Property and Oxidation Behaviours of (Mo,Cr)Si2 + ZrO2 Composite Produced by Pressure-Less Sintering

A composite of (Mo0.9Cr0.1)Si2+15vol% ZrO2 was prepared with powder metallurgy and pres-sure-less sintering, aiming at applications of high temperature structural materials. Mechanical properties of the composites were assessed with hardness, fracture toughness Kc and KIC tested using indentation fracture and SEVNB methods, flexure strength at room temperature and 1200˚C, and isothermal oxidation at 1400˚C. The results showed that the native silica oxide on the silicide feedstock surface, and in turn, the SiO2 in the sintered bulks was significantly re-duced in terms of Cr-alloying. (Mo0.9Cr0.1)Si2 and (Mo0.9Cr0.1)Si2+15vol% ZrO2 composite exhib-ited enhanced sinterability, owing to the formation of (Cr, Mo)5Si3. Fracture toughness of the composite was increased by a factor of 1.6 of that of the monolithic silicide. Mechanical prop-erty of the composite was not affected by Cr addition. However, the high temperature oxidation resistance was greatly improved in the (Mo0.9Cr0.1)Si2+15vol%ZrO2 composite compared with the as-sintered MoSi2+15vol%ZrO2. The Cr-alloying effects on feedstock native oxides, micro-structure, mechanical property and high temperature oxidation resistance were discussed.