The Wear Mechanism of Carbide Tool when Machining Carbon Steels

Turning test was performed by a carbide tool on several carbon steels having various carbon contents and the worn surface of the tool and its cross-section were surveyed by the electron probe X-ray micro-analyzer in order to estimate the wear mechanism of carbide tools. Relation among the tool wear, cutting temperature, thickness of the diffused layer and the hardness of work material was investigated through the experimental findings concerning the decrease of cobalt content on the tool surface, the diffusion of carbon, and the weakening of tool.It is found that the tool wear is caused mainly by the diffusion of carbon from the carbide constituents of the tool material into the work steel, which changes the structure of carbides and weakens the tool crystals.From both the experimental data and the theory, it is proved that the wear velocity of carbide tool is resticted by the diffusion velocity of carbon through the matrix of the tool. And the thickness of the diffused layer beneath the tool surface increases as the cutting temperature is raised such that the hardness of work material is decreased, and as the carbon content of the work material is decreased.