Cyclic Oxidation and Hot Corrosion Behaviour of Ti-48Al-2Cr with Aluminide Coatings

Abstract

Aluminide coating was directly applied onto Ti-48Al-2Cr alloy using electro-spark deposition (ESD) technique. The coating has a thickness of 15-20 μm, a gradient composition, and a metallurgical bonding to the substrate. Cyclic oxidation and hot corrosion tests were carried out at 800°C to evaluate the protective ability of the coating under relatively severe corrosion environments. It was shown that under both test conditions, a uniform and compact external scale mainly composed of α-Al 2 O 3 formed on the coated specimens. This scale exhibited excellent spallation and hot corrosion resistance. While the scale with multi-layered structure formed on Ti-48Al-2Cr under cyclic oxidation condition consisted of TiO 2 and α-Al 2 O 3 , which suffered severe cracking and spallation after extended oxidation. During hot corrosion test, this layer spalled away extensively and dissolved partially into the molten salt. These results showed that aluminide coated Ti-48Al-2Cr could undergo severe oxidation and hot corrosion conditions.