)

The techniques of plasma spraying are suitable for deposition of metals, ceramics or composites. Atmospheric plasma spraying of metals is accompanied by their oxidation. The oxidation of nickel during its spraying gives rise to NiO. During the flight of molten nickel particles in the plasma plume, the first stage of the oxidation reaction takes place. To determine the amount of NiO grown during this stage, oxidation can be stopped abruptly by trapping and quenching the particles in liquid nitrogen. If, on the other hand, the flying molten particles are allowed to hit a solid substrate, a plasma deposit or coating is built up. The period starting at the moment of the particle impact and solidification corresponds to the second oxidation stage. This is finished by cooling down the system substrate coating. Plasma spraying of nickel was conducted using a water-stabilized plasma gun. To study the structure and optical properties of the oxidation products, it is necessary to remove the metallic phase from the samples. This was done by a technique of metal dissolution described previously. After the first oxidation stage, if the particles are trapped in liquid nitrogen, NiO is obtained by rapid solidification of oxide melt grown on the surface of the flying particles as a result of a gas molten Ni reaction. The colour of solid NiO formed in this way is green, which corresponds to a region of high reflectance between 1.9 and 2.7 eV. The green colour is typical of stoichiometric NiO and is due to octahedral Ni2+ ions. The second oxidation stage is characterized by a gas solid Ni reaction. It results in black NiO, whose colour follows from strong absorption of light in the whole visible range. The oxygen content in this oxide exceeds slightly the stoichiometric value. The light absorption is due to free charge carriers, i. e. holes, whose presence is a consequence of the deviation of NiO from stoichiometry.

Volenk, K.; Ctibor, P.; Dubsk, J.; Chrska, P.; Hork, J.

2004-03-01

430

Simulation of Effervescent Atomization and Nanoparticle Characteristics in Radio Frequency Suspension Plasma Spray  

NASA Astrophysics Data System (ADS)

In this paper, a comprehensive model was developed to investigate the suspension spray for a radio frequency (RF) plasma torch coupled with an effervescent atomizer. Firstly, the RF plasma is simulated by solving the thermo-fluid transport equations with electromagnetic Maxwell equation. Secondly, primary atomization of the suspension is solved by a proposed one-dimensional breakup model and validated with the experimental data. Thirdly, the suspension droplets and discharged nanoparticles are modeled in Lagrangian manner, to calculate each particle tracking, acceleration, heating, melting and evaporation. Saffman lift force, Brownian force and non-continuum effect are considered for nanoparticle momentum transfer, as well as the effects of evaporation on heat transfer. This model predicts the nanoparticle trajectory, velocity, temperature and size in the RF suspension plasma spray. Effects of the torch and atomizer operating conditions on the particle characteristics are investigated. Such operating conditions include gas-to-liquid flow ratio, atomizer orifice diameter, injection pressure, power input level, plasmas gas flow rate, and powder material. The statistical distributions for the multiple particles are also discussed for different cases.

Xiong, Hong-Bing; Qian, Li-Juan; Lin, Jian-Zhong

2012-03-01

431

Optical and Electrical Properties of Heterogeneous Coatings Produced by Aluminum Powder and Boehmite Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Spectral selective materials have attracted an increasing interest because of Concentration Solar Power Plant. Those materials are expected to exhibit specific optical properties at temperatures higher than 450 C. Plasma-spraying process is commonly used to manufacture high-temperature coatings. In this study, heterogeneous coatings made of aluminum and alumina were produced by spraying both powder and suspension of boehmite clusters. Both optical and electrical properties were measured because, according to the Hagen-Ruben's law, the higher the resistivity the lower the reflectivity. The reflectivity was assessed by spectrometry at 10 m and the resistivity by the four-points technique. The results were combined with the diameter of flattened lamellae and the volume fraction of alumina in the coatings. Then the highest reflectivity is achieved with a metallic coating exhibiting high flattening degree, while the coatings containing a large amount of alumina exhibit the lowest reflectivity and the highest resistivity.

Brousse-Pereira, E.; Wittmann-Teneze, K.; Bianchi, V.; Longuet, J. L.; Del Campo, L.

