A Comparison of Oxidation Behavior of Al Coatings Prepared by Magnetron Sputtering and Arc Ion Plating on y-TiAl

The micro-structure, the morphology and the oxidation resistance of Al coatings deposited using magnetron sputtering (MS) and arc ion plating (AIP) were investigated by means of SEM, EDS and XRD. A more compact and uniform Al coating with small grain size was deposited on γ-TiAl by MS method. A protective surface structure consisting of an oxide scale, an Al-rich layer and an interdiffusion layer was formed after oxidation test. However, the Al coatings prepared by AIP showed a poorer oxidation resistance due to the existence of a large amount of pores in the coatings, which played a role of channels for oxygen transportation and induced seriously the internal oxidation and the coating degradation finally. The non-protective scales consisting of Al2O3 and TiO2 were formed after quasi-isothermal oxidation test at 900 °C for 173 h. The results indicate that the Al coatings deposited by MS exhibit a better oxidation resistance than those by AIP.