The characteristics of vacuum sintered M3/2 type HSSs with MoS2 addition

The preparation of composite self-lubricating high-alloyed Fe-based material suitable for different anti-wear applications was studied. As a base, two conventional high-speed steel (HSS) AISI M3/2 and M35 were selected. Dry powder mixtures were prepared from prealloyed water-atomised powders and 0.5–3 wt.% of solid lubricant. As solid lubricant, MoS2 was chosen. Composite materials were prepared by uniaxial cold compaction of powder mixtures and vacuum sintering of compacts. The uniaxial compaction tests showed that the addition of MoS2 enhances the compressibility of powder mixtures. The influence of MoS2 on the densification of selected HSSs during heating was studied by thermo-gravimetry, differential thermal analysis and MS. These analyses showed that significant weight losses occur. They are a consequence of deoxidation reaction which occurs among surface oxides of powder particles and carbon from solid solution. Vacuum sintering of green compacts was performed in temperature range of 1160–1300 °C. Microstructural and mechanical characteristics of sintered composites were determined. Investigations showed that the addition of MoS2 enhances the sinterability. Densification proceeds by the reactive supersolidus liquid-phase sintering process because of the reaction between MoS2 and the steel matrix. A fine dispersion of (Cr, V, Fe)-based sulphide particles in steel matrix is formed. This has a beneficial influence on the tribological properties of synthesised composite materials.