Abstract: P110 steel has good comprehensive mechanical properties and is widely used as casing in oil and gas wells. When using cemented carbide tools for underwater milling and fishing, the wear is serious. In this paper, the wear ratio of drilling P110 steel with three different kinds of super-hard abrasive grains and binders has been experimentally studied, the surface morphology of abrasive grains on the tool surface has been tracked and observed, and the graphitization of diamond abrasive grains has been analyzed. The experimental results show that under the same processing conditions, the end wear of the three different core drills is roughly the same, but the side wear of the core drill using diamond abrasive particles is significantly less than that of the core drill using cubic Boron Nitride abrasive particles. Under the condition of underwater machining, the end face diamond abrasive grains will produce graphitization, but the diamond abrasive grains still maintain a certain cutting ability. The hardness of the bond affects the exposure of abrasive particles, which results in the performance of the tool under different working conditions.