Abstract: Aiming at the problems of PCBN tool serious wear and short cutting life were prominent in hard cutting, the cryogenic PCBN tools and the high speed hard turning AISI 4340 steel tests were carried out to study the effects of cryogenic treatment on the surface integrity (including microstructure, roughness, microhardness and residual stress) and cutting performances of PCBN tools, and the method of improving PCBN tool wear resistance and tool life was explored. The results show that the defects such as shrinkage cavity and porosity on the surface of the tools are significantly reduced or even disappeared, and the surface morphology is improved after cryogenic treatment. However, the surface roughness of the tools is improved. The surface microhardness and residual stress of the tools are increased. The influences of surface morphology and surface residual stress on tool life are great, followed by surface microhardness, and the surface roughness has little effects on tool life. The treated tool adhesion and oxidation wear are reduced, and the maximum tool life may be increased by 24.78%. It may be seen that cryogenic treatment may effectively improve the surface integrity of PCBN tools, so as to improve the tool life. 

Key words: cryogenic treatment, PCBN tool, surface integrity, cutting performance, AISI 4340 steel

摘要： 针对PCBN刀具在硬切削加工中磨损严重、切削寿命短的问题，开展了PCBN刀具深冷处理试验和经深冷处理的PCBN刀具高速硬车削AISI 4340钢的试验，研究深冷处理对PCBN刀具表面完整性（包括微观形貌、粗糙度、显微硬度和残余应力）及切削性能的影响规律，探究提高PCBN刀具耐磨性和刀具寿命的方法。研究结果表明，经过深冷处理之后，刀具表面缩松缩孔等缺陷明显减少甚至消失，表面形貌得到改善，但刀具表面粗糙度增大；刀具表面显微硬度、残余应力均得到提高；表面形貌和表面残余应力对刀具寿命影响较大，其次是表面显微硬度，表面粗糙度对刀具寿命影响较小。深冷处理后，刀具黏结、氧化磨损减少，刀具寿命较未处理刀具提高24.78%，可见，深冷处理可有效改善PCBN刀具表面完整性，从而提高刀具寿命。

关键词: 深冷处理, PCBN刀具, 表面完整性, 切削性能, AISI 4340钢