Reaction Diffusion Behaviors for Interface Between Ni-Based Super Alloys and Vacuum Plasma Sprayed MCrAlY Coatings

1999 ◽  
Vol 121 (3) ◽  
pp. 476-483 ◽  
Author(s):  
Y. Itoh ◽  
M. Tamura
Keyword(s):  
Simulation Analysis ◽  
Reaction Diffusion ◽  
Compound Layer ◽  
Vacuum Plasma Spray ◽  
Aluminum Compound ◽  
Vacuum Plasma ◽  
Diffusion Layers ◽  
Mcraly Coatings ◽  
Plasma Sprayed ◽  
Diffusion Behaviors

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. Three kinds of substrate, equiaxis IN738LC, directional solidified CM247LC and single-crystal CMSX-2, and the four kinds of vacuum plasma sprayed MCrAlY coating have been selected for these experiments. The experimental results showed that the reaction diffusion layers consisted of aluminum compound layer and aluminum depleted layer, excepting that the aluminum depleted layer could not be observed in the case of CoNiCrAlY and NiCoCrAlY coatings. It also indicated that the diffusion thickness could be observed to follow a parabolic time dependence. The order of reaction diffusion rate was NiCrAlY > CoCrAlY > CoNiCrAlY > NiCoCrAlY independent of the substrates. A convenient computer-aided system was developed for analyzing the reaction diffusion behaviors at the interface between coating and substrate. It was also clear that the estimated results of long time diffusion behaviors by simulation analysis was in good agreement with experiments.

Aluminizing Behaviors of Vacuum Plasma Sprayed MCrAlY Coatings

2002 ◽  
Vol 124 (2) ◽  
pp. 270-275 ◽  
Author(s):  
Y. Itoh ◽  
M. Saitoh ◽  
Y. Ishiwata
Keyword(s):  
High Temperature ◽  
Diffusion Rate ◽  
Nickel Content ◽  
Reaction Diffusion ◽  
Vacuum Plasma Spraying ◽  
Temperature Oxidation ◽  
Vacuum Plasma ◽  
Mcraly Coatings ◽  
Heat Treated ◽  
Plasma Sprayed

The objective of this study is aluminide overlay coatings of MCrAlY sprayed by a vacuum plasma spraying (VPS) process for the protection against high-temperature corrosion and oxidation of gas turbine components. Diffusion coating processes have been applied for many years to improve similarly the environmental resistance by enriching the surface of nickel-based superalloys with chromium, aluminum, or silicon element. Recently, aluminizing of MCrAlY coatings is used for improving further the high-temperature oxidation resistance. However, the aluminizing properties of plasma-sprayed MCrAlY coatings, which have an important effect on the coating performance, have not been clarified. In this study, five kinds of plasma-sprayed MCrAlY (CoCrAlY, CoNiCrAlY, CoNiCrAlY+Ta, NiCrAlY, and NiCoCrAlY) coating were selected for pack-aluminizing tests. The as sprayed and the heat-treated (1393 K, 2 h, argon cooled and 1116 K, 24 h, argon cooled) MCrAlY specimens were Al-Cr-Al2O3-NH4Cl pack-aluminized at 1173, 1223, and 1273 K for 5, 10, and 20 h, respectively. The experimental results showed that the aluminizing process formed the aluminum rich layers of NiAl or CoAl phase. It also indicated that the thickness of the aluminum rich layer showed a parabolic time-dependence in all MCrAlY coatings. The order of reaction diffusion rate was NiCoCrAlY=NiCrAlY>CoNiCrAlY>CoNiCrAlY+Ta>CoCrAlY. There was a tendency that the reaction diffusion rate by aluminizing increased with increasing nickel content in the MCrAlY coatings and the reaction diffusion rate of as sprayed MCrAlY coatings is faster than that of the heat-treated MCrAlY coatings.

