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.

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.

scholarly journals Microstructure and Mechanical Properties of Vacuum Plasma Sprayed HfC, TiC, and HfC/TiC Ultra-High-Temperature Ceramic Coatings

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 124
Author(s):  
Ho Seok Kim ◽  
Bo Ram Kang ◽  
Seong Man Choi
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Single Layer ◽  
Ceramic Coatings ◽  
Hafnium Carbide ◽  
Vacuum Plasma Spraying ◽  
Vacuum Plasma ◽  
Coating Layers ◽  
Hardness Values ◽  
Ultra High Temperature

To improve the oxidation resistance of carbon composites at high temperatures, hafnium carbide (HfC) and titanium carbide (TiC) ultra-high-temperature ceramic coatings were deposited using vacuum plasma spraying. Single-layer HfC and TiC coatings and multilayer HfC/TiC coatings were fabricated and compared. The microstructure and composition of the fabricated coatings were analyzed using field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The coating thicknesses of the HfC and TiC single-layer coatings were 165 µm and 140 µm, respectively, while the thicknesses of the HfC and TiC layers in the HfC/TiC multi-layer coating were 40 µm and 50 µm, respectively. No oxides were observed in any of the coating layers. The porosity was analyzed from cross-sectional images of the coating layers obtained using optical microscopy. Five random areas for each coating layer specimen were analyzed, and average porosity values of approximately 16.8% for the HfC coating and 22.5% for the TiC coating were determined. Furthermore, the mechanical properties of the coating layers were investigated by measuring the hardness of the cross section and surface roughness. The hardness values of the HfC and TiC coatings were 1650.7 HV and 753.6 HV, respectively. The hardness values of the HfC and TiC layers in the multilayer sample were 1563.5 HV and 1059.2 HV, respectively. The roughness values were 5.71 µm for the HfC coating, 4.30 µm for the TiC coating, and 3.32 µm for the HfC/TiC coating.

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]

Vacuum Plasma Spraying of Pre-reacted MoSi2 and SiC-Reinforced MoSi2 Produced by a New Kind of Powder Processing

2000 ◽  
Author(s):  
B. Wielage ◽  
S. Steinhäuser ◽  
G. Reisel ◽  
I. Morgenthal ◽  
R. Scholl
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Plasma Spraying ◽  
Powder Processing ◽  
Protective Coatings ◽  
High Energy ◽  
Vacuum Plasma Spraying ◽  
Temperature Oxidation ◽  
Vacuum Plasma ◽  
Brittle Ductile Transition

Abstract Molybdenum silicides have the potential as protective coatings for high-temperature applications because of their high melting point and their high-temperature oxidation resistance. Reinforcing MoSi2 with SiC shows an improvement of its low toughness at room temperature and low creep resistance at temperatures above the brittle-ductile transition temperature of approximately 700-1000 °C. A new kind of powder processing was used to produce MoSi2 and MoSi2-SiC as a feedstock for thermal spraying. Mixtures of the elemental powders, molybdenum and silicon, were prepared by milling and subsequent heat treatment to get highly dispersed, pre-reacted powders. As high-energy milling equipment, a planetary ball mill was used to prepare the powders. In the case of reinforcement, SiC was mixed to the pre-reacted MoSi2 at the end of the milling process, that means before heat treatment. On these as-milled powders, X-ray diffraction characterization (XRD), scanning electron microscopy (SEM), electron probe micro analysis (EPMA) and determination of the oxygen level were carried out. Vacuum plasma spraying has been used to deposit the powders onto a carbon steel substrate. Evaluated coating characteristics were the microstructure (SEM), phases (XRD), EPMA, oxygen content, microhardness and surface roughness. Tests at high temperatures will be considered in future work.

