Ni-Cr合金钎焊金刚石砂轮机理的研究

Research on Brazing Behaviour between Diamond Grinding Wheel and NiCr Alloy

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、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 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。

The present study shows that a commercially available NiCr alloy can be used as an active filler material for brazing diamond grit. Furnace brazing was carried out in a current of argon. SEMEDS microanalyses showed 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 NiCr alloy melt was realized through Cr 7C 3 , which was produced by interaction between Cr atoms of NiCr 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 interdiffusion of iron and chromium. 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.