Ni—Cr合金与金刚石和钢基体界面微区的分析研究

利用扫描电镜X射能谱，结合金相及试验样逐层的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休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，这时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。

Micro-analysis of Interface between Ni-Cr Alloy and Diamond

The brazing of a monolayer of diamond grinding wheel with active filler metals has distinct advantages over conventional electroplated diamond grinding wheel in terms of faster cutting and longer life. The study shows that a commercially available Ni-Cr alloy can be used as an active filler material for brazing diamond grit. Furnace brazing is carried out in a current of argon. SEM-EDS microanalyses show 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 reveals that the wetting and bonding behaviour on diamond surface by Ni-Cr alloy melt is realized through 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 reveal that the bond between the alloy and the steel substrate is established through a cross-diffusion of iron and chromium. Finally a grinding test show that the wear modes of such a brazed grinding wheel are mainly grit fracture and attrition rather than grit dislodgement from the bond.