航空齿轮钢16Cr3NiWMoVNbE的真空低压渗碳

对航空齿轮钢16Cr3NiWMoVNbE进行真空低压渗碳热处理，研究了真空渗碳、淬火、冰冷处理以及回火工艺对材料的组织和性能的影响。结果表明：实验钢经渗碳淬火处理后，从表面到心部的组织可分为碳化物区、碳化物与针状马氏体混合区、针状马氏体区和心部板条马氏体区。在碳化物区的晶界有大量的块状Cr碳化物析出，在析出位置Ni元素较少。在针状马氏体和板条马氏体基体中细小的析出物为Nb、V、Mo微合金元素的碳化物。从渗碳钢表面到心部，随着碳浓度的降低硬度曲线呈现先升高后降低的趋势，渗层深度为0.95 mm。冰冷处理使残余奥氏体进一步转化为马氏体，使实验钢的硬度大幅度提高。

Vacuum Low-pressure Carburization of Gear Steel 16Cr3NiWMoVNbE for Aviation

The combined process of vacuum low-pressure carburizing heat treatment for aviation gear steel 16Cr3NiWMoVNbE was investigated, with the emphasis on the effect of carburizing, quenching, cryogenic treatment and tempering process on the microstructure and mechanical properties of the steel. The results show that after carburizing and quenching, the cross sectional microstructure of the steel, can be differentiated as carbide region, mixed region of carbide and acicular martensite, acicular martensite region and lath martensite region from the surface to the center. A large number of blocky Cr carbides precipitated at grain boundaries in the carbide region, where very little Ni can be detected. The fine precipitates in the acicular martensite and the lath martensite matrix are carbides of the microalloying elements Nb, V, and Mo. After the carburization, the carbon concentration of the carburized steel decreases gradually from the surface to the center, correspondingly, the hardness increased first and then decreased, and the depth of carburized layer was 0.95 mm. The subzero treatment at -70^oC promotes the transformation of retained austenite to martensite, which greatly improves the overall hardness of the carburized steel.