Effect of oxidation resistant Al3Ti coating on tensile properties of a near α-Ti alloy

Near α Ti-alloys are used in compressor parts of advanced gas turbines engines at temperatures up to about 600 °C. Long term high temperature exposure of these alloys in air is expected to degrade their mechanical properties and limit their life and/or performance. Therefore, an appropriate oxidation resistant coating may be necessary to protect such alloys during high temperature use. The present study examines the effect of oxidation resistant Al3Ti coating deposited through pack aluminizing method on the tensile properties of a near α alloy called Titan 29A. Tensile properties have been evaluated at RT and 600 °C after exposing the coated tensile samples (up to 2000 h) at 650 °C in air. The RT ductility of the alloy was severely affected after oxidation exposure despite the presence of the coating. However, the ductility at 600 °C was much less affected. The strength of the coated alloy after the oxidation exposure largely remained unchanged at both the above temperatures. The effect of oxidation exposure on the mechanical properties of the coated near α alloy has been correlated with microstructural and fractography observations.