Structure of Сdiamond–(WC–6Co)–ZrO2 Composites Formed by Electrical Plasma Spark Sintering
В. А. Мечник, Mirosław Rucki, Boranbay Ratov, Н. А. Бондаренко, É. S. Gevorkyan, V. М. Kolodnitskyi, V. Chishkala, Оксана Морозова, Vitalii Kulich
Abstract
The effect produced by different concentrations of ZrO2 additives (from 0 to 10 wt %) on the morphology, structure, and content of diamond grains in the hard-alloy matrix of Сdiamond–(WC–6Co) diamond-containing composites (DCCs) formed by electrical plasma spark sintering within a temperature range of 20–1350°C at a pressure of 30 MPa for 3 min has been studied. Stable correlations have been established between the ZrO2 additive content and the average size of WC grains, the microstructural parameters, and the strength of adhesion between diamond grains and the hard-alloy matrix. It has been shown that a coarse-grain structure is formed in the hard-alloy matrix of the initial Сdiamond–(WC–6Co) sample both with direct contact between WC grains and with large cobalt binder areas as a reason for the weak adhesion between the diamond grains and hard-alloy matrix and the premature loss of diamond grains by the matrix in the process of its operation. After ZrO2 micropowder is added to the composite, a more fine-grained structure with thin cobalt binder interlayers between WC grains is formed in the hard-alloy matrix to essentially strengthen its adhesion with the diamond grains. This increases the ability of the hard-alloy matrix to retain the diamond grains from their premature loss from DCCs under operation alongside with their mechanical and performance characteristics. The highest ability of the hard-alloy matrix to retain the diamond grains from premature loss was observed at a ZrO2 content of 10 wt %. The synthesis of composites with ZrO2 additives provides significant economic benefits not only due to a decrease in the energy consumption in the process of sintering, but also due to an abrupt decrease in the cost of composites.