2012-12-01

432

Controlling of Nitriding Process on Reactive Plasma Spraying of Al Particles  

NASA Astrophysics Data System (ADS)

Reactive plasma spraying (RPS) has been considered as a promising technology for in-situ formation of aluminum nitride (AlN) thermally sprayed coatings. To fabricate thick A lN coatings in RPS process, controlling and improving the in-flight nitriding reaction of Al particles is required. In this study, it was possible to control the nitriding reaction by using ammonium chloride (NH4Cl) powders. Thick and dense AlN coating (more than 300 ?m thickness) was successfully fabricated with small addition of NH4Cl powders. Thus, addition of NH4Cl prevented the Al aggregation by changing the reaction pathway to a mild way with no explosive mode (relatively low heating rates) and it acts as a catalyst, nitrogen source and diluent agent.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2011-10-01

433

Preparation and characterization of molybdenum disilicide coating on molybdenum substrate by air plasma spraying  

NASA Astrophysics Data System (ADS)

MoSi2 oxidation protective coatings on molybdenum substrate were prepared by air plasma spraying technique (APS). Microstructure, phase composition, porosity, microhardness and bonding strength of the coatings were investigated and determined. Oxidation behavior of the coating at high temperature was also examined. Results show that composition of the coatings is constituted with MoSi2 and Mo5Si3, the surface morphology is described as flattened lamellar features, insufficiently flattened protuberance with some degree of surface roughness, a certain quantity of spherical particles, microcracks and pores. Testing results reveal that microhardness and bonding strength of the coatings increase, and porosity decreases with increasing power or decreasing Ar gas flow rate. Moreover, with decreasing the porosity, the microhardness of the coatings increases. The bonding strength of the coatings also increases with increasing spray distance. The MoSi2 coated Mo substrate exhibited a good oxidation resistance at 1200 C.

Wang, Yi; Wang, Dezhi; Yan, Jianhui; Sun, Aokui

2013-11-01

434

Characterization of Thermal Diffusion Related Properties in Plasma Sprayed Zirconium Coatings  

NASA Astrophysics Data System (ADS)

Zirconium (Zr) metal is of interest for chemical corrosion protection and nuclear reactor core applications. Inert chamber plasma spraying has been used to produce thin Zr coatings on stainless steel (SS) substrates. The coatings were deposited while using transferred arc (TA) cleaning/heating at five different current levels. In order to better understand thermal diffusion governed processes, the coating porosity, grain size and interdiffusion with the substrate were measured as a function of TA current. Low porosity (3.5 to <0.5%), recrystallization with fine equiaxed grain size (3-8 ?m diameter) and varying elemental diffusion distance (0-50 ?m) from the coating-substrate interface were observed. In addition, the coatings were low in oxygen content compared to the wrought SS substrates. The Zr coatings sprayed under these conditions look promising for highly demanding applications.

Hollis, K. J.; Hawley, M. E.; Dickerson, P. O.

2012-06-01

435

An analytical and experimental study of plasma spraying of alumina: Final program and abstracts  

SciTech Connect

As part of an investigation of the the dynamics that occur in the plume of a typical thermal spray torch, an analytical and experimental study of the plasma spraying of alumina is being performed; preliminary results are reported here. Numerical models of the physical processes in the torch column and plume were used to determine the temperature and flow fields. Computer simulations of particle injection (15, 34, and 53 ..mu..m alumina particles) are also presented. The alumina experiments were conducted at a 35 kW power level using a 100 scfh argon and 15 scfh hydrogen gas mixture for two alumina powders. The quality of the coatings is discussed with respect to porosity, sample metallography, and microhardness. 6 refs., 5 figs., 1 tab.

Varacalle, D.J. Jr.

