Al-WC composite coating on AZ91D Mg alloy by low power pulsed laser cladding

Laser cladding coatings were fabricated on AZ91D magnesium alloy using Al and WC powders with a weight percentage ratio of 95 : 5, 90 : 10, and 85 : 15 by a low power pulsed Nd:YAG laser. During the process of laser cladding, most of WC was decomposed. Tiny white granular resultant Al18Mg3W2 was detected in all coatings, while bright white Al4W particles with clustering tendency were found only in the 10 and 15 wt.% WC coatings because of relatively high WC content. alpha-Al, alpha-Mg, Al3Mg2, and Al12Mg17 were also detected at the coatings. The hardness of the coatings increased by 3-4 times compared with that of the substrate. The corrosion resistance of the coatings was also improved markedly, mainly the passivation phenomenon was observed in all coatings, which may benefit from the formation of oxidation film Al2O3 . H2O on the surface of the coatings due to high Al concentration.