| Abstract | The formation of the inter-diffusion zone (IDZ) 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°C, 900°Cand 1000°C for 2 h. SEM, EPMA, EDS and XRD were performed to analyze the microstructure of the IDZ and the results were interpreted using the 1002°C isothermal ternary Nb-Ni-Cr phase diagram. It was found that at 800°C the IDZ has a single NbNi₃ layer; at 900°C the IDZ consists of an outer NbNi₃ layer, a thin intermediate NbCr₂(HT) layer and an inner Nb₇Ni₆ layer; at 1000°C the IDZ has three well-developed layers: an outer NbNi₃ layer, an intermediate NbCr₂(HT) layer and an inner Nb₇Ni₆ layer. A small amount of Cr exists in both NbNi₃ and Nb₇Ni₆ phases as solid solution, and a large amount of Ni in NbCr₂(HT) phase as solid solution. |
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