Laser modified coatings for advanced energy systems

Abstract

Among the advanced technologies being considered for the next generation of energy production and conversion are combustion turbines (with and without combined cycle), integrated gasification combined cycle, high temperature fuel cells and high temperature batteries. In these applications, materials are exposed to high temperature, high pressure and an erosive/corrosive environment. Laser modified surface coatings represent a potentially attractive method of improving material properties to provide better performance under these conditions. An experimental program is described to characterize plasma sprayed coatings on stainless steel and Inconel substrates before and after melting the coatings with a carbon dioxide laser.Several different types of metal powder coatings have been treated with the beam from a 1.5 kW CO2 laser focused with a cylindrical lens. Good results were obtained with self-fluxing alloys (eg Co-40%, Cr-18%, Mo-6%. Si-3.5%, B-3%, Fe-2.5%, C-0.2%, Ni-Bal), which yielded a uniform, pore-free coating with good bonding to the substrate. At the other extreme, high temperature coatings of the MCrAlY type (eg Cr-17.5%, Al-5.5%, Co-2.5%, Y-0.5%, Ni-Bal), formed random balls or droplets on the surface after the laser processing. The coating that yielded the best combination of high temperature oxidation resistance and good laser processability was iron aluminide (Fe3Al: Al-14.8%, Cr-2.1%, Fe-Bal). The results of high temperature performance testing of this coating will be presented.Among the advanced technologies being considered for the next generation of energy production and conversion are combustion turbines (with and without combined cycle), integrated gasification combined cycle, high temperature fuel cells and high temperature batteries. In these applications, materials are exposed to high temperature, high pressure and an erosive/corrosive environment. Laser modified surface coatings represent a potentially attractive method of improving material properties to provide better performance under these conditions. An experimental program is described to characterize plasma sprayed coatings on stainless steel and Inconel substrates before and after melting the coatings with a carbon dioxide laser.Several different types of metal powder coatings have been treated with the beam from a 1.5 kW CO2 laser focused with a cylindrical lens. Good results were obtained with self-fluxing alloys (eg Co-40%, Cr-18%, Mo-6%. Si-3.5%, B-3%, Fe-2.5%, C-0.2%, Ni-Bal), which yielded a uniform, pore-...