2012 Volume 53 Issue 6 Pages 1130-1137
Microstructures and element distribution at the interface between a tool surface and a residue of low-carbon free cutting steel, which was left behind and accumulated on the tool surface during machining, were observed and analyzed by transmission electron microscopy (TEM) and laser-assisted three dimensional atom-probe tomography (LA3DAP). The residue of the machined steel was composed of fine ferrite grains a few hundred nanometers in size, which were considered to be a result of a grain refinement process by severe plastic deformation. Tungsten carbide (WC) particles embedded in the tool were sharply worn at the interface, and the interface was found to be flat and sharp on a nanometer scale. The deposited steel on the worn tool surface was tightly bound and the interface was successfully analyzed by LA3DAP in transverse direction. It was shown that tungsten atoms from the WC particles had diffused into the deposited steel with a distance of approximately 10 nm from the interface. These findings indicate that the wear of tool upon machining low-carbon free cutting steels proceeds mainly by the diffusional wear mechanism.