16Mn钢在空气和3.5% NaCl溶液中的疲劳行为

Fatigue Behaviour of 16Mn Steel in Air and 3.5% NaCl Solution

采用哑铃状平板试样,分别研究了16Mn钢在空气中和3.5%NaCl溶液中的疲劳行为,获得了S-N曲线,并对疲劳试样的表面和断口形貌进行了观察。结果表明:3.5%NaCl溶液(与空气相比)使16Mn钢的疲劳强度有较大程度的降低,在空气中16Mn钢的疲劳极限为200 MPa,而在3.5%NaCl溶液中该钢则不存在疲劳极限;空气中的疲劳试样只有一个萌生于试样表面基体的裂纹源,而3.5%NaCl溶液中该钢的疲劳试样一般有多个裂纹源,除了极少数萌生于试样表面基体处,其余均萌生于表面的点蚀坑;空气中疲劳试样裂纹扩展区的断口形貌以疲劳辉纹为主,而3.5%NaCl溶液中的则以沿晶开裂等脆性特征为主。此外还对空气中16Mn钢的疲劳极限进行了预测,预测值与试验值基本吻合。

The fatigue behaviour of 16Mn steel in air and 3. 5% NaCl solution were studied by dumble-shaped plate type specimens. The S-N curves show that the fatigue strength of 16Mn steel in 3. 5% NaCl solution was much lower than that in air. The fatigue limit of it in air was 200 MPa, but there was no fatigue limit in 3.5% NaCl solution. Surface and fractography observation results show that the fatigue cracks in air were initiated from the matrix of surface, while most of fatigue cracks in 3. 5% NaCl solution were initiated from surface pits, except for some from the matrix of surface. The typical feature of the fatigue crack propagation region in air was fatigue striations, while that in 3. 5% NaCl solution was intergranular crack characteristic. It was found that the fatigue limit of 16Mn steel in air could be predicted by empirical equation, and the predicted fatigue limit was agreeable to the experimental fatigue limit.