The influence of physicochemical surface treatment of on the content and composition of inclusions and impurities in synthetic diamonds

Abstract

The purpose of the work was to conduct research to determine the content and composition of intracrystalline inclusions and impurities in synthetic diamond powders used in grinding production. The research was conducted on diamond grinding powders of the AC20 (according to regulatory documents of Ukraine) grade with a grain size of 125/100, obtained in the Ni-Mn-C system, before and after their thermochemical treatment in an alkaline melt1. Physico-mechanical characteristics were determined: compressive strength; the specific magnetic susceptibility. The total content of inclusions and impurities was determined in the form of unburned residue, obtained after long-term high-temperature treatment to a constant mass. The surface condition, total content, and elemental composition of the original diamond grinding powders and unburned residues before and after thermochemical treatment were determined by the SEM and X-ray spectral microanalysis (processing in an alkaline melt at a temperature not exceeding 600°C). It is shown that their strength is slightly reduced as a result of the thermochemical treatment of the surface of diamond grinding powders. Due to the dissolution of a certain part of inclusions and impurities, there is a decrease in the quantitative content of the non-combustible residue by 2 times and a weakening of the magnetic properties by approximately 1.4 times. The total content of inclusions and impurities in diamond powders after their thermochemical treatment decreases by approximately 5wt.%, and the content of carbon solvent alloy elements (Mn+Ni) - by 6wt.%. Additional chemical elements (Mg, K, Ca, Fe) were detected in X-ray spectra microanalysis from the surface of diamonds after their thermochemical treatment, which were not present in the composition of diamonds before treatment. The total quantity and elemental composition of unburnt residues of grinding powders before and after thermochemical treatment decreases by 2.4 times, and the content of carbon solvent alloy elements (Mn+Ni) in them by 1.7 times.