ROLLER CONE FOR DRILL BIT HAVING IMPROVED RESISTANCE TO FATIGUE CRACKING

摘要

A roller cone for a drill bit is disclosed which includes a cone body having a plurality of sockets. An interior portion of at least one of the sockets is treated on an interior surface of the socket to provide a residual compressive stress proximate the interior of the socket to reduce stress cracking. Forms of treating include shot peening, laser shock peening and hammer peening. In one embodiment, the socket is treated over approximately the lower 50 percent of the lateral wall. In another embodimen t, the socket is treated on the bottom surface from the lateral wall inward approximately 33 percent of the diameter of the socket. Another aspect of the invention is a roller cone for a drill bit including a cone body having a plurality of sockets formed in th e cone. In this aspect, an interior portion of at least one of the sockets is locally anneal ed on an interior surface of the socket. In one embodiment, the socket is locally annealed ove r approximately the lower 50 percent of the lateral wall. In another embodimen t, the socket is locally annealed on the bottom surface from the lateral wall inwar d approximately 33 percent of the diameter of the socket.