抄録
WC ceramic was coated on the smooth specimen of annealed tool steel (JIS: SKD6) by high-speed flame spraying, and the tensile test of the specimen was carried out to obtain interfacial energy, where the load was applied parallel to the film. With increasing load the film is divided repeatedly by occurence of cracks, and the film delamination begins after the crack interval reaches a certain value. The crack interval of film at the delamination increases and the interfacial energy slightly decreases with an increase in film thickness. The finite element analysis shows that the tensile stress at the center of film and the shear stress at the edge of film decrease with a decrease in film length, and the difference between both stresses increases with a decrease in film thickness. The analysis not only shows that the repeating film division continues as long as the tensile stress in the film reaches a critical tensile strength σc before the shear stress at the interface reaches a critical shear strength τc, but also explains the film thickness dependency of crack interval. By considering the analysis and the result of experiment, the crack interval, Lc, at the delamination of film can be expressed by the following equation,
Lc/B2=α(σc/τc)(B1/B2)κ
where, B1 and B2 are the thickness of film and substrate, respectively, and α and κ are the constants.
