窒化チタン被覆炭素鋼の疲労強度特性に及ぼす被膜割れの影響

概要

論文の詳細を見る
rights: 本文データは社団法人日本機械学会の許諾に基づきCiNiiから複製したものであるTo clarify the effect of flaws in coating film on fatigue strength, cantilever-type rotating bending fatigue tests were conducted in air and in saline solution (3.0%NaCl) using the specimens of 0.37% C steel with flaws in titanium nitride (TiN) thin film coated by PVD and CVD methods. Flaws in the coating film on specimen surface were introduced by the application of 1.1～1.6% static tensile strain before the test. The obvious decrease in fatigue life of the coated specimen with flaws was observed in both environments, as compared with that of an uncoated specimen and coated one without flaws. This behavior occured markedly at the fatigue in air, that is, the decrease of fatigue life is 90～75% in air to 70～50% in saline solution. Though film thickness is 3～5μm, the flaw in the film acts as a notch effect for crack initiation on substrate. Many cracks were induced in the substrate directly under a flaw and formed a large crack by coalescence at the early stage of fatigue in air. In corrosion fatigue, corrosion pits at which crack initiates occur on the substrate under a flaw at the early stage of fatigue process and the incubation period prior to formation of pits disappears.
1994-03-25