Microstructure and Corrosion Properties of Biodegradable Mg/MgO Composite Coating on Mg Alloy Prepared by High Velocity Suspension Flame Spraying

A biodegradable Mg/MgO composite coating was deposited onto AZ31B magnesium alloy by high-velocity suspension flame spraying technique using nano-sized MgO and micron-sized Mg powders. Phase constitution, microstructure, mechanical property and corrosion behavior of Mg/MgO composite coatings with different Mg/MgO ratios were investigated. Mg/MgO composite coatings with different Mg/MgO ratios presented rough and porous surfaces with typical features of solid-fluid co-deposition and exhibited well bonding coating/substrate interfaces with some pores within the coatings. Mg/MgO composite coatings prepared by co-deposition of Mg/MgO mixed powder were mainly composed of Mg rather than MgO indicating superior deposition of Mg. Microhardness, elastic modulus and tensile strength of Mg/MgO composite coatings were influenced by the Mg/MgO ratio. Mg/MgO composite coatings presented a limited corrosion protection for Mg alloy substrate after immersion in Hanks’ simulated body fluid for different times. Corrosion behavior of Mg/MgO composite coatings was also discussed. This study proposed a strategy to prepare biodegradable Mg/MgO composite coating on metal substrates for potential applications in the implant field.