Structure, micro-hardness and corrosion behaviour of the Al–Si/Al2O3 coatings prepared by laser plasma hybrid spraying on magnesium alloy

• Al2O3 was sprayed on the Al–Si transition layer by laser plasma hybrid spraying.
• Al–Si transition layer was applied between substrate and Al2O3 surface coating.
• The effects of laser power on the porosity of coatings were studied.
• The corrosion resistance of the Al–Si/Al2O3 coatings on substrate was discussed.

An Al–Si/Al2O3 coating was successfully prepared on the surface of the AZ91D magnesium alloy substrate by a new technology laser plasma hybrid spraying in this paper, and the influence of laser power on the structure and property of the coating was studied simultaneously. The performance of the coating, such as the morphology, porosity, phase composition, micro-hardness, was characterized. The results showed that the Al–Si transition layer significantly improved the adhesion between the coating and the substrate. With the increasing of laser power, the unfused particles in the coating decreased and the coating was more compact. The porosity of the coating decreased firstly and then increased with the increasing of laser power, and the lowest porosity was 3.6%. The bonding strength of the coating was 25.62 MPa and the highest hardness was up to HV0.05470 (4.61 GPa). The corrosion resistance of the coating can exceed 900 h under neutral salt spraying conditions.