A comparison of the reciprocating sliding wear behaviour of steel based metal matrix composites processed from self-propagating high-temperature synthesised Fe–TiC and Fe–TiB 2 masteralloys

Abstract

Steel matrix particulate composites were processed by direct addition of various powders to molten medium carbon steel. Fe–TiC and Fe–TiB 2 powders were produced using a self-propagating high-temperature synthesis (SHS) reaction and consisted of a dispersion of fine TiC (5–10 μm) and TiB 2 particles (2–5 μm), respectively in an iron binder. Addition of the Fe–TiC powder to the steel resulted in the formation of a metal matrix composite containing a homogeneous dispersion of TiC particles. However, addition of the Fe–TiB 2 powder resulted in the formation of a parasitic Fe 2B phase and TiC within the steel microstructure. In response to this an SHS masteralloy composed of Fe–(50% TiB 2+50%Ti) was manufactured which, when added to steel, prevented the formation of Fe 2B and resulted in a composite containing a mixture of TiB 2 and TiC particles. Dry reciprocating sliding wear behaviour of the three composite materials and their unreinforced counterpart was investigated at room temperature against a white cast iron counterface. Relative wear behaviour of the materials varied as a function of load. In all cases, the composite manufactured by addition of Fe–TiB 2 (yielding Fe 2B and TiC phases in the steel) exhibited wear rates greater than three times that of the unreinforced alloy. However, improvements in wear resistance over the base steel of up to two and a half times were observed with the other composites where the desired TiC and/or TiB 2 phases were retained in the steel. Scanning electron microscopy has been used to interpret wear behaviour in relation to both the as-cast microstructures of the composites and the wear scar microstructures observed.