Reactive plasma spraying of MoSi 2 using an Ar-10%CH 4 powder carrier gas

Abstract

Plasma spraying of MoSi 2 using an Ar-10%CH 4 powder carrier gas mixture was investigated as a way of incorporating carbon and carbide particles into spray deposits of MoSi 2 which could subsequently getter SiO 2 after elevated-temperature exposure. After hot isostatic pressing (HIP) at 1800°C and 206 MPa for 1 h a decrease in oxygen from approximately 2580 to 750 ppm resulted in the spray deposits of MoSi 2 produced with the ArCH 4 powder gas carrier. A factor of 3 increase in yield strength was observed in these deposits when compared to conventional hot-pressed MoSi 2 matrix. The temperatures between 1100 and 1400°C. This increase was attributed to a decrease in SiO 2 in the MoSi 2 matrix. The presence of SiC particles was identified in as-sprayed deposits of MoSi 2 and after HIP. Silicon carbide particles in the as-sprayed condition resulted from inflight reactions between MoSi 2 and carbon present in the methane gas. Spray deposits of MoSi 2, without the use of the ArCH 4 powder carrier gas, were also produced in order to establish a baseline in elevated temperature behavior.