Improved plasma-sprayed Ni-Co-Cr-Al-Y and Co-Cr-Al-Y coatings for aircraft gas turbine applications

Abstract

18 plasma-sprayed coating systems, nine based on the Ni-Co-Cr-Al-Y composition and nine based on the Co-Cr-Al-Y composition, were evaluated to identify coating systems which will provide equivalent or superior lives to those of coatings of Ni-Co-Cr-Al-Y and Co-Cr-Al-Y respectively produced by electron beam physical vapor deposition. Ni-Co-Cr-Al-Y-type coatings were examined on a single-crystal alloy and the Co-Cr-Al-Y-based coatings were optimized on the B1900-Hf alloy. Cyclic burner rig oxidation and hot corrosion and tensile ductility tests were used to evaluate the coatings. For the single-crystal alloy, a low pressure chamber plasma-sprayed (Ni-Co-Cr-Al-Y)-Si coating exhibited an oxidation life improvement of better than a factor of 2 at 1121°C (2050°F) over the vapor- deposited Ni-Co-Cr-Al-Y material while showing equivalent tensile ductility. A silicon-modified Co-Cr-Al-Y coating prepared by plasma spraying in a low pressure chamber was found to be more durable than the baseline vapor-deposited Co-Cr-Al-Y coating on the B1900-Hf Alloy. © 1981.