Features Structure of the Сdiamond‒(WC‒Co)‒ZrO2 Composite Fracture Surface as a Result of Impact Loading

Abstract—

The effect of the addition of ZrO₂ micropowder (in the range from 0 to 10%) on the structural changes of the hard alloy matrix in the area of fracture as a result of impact loading of a sample of composite diamond-containing material (DCM) 25С_diamond–70.5WC‒4.5Co wt % was studied, formed by the method of spark plasma sintering in the temperature range from 20 to 1350°С at a pressure of 30 MPa for 3 min. It was found that in the DCM sample without ZrO₂ additive, the structure of the hard alloy matrix has the appearance characteristic of brittle fracture, which is evidenced by the smooth relief of the fracture surface. In this case, the destruction of the DCM sample occurs by chipping of the components of the hard alloy matrix, which leads to a decrease in its wear resistance. The introduction of the ZrO₂ additive in the amount of 4% into the composition of DCM causes a change in the structure of the fracture surface. On the fracture surface of the carbide matrix of the DCM sample, nanopores with a structural size of ~100–500 nm are formed as a result of viscous (pitting) fracture. At the same time, in addition to the formation of dimples on the fracture surface of the hard alloy matrix, a highly developed relief is simultaneously formed on the surface of the diamond grain, which is evidence of improved diamond retention and increased wear resistance of the composite. With a further increase to 10% of the ZrO₂ additive in the DCM composition, a more pronounced microrelief with the presence of deep dimples and microcracks is formed on the fracture surfaces of the hard alloy matrix and diamond grain. It is proposed to use the type of relief of the fracture surface of sintered DCM samples during impact fracture at room temperature as an assessment of the characteristics of the strength of diamond retention.