Vacuum Plasma Sprayed ZrO2-Based Thermal Barrier Coatings for Aerospace Applications

1998 ◽  
Author(s):  
T. Brzezinski ◽  
A. Cavasin ◽  
S. Grenier ◽  
E. Kharlanova ◽  
G. Kim ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Temperature Drop ◽  
Single Step ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Vacuum Plasma Spray ◽  
Barrier Coatings ◽  
Vacuum Plasma ◽  
Plasma Sprayed

Abstract Zirconia-based thermal barrier coatings (TBCs), produced using Vacuum Plasma Spray (VPS) technology, were recently subjected to burner rig testing. The VPS TBC performance was compared to TBCs deposited using conventional Atmospheric Plasma Sprayed (APS) and Electron Beam Physical Vapor Deposition (EB-PVD) techniques. All of the coatings consisted of an MCrAlY bond coat and a partially stabilized ZrO2-8%Y2O3 (PSZ) top coat. The TBC coated pins (6.35 mm in diameter) were tested using gas temperatures ranging from 110CC to 1500°C. The pins were tested to failure under severe conditions (1500°C gas temperature, with no internal cooling). The initial testing indicated that under typical operating gas temperatures (1400°C), the VPS TBC performance was comparable, if not superior, to conventional TBCs. Following the encouraging results, thick composite TBCs, produced in a single-step operation, were investigated. Preliminary work on ZrO2-8% Y2O3/Ca2SiO4 composite TBCs with interlayer grading included thermal shock testing and temperature drop measurements across the TBC. The composite TBC thicknesses ranged from 850µm to 1.8 mm. Initial results indicate that thick adherent composite TBCs, with high resistance to severe thermal shock, can be produced in a single step using the VPS process.

Mechanical Properties of Overaluminized MCrAlY Coatings at Room Temperature

2005 ◽  
Vol 127 (4) ◽  
pp. 807-813 ◽  
Author(s):  
Yoshiyasu Itoh ◽  
Masahiro Saitoh
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Volume Fraction ◽  
Bend Strength ◽  
Vacuum Plasma Spraying ◽  
Temperature Oxidation ◽  
Vacuum Plasma ◽  
Mcraly Coatings ◽  
Aluminum Compounds ◽  
Plasma Sprayed

The objective of this study is to compare the mechanical properties of overaluminized MCrAlY coatings sprayed by a vacuum plasma spraying process for the protection against high-temperature corrosion and oxidation in the field of gas turbine components. Recently, the overaluminized MCrAlY coatings are used for improving further the high-temperature oxidation resistance. However, the mechanical properties of aluminized MCrAlY coatings, which have an important effect on coating lives, have not been clarified. Five kind of freestanding MCrAlY specimens (CoCrAlY, CoNiCrAlY, CoNiCrAlY+Ta, NiCrAlY, NiCoCrAlY) were machined from the thick vacuum plasma sprayed (VPS) coatings. And, the heat-treated MCrAlY specimens (1393 K, 2 h, argon cooled and 1116 K, 24 h, argon cooled) and the overaluminized specimens (Al-Cr-Al2O3-NH4Cl pack, 1173–1273 K, 10 h) after the heat-treatment were used. The experimental results suggested that the volume fraction of precipitated aluminum compounds in the VPS MCrAlY coatings and the residual stress induced by the overaluminizing treatment had important effects on the mechanical properties. The Vickers hardness and Young’s modulus of the overaluminized MCrAlY coatings showed higher values in comparison with the VPS MCrAlY coatings. There was a tendency that the bend strength of overaluminized VPS MCrAlY coatings decreased by the aluminizing treatment and also with increasing volume fraction of precipitated aluminum compounds in the VPS MCrAlY coatings. It was also confirmed that the bend strength of aluminized layers themselves was reduced with increasing volume fraction of precipitated aluminum compounds in the VPS MCrAlY coatings. These tendencies were caused by the enrichment of brittle precipitates, such as NiAl and/or CoAl intermetallic compounds.

Light-Emitting Characterization of Vacuum Plasma Sprayed Silicon Coatings

2014 ◽  
Vol 602-603 ◽  
pp. 989-992
Author(s):  
Ya Ran Niu ◽  
Xue Bin Zheng ◽  
Xuan Yong Liu ◽  
Heng Ji ◽  
Chuan Xian Ding
Keyword(s):  
Vacuum Plasma Spray ◽  
Light Emitting ◽  
Vacuum Plasma ◽  
Spray Technique ◽  
Before And After ◽  
Raman Measurement ◽  
Silicon Coating ◽  
Plasma Sprayed ◽  
Vapor Treatment

In the present work, the light-emitting property of silicon coating was explored and the related morphologies and chemical structure of silicon coating were characterized. Silicon coating was prepared by vacuum plasma spray technique and chemically treated by HNO3/HF vapor. The coatings before and after the vapor etching were characterized by field emission scanning electron microscopy and micro-raman spectroscopy. The photoluminescence spectra of the silicon coatings treated with different time were examined. It is found that pores of micrometer and microcracks formed on the surface of silicon coatings after the treatment. The treated silicon coatings exhibited room temperature visible photoluminescence with emission wavelength around 650 nm after excitation. The results of micro-raman measurement proved that there were polysilane and oxygen related functional groups appeared on the coating surface after the vapor treatment, which was supposed to be responsible for the photoluminescent phenomena.

