Al/SiCp and Al11Si/SiCp coatings on AZ91 magnesium alloy by HVOF

• Al/SiC and Al11Si/SiC coatings have been successfully obtained by HVOF.
• Most influential spraying parameter into the coating properties is the % SiCp.
• The coatings exhibited low porosity, high adhesion strength and high hardness.
• Optimum spraying conditions were obtained through the Taguchi DOE method.
• DOE method has proved valid for optimizing spraying variables.

High velocity oxygen-fuel (HVOF) thermal spray has been used to fabricate Al, Al11Si and metal matrix composite (Al/SiCp and Al11Si/SiCp) coatings on the AZ91 Mg alloy. Taguchi design of experiment (DOE) methodology was used to analyze the influence of the HVOF spraying conditions (% SiCp in feedstock, spraying distance, number of layers and gun speed) in the main characteristics of the coatings (actual amount of reinforcement in the coating, porosity and thickness) and in some properties of the coatings such as hardness and adhesion. In general, for the same HVOF spraying conditions, the coatings fabricated using Al11Si as matrix presented higher thickness and lower incorporation of reinforcement, as well as higher hardness and adhesion values in comparison with those of pure Al matrix coatings. Independently of the matrix used, the % SiCp in feedstock and spraying distance seem to be the most important spraying parameters in controlling the properties of the sprayed coatings.