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℃, 900℃ and 1000℃ 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℃ isothermal ternary Nb-Ni-Cr phase diagram. It was found that at 800℃ the IDZ has a single NbNi3 layer; at 900℃ the IDZ consists of an outer NbNi3 layer, a thin intermediate NbCr2(HT) layer and an inner Nb7Ni6 layer; at 1000℃ 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.
