用表面裂纹法研究表面强化层的疲劳裂纹扩展抗力

A Study of Resistance to Propagation of Fatigue Crack within Surface-Hardened Layers by Surface-Flawed Testing Method

本文采用表面裂纹法研究了碳氮共渗、氮化及滚压强化层的疲劳裂纹扩展抗力．与常规的紧凑拉伸试验法相比，前者能灵敏地反映出表面强化层组织及性能的影响，后者却难于实现．试验证实碳氮共渗层中由于残留奥氏体应变诱发马氏体，导致疲劳裂纹扩展抗力提高；滚压强化及渗氮均能提高表面压应力，也使疲劳裂纹扩展抗力明显提高．

In this paper, a study is made of the resistance to the propagation of fatigue crackwithin carbonitrided, nitrided and roll-hardened layers with the surface-flawed testingmethod. This method can reveal sensitively the effect of microstructure and the property ofsurface-hardened layers. But the conventional compact tensile test cannot realize this effect.The results verify that the resistance to the propagation of the fatigue crack increaseds due tothe formation of the strain--induced martensite from the retained austenite within the carbonitrided layer, and that the surface compressive stress as well as the resistance to the propagation of the fatigue crack clearly increased with the processes of rolling strengthening andnitriding.