无黏结剂层状BN增韧cBN刀具材料的研究

Binderless Layered BN Toughened cBN for Ultra-precision Cutting

无粘结剂cBN材料制作的切削刀具韧性较差,并且这种材料的合成压力高。为此,本研究在工业压力下制备了超硬、高韧的新型无粘结剂层状BN增韧cBN(Lt-cBN)块材,通过切削硬质合金实验,分析了Lt-cBN材料内部微观结构对其切削性能和耐磨性的影响。研究结果表明:Lt-cBN材料的韧性高达8.5 MPa·m^(1/2),可超精密切削硬质合金,获得了粗糙度R_(a)低于10 nm的超光滑表面;Lt-cBN材料内部存在少量层状BN,不仅提高了韧性,还降低了表层材料的非晶化程度及磨损速率;相对于商品化的纯相cBN材料,Lt-cBN材料展现出更好的切削性能和耐磨性;Lt-cBN材料的主要磨损形式为后刀面的部分非晶化,并在摩擦作用下逐渐被去除而导致的磨料磨损。

Poor toughness and high synthesis pressure of binderless cBN limits its application in the field of cutting tool.To enhance its toughness,an advanced layered BN toughened cBN(Lt-cBN)bulk was developed under industrial pressure.Then,the cutting performance and wear resistance of Lt-cBN was analyzed based on the unique microstructure during tungsten carbide cutting.It is found that the Lt-cBN reaches a high fracture toughness of 8.5 MPa·m^(1/2),and is capable of realizing ultra-precision cutting of tungsten carbide with smooth surface of roughness lower than R_(a) 10 nm.The layered BN at the intersection of cBN grains within Lt-cBN contributes to the enhanced toughness,which further slows down the transformation of amorphization as well as the wear rate of the surface layer.Thus Lt-cBN exhibits better cutting performance and wear resistance in contrast to commercial binderless pure cBN material.The wear of Lt-cBN can be explained by the soft partially amorphous layer formed on the flank surface being rubbed and continuously removed in the form of abrasive wear.