XRD and XPS studies on surface MMC layer of SiC reinforced Ti-6Al-4V alloy

Overlapping tracks were produced by laser processing using a powder SiC (6 μm) preplacement technique which has been developed to modify the surface structure of a Ti-6Al-4V alloy. A continuous-wave CO2 laser was used for the processing which produced six overlapping tracks covering 14 mm across the surface of a 10 mm thick plate. Under spinning beam conditions, a surface alloyed/metal matrix composite (MMC) layer over 300 μm in depth was produced on the alloy. The surface contained a complex microstructure, but with no cracks and only two pores at the melt/HAZ interface. Using XRD and XPS analysis, it was shown that the solidified melt consisted of α′-Ti, Ti0.55C0.45 and Ti5Si3 phases, which vary with melt depth and with the particular group of overlapping tracks examined. Therefore, no new phases to those previously identified in single track laser processing experiments were found in this work.