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本文测试了18Cr2Ni4WA钢三种典型组织——粒状贝氏体,粒贝的高温回火组织和马氏体的高温回火组织的疲劳裂纹扩展速率(da/dN毫米/周次)及门槛值(△K_(th)公斤·力毫米~(3/2)),分析了断口形貌及裂纹扩展路径,研究了三种组织的疲劳裂纹扩展特性,着重讨论了不同结构、大小、数量和分布的弟二相对疲劳断裂行为的影响。结果表明:组织类型对da/dN有一定的影响,尤其是对疲劳裂纹扩展门槛值△K_(th)影响较大。粒贝具有较好的裂纹扩展抗力;粒贝的高温回火组织次之:马氏体的高温回火组织最差。粒贝中的(M-A)组织强烈阻碍裂纹扩展;马氏体高温回火组织中分布于晶内的细小碳化物阻碍裂纹扩展不明显,分布于晶界的片状碳化物促进沿晶断裂-——这是导致三种组织的疲劳裂纹扩展特性不同的重要原因。
In this paper, the fatigue crack growth rate (da / dN mm / cycle) and the threshold value (da / dN mm) of the three typical microstructures of 18Cr2Ni4WA steel, ie, granular bainite and tempered high temperature tempering microstructure and martensite, △ K_ (th) Kg · force mm ~ (3/2)). The fracture morphology and crack propagation path were analyzed. The fatigue crack propagation characteristics of the three kinds of microstructures were studied. The effects of different structures, sizes, quantities and distributions Influence of second relative fatigue fracture behavior of younger brother. The results showed that the type of tissue had a certain effect on da / dN, especially the △ K th thresholding of fatigue crack growth. Shellfish has better resistance to crack propagation; shell tempered high temperature tempering followed by: martensite tempering the worst organization. (MA) in the shellfish strongly hinders the crack propagation; the fine carbides distributed in the martensite and high temperature tempering tissues prevent the crack growth from being obvious, and the flaky carbides distributed in the grain boundary promote the intergranular fracture- - This is an important reason for the different fatigue crack propagation characteristics of the three kinds of tissues.