Microstructure Characteristics and High-Temperature Oxidation Behavior of Plasma-Sprayed and Laser-Remelted MCrAlY Coatings on TiAl Intermetallics

2011 ◽  
Author(s):  
Zongjun Tian ◽  
Lida Shen ◽  
Zhidong Liu ◽  
Yinhui Huang
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Plasma Spraying ◽  
High Temperature Oxidation ◽  
Intermetallic Alloys ◽  
Laser Remelting ◽  
Temperature Oxidation ◽  
Mcraly Coatings ◽  
Tial Intermetallics ◽  
Plasma Sprayed

In order to further improve the high-temperature oxidation resistance of TiAl intermetallic alloys, MCrAlY coatings were fabricated by plasma spraying and plasma spraying-laser remelting technologies. The microstructures of the as-sprayed and laser-remelted MCrAlY coatings were studied. In addition, the oxidation behaviors at 850 °C for three samples were investigated. One sample is the matrix of TiA1 intermetallic alloys, the other one is processed by plasma-spraying MCrAlY coatings, and the third one is processed by plasma-spraying and laser-remelting MCrAlY coatings. It was revealed that the oxidation resistance of TiAl intermetallics is weak due to lack of protection of Al2O3 film formed on the surface. The plasma-sprayed MCrAlY coatings have better oxidation resistance than the TiAl intermetallics although the plasma-sprayed MCrAlY coatings have high density of porosity and a typical layered structure. It is demonstrated that most of the holes can be eliminated by laser remelting, leading to the best oxidation resistance of the third sample with the laser-remelted coatings. The high oxidation resistance of the laser-remelted coatings is mainly attributed to three aspects: firstly, an Al enriched zone on the coating surface is formed during laser remelting, which is transformed into a protective Al2O3 film during oxidation process. Secondly, laser remelting eliminates most of the defects in plasma-sprayed coatings and enhances its density, thus decreases the channel of oxidation diffusion in high temperature oxidation process. Thirdly, rapid cooling of laser remelting results in a grain refinement and a preferred oxidation of Al at the initial stage, leading to a reduction of oxidation rate.

SANDVIK 3R12HT

Alloy Digest ◽  
2002 ◽  
Vol 51 (4) ◽  
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
Bend Strength ◽  
Steel Company ◽  
Temperature Performance ◽  
Metallurgical Processing

Abstract Sandvik 3R12HT is an improved version of Type 304L for better mechanical properties at high temperatures. This is accomplished by improved metallurgical processing and a modified chemistry. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength as well as creep. It also includes information on high temperature performance and corrosion resistance as well as heat treating and joining. Filing Code: SS-850. Producer or source: Sandvik Steel Company.

Preparation of WC-TiC-Ni3Al-CaF2 functionally graded self-lubricating tool material by microwave sintering and its cutting performance

2020 ◽  
Vol 39 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Siwen Tang ◽  
Rui Wang ◽  
Pengfei Liu ◽  
Qiulin Niu ◽  
Guoqing Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Microwave Heating ◽  
Cutting Performance ◽  
Conventional Heating ◽  
Hard Alloys ◽  
Dry Cutting ◽  
Temperature Oxidation ◽  
Lubricating Material ◽  
Heating Technology

AbstractWith the concern of the environment, green dry cutting technology is getting more and more attention and self-lubricating tool technology plays an important role in dry cutting. Due to the demand for high temperature performance of tools during dry cutting process, cemented carbide with Ni3Al as the binder phase has received extensive attention due to its excellent high temperature strength and high temperature oxidation resistance. In this paper, WC-TiC-Ni3Al-CaF2 graded self-lubricating material and tools were prepared by microwave heating method, and its microstructure, mechanical properties and cutting performance were studied. Results show that gradient self-lubricating material can be quickly prepared by microwave heating technology, and the strength is equivalent to that of conventional heating technology. CaF2 not only plays a role in self-lubrication, but also refines the grain of the material. A reasonable gradient design can improve the mechanical properties of the material. When the gradient distribution exponent is n1 = 2, the material has high mechanical properties. Cutting experiments show that the WC-TiC-Ni3Al-CaF2 functional gradient self-lubricating tool has better cutting performance than the homogeneous WC-TiC-Ni3Al hard alloys.

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