Rock bit with wear-and fracture-resistant hardfacing

摘要

An improved hardfacing for teeth and other surfaces of milled tooth rock bits comprises a hard phase of carbide particles embedded in a toughened steel matrix containing no more than 10 percent by volume of combined eta phase and oxide particle components. Eta phase and oxide particle formation is minimized during oxyacetylene welding by positioning the weld rod in a preferred region of the torch flame while welding the hardfacing to the rock bit. The matrix is strengthened by uniformly dispersing ultra-fine carbide or boride particles in the steel alloy. The hardfacing is further toughened by selecting tough carbide particles for the hard phase. Accordingly, the hard phase comprises spherical cast carbide and spherical cemented carbide particles having particle sizes in the range of from 75 mu m to 590 mu m.