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

Abstract

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 30wt.% 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.