Mechanical and Tribological Properties of TiC-Reinforced HSS-Based Composites with an Interpenetrating Network for High Temperature Self-Lubrication Applications

Abstract

Porous M3/2 type high speed steel (HSS) preforms reinforced with both TiC and Cu₃P were fabricated using a kind of complex as pore forming agent via vacuum sintering process. The porous preforms were infiltrated with Pb-Sn-Ag based solid lubricants using a self-made vacuum high pressure infiltration furnace to create almost fully dense self-lubrication composites, where both solid lubricant phase and matrix phase were interpenetrating throughout the microstructure. By means of scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS), it was found that Pb-Sn-Ag based solid lubricants are well dispersed and embedded in the HSS matrix. The hardness, microstructure and crushing strength of the sintered preforms and the composites were evaluated. The friction and wear properties of the materials were estimated by a pin-on-disc wear machine under dry conditions at room temperature, 300, 500, 600, 700 and 800 °C. The hardness, crushing strength and wear resistance of the preforms and the composites were improved significantly by the additions of both TiC and Cu₃P more than by only TiC. It is evidence that very little densification of pore walls occurs during solid state sintering of M3/2 HSS preforms. However, higher densification is achieved in the case of supersolidus sintering. By adding 7 wt.% Cu₃P and 15 vol.% TiC into the HSS matrix, the best comprehensive properties of mechanics and tribology have been obtained for the preforms and the composites. The composites infiltrated with Pb-Sn-Ag based solid lubricants showed very low friction coefficient and wear rate at elevated temperature.