Study On Vacuum Brazing Process And Properties Of C-BN Wear-Resistant Layer On TC4 Alloy

TC4 alloy is widely used in the field of Aeronautics, Astronautics and civil industry because of its excellent comprehensive performance, but poor performance of wear resistance was greatly restricted the use of TC4 alloy under high wear condition, in order to improve its wear resistance, the preparation of good wear resistance of carbide, nitride and boride layer on the surface of the TC4 was used.c-BN is a kind of ceramic materials with high hardness, good thermal stability, the c-BN products prepared by brazing, combined with high strength, long service life, has been unanimously praised by the industry.This article explores using AgCu InT, TiZrCuNi two different active filler metal utilized to braze c-BN wear-resistant layer on TC4 by vacuum brazing. Research on influence law of weldability between active filler metal and c-BN particles affected by the performance of active filler metal, brazing temperature, vacuum degree, heat preservation time and so on, Analyzed microstructure and formation mechanism of the interface between active filler metal and c-BN particles, element diffusion and distribution between active filler metal and TC4, and the c-BN wear-resistant layer`s combination of strength and wearability were determined.The experimental results show that AgCuInTi filler metal under the technological conditions of vacuum higher than 10-2 pa, brazing temperature 750℃, holding 5min, TiZrCuNi filler metal under the technological conditions of vacuum higher than 10-2 Pa, brazing temperature 950℃, holding 3min prepared c-BN wear-resisting layer were smooth, beautiful, well-knit; During brazing Ti in active filler metal transferred preferentially to the surface of the c-BN, and bonding behavior on c-BN surface by active filler metal is realized through TiN and TiB2 which are produced by interaction between Ti atoms of active filler metal and N or B atoms of c-BN surface. Thus, the chemical metallurgic bonding has been formed in the interface between active filler metal and c-BN; at the interface of AgCu In Ti filler metal and TC4 matrix, Ag, Cu, Ti element content presents gradient distribution, at the interface of Ti ZrCuNi filler metal and TC4 matrix, Ti, Zr, Cu element content presents gradient distribution, and a small amount of diffusion to occured in the TC4, Ti elements in TC4 diffusion to one side of the filler metal and a amount were dissolution; the bond strength of c-BN wear resistant layers was decreased with the increase of the volume fraction of c-BN particles, with the increase of the volume fraction of c-BN particles, the amount of wear increases decreased at first then increased, when the volume fraction of c-BN is about 50%, the wear is the least, and the wear resistance is better.