Hardfacing with multiple grade layers

摘要

An earth-boring bit has hardfacing that has multiple grades and an overlapped portion. One of the layers is of a different grade than the other so as to provide more wear resistance. The other provides more toughness than the wear resistant layer. The more wear resistant layer has a greater volumetric density of carbide particles. The greater density is primarily achieved by using a majority of the particles of smaller dimension than in the less wear resistant hardfacing. The overlapped portion may be on an outer or gage end of the outer row of teeth.