Sliding wear resistance of metal matrix composite layers prepared by high power laser

Abstract

Two laser surface engineering techniques, Laser Cladding and Laser Melt Injection (LMI), were used to prepare three different metal matrix composite layers with a thickness of about 1 mm and approximately 25–30% volume fraction of ceramic particles. SiC/Al–8Si, WC/Ti–6Al–4V and TiB 2/Ti–6Al–4V layers were prepared by a Laser Melt Injection process, whereby additional material in the form of ceramic particles is injected into the molten substrate. As a result, a microstructure characterized by hard ceramic particles distributed in a metal matrix with very strong bonding is formed in the surface layer of the treated metal. A TiB/Ti–6Al–4V metal matrix composite layer was produced on Ti–6Al–4V substrates by conventional laser cladding. A mixture of TiB 2/Ti powders has been used as a precursor to obtain two microstructurally distinct layers, namely eutectic and primary TiB particles dispersed in the Ti–6Al–4V matrix. Sliding wear properties of these metal matrix composites layers were studied at boundary lubrication conditions and compared with the wear of the substrate materials. The observed wear mechanisms are summarized and related to detailed microstructural observations. The layers have been found to show excellent interfacial bonding, coupled with dramatically improved tribological properties expressed through a relative wear resistance value ranging from 30 to 1500.