Improved aluminide/MCrAlX coating systems for super alloys using CVD low activity aluminizing

Chemical vapor deposition (CVD) low activity aluminizing was used to manufacture duplex diffusion aluminide (with and without platinum)/MCrAlX coatings for super alloy gas turbine engine components. Bulk chemical analysis of aluminized MCrAlX foils indicated that the CVD low activity process removes potentially harmful elements (such as chromium, sulfur and phosphorus) from the MCrAlX during aluminizing, while pack cementation increased the concentrations of some impurities. The cyclic oxidation resistance of duplex coatings (aluminide/MCrAlX) made using pack cementation aluminizing and CVD low activity aluminizing was compared. Oxidation test results demonstrate the CVD aluminide/MCrAlX coating system exhibited much better oxidation resistance than a similar duplex coating system made using pack cementation. The experimental program is outlined, plus the experimental results are presented and discussed.