Performance Metrics and Experimental Testing of Erosion Resistant Compressor Blade Coatings

Abstract

A durability test rig for erosionresistant gas turbine engine compressor blade coatings was designed and commissioned. Bare and coated 174PH steel modified NACA 6505profile blades were spun at an average speed of 10,860 rpm and exposed to garnet sandladen air for 5 h at an average sand concentration of 2.5 g/(m3 of air) and a blade leading edge (LE) Mach number of 0.50. The rig was designed to represent a first stage axial compressor. Two 16 خ¼mthick coatings were tested: Titanium nitride (TiN) and chromium–aluminum–titanium nitride (CrAlTiN), both applied using an arc physical vapor deposition (PVD) technique. A composite scale, defined as the LeitheadAllanZhao (LAZ) score, was devised to compare the durability performance of bare and coated blades based on massloss and blade dimension changes. The bare blades' LAZ score was set as a benchmark of 1.00, with the TiNcoated and CrAlTiNcoated blades obtaining respective scores of 0.69 and 0.41. A lower score identified a more erosionresistant coating. Major locations of blade wear included: trailing edge (TE), LE, and rear suction surface (SS). TE thickness was reduced, the LE became blunt, and the rear SS was scrubbed by overtip and recirculation zone vortices. The erosion effects of secondary flows were found to be significant. Erosion damage due to reflected particles was absent due to a low blade solidity of 0.7. The rig is best suited for durability evaluation of erosionresistant coatings after (AF) being proven worthy of consideration for gas turbine engines through ASTM standardized testing.