Achieving higher plant efficiencies in thermal power plants is one of the major global challenges from the viewpoint of reducing carbon dioxide emission levels, particularly in coal-fired boilers. To this end, the goal in the development of ultra supercritical (USC) coal-fired boilers is to increase steam temperature from current value of 600°C to 700°C. The key to achieving 700°C USC boilers lies in the development of higher creep rupture strength alloys such as Ni-based and Fe-Ni based alloys, which have capability of operating under high stresses at these higher temperatures. Other key requirements for these materials are high temperature corrosion resistance against coal ash corrosion and steam oxidation in super-heater and re-heater tubes used for USC boilers. In this paper, high temperature corrosion properties of several candidate alloys for 700°C USC boilers have been studied using laboratory tests.

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