High temperature load–deflection behaviour of reaction bonded SiC (RBSC)

Preforms of commercial SiC (0.2 and 23.65 μm particle diameter) and petroleum coke powders were infiltrated with Si to prepare reaction bonded SiC (RBSC) with varying amount of residual Si phase (16.5–42.0% v/v). Load–deflection behaviour of the infiltrated materials was studied with the help of a 4-pt. bending strength tester at room temperature, 1300 and 1370°C. The high temperature deformation of the material showed marked difference from the room temperature behaviour. At 1300°C at a constant level of load (150 N), deflection increased from 0.16 mm to >0.58 mm with increase in residual Si from 16.5 to 42.0% v/v in the case of fine grained RBSC; for coarse grained material, the corresponding increase was observed to be from 0.11 to 0.24 mm with an increase in Si from 16.5 to 24.1% v/v. The room temperature load–deflection behaviour was found to be mostly elastic in nature. Reflected light optical microscopy (RLM) of deformed specimens and scanning electron microscopy (SEM) of fractured surfaces revealed the evidence of plastic flow that appears to be set in by high ductility of the residual Si causing deformation at high temperatures.