Accessory gear boxes (AGB) made of aluminum are used in amongst other things, helicopter engines. They are exposed to fretting and may during inspections be deemed too damaged and consequently scrapped. These are complex and expensive components which, if possible, to repair, could save materials, energy and time. In Sure2Coat, accessory gear boxes used in Avio Aeros products have been used as test case for applying cold spray, machining and electrophoretic coating methods to repair and strengthen damaged units instead of scarpping them.

Extending the Lifetime of Complex Aeronautical Components

Sure2Coat has addressed how to extend the life of metallic aeronautical components characterized by complex shapes, and how to implement innovative corrosion-protection surface treatments and thereby reducing the environmental footprint. In addition, automatic repair line has been looked into and prototype have been developed.

Cold spray (CS) is used for restoration of aluminum gear box components damaged by fretting by spraying aluminum particles at high velocity at the damaged area so that the energy of impact makes them merge with the existing surface and rebuilds damaged features without melting the base material avoiding detrimental distortion, oxide formation, and heat-affected degradation commonly associated with conventional technology such as welding or thermal spray. After the cold spray has built up the layer, it needs to be machined back to its target shape.

Sure2Coat also improved corrosion protection by application of an environmentally friendly e‑coating (electrophoretic application of a coating) which provides robust protection by a sustainable methodology free of hazardous chemicals.

Avio Aero has been the main industrial partner in the use case, responsible for identifying the main challenge, criteria for repaired components and to evaluate the process and industrial application. POLIMI conducted the development of the cold spray method and worked in close collaboration with SUPSI for the automation of the repair process. CIDETEC led the development of the e-coating process and coated complex shapes at their facility.

Sure2Coat has during the project period been able to develop a full repair strategy combining cold spray technology, e-coating and automation enabling this method to a wide range products and stakeholders potentially saving significant material and energy consumption through increased repair of complex metal-based products instead of scrapping and replacing with new, expensive products.

Future Developments and Industrial Scaling

Sure2Coat partners Avio Aero, POLIMI and CIDETEC will continue to develop and refine the repair and protections technologies and SUPSI the integration into repair lines. In more detail, the next developments for Avio Aero could include the development of alternative anticorrosion coatings for the repair process, with localized application tailored to complex geometries. Further work may also focus on the application of cold spray on aluminum‑based alloys for gearbox components, including studies on the impact of deposition angle on the resulting mechanical properties. In addition, the automation of the complete repair sequence at the full‑component level represents a key opportunity for further industrial implementation.

Contact

For more information, please contact Martin Fossen, Senior Research Scientist, SINTEF: