Higher efficiencies and lower costs in coal-fired power plant operations can be achieved by using high steam temperatures. However, the use of high steam temperatures increases the surface temperatures on the boiler-finishing superheaters, necessitating the use of advanced austenitic steels with adequate high temperature strength. Unfortunately, austenitic steels have poor corrosion resistance to the coal ash generated in the coal combustion process. This project will develop a laser surface-modification technology to produce rapidly solidified metallic glass structures in surface layers, which will improve coal ash corrosion resistance of the austenitic stainless steels. The feasibility of enhancing corrosion resistance of austenitic steels by thick protective coatings, consisting of 50% Cr and 50% Ni deposited by a laser fusion technology, will also be explored. Phase I will evaluate the coal ash corrosion resistance of austenitic samples coated with these two different types of laser surface modification technologies in a laboratory scale, simulated coal combustion environment. The optimum coating process and coating process parameters will be selected for comprehensive characterization and testing studies, including exposures to the real boiler environment in Phase II.
Commercial Applications and Other Benefits as described by the awardee: Coatings produced by this laser processing approach should possess high corrosion, oxidation, and wear resistance. The electrical utility industry could save on the materials costs involved in replacing superheater tubes, and also benefit from reduced downtime, and a reduced probability of catastrophic failure.
