航空轴承钢渗碳热处理组织演变行为研究

利用EPMA与XRD等实验方法对航空轴承钢在渗碳热处理过程中的微观组织演变行为进行定性及定量分析.结果表明:在渗碳淬火处理后，试样表层及次表层组织中有大量的碳化物及少量的残留奥氏体，其中碳化物为M₂₃C₆和M₆C.随着渗层深度的增加，碳化物含量减少，残留奥氏体含量增加.经过二次淬火处理后，奥氏体与马氏体中碳质量分数增加，使得淬火后残留奥氏体质量分数大幅度增加，在渗层0.1mm处达到22.7%.经过两次深冷与回火处理后，马氏体与奥氏体中碳质量分数降低，碳化物含量增加，渗层硬度提升.

Investigation on Microstructure Evolution of Aviation Bearing Steel During Carburizing Heat Treatment

The microstructure evolution of an aviation bearing steel during carburizing heat treatments was analyzed qualitatively and quantitatively by EPMA and XRD. Results show that after carburizing and direct quenching， the microstructures on sample surfaces and near the surfaces include numerous carbides and a small amount of retained austenite， where the carbides are M₂₃C₆and M₆C. With increasing carburizing depth， the fraction of carbides decreases and the retained austenite increases. After the secondary quenching， the mass fraction of carbon in austenite and martensite increases. This results in a significant increase of retained austenite fraction after quenching， which reaches 22.7% at 0.1mm of the carburized layer. After twice cryogenic and tempering treatments， the mass fraction of carbon in martensite and austenite decreases. Meanwhile， the carbide fraction increases， leading to the increased hardness of the carburized layer.