Correlation with Cracking Behavior of Coating Film and Fatigue Strength in Alumina Coated Stainless Steels

摘要

Static tensile test and a cyclic plane bending tests in alumina coated stainless steels werernconducted in ambient air to investigate the relationship between the cracking or decohesion of coatingrnfilm and fatigue behaviors of the base metal, respectively. The coating processes employed were thernplasma-chemical vapor deposition method and the ion-plating, one of physical vapor depositionrnmethods. The static tensile tests in coated specimens showed a similar stress-strain curve with that in thernbase metal, except for the crystalline alumina coated specimen with a lower strength. The critical strainrncorresponding to crack initiation in the coating film as well as the fatigue strength in the coatedrnspecimens varied depending on the coating process employed. An increase of the fatigue limit andrnprolonged fatigue lifetime in most coated specimens was observed as compared with that of the basernmetal. In the case of ion plated specimen fatigued at a high stress amplitude level, fatigue cracks wererninduced in the substrate where the coating film had cracked and delaminated. These led to a shorterrnfatigue life than the base metal. Both the suppression effect of slip deformation in the substrate due tornthe coating film and the damage behavior in the coating film influenced the fatigue strength of therncoated specimens.