Mechanical properties of diamond grinding discs brazed in a continuous-belt tunnel furnace or vacuum furnace

Abstract

A new method for brazing diamond grains is presented. The brazing was conducted in a continuous-belt tunnel furnace under a dissociated ammonia atmosphere, which allows for a continuous large-scale production and greatly enhances productivity. To compare the brazing quality, identical samples were also brazed in a traditional vacuum oven. The surface morphology and interfacial microstructure were characterized, and the residual stresses, the static compressive strength, and the impact toughness were determined for both types of brazed diamond samples. Furthermore, grinding tests were conducted using the brazed diamond grinding discs. The results revealed that graphitization did not occur on the surface of the diamond grits. Cr3C2 and Cr7C3 were found at the interface between the diamonds and the Ni-Cr filler alloy brazed in the tunnel furnace. The residual stresses in the tunnel-brazed diamond grits were smaller than the stresses in the vacuum-brazed diamond grits in case of an identical measuring height, and the static compressive strength and the impact toughness of the etched tunnel-brazed diamond grits were 2316.7 MPa and 66.5 %, respectively, which was higher than the values obtained for the vacuum-brazed diamond grits (1865.6 MPa and 59.3 %). After grinding a granite test sample using the brazed diamond grinding discs, the fraction of abrasive grains pulled out from the surface of the tunnel-brazed grinding disc was slightly higher than the fraction of grains pulled out from the surface of the vacuum-brazed disc, whereas the overall abrasive grain fracture rate was lower at the same grinding length.