Using a DOE Approach to Optimize a LVPS Bond Coat and APS Top Coat for TBC Systems

A primary coating system commonly used on high pressure turbine (HPT) components is a Low Vacuum Plasma Spray (LVPS) applied MCrAlY bond coat with an air plasma spray (APS) applied 7% yttria stabilized zirconia (YSZ) top coat. While these coating systems have been successfully sustained on HPT components over the last 30 years, the coating application technologies have vastly improved. A thermal barrier coating system applied by an Oerlikon Metco O3CV vacuum plasma gun and a Sinplex plasma torch were optimized using a design of experiments (DOE) approach. Two 3-variable 2-level DOE’s were simultaneously conducted for bond coat and top coat. All samples were exposed to a furnace cyclic test (FCT) to measure performance. After the test, the samples were cross-sectioned for metallurgical evaluations. Microstructural analysis and chemical composition measurements via energy dispersive spectroscopy (EDS) were performed for correlation with the furnace cyclic test results. Erosion testing was done to verify the FCT results and is also presented.