Determination of the ductile to brittle temperature transition of aluminide coatings and its influence on the mechanical behavior of coated specimens

The ductility of various coatings deposited by chemical vapor deposition, pack cementation and slurry processes on Fe- and Ni-based alloys was characterized by indentation at room temperature. A hot indentation apparatus has also been developed to more rapidly determine the ductile to brittle transition temperature of coated specimens. Creep testing has been conducted on bare and coated alloy 230 (NiCrW) specimens at 800 °C with a significant decrease in creep life observed. Based on the observed failure of coated 230 specimens, the impact of coating ductility on substrate creep properties is discussed.