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

Abstract

Abstract:For the use of Nb-base alloys at high temperatures, a high oxidation resistant coating such as a NbSi 2 coating is required. In the present study, to clarify the physico-chemical compatibility between Nb and NbSi 2 , 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 towards to the Nb side, leading to the formation of a Nb 5 Si 3 layer. The growth followed a parabolic rate law, and the growth rate constant was expressed by k p (m 2 s -1 ) =7.98 x10 -10 exp(-131.84 kJmol -1 /RT). In addition, behavior of boron in the Nb/NbSi 2 interfacial reaction was clarified.