Interfacial characteristics and mechanical properties of the vacuum brazing diamond grains segment with Ni-Cr composite active filler and tungsten carbide reinforcement

Abstract

Herein, composite brazing fillers were fabricated by adding reinforced tungsten carbide (WC) particles into Ni-Cr alloy and the composite segment of diamond grains was prepared by vacuum brazing using the composite fillers at a brazing temperature of 1030 °C for a dwelling time of 20 min. The thermal damage degree of the brazing diamond and mechanical properties, such as hardness, wear resistance and bending strength, of the segment were examined in detail. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were carried out to analyze the interfacial characteristics of the brazing diamond and segments. The results revealed that the static strength and impact toughness of the diamond grains, brazed by the composite fillers, were higher than the diamond grains brazed by pure Ni-Cr fillers. Raman spectra also indicated that the degree of graphitization and thermal damage of the diamond had been reduced. In the brazing process, the chemical and metallurgical reactions occurred between the composite fillers and diamond grains, which resulted in the formation of Cr3C2 and Cr7C3 compounds. At the same time, bonding phases were formed between WC particles and Ni-Cr particles. Furthermore, WC particles reduced the reaction intensity of the diamond and fillers, which resulted in the molding of the segments into a fixed shape. When the additive amount of WC particles was 30%, the hardness, wear resistance and bending strength of the composite diamond grains segment matrix reached the highest values. Moreover, the mechanical properties of the diamond grains, brazed by Ni-Cr filler and added WC particles were higher than the segment brazed by pure Ni-Cr fillers. The present study opens up avenues for further research on the development of multilayer brazing superhard abrasive tools.