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本文主要研究双重淬火工艺(1200℃淬火,650℃回火+860℃淬火)对40Cr钢的显微组织和疲劳裂纹扩展行为的影响。研究结果表明,双重淬火可显著细化奥氏体晶粒和淬火后的显微组织,并使淬火组织中的板条马氏体和马氏体板条间的薄膜状残留奥氏体显著增多。无论是在200℃,或是在400℃回火态,双重淬火均可使da/dN明显降低,a_c明显增大,N_p显著提高。在200℃或400℃回火态,40Cr钢的疲劳断裂机制是沿晶与穿晶的混合,双重淬火对疲劳裂纹扩展初期的断裂机制无明显影响。
In this paper, the effects of dual quenching process (1200 ℃ quenching, 650 ℃ tempering + 860 ℃ quenching) on the microstructure and fatigue crack growth behavior of 40Cr steel were studied. The results show that the dual quenching can significantly refine the austenite grains and the microstructure after quenching, and quench the martensite and martensite lath between the film-like retained austenite was significantly increased . Whether quenched at 200 ℃ or 400 ℃, the da / dN can be obviously decreased by double quenching, the a_c obviously increases and the N_p significantly increases. At 200 ℃ or 400 ℃ tempered, the fatigue fracture mechanism of 40Cr steel is a combination of intergranular and transgranular. Double quenching has no obvious effect on the fracture mechanism in the initial stage of fatigue crack growth.