Erosion resistance of laser clad Ti-6Al-4V/WC composite for waterjet tooling

In waterjet operations, milled surfaces are left with some undesirable dimensional artefacts, thus the use of abrasion resistant mask has been proposed to improve the surface quality of machined components. In this study, the erosion performance of laser clad Ti-6Al-4V/WC composite coating subjected to plain water jet (PWJ) and abrasive water jet (AWJ) impacts to evaluate its potentials for use as waterjet impact resistant mask material and coating on components was investigated. Results showed that composite with 76 wt.% WC composition subjected to PWJ and AWJ impacts offered resistance to erosion up to 13 and 8 times that of wrought Ti-6Al-4V respectively. Scanning electron microscopy (SEM) examination of the eroded composite surfaces showed that the erosion mechanism under PWJ impacts is based on the formation of erosion pits, tunnels and deep cavities especially in the interface between the WC particles and the composite matrix owing to lateral outflow jetting and hydraulic penetration. Composite suffered ploughing of the composite matrix, lateral cracking and chipping of embedded WC particles and WC pull-out under AWJ impacts. The composite performance is attributed to the embedded WC particles and the uniformly distributed nano-sized reaction products (TiC and W) reinforcing the ductile β-Ti composite matrix, with its mean hardness enhanced to 6.1 GPa. The capability of the Ti-6Al-4V/WC composite coating was demonstrated by effective replication of a pattern on a composite mask to an aluminium plate subjected to selective milling by PWJ with an overall depth of 344 μm. Thus, composite cladding for tooling purpose would make it possible to enhance the lifetime of jigs and fixtures and promote rapid machining using the water jet technique.