Fatigue strength of ceramic-coated steel at elevated temperature.

Abstract

Fatigue strengths of ceramic-coated steel at room and elevated (773K) temperatures were almost identical. Although, at room temperature, fatigue strength of substrate steel was higher than that of ceramic-coated steel, at elevated temperature, fatigue strength of ceramic-coated steel was higher than that of substrate steel. Fatigue-fracture processes of ceramic-coated steel were as follows. At a significantly early stage of fatigue, a fatigue crack is initiated at the surface of the ceramic layer and propagates quickly to the metal layer. The propagating fatigue crack continues to grow into the substrate; there is no initiation of another fatigue crack at the interface between ceramic and metal layers. Fatigue strength of the specimen with a thick ceramic-coating layer was higher than that with a thin ceramic layer. This result will be understood, considering that the thickness of the ceramic layer corresponds to an initial defect size.