Elevated-temperature mechanical behavior of plasma-sprayed MoSi 2SiC

Abstract

The elevated-temperature mechanical behavior of a plasma-sprayed MoSi 2-9vol.%SiC particulate composite was investigated over the temperature range 1100–1500°C. At temperatures of 1200 °C or less the stress exponent of 2.3–2.5, grain size exponent of −2.2, activation energy for creep of about 300 kJ mol −1, equiaxed grains after deformation and no deformation-induced dislocations suggest grain boundary sliding controlled by lattice diffusion of either Mo or Si as the dominant deformation mechanism. At temperatures of above 1300 °C the stress exponent is 1.3–1.5 and the activation energy for creep is 190 kJ mol −1. It is believed that the dominant deformation mechanism in this temperature range is grain boundary sliding controlled by grain boundary diffusion. The decrease in the stress exponent and activation energy for creep is thought to be a result of melting or softening of an amorphous silica grain boundary phase. The creep resistance of the plasma-sprayed MoSi 2SiC composite is lower than that for MoSi 2SiC composites produced using powder metallurgy and in-situ techniques as a result of its finer grain size and/or lower volume fraction of SiC.