Effect of a magnetron sputtered (Al2O3–Y2O3)/(Pt–Au) laminated coating on hot corrosion resistance of 8Nb–TiAl alloy

Novel (Al2O3–Y2O3)/(Pt–Au) laminated coatings were prepared on 8Nb–TiAl alloy by magnetron sputtering methods. (Na2SO4–NaCl)-induced hot corrosion and cyclic oxidation tests were adopted to investigate the high-temperature corrosion behaviours and the mechanical properties of the as-prepared laminated coatings. The results revealed that the multi-sealed (Al2O3–Y2O3) and (Pt–Au) layers can effectively suppress the inward diffusion of oxygen and corrosive fused salt to an extremely low level at 1000 °C and 900 °C respectively. Consequently, the high-temperature corrosion resistance of the 8Nb–TiAl alloy can be significantly improved. In addition, cyclic tests revealed the (Al2O3–Y2O3)/(Pt–Au) laminated coating can exhibit enhanced spallation and fracture resistance, which are attributable to the brittle/ductile laminated composite structure by means of energy release mechanisms and the increased thermal expansion coefficient of the coating by the addition of Pt–Au alloy.