Effects of coating porosity, thickness and residual stress on stress and fatigue behavior of micro-arc oxidation coated aero Al alloys

The stress analysis of micro-arc oxidation (MAO) coated aero Al alloys is the basis to reveal the mechanism of fatigue deterioration. To clarify effects of the coating defects on fatigue life, a stress calculation model with micropores and residual stress is established based on shear lag model in this study. The effects of porosity, substrate elastic modulus, coating thickness and residual stress on the stress are explored. The results indicate that the coating porosity and thickness are the critical factor affecting coating normal stress and interfacial shear stress, respectively. In addition, the residual stress significantly affects the interfacial normal stress. The increasing stress caused by low porosity and residual tensile stress and stress concentration at the large-sized defects are the key factors for fatigue degradation.