添加Ni/C对Ni-Cr合金制备钎焊金刚石工具的影响

Effect of adding Ni/C on fabrication of diamond tools brazed with Ni-Cr alloy

为了进一步提高钎焊金刚石工具的使用性能,采用添加3%、5%Ni/C的Ni-Cr合金在保护气氛炉制备钎焊金刚石试样,钎焊温度为1 050℃,保温5 min;利用扫描电镜对钎焊后金刚石形貌和钎焊层组织进行分析,用维氏硬度仪测试钎焊层硬度。结果表明:添加Ni/C的Ni-Cr合金对金刚石具有较好的润湿性,能实现钎焊层对金刚石的高强度连接;碳化物在金刚石表面形核长大,与金刚石具有一定的位向关系;Cr7C3的形貌为空心,钎焊层中形成簇状共晶石墨,都与添加的Ni/C有关;钎焊层中残存有少量Ni/C,钎焊层硬度由820HV0.2降低至700HV0.2,有利于降低金刚石钎焊后热应力和提高磨粒后期出露。

In order to further improve the performance of brazed diamond tools,Ni-Cr brazing alloy added with Ni/C of 3%,5%was utilized to braze diamond in protective furnace with temperature 1 050 ℃ and holding time 5 min. The diamond morphology and the brazed joint microstructure were analyzed with scanning electron microscope and the brazed joint hardness was measured with Vickers. The results show that Ni-Cr alloy added with Ni/C has good wettability to diamond,high strength bonding between diamond and brazing layer is achieved. Carbide crystallizes and nucleates on the surface of diamond,which has an orientation relationship with the diamond. The morphology of Cr7C3 is hollow,and cluster eutectic graphite forms in the brazing layer,which has a relationship with Ni/C adding. There is a small amount of Ni/C within brazing layer,the brazed joint hardness falls from830HV0.2 to 700HV0.2,which is beneficial to decreasing the thermal stress and improving the protrusion of the later grinding.