Nano-Technology Coatings for Erosion Protection of Turbine Components

Solid particle erosion (SPE) and liquid droplet erosion (LDE) cause severe damage to turbine components and lead to premature failures, business loss and repair costs to power plant owners and operators. Under a program funded by the Electric Power Research Institute (EPRI), TurboMet International (TMET) and Southwest Research Institute (SWRI) have developed hard erosion resistant nano-coatings and conducted evaluation tests. These coatings are targeted for application in steam and gas turbines to mitigate the adverse effects of SPE and LPE on rotating blades and stationary vanes. Based on a thorough study of the available information, most promising coatings such as nano-structured titanium silicon carbo-nitride (TiSiCN), titanium nitride (TiN) and multilayered nano coatings were selected. State-of-the-art nano-technology coating facilities at SwRI were used to develop the coatings. Plasma enhanced magnetron sputtering (PEMS) method was used to apply these coatings on various substrates. Ti-6Al-4V, 12Cr, 17-4PH, and Custom 450 stainless steel substrates were selected based on the current alloys used in gas turbine compressors and steam turbine blades and vanes. Coatings with up to 30 micron thickness have been deposited on small test coupons. Initial screening tests on coated coupons by solid particle erosion testing indicate that these coatings have excellent erosion resistance by a factor of 20 over the bare substrate. Properties of the coating such as modulus, hardness, microstructural conditions including the interface, and bond strength were determined. Tests are in progress to determine the effects of coatings on the tensile and high-cycle fatigue strengths of these alloys.