Oxidation behavior of Mo≤5Si3C≤1 and its composites

The oxidation behavior of Mo≤5Si3C≤1 and its composites was studied in air over the temperature range of 500°C–1600°C. Experiments revealed poor oxidation resistance of monolithic Mo≤5Si3C≤1 at high temperature. The oxidation was quite rapid at 1200°C and above, resulting in complete oxidation of specimens in a short time. The addition of 2.0 wt% boron was found to produce a Mo≤5Si3C≤1 composite with three other phases of MoB, MoSi2, and SiC, and showed remarkable improvement in oxidation resistance. The mechanism for the improvement was attributed to the viscous sintering of the scale to close the pores formed during the initial oxidation period. Oxidation tests were also conducted on SiC-Mo≤5Si3C≤1 composite at 800°C, 1300°C and 1600°C for more than 100 hours. The oxidation resistance of the composite was found to be very good. The results demonstrate that, though oxidation resistance of monolithic Mo≤5Si3C≤1 is far insufficient for high-temperature applications, boron-modification and/or composites with SiC are viable methods to improve oxidation resistance to a practically acceptable level.