Fretting fatigue at elevated temperature in a Cr-Mo-V steam-turbine steel.

Abstract

Fretting fatigue tests at room and elevated temperatures were carried out using a Cr-Mo-V steam-turbine steel. The fretting reduced the fatigue strengths by a factor of two at an elevated temperature (773 K) as well as at room temperature. The friction coefficients between the specimen and the contact pads increased in proportion to the appropriate stress amplitude. No significant difference in this behavior of the friction coefficient was observed between room and elevated temperatures. Predictions of fretting fatigue lives were made on the basis of the cyclic J-integral analysis proposed in the previous paper, where the frictional force between the fretting pad and the specimen was taken into consideration. The predicted lives were in good agreement with the experimental results at room temperature. At the elevated temperature, the predicted lives were shorter than the experimental ones, as a resulted of crack closure due to significant exidation. The predicted lives at the elevated temperature, where the oxidation-induced crack closure was taken into consideration, were in good agreement with the experimental results.