Process for laser hardening drilling bit cones having hard cutter

Abstract

A medium to high carbon steel body of a roller cone for a drilling bit is machined to final dimensions, and is thereafter rendered absorbent to laser light by application of black paint or black etch. Holes for hard tungsten carbide or like inserts are drilled in the light absorbent steel body. The entire steel body, including the holes, is subjected to a laser treatment which, however, is effective to raise to above austenitizing temperature only the dark light absorbent surfaces. Walls of the insert holes, being shiny, reflect the laser light and are not effected by it. Rapid self-quenching of the laser heated surfaces results in a hard martensitic layer in the external surface, with a surface hardness of 57 to 60 Rockwell C units. The seal gland, heel, and spindle bore areas of the roller cones are hardened similarly by exposure to laser light. In an alternative process, the hard tungsten carbide or like inserts are press fitted into the holes before the laser treatment. The subsequent laser treatment does not affect the inserts adversely, because the inserts, too, have shiny light reflective surfaces, and therefore do not absorb the laser light.