Preparation and Performance of an Abradable NiCrFeAlBN-YSZ-NiCrAl Layered Seal Coating for Aircraft Engines

Ti2AlNb alloys are often used to fabricate high-pressure compressor blades and casings in aircraft engines with high thrust/weight ratios. In this study, a three-layered seal coating, NiCrFeAlBN-YSZ-NiCrAl, was prepared by thermal spraying on a titanium alloy (Ti2AlNb) substrate. The microstructure, surface hardness, and bond strength of coatings as well as their thermal cycling performance and abradability under simulated working conditions were investigated. The coating surface hardness was 61 HR15Y and the bond strength was 7.13 MPa. The coating maintained a good bonding to the substrate with no cracks after 40 cycles of water-cooling from 750 °C to room temperature. The abradability of the as-sprayed coating and the coating heat-treated at 750 °C for 200 h was tested against a Ti2AlNb blade at 750 °C, with a tip line speed of 300 m/s, and feed rates of 5, 50 and 480 m/s. The coating wear mechanisms involved micro-ruptures. The Cr2O3 phase formation and a decrease in the number of micropores in the heat-treated coating decreased its abradability.