Abstract: In order to solve the problems of steel body PDC bit, including the lower hardness, poor wear resistance, poor drilling fluid erosion ability of the bit's body, the preferred mothod for steel body PDC bit surface hardening and preferred material for surface cladding were obtained by means of theoretical analysis and laboratory experiment, and established the flame spray welding technology using for cladding hardening on the bit surface.The results of field test show that the steel surface hardening layer with the cladding materials which are composed of Ni60 and WC of mass fraction 25%-30% has good quality, its abrasion resistance and erosion resistance can satisfy drilling requirements.