Abstract: In the high-speed hard turning processes for hardened bearing steels, there were some problems such as rapid tool wear, serious chip entanglement and poor machined surface quality. The high-speed hard turning tests of GCr15 bearing ring were carried out with PCBN tools using high-pressure cryogenic CO2 jet as cooling medium, and compared with high-pressure emulsion and high-speed dry cutting, and the effects of cooling conditions and cutting parameters on cutting performances and machined surface quality were analyzed. The results show that within a certain range of the cutting parameters, the use of high-pressure cryogenic CO2 jet assisted cutting may effectively reduce tool wears and improve chip breakings, but it is also more likely to chipping when the tools are in the stage of severe wear. When the cutting speed is high, the high pressure cryogenic CO2 jet may improve the surface quality of the workpieces more significantly, effectively reduce the surface roughness of the workpieces, increase the residual compressive stresses and surface microhardnesses.

Key words: cryogenic machining, polycrystalline cubic boron nitride(PCBN) tool, hardened bearing steel, tool wear, machined surface quality

摘要： 针对高速硬车削淬硬轴承钢时刀具磨损快、切屑缠绕严重和已加工表面质量差等问题，以高压低温CO2射流为冷却介质，应用聚晶立方氮化硼（PCBN）刀具进行了GCr15轴承套圈高速硬车削试验，并与高压乳化液冷却和高速干切削进行对比，分析了冷却条件和切削参数对刀具切削性能和加工表面质量的影响。研究结果表明：在一定的切削参数范围内，使用高压低温CO2射流辅助切削可以有效降低刀具磨损、改善切屑缠绕情况，但当刀具处于剧烈磨损阶段时，刀具更容易产生崩刃而失效；当切削速度较大时，高压低温CO2射流对工件表面质量的提升更为显著，有效降低了工件表面粗糙度、增大了残余压应力和表层显微硬度。

关键词: 低温加工, 聚晶立方氮化硼刀具, 淬硬轴承钢, 刀具磨损, 加工表面质量