1988-01-01

436

Characteristics of MCrAlY coatings sprayed by high velocity oxygen-fuel spraying system  

SciTech Connect

High velocity oxygen-fuel (HVOF) spraying system in open air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Fe, Ni and/or Co) coatings can be applied to provide resistance against oxidation and corrosion to the hot parts of gas turbines. Also, it is well known that the thicker coating can be sprayed in comparison with any other thermal spraying systems due to improved residual stresses. However, thermal and mechanical properties of HVOF coatings have not been clarified. Especially, the characteristics of residual stress, that are the most important property from the view point of production technique, have not been made clear. In this paper, the mechanical properties of HVOF sprayed MCrAlY coatings were measured in both the case of as-sprayed and heat-treated coatings in comparison with a vacuum plasma sprayed MCrAlY coatings. It was confirmed that the mechanical properties of HVOF sprayed MCrAlY coatings could be improved by a diffusion heat treatment to equate the vacuum plasma sprayed MCrAlY coatings. Also, the residual stress characteristics were analyzed using a deflection measurement technique and a X-ray technique. The residual stress of HVOF coating was reduced by the shot-peening effect comparable to that of a plasma spray system in open air. This phenomena could be explained by the reason that the HVOF sprayed MCrAlY coating was built up by poorly melted particles.

Itoh, Y.; Saitoh, M.; Tamura, M.

2000-01-01

437

Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical properties.  

PubMed

Flame-spheroidized feedstock, with excellent known heat transfer and consistent melting capabilities, were used to produce hydroxyapatite (HA) coatings via plasma spraying. The characteristics and inherent mechanical properties of the coatings have been investigated and were found to have direct and impacting relationship with the feedstock characteristics, processing parameters as well as microstructural deformities. Processing parameters such as particle sizes (SHA: 20-45, 45-75 and 75-125 microm) and spray distances (10, 12 and 14 cm) have been systematically varied in the present study. It was found that the increase of particle sizes and spray distances weakened the mechanical properties (microhardness, modulus, fracture toughness and bond strength) and structural stability of the coatings. The presence of inter- and intralamellar thermal microcracks, voids and porosities with limited true contact between lamellae were also found to degrade the mechanical characteristics of the coatings, especially in coatings produced from large-sized HA particles. An effort was made to correlate the effects of microstructural defects with the resultant mechanical properties and structural integrity of the plasma-sprayed hydroxyapatite (HA) coatings. The effects of different heat treatment temperatures (600, 800 and 900 degrees C) on the mechanical properties of the coatings were also studied. It was found that a heat treatment temperature of 800 degrees C does enhance the microhardness and elastic modulus of the coatings significantly (P < 0.05) whereas a further increment in heat treatment temperature to 900 degrees C did not show any discernable improvements (P > 0.1). The elastic response behaviour and fracture toughness of both the as-sprayed and heat-treated HA coatings using Knoop and Vickers indentations at different loadings have been investigated. Results have shown that the mechanical properties of the coatings have improved significantly despite increasing crack density after heat treatment in air. Coatings produced from the spheroidized feedstock of 20-45 microm (SHA 20-45 microm) sprayed at a stand-off distance of 10 cm were found to possess the most favourable mechanical properties. PMID:10811304

Kweh, S W; Khor, K A; Cheang, P

2000-06-01

438

Effect of steam treatment during plasma spraying on the microstructure of hydroxyapatite splats and coatings  

NASA Astrophysics Data System (ADS)

The major problems with plasma sprayed hydroxyapatite (HA) coatings for hard tissue replacement are severe HA decomposition and insufficient mechanical properties of the coatings. Loss of crystalline HA after the high-temperature spraying is due mainly to the loss of OH- in terms of water. The current study used steam to treat HA droplets and coatings during both in-flight and flattening stages during plasma spraying. The microstructure of the HA coatings and splats was characterized using scanning electron microscope, Raman spectroscopy, Fourier transform IR spectroscopy, and x-ray diffraction. Results showed that a significant increase in crystallinity of the HA coating was achieved through the steam treatment (e.g., from 58 to 79%). In addition, the effects were dependent on particle sizes of the HA feedstock, more increase in crystallinity of the coatings made from smaller powders was revealed. The Raman spectroscopy analyses on the individual splats and coatings indicate that the mechanism involves entrapping of water molecules by the individual HA droplets upon their impingement. It further suggests that the HA decomposition has already taken place before the impingement of the droplets on precoating or substrate. The improvement in crystallinity and phases, for example, from tricalcium phosphate and amorphous calcium phosphate to HA, was achieved by reversing the HA decomposition through providing extra OH-. Furthermore, the steam treatment during the spraying also accounts for remarkably increased adhesion strength from 9.09 to 23.13 MPa. The in vitro testing through immersing the HA coatings in simulated body fluid gives further evidence that the economic and simple steam treatment is promising in improving HA coating structure.

