Hardmetal facing for earth boring drill bit

摘要

A steel tooth rolling cutter earth boring drill bit includes a bit body with a threaded upper end for attachment to the end of a drill string, and a lower end including three legs extending downwardly from the bit body and with a rolling cutter rotatably mounted on each leg. A layer of wear resistant material is applied to a portion of each rolling cutter and comprises wear resistant particles in a substantially steel matrix. The steel matrix is integrally formed with the cutter in a rapid, solid state densification powder metallurgy (RSSDPM) process, and includes a duplex microstructure comprising from about 10 to 40 volume percent austenite and from about 60 to 90 volume percent martensite. The duplex microstructure may be achieved by incorporating a minor fraction of pure nickel and/or manganese powder in the powder mix used in the process, thereby providing nickel or manganese enrichment of the austenitic zones of the matrix.