Thermally Sprayed HVOF Coatings for Steam Turbine Applications

Abstract

The demands imposed on the coated components differ according to their purpose. Nevertheless, all the used materials have to resist degradation due to the influence of the surrounding environment. In the most challenging areas of applications, such as the power industry, the high temperature is often accompanied by a corrosive-aggressive environment, further increasing the materials requirements. In such conditions, the superior thermally sprayed coatings can be applied to increase the components wear resistance simultaneously to oxidation protection. The paper is focused on the evaluation of HVOF (High Velocity Oxygen Fuel) sprayed Co and Ni superalloy coatings behavior at room and high temperature under different types of mechanical loading and their resistance to high temperature oxidation, in comparison with CrC-based hardmetal coatings. The heat-induced microstructure changes are discussed, together with the potential of intentional heat-treatment for performance improvement. In general, the superalloy coatings proved its superior properties and performance in the demanding environment despite of being less wear resistant compare to hardmetals.