抄録
Ion nitriding has been used to improve the wear resistance of machine elements such as gears, rollers, etc.. However, it is scarcely known that ion nitriding causes an appreciable reduction in bending impact fatigue strength.
Together with the conventional tension and Charpy impact tests, the cyclic impact tests were carried out to clarify the effect of case hardening by ion nitriding on the bending impact fatigue strength of a high tension steel (HT80), where a low carbon alloy steel (SM50) was used as a reference material. In the case of the low carbon alloy steel with a tensile strength of about 500MPa, ion nitriding reduced the impact fatigue life to about one tenth of the same steel without nitriding. The reduction ratio became smaller (about 1/3) in the case of the high tension steel with a tensile strength of about 800MPa. The impact fatigue strength of nitrided steel is closely related to the impact resistance determined by the Charpy impact test.
