Ti-6Al-4V strengthened by laser melt injection of WCp particles

The laser melt injection (LMI) process has been explored to create a metal-matrix composite consisting of 80 pm sized WC particles embedded in a Ti-6Al-4V alloy. In particular the influences of the processing parameters, e.g. power density, scanning speed and powder flow rate, on the dimensions and microstructure of the laser track have been examined. The microstructure was investigated by advanced transmission electron microscopy including energy filtering techniques and scanning electron microscopy with an integrated electron back-scatter diffraction/orientation imaging microscopy. Typical dimensions of a single laser track are a width of 1.8 mm and a depth of 0.7 mm. The volume fraction of the WC particles is about 0.25-0.30. An important finding is that the particle distribution is homogeneous and that the particles are injected over the whole depth and whole width of the melt pool. Only occasionally a crystal orientation relation between WC, W2C and TiC is observed. A substantial increase in wear resistance was observed, i.e. 0.5 x 10(-6)mm(3)/Nm for the WCp laser embedded and 269 x 10(-6)mm(3)/Nm for the untreated Ti-6Al-4V alloy at the same contact stress (20 MPa). (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.