Increasing the durability of an impregnated diamond core bit for drilling hard rocks

Abstract

Wear rates of impregnated diamond core bits made from two composite diamond-containing materials (CDM) are studied by spark plasma sintering (SPS) in the temperature range 20–1350 ºC at a pressure of 30 MPa for 3 minutes while drilling granite. The addition of chromium diboride (CrB2) micropowder in an amount equal to 2% of the composition of CDM 25Cdiam–70.5WC–4.5Co leads to a twofold decrease in the wear rate. The wear resistance of crowns made from CDM 25Cdiam–70.5WC–4.5Co and 25Cdiam–68.62WC–4.38Co‒2CrB2 is maximized at a rotary speed of 250 rpm and an axial load of 900 kg, and minimized at 750 rpm and 1250 kg. The increase in wear resistance of the 25Cdiam–68.62WC–4.38Co‒2CrB2 crown is due to the refinement of the grains of the main wolfram carbide (WC) phase and the formation of strong adhesion of the diamond grains to the carbide matrix. Keywords: impregnated diamond core bit; composite; tungsten carbide; cobalt; chromium diboride; durability; spark plasma sintering.