Characterization of microstructure and oxidation resistance of Y and Ge modified silicide coating on Nb-Si based alloy
July 17-21, 2016
Y and Ge modified silicide coating was prepared on the Nb-Si based alloy by Si–Ge–Y co-deposition at 1300°C for 10h. The coating consists of an outer layer and a transitional layer(Fig.1a). The outer layer is consist of( Nb , X )(Si, Ge)2(X represents Ti, Cr, Ge and Hf elements) and the transitional layer is composed of ( Nb , X )5(Si, Ge)3. The mass gain of the coated specimen is 2.78 mg cm−2 after oxidation at 1250 °C for 100 h(Fig.1b), which reveals that Ge and Y modified silicide coating exhibits better oxidation resistance than Ge-modified silicide coating and Y element is significantly beneficial for the oxidation resistance. The results indicate that Y refines grain size due to the formation of Y3Al5O12 particles at grain boundaries, which could promote the rapid formation of protective SiO2 and GeO2 scale, and then oxygen diffusion could be decreased. Therefore, the oxidation resistance of the coating is improved.
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Chungen Zhou, lijing Zheng, and Huarui Zhang, "Characterization of microstructure and oxidation resistance of Y and Ge modified silicide coating on Nb-Si based alloy" in "Beyond Nickel-Based Superalloys II", Chair: Dr Howard J. Stone, University of Cambridge, United Kingdom Co-Chairs: Prof Bernard P. Bewlay, General Electric Global Research, USA Prof Lesley A. Cornish, University of the Witwatersrand, South Africa Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/superalloys_ii/63