Aircraft must operate in extreme operating conditions, but offering full guarantees of operation and safety. In addition, within the general policy of promoting sustainable transport modes, the demands of greater and increasing efficiency and lower environmental impact are present in all new developments. Much of the ecological footprint reduction strategies focus on materials and their performance, which involves improving the surface properties of these materials in extreme operating conditions, using environmentally friendly surface engineering technologies. This is true both in the aeronautical field and in other modes of transport, and is fully aligned with the priority (R4) established in the Challenges of the State Program of R & D & I oriented to the challenges of the Society: Smart, sustainable and integrated transport (in addition to the Action on Climate Change and Efficiency in the Use of Resources and Raw Materials (R5)). In this sense, the biggest problems addressed by surface engineering solutions focus on corrosion, wear, friction forces, adhesion and flushing of materials (e.g. tribology), surface mechanical properties, fatigue, etc. under extreme operating conditions. However, the solutions used today often suffer from performance limitations and a strong environmental impact. This is the case of cadmium coatings, hard chromium (hexavalent chromium), and treatments in different baths, e.g. nitrurations, sulphins, etc. As substitutes, this project uses the development of alternative technologies of surface treatments and environmentally friendly coatings: — Zn-Ni coatings. They have the potential to replace highly toxic Cd coatings. — Thermal projection technologies, based on deposition technology (HVOF-LF; HVOF-Air; Cold Spray), automated deposition processes, super-finishing processes and deposition processes of nano structured coatings. — Post discharge plasma, which has technological advantages over conventional oxy-nitrition processes (via salt bath, gas nitriding and ion nitriding), being also environmentally friendly. The interest of these new technologies is not limited only to the aeronautical field, where however specific applications have been identified in which they could potentially be implemented, given the suitability of the new processes and the limited performance offered by the existing processes (environmentally harmful), and that are contemplated in the project as demonstrators: — Crane drum. It is a component of the in-flight supply system, which requires, for its proper operation, good corrosion resistance properties and good surface mechanical properties. “Stop.” In this case, it is a component of the system for fixing and launching loads on transport aircraft. Extreme contact pressures with the parachute counterpart lead to the adhesion of material (aluminium) and increased friction forces, which drastically reduces the life of the component. — Pistons on landing gears. In this case, the requirements demanded of the materials of the component pass through a good mechanical resistance of the surface, an adequate corrosion resistance, and a good surface finish (thus ensuring key parameters of friction, tightness, wear, etc. in operation), in addition to the fact that these properties are accompanied by a good resistance to fatigue.