Li, H.; Khor, K. A.; Cheang, P.

2006-12-01

439

Correlation of microstructure and wear resistance of ferrous coatings fabricated by atmospheric plasma spraying  

NASA Astrophysics Data System (ADS)

The correlation of microstructure and wear resistance in ferrous coatings applicable to diesel engine cylinder bores was investigated in this study. Seven kinds of ferrous spray powders, two of which were stainless steel powders and the others blend powders of ferrous powders mixed with Al2O3-ZrO2 powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the ferrous coatings showed that various Fe oxides such as FeO, Fe2O3, and ?-Fe2O3 were formed in the martensitic (or austenitic) matrix as a result of the reaction with oxygen in air. The blend coatings containing ?-Al2O3 and t-ZrO2 oxides, which were formed as Al2O3-ZrO2 powders, were rapidly solidified during plasma spraying. The wear test results revealed that the blend coatings showed better wear resistance than the ferrous coatings because they contained a number of hard Al2O3-ZrO2 oxides. However, delamination occurred when cracks initiated at matrix/oxide interfaces and propagated parallel to the worn surface in the case of the large hardness difference between the matrix and oxide. The wear rate of the coating fabricated with STS316 powders was slightly higher than other coatings, but the wear rate of the counterpart material was very low because of the smaller matrix/oxide hardness difference due to the presence of many Fe oxides. In order to reduce the wear of both the coating and its counterpart material, the matrix/oxide hardness difference should be minimized, and the hardness of the coating should be increased over a certain level by forming an appropriate amount of oxides.

Hwang, Byoungchul; Ahn, Jeehoon; Lee, Sunghak

2002-09-01

440

The structure and thermal properties of plasma-sprayed beryllium for the International Thermonuclear Experimental Reactor (ITER)  

SciTech Connect

Plasma spraying is being studied for in situ repair of damaged Be and W plasma facing surfaces for ITER, the next generation magnetic fusion energy device, and is also being considered for fabricating Be and W plasma-facing components for the first wall of ITER. Investigators at LANL`s Beryllium Atomization and Thermal Spray Facility have concentrated on investigating the structure-property relation between as-deposited microstructures of plasma sprayed Be coatings and resulting thermal properties. In this study, the effect of initial substrate temperature on resulting thermal diffusivity of Be coatings and the thermal diffusivity at the coating/Be substrate interface (interface thermal resistance) was investigated. Results show that initial Be substrate temperatures above 600 C can improve the thermal diffusivity of the Be coatings and minimize any thermal resistance at the interface between the Be coating and Be substrate.

Castro, R.G.; Bartlett, A.; Elliott, K.E.; Hollis, K.J.

1996-09-01

441

Regimes of expansion of a collisional plasma into a vacuum  

NASA Astrophysics Data System (ADS)

The effect of elastic Coulomb collisions on the one-dimensional expansion of a plasma slab is studied in the classical limit, using an electrostatic particle-in-cell code. Two regimes of interest are identified. For a collision rate of few hundreds of the inverse of the expansion characteristic time ?e, the electron distribution function remains isotropic and Maxwellian with a homogeneous temperature, during all the expansion. In this case, the expansion can be approached by a three-dimensional version of the hybrid model developed by Mora [P. Mora, Phys. Rev. E 72, 056401 (2005)]. When the collision rate becomes somewhat greater than 104?e-1, the plasma is divided in two parts: an inner part which expands adiabatically as an ideal gas and an outer part which undergoes an isothermal expansion.

Thaury, C.; Mora, P.; Adam, J. C.; Hron, A.

