Thermal Fatigue of MoSi2 and a MoSi2-10 vol% TiC Composite

Induction heating of disk shaped specimens was used to study thermal fatigue behavior of hot pressed MoSi2, hot pressed and hot isostatically pressed (HIPed) MoSi2, and a MoSi2-10 vol% TiC particulate composite. Specimens were subjected to 5 s, 30 s, and 300 s heating and cooling cycles between temperature limits of 700°C and 1200°C. Specimens of both the hot pressed and the hot pressed and HIPed polycrystalline MoSi2 material failed by transgranular cracking on the initial temperature ramp of the 5 s and 30 s cycles. Only when the severity of the thermal cycle was reduced (300 s heating/300 s cooling) was thermal fatigue cracking avoided in the HIPed MoSi2. In sharp contrast, the MoSi2-10% TiC composite remained uncracked when subjected to the severe 30 s heating/30 s cooling cycle. The fatigue results are discussed with reference to the initial microstructure of the specimens and the stress-strain history of the specimens which was obtained by a thermoelastic finite element analysis.