基体强度与氮化钢的疲劳

Matrix Strength and Fatigue of Nitrided Steel

通过改变预处理回火温度，研究了基体强度对氮化钢渗氮件三点弯曲疲劳强度的影响。结果表明：硬基的光滑渗氮试样比软基者的σａ提高２２％，此增益归因于３种相关的因素延滞表面疲劳裂纹的萌生及其进入快速扩展阶段的有利作用。

The effects of matrix strength on three-point bent fatigue strength for the nitriding parts made from the nitrided steel have been studied by changing tempering temperature during pre-treatment.The results show that the toughness and the breaking stress of the nitrided layer can be reduced by nitriding treatment. However, the strength of extension of the nitriding parts can be increased with the fall of tempering temperature and the rise of matrix strength.The diffusion layer of the harder matrix specimens has got a larger residual compression stress by a heredity effect of pre-temper structure in the nitrided layer.The resistance to plastic flow of the specimen core can be increased because of the rise of matrix strength.Therefore there is still a 22% increase of σa for smooth nitrided specimens which are the hard matrix as compared with the soft matrix. The increment of the fatigue strength is due to the favorable functions of the three factors above to delay gemination and extension of the fatigue crack at the surface of nitrided layer.