Oxidation of Niobium Particulate-Reinforced MoSi sub 2

The effect of particulate ( --35 + 80 mesh) addition of Nb by 20 vol.% on the oxidation resistance of MoSi ( --326 mesh) composite exposed to air at 500 and 1200 deg C for 20 h was studied using optical and electron microscopy and X-ray diffraction. The composite was prepared by loading the powder mixture into a Nb can which was degassed, sealed and hot isostatically pressed at 1700 deg C fr 1 h under 207 MPa Ar pressure. The oxidation curves of the composite show losses in mass at both temperatures with spalling of Nb-particles and vapourization of Mo-containing species from unprotected surfaces in the vicinity of oxidized or spalled Nb-particles. Graphs, Photomicrographs. 10 ref.--B.C.