Phenomenological Aspect of Hydrogen Enviroment Embrittlement of SNCM439 Steels
Phenomenological Aspect of Hydrogen Enviroment Embrittlement of SNCM439 Steels
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SNCM439 钢氢环境脆化现象学
DOI：
10.2355/tetsutohagane.96.76
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
K. Ohnishi
中科院分区：
文献类型：
--
作者：
Hironobu Arashima;Satoru Masada;H. Itoh;K. Ohnishi
研究了SNCM 439钢（Ni-Cr-Mo钢）在室温20 MPa氢气中、800 ~ 1200 MPa不同抗拉强度下热处理后的氢环境脆化行为。拉伸试验结果表明，氢环境脆化表现为塑性下降，而试样的抗拉强度没有变化。虽然试样的均匀延伸率在空气和氢气中是相同的，但在氢气中局部收缩随着拉伸强度的增加而减小。与表面光滑的试样相比，抗拉强度超过1000 MPa的试样的缺口抗拉强度显著降低。对试样断口的分析表明，在氢气中裂纹是从试样的外部萌生的，而在空气中裂纹是从试样的中心萌生的。断裂模式是相同的，在这两个缺口和无缺口试样的拉伸试验，氢致准解理断裂的存在。结果表明，在高脆化材料中，沿晶断裂占主导地位，准解理断裂先于沿晶断裂。即使在沿晶断裂为主的缺口试样中，也观察到缺口下方的准解理断裂。这些行为表明，高强度试样的氢脆敏感性更显著，氢渗透和氢环境脆化导致的准解理断裂的形成需要较大的塑性变形。
The hydrogen environment embrittlement of SNCM439 steels (Ni–Cr–Mo steels) was investigated in 20-MPa hydrogen gas at room temperature at different tensile strengths ranging from 800 to 1200 MPa by heat treatments. The results of tensile tests revealed that hydrogen environment embrittlement was observed as decrease of ductility, whereas the tensile strength of the specimens did not change. Although the uniform elongation of the specimens was the same in air and hydrogen, local contraction decreased with increasing tensile strength in hydrogen. In contrast to the specimens with smooth surface, the notch tensile strength of the specimens having a tensile strength of over 1000 MPa remarkably decreased. The analysis of fractures in the specimens revealed that a crack was initiated from the external of the specimens in hydrogen, whereas it was initiated from the center of the specimens in air. The fracture mode was the same in both the tensile tests with notched and notchless specimens, and the presence of hydrogen induced quasi-cleavage fracture. It was observed that intergranular fracture was dominant in highly embrittled materials, and quasi-cleavage fracture was ahead of intergranular fracture. Even in the notched specimens whose intergranular fracture was dominant, quasi-cleavage fracture was observed beneath the notch. These behaviors indicate that the susceptibility to hydrogen embrittlement was more remarkable in specimens with high tensile strength, and the large plastic deformation required for the formation of quasi-cleavage fracture induced hydrogen penetration and hydrogen environment embrittlement.