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-TiB2 masteralloys

Steel matrix particulate composites were processed by direct addition of various powders to molten medium carbon steel. Fe-TiC and Fe-TiB2 powders were produced using a self-propagating high-temperature synthesis (SHS) reaction and consisted of a dispersion of fine TiC (5-10 mum) and TiB2 particles (2-5 mum), 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-TiB2 powder resulted in the formation of a parasitic Fe2B phase and TiC within the steel microstructure. In response to this an SHS masteralloy composed of Fe-(50% TiB2 + 50%Ti) was manufactured which, when added to steel, prevented the formation of Fe2B and resulted in a composite containing a mixture of TiB2 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 counter-face. Relative wear behaviour of the materials varied as a function of load. In all cases, the composite manufactured by addition of Fe-TiB2 (yielding Fe2B 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 TiB2 phases were retained in the steel. Scanning electron microscopy has been used to interpret wear behaviour in relation to both the as-cast micro structures of the composites and the wear scar microstructures observed. (C) 2002 Elsevier Science B.V. All rights reserved.