Layer by layer to better surfaces
"HEBe": New technology for more efficient surface coating
Thermal coating has been an integral part of the manufacture and repair of high-quality components for more than 50 years and a core element of engine repair. The process involves the application of metallic and ceramic layers. The spray additives used are first melted and then spun onto the prepared surface with a high kinetic energy. The molten particles deform upon impact and spread over the substrate. They release their heat to the colder base material, solidify, contract and can thus join mechanically to the surface irregularities on the base material. Apart from use in repairing and restoring damaged, worn and corroded components, thermal spraying processes for coating metallic materials are now used primarily for manufacturing preventive surface properties.
Many properties, such as protection from corrosion and wear and tear, smoothness and thermal insulation of the base material, can therefore be significantly improved by applying these functional layers. However, thermal coating processes not only allow many repairs, they are above all significantly more economical and resource-friendly than the use of new parts. In order to minimize time and costs, increase quality and the scope of application as well as perform new repairs for engine, landing gear and component repairs, Lufthansa Technik initiated the interdisciplinary research and development project "HEBe", a German acronym for high-efficiency near-net-shape coating process. A process was developed here strategically that allows low-cost, environmentally-friendly thin coatings with high surface quality.
Together with innovation partners Thermico GmbH, the Jülich Research Center (Forschungszentrum Jülich), RWTH Aachen and the Technical University of Braunschweig, it has been possible based on parameter studies to identify the main influencing factors, such as size and scaling effects and impact of standard geometries on the surface quality. New and more cost-effective spray powder and nano-based materials provide the basis for an economical and competitive process. A newly developed in-process measurement technology together with active control during the treatment process allows targeted near-net-shape coating. This will largely eliminate the need for downstream process steps in the future, such as control measurements or remachining.
Supported by the Federal Ministry for Economics Affairs and Energy (BMWi), the project ran from July 2012 to July 2015 and succeeded in allowing tungsten carbide-containing spray powder to be supplemented or replaced partially with other carbides. Dependence on rare earths and heavy metals will reduce in the future as a result of this development. A number of work steps, such as coating, measuring and calculating, can now be performed in one system based on modified parameters. Finer particles, which form a homogeneous layer and significantly improve the quality of the individual layers, as well as the newly developed optical measurement system and a self-regulating control loop will allow a highly efficient near-net-shape coating process in the future.
Lufthansa Technik made many new findings based on the results of the "HEBe" project for improving wear factors of engine, landing gear and device components and extending their life cycle. Shorter setup and throughput times, fast and cost-efficient developments and processes as well as technologically new repairs and products play their part in achieving substantial economic improvements in component maintenance. What's more, Lufthansa Technik will be able to offer cost-efficient alternatives for galvanic hard chromium plating of components in the future, a process that is no longer permitted by some OEMs and also no longer seems appropriate from a current ecological perspective. This brings Lufthansa Technik one more important step closer to its goal of "Green MRO".