ISOTHERMAL OXIDATION BEHAVIOR OF A NiCoCrAlYSiB+AlSiY GRADIENT COATING
WANG Weixin1, 2), JIANG Sumeng1), WEI Guangzhi2), MA Jun1), GONG Jun1), SUN Chao1)
1) State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016
2) The Materials and Metallurgical College, Guizhou University, Guiyang 550003
Cite this article:
WANG Weixin JIANG Sumeng WEI Guangzhi MA Jun GONG Jun SUN Chao. ISOTHERMAL OXIDATION BEHAVIOR OF A NiCoCrAlYSiB+AlSiY GRADIENT COATING. Acta Metall Sin, 2011, 47(5): 578-586.
Abstract Conventional NiCoCrAlYSiB coating and (NiCoCrAlYSiB+AlSiY) gradient coating were prepared by using arc ion plating (AIP) on the Ni base single crystal superalloy substrate. Comparative studies of the morphology and microstructure together with high temperature oxidation behaviors at 1000, 1100 and 1150 ℃ for the two different coatings were investigated. The results show that after vacuum annealing, the conventional coating is mainly composed of general γ'/γ and a small quantity of β-NiAl dispersed in γ'/γ while the outer layer of the gradient coating consists of β-NiAl and dispersed β-Cr and Cr3Si in β-NiAl and the inner layer consists of Cr-rich phases plus minor β-NiAl. The conventional coating has excellent oxidation resistance only at 1000℃, while it degraded rapidly at 1100 ℃ and 1150 ℃, on which surface spinel formation was observed; however, the gradient coating has more excellent oxidation resistance than the conventional one at all the three temperatures. After oxidation for 300 h at 1100℃, there still exists a great amount of β-NiAl, and even after oxidation for 300 h at 1150℃, Al content is higher than 8% (mass fraction), in which a small amount of β-NiAl and supersaturated γ'/γ insure the formation and self repair of alumina.
