Abrasion, sliding wear, corrosion, and cavitation erosion characteristics of a duplex coating formed on AZ31 Mg alloy by sequential application of cold spray and plasma electrolytic oxidation techniques

Abstract

In order to improve the comprehensive surface properties (corrosion and wear resistance) of an AZ31 Magnesium (Mg) alloy, the Cold Spray (CS) and the Plasma Electrolytic Oxidation (PEO) techniques were utilized sequentially to fabricate a double-layered (duplex) coating. An alumina (Al2O3) reinforced aluminum CS layer was first deposited on the AZ31 Mg alloy substrate surface, and the PEO process was applied on the CS layer subsequently to obtain an Al-based PEO coating. The microstructure, mechanical properties, corrosion, abrasive wear, dry sliding wear, and cavitation erosion resistances were evaluated to quantify the surface condition before and after the aforementioned treatments. The results revealed that the Al-based PEO coating possessed more compact microstructure, higher micro-hardness (1100 HV0.025) and higher bond strength (27 MPa) than the Mg-based PEO coating (412 ± 61 HV0.025 and 20 MPa). The Al-based PEO coating also offered a superior protection to AZ31 Mg alloy against abrasion (0.010 mm3/N m, dry sliding wear (5.14 × 10−5 mm3/N m, corrosion (5.18 × 10-7 A/cm2), and cavitation (5 × 10-4 mm3/s) compared to the single-layered coatings (Mg-based PEO coating and CS coating).