Influence of isothermal oxidation on microstructure of YSZ and Mullite-YSZ thermal barrier coatings

Abstract

Microstructural changes in conventional yttria stabilized zirconia (YSZ) and multilayer Mullite-YSZ/YSZ (M-YSZ) thermal barrier coatings were compared based on high temperature isothermal oxidation at the temperatures of 1050, 1150 and 1250 °C. Both types of thermal barrier coatings were produced from commercially available powders utilizing atmospheric plasma spray technique. Initial M-YSZ powder mixture consisted of 29 vol. % of Mullite and 71 vol. % of YSZ. Inconel Alloy 713LC nickel-based superalloy was used as a substrate material (cylinders, 25 mm in diameter and 10 mm in thickness). The TBCs lifetime, phase stability, thickness of the thermally grown oxide layer, porosity, and changes in microstructure after high temperature testing were evaluated using light microscope, scanning electron microscope equipped with EDX analyzer, and XRD technique.Microstructural changes in conventional yttria stabilized zirconia (YSZ) and multilayer Mullite-YSZ/YSZ (M-YSZ) thermal barrier coatings were compared based on high temperature isothermal oxidation at the temperatures of 1050, 1150 and 1250 °C. Both types of thermal barrier coatings were produced from commercially available powders utilizing atmospheric plasma spray technique. Initial M-YSZ powder mixture consisted of 29 vol. % of Mullite and 71 vol. % of YSZ. Inconel Alloy 713LC nickel-based superalloy was used as a substrate material (cylinders, 25 mm in diameter and 10 mm in thickness). The TBCs lifetime, phase stability, thickness of the thermally grown oxide layer, porosity, and changes in microstructure after high temperature testing were evaluated using light microscope, scanning electron microscope equipped with EDX analyzer, and XRD technique.