PERFORMANCE OF GAS TURBINE MATERIALS IN 'DIRTY FUEL' ENVIRONMENTS

摘要

Gas turbines are critical components in the combined cycle power systems being developed to generate electricity from solid fuels, such as coal and biomass. The use of such fuels to produce fuel gases introduces the potential for significant corrosive and erosive degradation of gas turbine blades and vanes. Series of laboratory and burner rig tests have been carried out to investigate the performance of current and candidate gas turbine materials in environments anticipated in gas turbines fired on coal and biomass derived gases. Depending on the composition of the solid fuel(s) and their mix, these gas turbine component environments include a range of levels and pressures of SO{sub}x and HCl gases, as well as ranges of Na, K, Pb and Zn. These fuel dependent differences in the component environments will result in significantly different deposit compositions and deposition fluxes onto the components. The candidate materials have included IN738LC and CMSX-4 with overlay MCrAlY, diffusion (Pt-Al) and thermal barrier (APS and EB-PVD) coatings. The laboratory tests have been carried out using controlled atmosphere furnaces and the deposit re-coat test method. This type of testing permits the detailed control of the corrosive environment of test samples. The burner rig tests have been carried out using a natural gas fired burner rig that allows the controlled injection of contaminants in the form of gaseous (i.e. SO{sub}x and HC1) and liquid/vapour (i.e. Na, K, Pb, Zn). In both types of testing, data on the performance of the materials has been obtained using dimensional metrology: pre-exposure contact measurements and post-exposure measurements of features on polished cross-sections. These measurement methods allow distributions of damage data to be determined and fit in with the COST522 move towards standardised methods of data collection and presentation. In addition, the types of damage observed have been characterised using standard scanning electron microscopy/energy dispersive X-ray analysis and optical microscopy to characterise the types of degradation observed and investigate the roles of difference contaminants in the observed hot corrosion damage to the gas turbine materials.