氩气保护条件下钎焊单层金刚石砂轮的研究

RESEARCH ON FURNACE BRAZING OF DIAMOND GRINDING WHEEL WITH Ni-Cr ALLOY UNDER ARGON ATMOSPHERE

利用氩气作为保护气体 ,以 Ni-Cr合金粉末做钎料 ,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的牢固的化学冶金结合。利用扫描电镜和 X射线能谱 ,结合 X射线衍射结构分析 ,发现在钎焊过程中 Ni-Cr合金中的 Cr元素分离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及钢基体之间都有较高结合强度的主要因素。

The brazing of a monolayer of diamond grinding wheel with active filler metals can show distinct advantages over conventional electroplated diamond grinding wheels in terms of faster cutting and longer life. The present study has shown that a commercially available Ni\|Cr alloy can be used as an active filler material for brazing diamond grit. Furnace brazing was carried out in a current of argon. SEM\|EDS microanalyses have shown that during brazing the chromium present in the alloy segregated preferentially to the surface of the diamond to form a chromium\|rich reaction product. X\|ray diffraction revealed that the wetting and bonding behaviour on diamond surface by Ni\|Cr alloy melt is realized through Cr 3C 2 and Cr 7C 3, which is produced by interaction between Cr atoms of Ni\|Cr alloy and C atoms of diamond surface at elevated temperatures. The analyses also revealed that the bond between the alloy and the steel substrate was established through a cross\|diffusion of iron and chromium and the formation of(Fe x Cr y )C\|type carbides. Finally, a grinding test showed that the wear modes of such a brazed grinding wheel were mainly grit fracture and attrition rather than grit dislodgement from the bond.