Characteristics of MCrAlY Coatings Sprayed by High Velocity Oxygen-Fuel Spraying System

1999 ◽  
Vol 122 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Y. Itoh ◽  
M. Saitoh ◽  
M. Tamura
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
High Velocity ◽  
Gas Turbines ◽  
High Velocity Oxygen Fuel ◽  
Hvof Spraying ◽  
Vacuum Plasma ◽  
Mcraly Coatings ◽  
Plasma Sprayed ◽  
Oxygen Fuel

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 coatings 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. [S0742-4795(00)00701-8]

scholarly journals Effect of Air Plasma Sprayed Flash Bond Coatings on Furnace Cycle Lifetime of Disks and Rods

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes ◽  
Edward J. Gildersleeve ◽  
Sanjay Sampath
Keyword(s):  
Crack Formation ◽  
Thermal Barrier ◽  
Vacuum Plasma Spray ◽  
Air Plasma ◽  
Bond Coatings ◽  
Bond Coating ◽  
Vacuum Plasma ◽  
Coating Roughness ◽  
Plasma Sprayed ◽  
Oxygen Fuel

Abstract Air plasma sprayed (APS) flash coatings on high velocity oxygen fuel (HVOF) bond coatings are well known to extend the lifetime of thermal barrier coatings (TBCs). Recent work compared flash coatings of NiCoCrAlY and NiCoCrAlYHfSi applied to both rods and disk substrates of alloy 247. For rod specimens, 100 h cycles were used at 1100 °C in wet air. Both flash coatings significantly improved the lifetime compared to HVOF-only and vacuum plasma spray (VPS)-only MCrAlY bond coatings with no statistical difference between the two flash coatings. For disk specimens tested in 1 h cycles at 1100 °C in wet air, the NiCoCrAlY flash coating significantly outperformed an HVOF-only NiCoCrAlYHfSi bond coating and a NiCoCrAlYHfSi flash coating. The flash coatings formed a mixed oxide-metal zone that appeared to inhibit crack formation and therefore extend lifetime. In addition to the flash coating increasing the bond coating roughness, the underlying HVOF layer acted as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. The lower Y+Hf content in the Y-only flash coating appeared to minimize oxidation in the flash layer, thereby increasing the benefit compared to a NiCoCrAlYHfSi flash coating.

Application of Taguchi Method for Optimization of Vacuum Plasma Sprayed CoNiCrAlY Coatings

2007 ◽  
Vol 124-126 ◽  
pp. 1549-1552
Author(s):  
Koo Hyun Lee ◽  
K.H. Ye ◽  
S.T. Kim ◽  
Chae Hong Jeon ◽  
Yo Seung Song ◽  
...  
Keyword(s):  
Taguchi Method ◽  
Flow Rate ◽  
Gas Flow ◽  
Vacuum Plasma Spray ◽  
Gas Flow Rate ◽  
Working Pressure ◽  
Carrier Gas ◽  
Vacuum Plasma ◽  
Plasma Sprayed ◽  
Carrier Gas Flow

Bond coatings, CoNiCrAlY, are prepared on Inconel 738 substrate by vacuum plasma spray (VPS). Mechanical properties of VPSed CoNiCrAlY coatings are investigated via Taguchi method and L18(21×37)orthogonal arrays to determine the optimal setting and the relationship of experimental variables. Seven parameters were considered as follows: (A) arc current; (B) primary gas flow rate; (C) secondary gas flow rate; (D) stand-off distance; (E) working pressure; (F) carrier gas flow rate (Ar); and (G) powder feeding rate.The effect of carrier gas flow rate on the porosity is determined to be the highest among the parameters investigated. Higher microhardness values are observed for the VPSed coatings as compared to the coatings prepared by conventional high velocity oxygen fuel probably due to low amount of the porosity.

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