Abstract
Research is being conducted to study the effects of particulate deposition from contaminants in coal synthesis gas (syngas) on the mechanical properties of thermal barrier coatings (TBC) employed on integrated gasification combined cycle (IGCC) turbine hot section airfoils. West Virginia University (WVU) had been working with US Department of Energy, National Energy Technology Laboratory (NETL) to simulate deposition on the pressure side of an IGCC turbine first stage vane. To model the deposition, coal fly ash was injected into the flow of a combustor facility and deposited onto TBC coated, angled film-cooled test articles in a high pressure (approximately 4 atm) and a high temperature (1560 K) environment. To investigate the interaction between the deposition and the TBC, a load-based multiple-partial unloading micro-indentation technique was used to quantitatively evaluate the mechanical properties of materials. The indentation results showed the Young’s Modulus of the ceramic top coat was higher in areas with deposition formation due to the penetration of the fly ash. This corresponds with the reduction of strain tolerance of the 7% yttria-stabilized zirconia (7YSZ) coatings.
Highlights
Development and analysis of gas turbine coating systems are being driven worldwide in an effort to produce higher efficiency and more durable turbine systems
Prior to any micro-indentation, confirmation that the molten deposit on top of the thermal barrier coatings (TBC) ceramic top coat agreed with the elemental composition of fly ash injected into the combustion facility (Table 2) was examined
This purpose of the current study was to analyze the effects on the mechanical properties of TBC coating systems from syngas particulate molten deposits after Murphy, Nix, Lawson, Straub, and Beer completed work on the effects of the particulate deposition on gas turbine vane film cooling [6]
Summary
Development and analysis of gas turbine coating systems are being driven worldwide in an effort to produce higher efficiency and more durable turbine systems. The purpose of the layer is to extend the life of the metallic substrate components below the YSZ coatings by insulating them at turbine operating temperatures, and lowering the surface temperature of the metallic substrate. A metallic bond coat (BC) is applied to the substrate in order to adhere the top coat to the substrate and to provide an aluminum reservoir for alumina, α-Al2O3, formation in the thermally grown oxide (TGO). TGO develops between the bond coat and ceramic top coat of the system under thermal operating conditions. The low thermal conductivity (k) of the TBC relative to the substrate allows for the gas turbine system to run at higher gas temperatures than the melting point of the substrate.
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