Interface characteristics and performance of pre-brazed diamond grains with Ni-Cr composite alloy

This study aims to improve the bonding strength of diamond abrasive grains to the matrix in sintering diamond segments. To achieve this goal, a new method of surface metallization of diamonds was developed by brazing using Ni-Cr composite alloy. The diamonds metallized by brazing are called pre-brazed diamonds. Brazing equipment was a vacuum resistance furnace. Diamond segments consisting of the pre-brazed diamonds and the metal matrix were fabricated. The static compressive strength and impact toughness of the pre-brazed diamonds were measured. The bending strength of the segments was also measured. The interfacial microstructure of the pre-brazed diamonds and the segment fracture surface were characterized. The compressive strength and impact toughness of the pre-brazed diamonds peaked when 30 wt.% Ni-Cr alloy was used in the Ni-Cr composite alloy. Elemental distribution showed that Cr mainly concentrated at the joining interface of the pre-brazed diamonds. An interfacial resultant composed of Cr3C2 and Cr7C3 was formed at the joining interface of the pre-brazed diamonds. A strong bond was formed at the joining interface between the pre-brazed diamonds and the metal matrix when sintering diamond segments.