2009-09-01

442

Parametric study of suspension plasma spray processing parameters on coating microstructures manufactured from nanoscale yttria-stabilized zirconia  

Microsoft Academic Search

A parametric study was conducted to determine the effect of suspension plasma spray (SPS) processing parameters, including plasma torch standoff, suspension injection velocity, injector location, powder loading in the suspension, and torch power, on the final microstructure of coatings fabricated from 80nm diameter yttria-stabilized zirconia (YSZ) powders. Coatings made with different conditions were analyzed via stereology techniques for the amount

Kent VanEvery; Matthew John M. Krane; Rodney W. Trice

443

Life cycle assessment of using powder and liquid precursors in plasma spraying: The case of yttria-stabilized zirconia  

Microsoft Academic Search

Plasma spraying using liquid precursors makes possible the production of finely-structured coatings and thin coatings. This technology has been investigated for nearly ten years in many laboratories and applications are now emerging, using conventional plasma equipment except for the feedstock injection system. While superior quality is expected from the nano-structured coatings, the question remains as to the impacts of using

A. Moign; A. Vardelle; N. J. Themelis; J. G. Legoux

2010-01-01

444

Rapid analysis of pentazocine in human plasma by liquid chromatography\\/mass spectrometry with sonic spray ionization  

Microsoft Academic Search

A rapid determination method for pentazocine in human plasma without complicated pretreatments has been constructed by liquid chromatography\\/mass spectrometry (LC\\/MS) with sonic spray ionization (SSI) using an Oasis HLB cartridge column. The reliability on our method was investigated for human plasma samples spiked with pentazocine and dextromethorphan as internal standard. The regression equation for pentazocine showed good linearity in the

Tetsuya Arinobu; Hideki Hattori; Akira Ishii; Takeshi Kumazawa; Xiao-Pen Lee; Sadao Kojima; Osamu Suzuki; Hiroshi Seno

2003-01-01

445

Modeling the Influence of Injection Modes on the Evolution of Solution Sprays in a Plasma Jet  

NASA Astrophysics Data System (ADS)

Solution precursor plasma spraying (SPPS) is a novel technology with great potential for depositing finely structured ceramic coatings with nano- and sub-micrometric features. The solution is injected into the plasma jet either as a liquid stream or gas atomized droplets. Solution droplets or the stream interact with the plasma jet and break up into fine droplets. The solvent vaporizes very fast as the droplets travel downstream. Solid particles are finally formed, and the particle are heated up and accelerated to the substrate to generate the coating. The deposition process and the properties of coatings obtained are extremely sensitive to the process parameters, such as torch operating conditions, injection modes, injection parameters, and substrate temperatures. This article numerically investigates the effect of injection modes, a liquid stream injection and a gas-blast injection, on the size distribution of injected droplets. The particle/droplet size, temperature, and position distributions on the substrate are predicted for different injection modes.

Shan, Y.; Coyle, T. W.; Mostaghimi, J.

2010-01-01

446

Tungsten Coating on Low Activation Vanadium Alloy by Plasma Spray Process  

SciTech Connect

Tungsten (W) coating on fusion candidate V-4Cr-4Ti (NIFS-HEAT-2) substrate was demonstrated with plasma spray process for the purpose of applying to protection of the plasma facing surface of a fusion blanket. Increase in plasma input power and temperature of the substrate was effective to reduce porosity of the coating, but resulted in hardening of the substrate and degradation of impact property at 77 K. The hardening seemed to be due to contamination with gaseous impurities and deformation by thermal stress during the coating process. Since all the samples showed good ductility at room temperature, further heating seems to be acceptable for the vanadium substrate. The fracture stress of the W coating was estimated from bending tests as at least 313 MPa, which well exceeds the design stress for the vanadium structure in fusion blanket.

Nagasaka, Takuya [National Institute for Fusion Science (Japan); Muroga, Takeo [National Institute for Fusion Science (Japan); Noda, Nobuaki [National Institute for Fusion Science (Japan); Kawamura, Masashi [Kawasaki Heavy Industries, LTD (Japan); Ise, Hideo [Kawasaki Heavy Industries, LTD (Japan); Kurishita, Hiroaki [Tohoku University (Japan)

2005-05-15

447

Theory of coherent transition radiation generated at a plasma-vacuum interface  

SciTech Connect

Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long wavelength radiation. This method of transition radiation generation has the capability of producing high peak power THz radiation, of order 100 (mu)J/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art THz sources.

Schroeder, Carl B.; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim P.

