Refractory metal silicides reinforced by in-situ formed Nb2O5 fibers and mullite nanoclusters

Abstract There is keen interest in the use of refractory metal silicides as structural materials or thermal barrier coatings for a high temperature environment. However, a long-standing problem for these materials is their poor thermal shock property. To address this challenge, Nb-Al-SiC elements were introduced into the MoSi 2 matrix and consolidated by in-situ hot pressing. We find that this treatment leads to improved performance of MoSi 2 composites in high temperature thermal shock resistance and bending strength. After in-situ HPing, the Nb, Al 2 O 3 particles, and SiC nanoclusters were uniformly dispersed in the MoSi 2 matrix and inhibited the movement of dislocation, resulting in a strengthening effect. During the thermal shock process, the fragmentized oxide layer present in the surface of the pure MoSi 2 alloy disappeared completely, and a dense multi-component oxide layer was formed in-situ on the surface of the MoSi 2 composites. The dense multi-component oxide layer was composed of SiO 2 glass, fiber-structured Nb 2 O 5 , and nano-sized mullite phases. The fiber structured and nano-sized oxide phases play an important role in strengthening the oxide layer.