METHOD AND APPARATUS FOR SELECTIVELY LEACHING PORTIONS OF PDC CUTTERS ALREADY MOUNTED IN DRILL BITS

摘要

A polycrystalline diamond compact (PDC) cutter having a body of diamond crystals containing cobalt is coated with Teflon which is impervious to hydrofluoric acid. After the Teflon coating is dried, a segment of the Teflon coating is removed and a mixture of 50% hydrofluoric acid and 50% nitric acid is supplied to the diamond crystal body through the template in the Teflon coating to leach out the cobalt catalyzing material contained within the body of diamond crystals. In an alternative embodiment, a similar process is used to coat a PDC drill bit and the PDC cutters mounted in the PDC drill bit. After the Teflon dries, a segment of the coating is removed and the acid mix is applied through the templates in the cutters to leach out the cobalt in each of the bodies of diamond crystals. In another alternative embodiment, a tube is placed over the PDC cutter, the tube having one or more templates exposing only the segment or segments of the cutting surface to the acid mix.