Manufacture of drill bits from new diamond materials at high pressures and temperatures

Abstract

The manufacture of diamond drill bits (diameter up to 212 mm) at pressures up to 1.5 GPa and temperatures up to 1250°C is described. This technology includes sintering by electric heating within a thermally and electrically insulating shell in a steel high-pressure chamber, for 120 min. Such high-pressure sintering is found to be a relatively rapid process, and the equipment may be employed repeatedly. Steel highpressure chambers of cylinder–piston type with working diameters up to 280 mm are developed and produced. In bit manufacture by this means, matrix material with diamonds may be pressed onto steel housing; alternatively, it is possible to use a powder housing with diamonds or with holes for subsequent attachment of diamonds by soldering or mechanical methods. Bits with model cutting elements made of polycrystalline carbonado diamonds are manufactured, and their operational properties are verified. In drilling a marble block under loads up to 50 kN, at speeds of 355 rpm, mechanical speeds up to 20 m/h are attained. In the technology developed, the cutting properties of carbonado diamonds may be retained, but the thermal stability matches that of PCD diamond–hard-alloy composites. The bits are rugged enough for use in the most challenging drilling conditions. The metal–ceramic matrix permits the reliable attachment of cutting elements made of ASPK diamond composites. It is strong and wear-resistant. This is an energy-saving technology with little environmental impact and is fast. It may be used to produce wear- and corrosion-resistant metal–ceramic housings, with subsequent attachment of diamonds by soldering or mechanical methods, on the basis of PCD composites with varying thermal stability.