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用表面残余压应力试样,U型弯曲试样(用其压缩区)和WOL恒位移缺口压缩试样,对18-8不锈钢在沸腾MgCl_2溶液中进行了压应力条件下的应力腐蚀试验。结果表明,三种试样分别经110小时,73-100小时以及262-324小时后都观察到了由压应力所产生的应力腐蚀裂纹,并获得了具有岩层状特征的准解理脆性断口,这和拉应力腐蚀时获得的解理断口明显不同。 压应力条件下应力腐蚀裂纹的孕育期比拉应力要高一个数量级,而且裂纹扩展缓慢,加上裂纹不能张开而难于辨认,故当试样中同时存在拉应力时将不会观察到压应力所产生的应力腐蚀裂纹。
The stress corrosion tests of 18-8 stainless steel in boiling MgCl 2 solution under compressive stress were carried out by compressing the specimen with residual compressive stress on the surface, U-shaped specimen (using its compression zone) and WOL constant displacement notch. The results show that the stress corrosion cracking caused by compressive stress is observed in all the three samples after 110 hours, 73-100 hours and 262-324 hours, respectively, and the quasi-cleavage brittle fracture with rock strata is obtained. This is clearly different from the cleavage fracture obtained when tensile stress is eroded. The stress corrosion cracking stress period is one order of magnitude higher than the tensile stress, and the crack propagation is slow, and the crack can not be opened and is difficult to identify. Therefore, no compressive stress will be observed when the tensile stress is simultaneously present in the sample The resulting stress corrosion cracking.