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

摘要

The laser melt injection (LMI) process has been explored to create a metal-matrix composite consisting of 80 μm 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 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, W_2C and TiC is observed. A substantial increase in wear resistance was observed, i.e. 0.5 * 10~(-6)mm~3/Nm for the WC_p laser embedded and 269 * 10~(6)mm~3/Nm for the untreated Ti-6Al-4V alloy at the same contact stress (20 MPa).