Study on the Oxidation Behavior of LPPS MCrAlY Coatings at High Temperature: Part II Coating Microstructure Development

2021 ◽  
Vol 1035 ◽  
pp. 584-590
Author(s):  
Kang Yuan ◽  
Zhao Ran Zheng
Keyword(s):  
High Temperature ◽  
Thermodynamic Simulation ◽  
Thermal Barrier ◽  
Microstructure Development ◽  
Temperature Oxidation ◽  
Bond Coats ◽  
Β Phase ◽  
Mcraly Coatings ◽  
Coating Microstructure ◽  
Simulation Results

MCrAlY can be used as bond coats for thermal barrier coatings (TBCs) with good ductility and excellent resistance against high temperature oxidation and hot corrosion. The behavior of the microstructure development in the MCrAlY coatings plays a key role on the oxidation resistance. In this paper, the microstructure in the coatings oxidized at 750~1100 °C was analyzed. The formation of the phases and their fraction were studied by comparing thermodynamic simulation results with the experimental observations. At higher temperatures (>1000 °C) β-to-γ’-to-γ phase transformation took place while at lower temperatures (<1000 °C) β phase would transfer to γ directly. The results show that the simulation can semi-quantitatively predict the microstructure formed in the coating.

Oxidation Behavior of LPPS MCrAlY Coatings at High Temperature: Part I TGO Growth and β Phase Depletion

2021 ◽  
Vol 1035 ◽  
pp. 539-544
Author(s):  
Zhao Ran Zheng ◽  
Kang Yuan
Keyword(s):  
High Temperature ◽  
Early Stage ◽  
Oxidation Kinetic ◽  
Thermally Grown Oxide ◽  
Temperature Oxidation ◽  
Β Phase ◽  
Mcraly Coating ◽  
Mcraly Coatings ◽  
Diffusion Controlled ◽  
Tgo Growth

MCrAlY can be used as bond coats for thermal barrier coatings (TBCs) with good ductility and excellent resistance against high temperature oxidation and hot corrosion. The behavior of the thermally grown oxide (TGO) scale formed at the MCrAlY coatings plays a key role on the oxidation resistance. In this paper, the oxidation kinetic curves of a MCrAlY coating at 900~1000 °C were obtained by measuring the thickness of the TGO scales. The curves basically conveyed parabolic laws, indicating a diffusion-controlled mechanism of the TGO growth. The thickness of TGO was positively correlated with the consumption of β phase during the early stage of the oxidation processes. After about the half-life of the β phase consumption, the depletion of the β phase significantly accelerated, which was caused by coating-substrate interdiffusion. In addition, the microstructure of the TGO was analyzed

High Temperature Oxidation of Thermal Barrier Coating Systems on RR3000 Substrates: Pt Aluminide Bond Coats

2001 ◽  
Vol 369-372 ◽  
pp. 615-622 ◽  
Author(s):  
K. Bouhanek ◽  
O.A. Adesanya ◽  
F.Howard Stott ◽  
Peter Skeldon ◽  
D.G. Lees ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coating ◽  
High Temperature Oxidation ◽  
Thermal Barrier ◽  
Temperature Oxidation ◽  
Bond Coats ◽  
Barrier Coating

High Temperature Oxidation and Microstructural Evolution of Modified MCrAlY Coatings

2013 ◽  
Vol 45 (3) ◽  
pp. 1401-1408 ◽  
Author(s):  
Giovanni Pulci ◽  
Jacopo Tirillò ◽  
Francesco Marra ◽  
Fabrizio Sarasini ◽  
Alessandra Bellucci ◽  
...  
Keyword(s):  
High Temperature ◽  
Microstructural Evolution ◽  
High Temperature Oxidation ◽  
Temperature Oxidation ◽  
Mcraly Coatings

Microstructure and Nanoindentation Studies of Hydridated Zircaloy-4 Claddings After High Temperature Oxidation

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Petra Gávelová ◽  
Patricie Halodová ◽  
Daniela Marušáková ◽  
Ondřej Libera ◽  
Jakub Krejčí ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxygen Concentration ◽  
Hydrogen Content ◽  
Oxygen Solubility ◽  
Pressurized Water ◽  
Temperature Oxidation ◽  
Β Phase ◽  
Significant Difference ◽  
Water Reactors ◽  
Increasing Temperature

Abstract Zirconium-based alloys are one of the most significant materials in thermal-neutron reactor systems. With very low neutron capture cross section, good corrosion resistance, mechanical strength and resistance to neutron radiation damage, zirconium alloys are used for fuel claddings. Cladding materials are still improved and tested in normal as well as critical reactor conditions. Zircaloy-4 (Zr-1.5Sn-0.2Fe-0.1Cr) is used for west types of light-water reactors, Pressurized Water Reactors (PWR). In our study, Zircaloy-4 cladding tubes were high-temperature oxidized in steam at the series of temperatures from 950 up to 1425 °C to simulate PWR reaching severe accident conditions. To observe the influence of hydrogen (H) diffusing from the coolant water on oxidation process, the specimens with ∼1000 ppm H were compared to the specimens with almost no hydrogen content. Wave Dispersive Spectroscopy (WDS) and nanoindentation were performed in line profiles across the cladding wall. Both methods contributed to verify the pseudobinary Zircaloy-4/oxygen phase diagram with focus on determination of phase boundaries. The increase of oxygen concentration with increasing temperature was observed. Moreover, oxygen concentration profiles and related change in nanohardness and Young's modulus showed the effect of hydrogen on the cladding microstructure. Hydrogen dissolved in metallic matrix increases the oxygen solubility in prior β-phase, the specimens with 1000 ppm H showed the higher oxygen content at almost all temperatures. As well, material hardening was observed on specimens with 1000 ppm H with significant difference in β-phase, measured on specimens exposed to lowest and highest oxidation temperature. Thus, with increasing temperature and hydrogen content, increased oxygen solubility affects the cladding ductility.

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.

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