Effect of process parameters on bead properties of A359/SiC MMCs welded by laser

Metal matrix composites are well known materials that present several positive features, mainly in terms of mechanical strength to weight ratio. On the other side, MMC’s are extremely difficult to machine (in particular by chip removal processes) and this difficulty has limited a wider diffusion. Welding, together with other joining technologies, could be a solution to limit the chip removal processes in the production of a MMC part, but this is not a problem-free process. This paper presents an experimental study on the laser welding of MMCs using both a CO2 and a diode laser source. The CO2 welding is performed in keyhole conditions (deep penetration), whereas the diode laser performs a conduction welding. Results show that the CO2 welding is greatly affected by the formation of Al4C3, that compromises the toughness of the bead. The content of Al4C3 can be reduced by acting on the process parameters, but cannot be completely eliminated. Instead, diode laser welding generates a sound bead, with negligible Al4C3 formation and of superior quality. Considering also the other positive features of this kind of sources (high efficiency and radiation wavelength, that is, highly absorbed by MMCs), diode laser welding seems to be highly recommendable for MMCs laser welding.