Low Temperature Oxidation Behavior of MoSi_2 Composites Strengthened and Toughened by Si_3N_4 Particles and SiC Whiskers

The oxidation behavior of MoSi2 composites strengthened and toughened by Si3N4 particles and SiC whiskers was investigated.The oxidation performances of pure MoSi2,MoSi2-Si3N4(p) and MoSi2+20vol%Si3N4+20vol%SiC at 773K were analyzed by thermo gravimetric analysis(TG).The surface micrograph and phases of the oxidation productions were analyzed using by SEM and X-ray.Pesting phenomena are observed in the pure MoSi2 and MoSi2+20vol%Si3N4 after oxidation,the relationship between gain weight and oxidation time is followed the straight-line law.The oxidation layer is loose and the main oxidation production is MoO3.While the relationship between the gain weight and oxidation time is followed parabolic law during the oxidation of MoSi2+40vol%Si3N4 and the oxidation rate is 0.04mg2/(cm4·h).The oxidation layer is dense and the main oxidation productions are SiO2 and Si2N2O.So the resistance to Pesting oxidation will increase with the content of Si3N4 increasing.There happens serious Pesting in the MoSi2+20vol%Si3N4+20vol%SiC after oxidation and the main oxidation production is short acicular MoO3.