Scientists from India’s Department of Science & Technology (New Delhi, India) have developed low-cost, iron- (Fe-) based intermetallic powder coatings that can be used as a corrosion resistant coating for materials exposed to harsher environments such as high-temperature thermal power plants. These coatings showed four times increased corrosion resistance in aqueous corrosive media as compared to mild steel.
Because wear and corrosion cause major damage over a range of service temperatures, component surfaces need to be protected with a suitable material for enhanced economic viability. For instance, coating the surface of a turbine blade can enhance its service life and increase its operation hours.
Currently, thermally sprayed coatings, including chromium carbide-nickel chromium powder and tungsten carbide-cobalt coatings, are known for their superior wear and high-temperature oxidation resistance applications. Such coatings are known to provide hardness, toughness, and better corrosion resistance under exposure.
However, these powder coatings are expensive due to their cobalt and nickel elements, along with toxicity found in chromium (Cr) in its hexavalent state. To address this, a team of scientists was assembled to synthesize Fe-based intermetallic powders, with coatings applied using a detonation spray coating technique.
In addition, a gas atomized Fe-aluminide powder was applied to mild steel substrates without any cracks or spalling. It exhibited better corrosion resistance when Cr and aluminum (Al) are in a solid solution with Fe than in the Fe-rich phases. These coatings demonstrated an increased wear resistance by 30-40% than mild steel, which leads researchers to believe that FeAlCr coatings can be used in high-temperature erosion resistance applications. More studies are currently underway to qualify the FeAlCr coatings for fireside corrosion protection of boiler components.
Source: Department of Science & Technology, www.dst.gov.in.