Recubrimientos resistentes a los fenómenos de degradación en las nuevas turbinas generadoras de energía por vapor de agua

Abstract

Increasing the efficiency of coal-fired power plants has been a goal for the power generation industry for many years, and would bring benefits not only in cheaper electricity but also with respect to reducing the carbon emissions. Such increases in efficiency are achieved through thermodynamic means, principally by increasing steam temperatures and pressures. The development and qualifications of high-temperature materials for critical components such as super heaters, thick section boiler components and turbine is the key to reaching such advance steam conditions Future high efficiency coal-fired steam power plants will operate at higher temperatures. Important efforts to develop new steels to protect high creep strength steels in order to allow operation of steam turbines at 650ºC, corresponding to efficiencies of 46-48%, are being carried out worldwide. Under steam atmosphere, existing ferritic and austenitic alloys, commonly employed in steam plants, form Cr containing oxides which become less protective at temperatures higher than 550º C. New alloy development activities have been very successful in improving the creep strength at higher temperatures, generally by lowering the chromium content[225,226]. However, when the Cr content is lower that 10 w%, such as P92, very thick oxide scales form, consisting of a top layer of Fe3O4 and an inner zone mainly (Fe, Cr)3O4 spinels (figure 77). These scales spall causing metal cross-section loss (figure 78 and 79), blockage and erosion of components located down-stream and also produce a thermal insulating effect resulting in overheating...