Creep behavior of plasma-sprayed SiC-reinforced MoSi2

Abstract

In a previous paper, the authors presented some preliminary results on the synthesis, room temperature fracture toughness and creep resistance of a SiC ([approximately]9 vol.%) - reinforced MoSi[sub 2] composite processed by a low pressure plasma deposition technique. The results of the constant stress tests as a function of temperature suggested a change in the rate-controlling creep mechanism at 1300[degree]C from one with a high activation energy at temperatures lower than 1300[degree]C to one with a low activation energy at temperatures higher than 1300[degree]C. The creep mechanism in the low activation energy region was attributed to be grain boundary sliding, which is assisted by the presence of an amorphous silica grain boundary phase which melts or softens at a temperature of approximately 1300[degree]C. It is the purpose of this paper to confirm the suggestion that a change in the rate-controlling creep mechanism as a function of temperature occurs in the plasma-sprayed SiC-reinforced MoSi[sub 2]. The stress exponent(n), activation energy (Q) for creep, and microstructure as a function of temperature were investigated. In addition, the effect of orientation on the creep behavior (with respect to the spray direction).