热处理工艺对8Cr4Mo4V钢疲劳裂纹扩展速率的影响

研究了四组不同工艺热处理的8Cr4Mo4V钢试样的疲劳裂纹扩展速率及其疲劳断口。结果表明:淬回火8Cr4Mo4V钢的室温疲劳裂纹扩展速率在裂纹稳定扩展阶段符合Paris公式,其大小与热处理工艺有关,主要取决于马氏体中的固溶碳含量,马氏体中的固溶碳含量越高,疲劳裂纹扩展速率也越大,而与该钢是否经过冷处理没有明显关系;淬回火8Cr4Mo4V钢疲劳断口的微观形貌以准解理为主,马氏体(211)晶面的X射线衍射峰半高宽越小,疲劳裂纹扩展速率也越小,疲劳断口上的拉伸残余应力则越大。

Effect of Heat Treatment Processes on Fatigue Crack Growth Rates of Hardened-tempered 8Cr4Mo4V Steel

Abstract： The fatigue crack growth rates and the fatigue fracture surfaces had been investigated about four groups of 8Cr4Mo4V steel specimens with different heat treatment processes. The result show that at room temperature the fatigue crtmk steady growth rates of the hardened-tempered 8Cr4Mo4V steel accorded with Paris relation. The fatigue crack growth rates related with the heat treatment process, depended mainly on carbon conten in the martensite, and did not obviously related with the cold treatment. The main microscopic appearance of the fatigue fracture surfaces was quasi cleavage. The narrower the X-ray FWHM of the martensite（211） was, the lower the crack growth rate was, and the greater the tensile residual stress on the fracture surface was.