CBN超硬磨粒工具的超声振动辅助钎焊结合界面微观组织和力学性能

Microstructure and mechanical properties of bonding interface for CBN superabrasive tool using ultrasonic vibration-assisted brazing method

采用高频感应钎焊方法制备钎焊CBN工具存在钎料层厚薄不均匀、连接界面内部易出现气孔等问题,导致钎料对磨粒的把持强度大幅下降、工具使用寿命显著降低。提出用超声振动辅助钎焊的工艺方法制备钎焊CBN工具,借助超声波在钎焊过程中的空化效应和振荡作用减少钎料合金内部的气孔,同时细化晶粒,以大幅提升磨粒的把持强度。结果表明:相比于普通钎焊工艺,采用超声振动辅助钎焊工艺的钎料合金铺展更均匀,区域内部气孔尺寸变小,相同面积上气孔数量减少了75%,单颗CBN磨粒的剪切力提高了27.7%。通过Ti-6Al-4V钛合金磨削对比试验可知:相比普通钎焊工具,超声振动辅助钎焊工具的法向磨削力降低了4.1%~19.6%,切向磨削力降低了8.3%~26.4%,磨削温度降低了5.3%~17.9%。此外,在相同材料去除体积下,超声振动辅助钎焊CBN工具的磨粒大块破碎现象明显减少,大幅提升了工具的耐磨性和使用寿命。

Single-layer brazed cubic boron nitride(CBN)abrasive tools exhibit numerious advantages,such as high abrasive bonding strength,a large chip storage space,and good sharpness,and have been widely used to machine various difficult-to-cut materials in the aerospace field.However,the problems have to be faced,including uneven filler layer thickness,numerous pores inside the interface area,resulting in a significant reduction in bonding strength between the bonding alloys and the abrasive,and the eventual service life reduction of tools.In this paper,ultrasonic vibration-assisted brazing is proposed to improve the bonding strength of abrasive grains.Results show that for ultrasonic vibrationassisted brazing,the filler alloy spreads more evenly,and the size of internal pores is smaller.In particular,the number of pores in the same area is reduced by 75%,and the shear force of a single CBN abrasive is increased by 27.7%.After the grinding trials with Ti-6Al-4V alloys using brazed CBN tools,the normal and tangential grinding forces are reduced by 4.1%~19.6%and 8.3%~26.4%,respectively,as well as the declination of the grinding temperature by 5.3%~17.9%once employing ultrasonic vibrations into induction brazing processes.Additionally,the ultrasonic vibration-assisted brazed tools show a significant reduction in large-block breakage at the same material removal volume,indicating the more excellent wear-resistance ability and longer service life of the tools.