窒化により表面改質した純チタンの疲労特性

概要

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An attempt was made to clarify the effect of nitriding on the fatigue strength (N_f=10^7) of pure titanium through some critical experiments concerning the fatigue properties of gas-nitrided pure titanium including a sample with a small artificial surface pit. The results are summarized as follows : (1) The reduction of fatigue strength occurs in the nitrided pure titanium with increase in the thickness of the hardened layer. (2) The small pit (d_p-80 μm) has little effect on reducing the fatigue strength of nitrided pure titanium, while such a pit gives a large reduction of the fatigue strength of unnitrided pure titanium. (3) Fractography of the fracture surface of nitrided pure titanium revealed that there exists a microfracture facetlike cleavage at the fatigue crack initiation site beneath the nitrided layer, while a small featureless facet associated with stage-I crack growth can be observed at the fracture edge of an unnitrided pure titanium. (4) The fatigue strength of nitrided pure titanium can be considered as a critical stress at which microcracking of the hardened layer occurs under cyclic loading.
一般社団法人日本機械学会の論文
1992-02-25