Corrosion and wear of PEO coated AZ91/SiC composites

Abstract

In this work, corrosion and wear resistance of uncoated and PEO coated AZ91/SiC/0-10p composites manufactured by semisolid processing is evaluated by corrosion tests in saline solution and ball-on-disc tests. AZ91/SiC composites show a globular microstructure with SiC clusters located at the interglobular regions. PEO coatings reveal a trilayered structure with thicker, less porous and softer regions at the locations of SiC clusters. Corrosion rate increases with increasing the volume fraction of reinforcement, which shows a cathodic activity and disrupts the continuity of the β-phase network. PEO improves the corrosion resistance, but it is also negatively influenced by the presence of the reinforcement. Tribological tests show a positive effect of the reinforcement on uncoated materials, whereas an opposite effect is found on PEO coated materials, probably due to the detachment of SiC particles from the coating