AgCuTi合金钎焊单层立方氮化硼砂轮

Brazing of Single Layer Cubic Boron Nitride Wheel with AgCuTi Alloy Under Vacuum Atmosphere

关键词:  砂轮  单层  钎焊  立方氮化硼  化学结合

Key words:  grinding wheel  monolayer  brazing  cubic boron nitride  chemical and metallurgical bonding

摘要:

为研制我国新一代单层钎焊CBN(立方氮化硼)磨料砂轮,尝试Ni-Cr和Ag-Cu-Ti两种活性钎料,在真空炉中钎焊。试验结果表明,Ni-Cr合金钎料对CBN磨料不浸润,钎焊后CBN磨料全部脱落;而Ag-Cu-Ti合金钎料对CBN则表现出良好的浸润性并将CBN牢牢钎焊住。借助扫描电镜、X射线能谱和X射线衍射对界面微区组织的分析研究表明,钎焊过程中Ag-Cu-Ti合金钎料中的Ti向CBN磨料界面富集,并与CBN磨料表面的N和B元素反应生成TiN和TiB,这是实现Ag-Cu-Ti合金钎料与CBN磨料高结合强度的关键因素。断口形貌的分析研究表明,CBN与Ag-Cu-Ti合金钎料间的断口发生在Ag-Cu-Ti合金钎料层,说明CBN磨料与Ag-Cu-Ti合金钎料的结合强度已超过了Ag-Cu-Ti合金钎料本身强度。最后将研制出的单层钎焊CBN磨料砂轮与传统电镀CBN砂轮进行了重负荷磨削对比试验,钎焊砂轮表现出明显的优势。

Abstract:

In order to develop new generation monolayer brazing CBN (cubic boron nitride) grinding wheels, two types of active filler alloys (Ni-Cr and Ag-Cu-Ti) were tested in vacuum furnace.The results show that a Ni-Cr alloy fails to wet and bond CBN grits,while a Ag-Cu-Ti alloy exhibits good wetting and bonding towards CBN grits.SEM EDS microanalyses have shown that during brazing Ti in Ag-Cu-Ti alloy segregated preferentially to the surface of the CBN to form a Ti rich reaction product.X-ray diffraction reveals that the wetting and bonding behaviour on CBN surface by Ag-Cu-Ti alloy melt are realized through TiN and TiB which are produced by interaction between Ti atoms of Ag-Cu-Ti alloy and N or B atoms of CBN surface at elevated temperatures.The rupture occurs in Ag-Cu-Ti alloy layer.It can be considered that chemical metallurgic bonding has formed in the interface between CBN grits and Ag-Cu-Ti alloy.Finally a monolayer brazing CBN grinding wheel with regular abrasive distribution was put forward to try a grinding test.The experimental results show distinct advantages over conventional electroplated CBN grinding wheel.