High temperature performance of a dual self-diffusion coating on TA9 alloy

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A ceramic plasma electrolytic oxidation (PEO) coating was prepared on an Al-sprayed TA9 surface to reinforce its high-temperature properties, including antioxygenic, wear-resisting and mechanical properties. The obtained results indicated that the middle Al layer had a bilateral diffusion ability, which sealed the micro pores of the PEO layer and formed an Al 3 Ti layer at the interface of the Al and Ti layers. The duplex coating efficiently improved the oxidation resistance and the oxidation rate was 5 times lower than that of TA9 matrix at 700°C. The ceramic PEO coating protected the Ti matrix from abrasion. The tensile strength of TA9 alloy after composite coating increased from 90 to 340 MPa after 5 days of oxidation and an elongation of 46% was maintained, which was attributed to the self-diffusion behavior of mediate Al layer. Post-heat treatment process remarkably improved the oxidation resistance and mechanical property but had limit enhancement in wear resistance. A two-layer self-assembly coating is suggested for surface modification of high temperature Ti alloys.