高速硬切削加工表面白层形成机理研究

白层是高速硬切削的特有现象，对加工表面完整性和零件的服役性能有着重要影响。针对高速硬切削加工表面白层问题，进行了对GCrl5淬硬轴承钢高速硬切削试验和表面白层测试，研究了不同切削条件下的白层形成机理，分析了切削速度和刀具磨损状态对白层特征的影响规律。分析结果表明，白层厚度随切削速度和后刀面磨损的增大而增大，而其分布的均匀性和连续性也将变差；切削速度和后刀面磨损的增加引起切削温度升高，导致加工表面快速淬火效应，使得白层厚度增大，其中切削速度的影响较为显著；在切削速度较低(100 m/min左右)时白层的形成机理主要为塑性变形，切削速度超过300 m/min则主要是马氏体相变所致，而在中间切削速度(200 m/min左右)时为2种机理的混合作用结果。

Mechanism of White Layer Formation on Machined Surface of High-speed Hard Machining

White layer is a unique phenomenon of high-speed hard machining and has significant effects on machined surface integrity and service performance. Focusing on the white layer in high-speed hard machining, the high-speed hard cutting experiment of hardened GCrl5 bearing steel and white layer tests are conducted. The formation mechanism of white layer under various cutting conditions is investigated, and the influence of the cutting speed and flank wear on white layer’s features is studied. Analysis results show that the thickness of white layer increases with increasing cutting speed and flank wear, and the uniformity and continuity of the distribution of white layer decreases. Increasing cutting speed and flank wear will increase cutting temperature and result in rapid quenching effect of the machined surface, which causes an increasing of the thickness of white layer. The cutting speed has a more significant influence on the white layer than flank wear. The formation mechanism of white layer is plastic deformation at lower cutting speed (about 100 m/min), and is martensitic phase transformation when the cutting speed exceeds 300 m/min. The formation mechanism of white layer at midrange speed (about 200 m/min) is a hybrid effect of plastic deformation and martensitic phase transformation.