钢的腐蚀疲劳断裂形态的探讨

本文通过钢在腐蚀疲劳(CF)条件下断裂表面的观察,较系统地探讨了钢的CF断裂形态特征。其结果表明,CF的断裂形态强烈地依赖于载荷、介质及其与钢本身之间的相互作用。按照环境对钢的作用强弱,可以出现疲劳辉纹、因均匀腐蚀变宽了的疲劳条纹、晶间腐蚀型疲劳条纹、应力腐蚀开裂(SCC)形态及氢脆(HE)开裂形态特征等。因此,CF断裂形态不具有独特的共同特征,说明CF断裂的机理是多样的。目前,用一种断裂模型(如叠加模型或竞争模型)去解释所有CF断裂现象无疑是困难的。

FRACTURE MORPHOLOGY OF STEELS UNDER CORROSION FATIGUE CONDITION

Through the observation of fracture morphology by electronfractography, it is shown that the fracture moprhology of steels is not governed by a single mechanism, but is strongly dependent upon interaction between stress, medium and steel. According to the corrosive action of medium to steel, there are observed the following cases: a)corrgsion is weak or absent, only striation is observed; b)when corrosion is strong, then it can be further divided into five cases: ⅰ)with general corrosion, attacked and widened striation is observed; ⅱ)with pitting corrosion, the pit was only a source of crack; ⅲ) with intergranular corrosion, characteristic intergranular corrosion striation can be observed; ⅳ) when the specimen, is sensitive to stress corrosion crac king (SCC) and K_(Imax)>K_(ISCC), the characteristic fracture morphology of SCC is. observed; ⅴ) when the specimen is sensitve to hydrogen embrittlement (HE)., characteristic HE morphology is observed, As there are several different kinds of CF mechanism, it is improper to explain all CF phenomena by one model of CF such as the superposition model or process competition model.