Rock bit with cobalt alloy cemented tungsten carbide inserts

A rock bit employs cemented tungsten carbide inserts for engaging a rock formation for drilling oil wells or the like. The cemented tungsten carbide inserts have as a binder phase a cobalt base alloy including from 10 to 35% by weight nickel, from 3 to 10% by weight chromium, from 1 to 6% by weight of molybdenum, and a balance primarily of cobalt. A particularly preferred composition has 6% by weight chromium, 17% by weight nickel, 4% by weight molybdenum and a balance of cobalt. Wear resistance is enhanced without loss of toughness in the inserts.