浸炭窒化鋼のピッティング寿命におよぼす窒素濃度の影響

概要

論文の詳細を見る
In recent years, carbonitriding has been coming under review in expectation of improving pitting life of transmission gears. This paper attempts to clarify the effect of nitrogen concentration on pitting life of carbonitrided steel. Carburized and carbonitrided JIS-SCr420 steel specimens with ground surface, partly followed by shot peening or subzero treatment before grinding, were tested by geared roller tester under the condition of a contact stress of 2.94GPa and a slip ratio of -40%. The surface concentration of nitrogen between 0.1 and 0.3 % is the best for pitting life. In other words, the amount of retained austenite around 30% shows the best performance. Improvement in pitting life with increasing retained austenite under the optimum amount is owing to decreasing surface roughness during pitting tests. Pitting life is lowered by excessive amount of retained austenite because the surface hardness is seriously decreased.