Ni-Cr合金真空钎焊金刚石砂轮的研究

利用真空炉中钎焊的方法 ,用 Ni- Cr合金做钎料 ,适当控制钎焊温度、保温时间和冷却速度 ,实现了金刚石与钢基体间的牢固连接。利用扫描电镜 X射线能谱 ,结合金相及试样逐层的 X射线结构分析 ,剖析了Ni- Cr合金与金刚石和钢基体钎焊界面的微区组织结构 ;揭示了 Ni- Cr合金对金刚石和钢基体表面的浸润和钎焊机理。即在钎焊过程中 Ni- Cr合金中的 Cr元素分离出在金刚石界面形成富 Cr层并与金刚石表面的C元素反应生成 Cr3C2 和 Cr7C3,在钢基体结合界面上Ni- Cr合金和钢基体中的元素相互扩散形成冶金结合 ,这是实现合金层与金刚石和钢基体都有较高结合强度的主要因素。最后重负荷磨削实验表明金刚石为正常磨损 ,没有整颗金刚石脱落。

Research on Furnace Brazing of Diamond Grinding Wheel with Ni-Cr All oy under Vacuum Atmosphere

The brazing of a monolayer of diamond grinding w heel with active filler metals can show distinct advantages over conventional el ectroplated diamond grinding wheel in terms of faster cutting and longer life. T he present study has shown that a commercially available Ni-Cr alloy can be us ed as an active filler material for brazing diamond grit. Furnace brazing was ca rried out in a current of vacuum. SEM-EDS micro-analyses have shown that durin g brazing the chromium present in the alloy segregated preferentially to the sur face of the diamond to form a chromium-rich reaction product. X-ray diffractio n revealed that the wetting and bonding behavior on diamond surface by Ni-Cr al loy melt is realized through Cr 3C 2 and Cr 7C 3 which is produced by intera ction between Cr atoms of Ni-Cr alloy and C atoms of diamond surface at elevate d temperatures. The analyses also revealed that the bond between the alloy and t he steel substrate was established through a cross-diffusion of iron and chromi um. Other researches only found a chromium-rich layer between the diamond and N i-Cr alloy. Finally, a grinding test showed that the wear modes of such a braze d grinding wheel were mainly grit fracture and attrition rather than grit dislod gement from the bond.