Erosion–Corrosion Behaviour of Nickel and Iron Based Superalloys in Boiler Environment

Abstract

Erosion–corrosion of engineering materials is encountered in a large variety of engineering applications including thermal power plants. In such environments, boiler steels are widely used, but they often degrade due to erosion–corrosion at temperatures exceeding 500 °C. Superalloys are used at temperatures above 500 °C due to their excellent mechanical properties and creep resistance at high temperature. In the present investigation, the erosion–corrosion performances of nickel- and iron-based superalloys were evaluated in the low temperature primary super heater zone of a thermal power plant. In this zone, the temperature of flue gases was around 540 °C and the samples were exposed to this environment for 10 cycles of 100 h duration. Weight change was measured after each cycle and the erosion–corrosion products were analyzed through SEM/EDAX, XRD and EPMA. All the superalloys showed weight loss, suggesting the contribution of erosion in erosion–corrosion. An interpretation of the erosion–corrosion mechanism is presented.