立方氮化硼刀具材料的激光水射流复合工艺加工方法

Laser/Waterjet(LWJ)Machining of Polycrystalline Cubic Boron Nitride Tool Material

研究了激光水射流(LWJ)复合工艺加工聚晶立方氮化硼(PCBN)切削机理.LWJ系统集合了高功率CO2激光束和低压水射流,采用快速加热和冷却,实现了沿加工路径的断裂萌生和扩展.通过扫描电镜(SEM)和拉曼实验,确定了相变导致的断裂扩展切削机理.实验结果表明:激光加工和水射流淬火导致试样表面首先产生划痕,同时部分立方氮化硼(cBN)沿切割路径相变为六方氮化硼(hBN).由于hBN比cBN占有更大的体积,这导致周围材料的拉伸应力受约束膨胀和扩展.应力驱动激光加工的沟槽沿厚度方向传播,使试样分离,完成材料的切割.相变致裂是一种有效的切削机理,该模型可作为控制加工参数以提高立方氮化硼材料的加工质量.

This paper investigated a novel ceramic material cutting mechanism through controlled crack propagation of the Polycrystalline Cubic Boron Nitride(PCBN)substrates with Laser/Waterjet(LWJ)machining system.The LWJ system inte-grates a high-power CO2 laser beam with a low-pressure waterjet,and applies rapid heating and quenching to achieve frac-ture initiation and propagation along the machining path.Cutting mechanism of phase transformation induced fracture propa-gation was identified through SEM and Raman tests.These tests results show that laser irradiation and waterjet quenching caused scratches on the sample surface,and part of cubic boron nitride(cBN)was transformed into hexagonal boron nitride(hBN)along the cutting path.Because hBN occupied more volume than cBN,this resultedin constrained expansion and development of tensile stresses in the surrounding materials.Furthermore,the stresses drove the laser machined groove to propagate through the thickness,thus separating the specimen and completing the cutting of the material.These results sug-gest that phase transformation induced fracture is an efficient mechanism and the model could be used as a guide to control processing parameter for improving cutting quality.