The formation of the inter-diffusion layer between NiCrAlY coating and Nb substrate during vacuum heat treatment was investigated. A NiCrAlY coating was applied on Nb substrate by cathode arc deposition. Vacuum heat treatments were carried out at 800, 900, and 1000°C for 2 h. SEM, EPMA, EDS, and XRD were performed to analyze the microstructure of the inter-diffusion layer and the results were interpreted using the 1002°C isothermal ternary Nb-Ni-Cr phase diagram. It was found that at 800°C the inter-diffusion layer has a single NbNi₃ layer; at 900°C the inter-diffusion layer consists of an outer NbNi₃ layer, a thin intermediate NbCr₂(HT) layer, and an inner Nb₇Ni₆ layer; at 1000°C the interdiffusion layer has three well-developed layers of an outer NbNi₃ layer, an inner Nb₇Ni₆ layer, and an intermediate layers comprising NbCr₂(HT) and NbNi₃. A small amount of Cr exists in both the NbNi₃ and the Nb₇Ni₆ phases as solid solution, and a large amount of Ni in the NbCr₂(HT) phase as solid solution.
Materials Transactions56, no. 3 (25 February 2015): 367–371.
Saito, Shigeru, Toshiyuki Takashima, Katsumi Miyama, Toshio Narita, and Linruo Zhao. ‘Formation of Inter-Diffusion Layer between NiCrAlY Coating and Nb Substrate during Vacuum Heat-Treatment’. Journal of the Japan Institute of Metals and Materials 78, no. 9 (2014): 359–63. https://doi.org/10.2320/jinstmet.j2014017.