Influences of laser powers on microstructure and properties of the coatings on the AZ91HP magnesium alloy

Al-Si alloy coatings were prepared on AZ91HP magnesium alloy by broad-beam laser cladding; the influences of the powers on the microstructure and properties of the coatings were discussed. It was found that the microstructure of the coatings at the powers of 3 and 3.5 kW was characterized by Mg2Si dendrites, and needle-like Mg2Al3 (hcp) dispersing in the Mg17Al12 matrix, whereas the coating at the power of 2.5 kW was composed of the petal-like Mg2Al3 (fcc) as well as the needle-like Mg2Al3 (hcp). The coating at the power of 4 kW appeared as α-Mg solid solution and Mg2Si, Mg17Al12, as well as Mg2Al3 (hcp). The coatings with the powers of 3 and 3.5 kW exhibited higher microhardness and better wear resistance because of more Mg2Si and Mg17Al12. However, the coating at the power of 2.5 kW displayed better corrosion resistance.