Microstructural Evolution of NiCoCrAlHfYSi and NiCoCrAlTaY Coatings Deposited by AC-HVAF and APS
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Microstructural Evolution of NiCoCrAlHfYSi and NiCoCrAlTaY Coatings Deposited by AC-HVAF and APS Yujun Han1,2,3 • Hongfei Chen1 • Dong Gao4 • Guang Yang1 • Bin Liu1 Yajie Chu2,3 • Jinkai Fan2,3 • Yanfeng Gao1
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Submitted: 4 January 2017 / in revised form: 12 July 2017 / Published online: 5 September 2017 Ó ASM International 2017
Abstract The chemical composition of NiCoCrAlHfYSi with a suitable particle size, deposited using an activated combustion-high velocity air fuel (AC-HVAF) spray, is a potentially promising process because dense, continuous and pure alumina can be formed on the surface of the MCrAlY metallic coatings after isothermal oxidation exposure. The NiCoCrAlHfYSi (Amdry386) and NiCoCrAlTaY (Amdry997) coatings were produced using ACHVAF and APS, respectively. Isothermal oxidation was subsequently conducted at 1050 °C in air for 200 h. This paper compares the characteristics of four coated samples, including the surface roughness, elastic modulus, hardness, oxide content, microstructural characteristics and phase evolution of thermally grown oxides (TGO). The growth of both the TGO and alumina scales in the TGO of the HVAF386 coating was relatively rapid. The h- to a-alumina phase transformation was strongly determined by the Hf and Si dopants in the HVAF386 coating. Finally, the extent of grain refinement and deformation storage energy
& Yujun Han [email protected] Yanfeng Gao [email protected] 1
School of Materials Science and Engineering, Shanghai University, Shanghai 200444, People’s Republic of China
2
School of Materials Engineering, Nanjing Institute of Technology, Nanjing 211167, Jiangsu, People’s Republic of China
3
Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing 211167, Jiangsu, People’s Republic of China
4
AVIC Commercial Aircraft Engine Co., Ltd. Shanghai, Shanghai 200241, People’s Republic of China
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in the HVAF997 coatings were determined to be significantly crucial for the h- to a-alumina phase transformation. Keywords h- to a-alumina phase transformation ACHVAF microstructural characteristics NiCoCrAlHfYSi (Amdry386) TGO (thermally grown oxides)
Introduction MCrAlY (M represents cobalt and/or nickel) coatings are often used for high-temperature corrosion resistance or as the bond coat of thermal barrier coating (TBCs) systems, and the methods of deposition often include low pressure plasma spray (LPPS), vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), electron beam physical vapor deposition (EB-PVD) and so on (Ref 1-3). To enhance the high-temperature resistance ability and overall stability of MCrAlY coatings, numerous methods have been attempted, including doping with a small quantity of active elements and refractory elements, such as Zr, Ta, and Hf (Ref 4), synthesis of nanoscale feedstock powders for thermal spray (Ref 5), ion implantation (Ref 6), and pulse radiation intermediate processing (Ref 7). Although these methods improved the performance and extended the lifetime of the MCrAlY
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