Surface engineering of Ti-6Al-4V by nitriding and powder alloying using a CW CO2 laser

A comparison has been made of the laser processing of Ti-6Al-4V (IMI-318) alloy by (a) nitriding under a dilute atmosphere, (b) preplaced 6 µm SiC powder and (c) a combination of (a) and (b). At least six laser tracks were overlapped. Microhardness maps allowed details of the variation in hardness with both melt depth and track number to be determined. The microstructure was characterised and related to the processing parameters, melt track dimensions, hardness and roughness data. It was found that the preheat generated due to the overlapping, influenced the individual track dimensions, microstructure and properties, which were also affected by the laser energy density and the nitrogen concentration in the nitriding atmosphere used in processing. Process (b) was shown to produce the smoothest surfaces, with Ra values