摘要
Abstract
Objectives:Al and TiN are commonly used components in PcBN synthesis under high temperature and high pressure.But the existing literature studying the TiN-Al bonding system always focuses on the single property vari-ation,such as relative density,hardness,fracture toughness,impact resistance or abrasion resistance,rather than the comprehensive performance when analyzing the samples.In this paper,the TiN-Al ratio and its effect on the structure and the comprehensive performance of PcBN is explored.Methods:The raw materials for the experiment are cBN powder sized 0.5-1.0 µm and binders of TiN powder sized of 2-10 µm and Al powder sized 1-2 µm.The high-temperat-ure and high-pressure preparation conditions are provided by a hydraulic cubic press.The sintering pressure is 5.5 GPa and the sintering temperature is 1 400℃,with a holding time of 10 minutes to obtain the PcBN sample.After grinding,polishing and other processing steps,the material properties are tested.The phase is analyzed using an X-ray diffracto-meter.The binding of cBN particles with the binder and its microscopic morphology are observed using a scanning elec-tron microscope.The actual density,the microhardness and the fracture toughness of the samples are tested separately.The wear ratio of the specimens are measured under the following conditions:an 80-mesh grit SiC grinding wheel for counter grinding,axial force of 300 N and spindle speed of 300 r/min.The wear ratio of the samples is quantified by the ratio of the wheel wear to the PcBN wear.Results:It is observed that the prepared PcBN consists of 4 phases:BN,AlN,TiN,and TiB2.As the proportion of Al increases,the diffraction peak intensities of AlN and TiB2 gradually become stronger while that of TiN gradually decreases.When the content of Al increases,the number of pores decreases to zero and the material become denser.The relative density of the samples reaches its maximum value of 99.02%at 9%TiN and 16%Al.The hardness,the fracture toughness and the abrasion resistance of PcBN increase initially and then de-crease as TiN content increases.Conclusions:The binding agents TiN and Al react with cBN,forming four phases:BN,TiB2,TiN and AlN.As the Al ratio increases,the proportions of AlN and TiB2 increase while that of TiN decreases.The comprehensive performance of PcBN is the best when the mass ratio of TiN∶Al in the binding agent is 9∶16,leading to uniform distribution of cBN and binder and ensuring a dense PcBN sintered body.At this condition,the relative dens-ity,the Vickers hardness,the fracture toughness and the wear ratio of the PcBN sample reach the maximum values,which are 99.02%,4 664 HV,6.60 MPa·m1/2 and 7 340,respectively.关键词
PcBN/高温高压/TiN-Al/配比/综合性能Key words
PcBN/high temperature and high pressure/TiN-Al/ratio/comprehensive performance分类
化学工程
