|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Materials for High Temperature Applications: Next Generation Superalloys and Beyond
||Oxidation of Alumina-forming MAX Phases in Turbine Environments
||James L. Smialek, Anita Garg, Bryan Harder, James Nesbitt, Timothy Gabb
|On-Site Speaker (Planned)
||James L. Smialek
High temperature turbine components require oxidation resistance or coatings. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that approaches Al2O3 and YSZ. Their Al2O3 scales grow according to cubic kinetics, with initial heating dominated by fast TiO2 growth. MAXthal 211© 'Ti2AlC' survived high pressure burner tests up to 1300C, with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on Ti2AlC exhibit remarkable durability up to 1300C in furnace tests, with at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy. Accordingly, sputtered Cr2AlC coatings helped prevent hot corrosion detriments in LCF of a disk alloy. Breakaway oxidation, scale spallation, interdiffusion, and coating processing still present challenges. However the properties of MAX phases provide some unusual opportunities in turbines.