Microstructure characterization of laser melt injected WC particles in Ti-6Al-V

The Laser Melt Injection (LMI) process is explored to create a protective Metal Matrix Composite (MMC) layer consisting of 80 mum sized WC particles embedded in the top layer of a Ti-6Al-4V alloy. In particular the influences of the main process parameters on the laser track dimensions and microstructure are examined. 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 homogeneous distributed WC particles is about 25 - 30%. Important is that by overlapping the single laser tracks larger surface areas may be treated. In the Ti-alloy melt pool matrix TiC and W dendrites are present. The bonding between the ceramic particles and metal matrix is realized by reactions that occurred during the laser process. Around the WC particles a W2C layer was detected. followed by a TiC layer. Occasionally a crystal orientation relation between WC, W2C and TiC is observed, depending on the WC interface. When the surface of the WC particle is close to (0001) the preferred growing direction [0001] can be retained while the misfit at the WC/W2C interface is minimized.