Sputtering and Characterization ofMAX-Phase Forming Cr Al C and Ti Al C Coatings and Their Application on γ-Based Titanium Aluminides

Abstract

MAX-phases are of increasing interest as coating material for high temperatureapplications due to their unique metallic as well as ceramic properties. Herein,the deposition of Cr2AlC and Ti3AlC2or Ti2AlC MAX-phase forming coatings bymagnetron sputtering is demonstrated. Using pure elemental targets, themanufacturing with a coating thickness of above 7 m is established. TheMAX-phase forming coatings are characterized by high-temperature X-ray dif-fraction (HT-XRD) measurements and provide a good oxidation behavior due tothe development of protective thermally grown oxide layers. The performance ofthe MAX-phases is strongly depended on the substrate material and theaccompanying interdiffusion processes. Therefore, the Ti–Al–C coating is favoredfor TiAl alloys due to the thermodynamic stability of the Ti2AlC MAX phase inparticular in the presence of the γ-TiAl phase. An excellent oxidation behavior isconrmed up to 300 h at 850C due to the development of an alumina layerabove a homogenous Ti2AlC phase coating. The Cr2AlC MAX-phase coatingdegrades after 100 h at 800C due to interdiffusion processes between coatingand substrate and the accompanying development of carbides and nitridephases. Nevertheless, the oxidation resistance of the Cr–Al– C-coated TiAl alloy isgiven by the formation of the Ti2AlC MAX-phase.