Thermomechanical fatigue(TMF) is a unique type of fatigue process when material is simultaneously subjected to fluctuating temperature and load. Isothermal fatigue life predictions are not suitable to TMF conditions since most of material properties and damage mechanisms are temperature dependent. There have been little studies of TMF on ferritic stainless steel since it is not generally used in high temperature. The 429EM stainless steel is ferritic stainless steel which will be used in exhaust manifold. Induction heater and suitable induction coil was developed to make the TMF waveform. Tensile tests, low cycle fatigue(LCF) tests and TMF tests were performed at several temperature from room temperature(RT) to 600℃. Elastic Modulus, yield stress and UTS decreased when temperature increased. Considerable cyclic hardening occurred during most of life. The relationship between fatigue life and temperature did not show simple monotonic relation. The longest life at same total strain range occurred at 200℃ and the shortest life occurred at 400℃. It is regarded as embrittlement of ferritic stainless steel near 400℃. The TMF life at same total mechanical strain range was much shorter than the shortest LCF life in the temperature range of TMF. The cycles to failure depended on the phase between temperature and strain energy density. The effect of phase to the life is very complex. The life of in-phase condition was shorter than that of out-of-phase condition during 350-550℃. But the phase effect during 350-650℃is negligible. Hysteresis loops of in-phase and out-of-phase are symmetric on the origin. To the result of this behavior, creep effect is negligible in this temperature range on 429EM stainless steel.