2003-06-26

448

Angular distribution of isothermal expansions of non-quasi-neutral plasmas into a vacuum  

SciTech Connect

A two dimensional planar model is developed for self-similar isothermal expansions of non-quasi-neutral plasmas into a vacuum of solid targets heated by ultraintense laser pulses. The angular ion distribution and the dependence of the maximum ion velocity on laser parameters and target thicknesses are predicted. Considering the self-generated magnetic field of plasma beams as a perturbation, the ion energy on edge at the ion opening angle has an increase of 2% relative to that on the front center. Therefore, the self-generated magnetic field of plasma beams is not large enough to interpret for the ring structures.

Huang Yongsheng [China Institute of Atomic Energy, Beijing 102413 (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Duan Xiaojiao; Shi Yijin; Lan Xiaofei; Tan Zhixin; Wang Naiyan; Tang Xiuzhang [China Institute of Atomic Energy, Beijing 102413 (China); He Yexi [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2008-04-07

449

Role of in-flight temperature and velocity of powder particles on plasma sprayed hydroxyapatite coating characteristics  

Microsoft Academic Search

This paper presents a systematic research on the process of thermal spraying of HA encompassing all stages of layer deposition: powder production and characterization (optimized production led to spherical 39.9010.61?m powder with 0.0% content of tri-calcium phosphate [TCP] or tetra-calcium phosphate [TTCP] phases), plasma jet properties influence on the in-flight powder properties (major influence of spray distance factor), the influence

Jan Cizek; Khiam Aik Khor

450

Hot corrosion behavior of low pressure plasma sprayed NiCoCrAlY+Ta coatings on nickel base superalloys  

Microsoft Academic Search

The hot corrosion behavior of NiCoCrAlY+Ta coatings obtained by low-pressure plasma spraying has been investigated (type I hot corrosion with T = 850°C). These coatings have been deposited on two nickel-base superalloys and on a cast alloy of the same composition as the coating. Comparison of the cyclic oxidation behavior at 850°C between the sprayed coating and the cast alloy

M. Frances; P. Steinmetz; J. Steinmetz; C. Duret; R. Mevrel

1985-01-01

451

Evaluation of human osteoblastic cell response to plasma-sprayed silicon-substituted hydroxyapatite coatings over titanium substrates.  

PubMed

Silicon-substituted hydroxyapatite (Si-HA) coatings have been plasma sprayed over titanium substrates (Ti-6Al-4V) aiming to improve the bioactivity of the constructs for bone tissue repair/regeneration. X-ray diffraction analysis of the coatings has shown that, previous to the thermal deposition, no secondary phases were formed due to the incorporation of 0.8 wt % Si into HA crystal lattice. Partial decomposition of hydroxyapatite, which lead to the formation of the more soluble phases of alpha- and beta-tricalcium phosphate and calcium oxide, and increase of amorphization level only occurred following plasma spraying. Human bone marrow-derived osteoblastic cells were used to assess the in vitro biocompatibility of the constructs. Cells attached and grew well on the Si-HA coatings, putting in evidence an increased metabolic activity and alkaline phosphatase expression comparing to control, i.e., titanium substrates plasma sprayed with hydroxyapatite. Further, a trend for increased differentiation was also verified by the upregulation of osteogenesis-related genes, as well as by the augmented deposition of globular mineral deposits within established cell layers. Based on the present findings, plasma spraying of Si-HA coatings over titanium substrates demonstrates improved biological properties regarding cell proliferation and differentiation, comparing to HA coatings. This suggests that incorporation of Si into the HA lattice could enhance the biological behavior of the plasma-sprayed coating. PMID:20574971

Gomes, Pedro S; Botelho, Cludia; Lopes, Maria A; Santos, Jos D; Fernandes, Maria H

2010-08-01

452

Influence of impact parameters of zirconia droplets on splat formation and morphology in plasma spraying  

