引張試験によるぜい性コーティング皮膜の界面強度評価

抄録

In order to evaluate the interfacial strength between coating film and substrate, a new equation was proposed by expanding the Kendall's equation to the case where the substrate material was in plastic deformation, and the tensile tests were carried out on steel specimens with thermally-sprayed ceramic film and heat-resistant paint film.
When a specimen with partially delaminated film is under tensile load, the interfacial energy between film and substrate, 2γ₁₂ is expressed by the following equation;
2γ₁₂=[P-bB₂σ_ys{1-(E_p/E_e)}]²/2b²·B₁E₁/B₂E_p(B₁E₁+B₂E_p)
where P is the load at the beginning of delamination, b is the width of specimen, B₁ and B₂ are the thickness of film and substrate, E₁ is the elastic constant of film, E_e, E_p and σ_ys are the elastic constant, plastic constant, and yield strength of substrate, respectively. The above equation is applicable also for the specimen with smooth film without precrack or partially delaminated portion as long as the cracking of film occurs before the delamination. The interfacial energy of ceramic film obtained by experiment reveals a maximum at a certain film thickness and decreases with an increase in film thickness. The interfacial energy of heat-resistant paint reveals almost the same behavior as the ceramic film, but the film thickness at maximum interfacial energy is much smaller than that of ceramic film.