TiN被覆鋼の平面曲げ疲労強度に及ぼす成膜後基板焼入れ処理の影響

概要

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In order to investigate the effects of the substrate post quenching on the fatigue strength of TiN coated steel, the plate bending fatigue test was carried out for two types of specimen; one was the specimen whose steel substrate (carbon tool steel, JIS SK 3) was quenched and tempered after TiN coating (specimen CQ), and the other was the conventional type specimen whose substrate was TiN coated after the substate was quenched and tempered (specimen QC). As the result, it was found that the fatigue limit of the specimen CQ was higher than that of the specimen QC. It was considered that the difference of the fatigue limit originated from the difference of the properties of TiN film, because the hardness of both substrates were almost equal and the difference could not be recognized in the fracture surfaces of their substrates. It was confirmed that the adhesive strength of TiN film was dractically improved by the substrate post quenching as reported in our previous studies. Also, on the fracture surface of TiN film of the specimen QC, the columnar structure was recognized more clearly compared with the specimen CQ, and its fracture surface showed the aspect of the aspect of the brittle fracture. From these results, it was indicated that such the changes of the adhesive strength and the microstructure of TiN film were concerned in the improvement of the fatigue strength by the substrate post quenching.
2006-11-25