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2585756 
Journal Article 
NANO-STRUCTURED EROSION RESISTANT COATINGS FOR GAS AND STEAM TURBINES 
Swaminathan, VPS; Wei, R; Gandy, DW 
2008 
447-470 
WOS:000282103000034 
Solid particle and liquid particle erosion in the compressor section of gas turbines and steam turbine vanes and blades lead to significant reduction in turbine efficiency over time. This results in increased downtime and operating cost of the power plants. Some of the conventional coatings and erosion protection shields used by the currently available commercial processes have limitations in their temperature and erosion protection capabilities. Under a project funded by the Electric Power Research Institute (EPRI), very hard nano coatings with thickness within 40 microns (about 1.5 mils) have been produced on test samples using a state-of-the-art Plasma Enhanced Magnetron Sputtering (PEMS) technique. Under Phase I of this EPRI project, several coatings were deposited on various substrate alloys for the initial screening tests. Titanium silicon carbonitride nano-composite (TiSiCN), stellite and modified stellite, TiN monolayer coatings and Ti-TiN, Ti-TiSiCN multi-layered coatings have been developed and screening tests completed in this project. The substrate selection is based on some of the alloys currently used in aeroderivative engine compressor blades, land based gas turbine compressor blades and vanes; steam turbine blades and vanes. They include Ti-6Al-4V alloy, 17-4 PH, Custom-450 and Type 403 stainless steels. The PEMS coating technique differs significantly from the conventional techniques such as air plasma spray (APS), low-pressure plasma spray (LPPS), diffusion coatings, chemical or physical vapor deposition (CVD or PVD) used on blades and vanes. PEMS method involves a magnetron sputtering process using a vacuum chamber with an independently generated plasma source from which high current density can be obtained. This method used heavy ion bombardment during coating deposition to increase the coating adhesion and create a highly dense microstructure. A novel method using trimethylsilane gas instead of solid targets was successful in producing this nanocomposite. The PEMS deposited stellite coatings did not show any erosion improvement and dropped from further development. However, other hard coatings developed in this project exhibited excellent solid particle erosion resistance - nearly 25 times higher than the uncoated substrates and 20 times higher than all other nitride coatings produced by traditional commercial processes. This paper covers a brief description of the deposition technology and various properties of the coatings. Hardness indentation and scratch tests were performed to assess the coating adhesion to the substrates. Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS), and X-Ray diffraction (XRD) analysis were used to study the microstructure and morphology of these coatings. Nanoindentation was conducted to determine the hardness and Young's modulus, while sand erosion tests were conducted to rank the erosion resistance of the coatings produced using several processing variables.