Silicide composite with niobium-based metallic phase and silicon- modified laves-type phase

摘要

A silicide-based composite toughened with a niobium-based metallic phase, and further containing a phase that significantly improves the oxidation resistance of the composite. The oxidation- resistant phase is a chromium-based Laves-type phase modified with silicon, which has been shown to greatly increase the oxidation resistance of silicide-based composites at temperatures of up to 1200 C. The oxidation-resistant silicide-based composite generally contains one or more silicide intermetallic phases, each of which is an M.sub.5 Si.sub. 3 -type phase where M is Nb+Ti+Hf. The niobium-based metallic phase contains niobium, titanium, hafnium, chromium, aluminum and silicon. The silicon-modified Laves-type phase is of the Cr.sub.2 M type where M is Nb+ Ti+Hf. A silicide-based composite contains, in atomic percent, about 12- 25% titanium, about 6-12% hafnium, about 15-25% chromium, about 1-8% aluminum and about 12-20% silicon, with the balance essentially niobium.