SciTech Connect

In this study, the effects of the impact parameters, namely, the diameter d{sub 0}, velocity V{sub 0}, and temperature T{sub 0}, of an impacting droplet of yttria-stabilized zirconia (YSZ) on splat morphology have been investigated systematically under plasma spraying conditions. In particular, fully molten droplets of 30-90 {mu}m in d{sub 0} that impact on a preheated quartz glass substrate at V{sub 0} of 10-70 m/s have been examined via hybrid plasma spraying. The degree of flattening of final splat morphology, {xi}, was found to be predicted by the relationship {xi}=0.43Re{sup 1/3}, where Re is the Reynolds number. The dimensionless spreading time of droplets, t{sub s}*=t{sub s}V{sub 0}/d{sub 0}, was distributed around 2.7, where t{sub s} is the spreading time of the droplet. The ideal maximum spread factor derived from the splat height was approximately proportional to Re{sup 1/4}. The latter two findings suggest that the analytical model developed by Pasandideh-Fard et al. [Phys. Fluids 8, 650 (1996)] can be applied to the droplet impact in plasma spraying especially for the case of YSZ. In addition, the thermal contact resistance of disk shaped splats decreased with the increase of V{sub 0} within the range of 10{sup -5}-10{sup -6} m{sup 2} K/W.

Shinoda, Kentaro; Koseki, Toshihiko; Yoshida, Toyonobu [Department of Materials Engineering, Graduate School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2006-10-01

453

Sintering and creep behavior of plasma-sprayed zirconia- and hafnia-based thermal barrier coatings  

Microsoft Academic Search

The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result of the sintering and creep processes are detrimental to coating thermal fatigue resistance and performance. In this paper, the sintering characteristics of ZrO28wt%Y2O3, ZrO225wt%CeO22.5wt%Y2O3, ZrO26w%NiO9wt%Y2O3,

Dongming Zhu; Robert A. Miller

1998-01-01

454

Monotonic and cyclic deformation behavior of plasma-sprayed coatings under uni-axial compressive loading  

Microsoft Academic Search

Monotonic and cyclic deformation behavior of thermal barrier coatings under uni-axial compressive loading was examined. Specimens of plasma-sprayed ZrO28% Y2O3, Al2O3, CoNiCrAlY and NiCr were fabricated to test the coating materials independent of the substrates. Stressstrain response was measured using the laser speckle straindisplacement gauge (SSDG). The coatings showed nonlinear stressstrain responses with considerably low elastic moduli compared with those

Hiroyuki Waki; Keiji Ogura; Izuru Nishikawa; Akira Ohmori

2004-01-01

455

Characterization of plasma-sprayed coatings using nondestructive evaluation techniques: Round-robin test results  

NASA Astrophysics Data System (ADS)

A round-robin test was implemented where nine European research institutions and universities applied different thermal, ultrasonic, and magnetic methods for measuring the thickness of plasma-sprayed coatings. The coatings, which had thicknesses ranging from 50 to 500 m, were applied on substrates of AISI 316, a standard industrial structural material, and on Armco iron in order to have a material of known thermal properties. Destructive testing was performed after the other methods had been applied, resulting in detailed information on the coating thickness, rugosity, and uniformity. The results obtained with the applied methods on the two unknown samples for each substrate type agreed within 20% with the destructive testing data.

Fabbri, L.; Oksanen, M.

1999-06-01

456

On the high-temperature oxidation protection behavior of plasma-sprayed Stellite6 coatings  

Microsoft Academic Search

High-temperature oxidation resistance of the superalloys can be greatly increased by plasma-sprayed coatings, and this is\\u000a a growing industry of considerable economic importance. The purpose of these coatings is to form long-lasting oxidation protective\\u000a scales. In the current investigation, Stellite-6 coatings were deposited on two Ni-base superalloys, Superni 601 and Superni\\u000a 718, and one Fe-base superalloy, Superfer 800H, by a

H. Singh; D. Puri; S. Prakash; V. V. Rama Rao

2006-01-01

457

Some studies on hot corrosion performance of plasma sprayed coatings on a Fe-based superalloy  

Microsoft Academic Search

NiCrAlY, Ni20Cr, Ni3Al and Stellite-6 metallic coatings were deposited on a Fe-based Superalloy (32Ni21Cr0.3Al0.3Ti1.5Mn1.0Si0.1CBal Fe). NiCrAlY was used as bond coat in all the cases. Hot corrosion studies were conducted on uncoated as well as plasma spray coated superalloy specimens after exposure to molten salt at 900 C under cyclic conditions. The thermogravimetric technique was used to establish kinetics of

