Comparison of the wear behavior of high speed steel grades obtained from conventional casting and laser cladding

Tools Steels are alloys which withstand severe mechanical and physicochemical stresses in service. Therefore their alloying design that involved both the original chemical composition and the casting route is crucial in order to achieve a tailored microstructure exhibiting enhanced wear performances.
Tools steels obtained from conventional casting processes had received lot of attention so far as they yield typical microstructure composed of a quasi-continuous network of coarse grain boundary carbides with grain size ranging between 20 to 200 µm. Direct energy deposition applied to Tools Steels represents a new emerging technique that may allow ultrafine grained microstructures due to the higher cooling rates achieved especially in the solidification range.
In this paper, four tool steels grades were studied, one of them being obtained from a conventional casting process and the other ones originated from the direct energy deposition. Differential Thermal Analysis helps enhancing the solidification sequence of the studied alloys, while their microstructure after subsequent heat treatment was characterized by the means of both optical and electron microscopes together with hardness measurements. Tribological tests carried out at room temperature and at high temperature were performed while using a “pin-on-disc” device. Based on the friction coefficient and the wear rate, the wear performances of the tool steel were determined and compared with one another. The influence of metallurgical features (the grain size, or the nature, the size and the distribution of carbides) on the wear behavior was also enhanced. The setting of the wear test parameters together with the microstructure of the studied materials seems to strongly influence the subsequent abrasion and wear mechanisms.