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

Abstract

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, MoS 2 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 MoS 2 enhances the compressibility of powder mixtures. The influence of MoS 2 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 MoS 2 enhances the sinterability. Densification proceeds by the reactive supersolidus liquid-phase sintering process because of the reaction between MoS 2 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.