Harpreet Singh; D. Puri; S. Prakash

2005-01-01

458

Hot Corrosion Resistance and Mechanical Behavior of Atmospheric Plasma Sprayed Conventional and Nanostructured Zirconia Coatings  

NASA Astrophysics Data System (ADS)

Conventional and nanostructured zirconia coatings were deposited on In-738 Ni super alloy by atmospheric plasma spray technique. The hot corrosion resistance of the coatings was measured at 1050C using an atmospheric electrical furnace and a fused mixture of vanadium pent oxide and sodium sulfate respectively. According to the experimental results nanostructured coatings showed a better hot corrosion resistance than conventional ones. The improved hot corrosion resistance could be explained by the change of structure to a dense and more packed structure in the nanocoating. The evaluation of mechanical properties by nano indentation method showed the hardness (H) and elastic modulus (E) of the YSZ coating increased substantially after hot corrosion.

Saremi, Mohsen; Keyvani, Ahmad; Heydarzadeh Sohi, Mahmoud

459

Plasma spraying of functionally graded hydroxyapatite\\/Ti6Al4V coatings  

Microsoft Academic Search

Functionally graded hydroxyapatite (HA)\\/Ti6Al4V coatings were produced by plasma spray process using specially developed HA-coated Ti6Al4V composite powders as feedstock. The microstructure, density, porosity, microhardness, and Young's modulus (E) were found to change progressively through the three-layered functionally graded coating that composed of the layers 50 wt.% HA\\/50 wt.% Ti6Al4V; 80 wt.% HA\\/20 wt.% Ti6Al4V, and HA. No distinct interface

K. A Khor; Y. W Gu; C. H Quek; P Cheang

2003-01-01

460

Synthesis and Preliminary Tests of Suspension Plasma Spraying of Fine Hydroxyapatite Powder  

Microsoft Academic Search

The synthetic hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a very useful biomaterial for numerous applications in medicine, such as e.g., fine powder for suspension plasma spraying.\\u000a The powder was synthesized using aqueous solution of ammonium phosphate (H2(PO4)NH4) and calcium nitrate (Ca(NO3)4H2O) in the carefully controlled experiments. The synthesized fine powder was characterized by X-ray diffraction (XRD) and scanning\\u000a electron microscope (SEM). The

Roman Jaworski; Christel Pierlot; Lech Pawlowski; Muriel Bigan; Maxime Quivrin

2008-01-01

461

Plasma-Sprayed Thermal Barrier Coatings: New Materials, Processing Issues, and Solutions  

NASA Astrophysics Data System (ADS)

Growing demands on thermal barrier coatings (TBCs) for gas turbines regarding their temperature and cyclic capabilities, corrosion resistance, and erosion performance have instigated the development of new materials and coating systems. Different pyrochlores, perovskites, doped yttria-stabilized zirconia, and hexaaluminates have been identified as promising candidates. However, processing these novel TBC materials by plasma spraying is often challenging. During the deposition process, stoichiometric changes, formation of undesired secondary phases or non-optimum amorphous contents, as well as detrimental microstructural effects can occur in particular. This article describes these difficulties and the development of process-related solutions by employing diagnostic tools.

Mauer, Georg; Jarligo, Maria Ophelia; Mack, Daniel Emil; Vaen, Robert

2013-06-01

462

Phase transformation of plasma-sprayed hydroxyapatite coating with preferred crystalline orientation.  

PubMed

Highly oriented hydroxyapatite coatings (HACs) were obtained on titanium substrates through a radio-frequency thermal plasma spraying (TPS) method. XRD patterns showed that the HACs had crystallites with [001] preferred orientation vertical to the coating's surface. XRD results also indicated that tetracalcium phosphate crystallites in the as-sprayed HAC were oriented in the (100) direction. XRD peaks corresponding to tetracalcium phosphate, tricalcium phosphate and calcium oxide were absent after heat and hydrothermal treatment. The orientation degree of the HAC was influenced little by such post-heat treatments. Considering the crystallographic relationship between the tetracalcium phosphate in the as-