The thermal shock fatigue behavior of Ti(C,N) based ceramets containing 20% nickel has been studied The results show that the formation of thermal shock fatigue cracking is related to the nucleation, growth and joining of microvoids distributed at the interfaces of Ti(C,N)/Ni phases The incubation period of crack formation decreases and the rate of crack propagation increases with increasing cyclic temperature and cooling rate within the cycles The effects are mainly caused by increases of thermal stress and temperature gradients within the specimens The introduction of a notch also has the same effect SEM examination has some striae on the thermal shock fatigue fracture surfaces The crack propagation is a continuous process on a macroscopic scale although discontinuous microscopically