1989 Volume 38 Issue 429 Pages 644-650
Static and cyclic fracture tests were performed on amorphous aluminum oxide thin films coated on Fe-42% Ni alloy base. The thin films were subjected to the static and cyclic tensile strains using a four-point bending test apparatus, and the initiation and propagation of cracks in the thin films were observed by an optical microscope. The effects of coating thickness and surface finishing of the metal, such as mirror polishing or machining, on the static and cyclic fracture strengths of Al2O3 thin coating films were investigated. Under cyclic loadings, the fracture of Al2O3 thin film was observed at a strain below the static fracture strain. The both static and cyclic fracture strengths were found to decrease with increasing coating thickness. It was also found that the surface finishing of base metal affected the fracture strength in such a way that the mirror polishing increased it.
