Interfacial reactions in Nb/NbSi2 and Nb/NbSi2–B systems

For the use of Nb-based alloys at high temperatures, a high oxidation resistant coating such as NbSi2 coating is required. In the present study, to clarify the physico-chemical compatibility between Nb and NbSi2, the extent of the interfacial reaction and the reaction products were studied at temperatures ranging from 1573 to 1773 K. Growth of the reaction layer formed in the interfacial reactions was caused by the preferential diffusion of Si toward to the Nb side, leading to the formation of a Nb5Si3 layer. The growth followed a parabolic rate law, and the growth rate constant was expressed by kp (m2 s−1) = 7.98 × 10−10 exp(−131.84 kJ mol−1/RT). In addition, behavior of boron in the Nb/NbSi2 interfacial reaction was clarified.