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

Abstract

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 Al3Ti 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.

Keywords

• Ti alloy
• Protective coating
• Self-diffusion
• Oxidation resistance
• Mechanical property
• Wear resistance