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WPC. Mechanical and metallurgical coatings for surface protection

A serious challenge of surface functionalisation is to get materials with improved corrosion resistance and wear resistance. This field of research has a deep impact in a large variety of industrial sectors (machining tools, metallurgy, aeronautic, automotive, etc.) where fixed and movable parts are subjected to aggressive environments, in most cases at very high temperatures.

An important group of tribological coatings, made of hard materials, is used to provide protection against wear and abrasion from hard counterparts and in some cases also to reduce friction.  Two different nanometric approaches are being formulated to accomplish the severe requirements imposed by real operation conditions: multilayers, and  nanocomposites.

A second group of tribological coatings, used as solid lubricants, are soft and lubricious, primarily applied to a hard material to reduce sliding friction. For instance, carbon-based coatings, also known as diamond-like carbon (DLC), and other soft metals, or even mixtures of them, can be employed to decrease the rolling contact fatigue fracture of sliding bearings.

In all these cases, the protection of surfaces against corrosion in aggressive environments and/or under high temperature requires of new formulations for coatings along with an advanced definition of the interface properties between the substrate and the coatings to meet more demanding tribological needs.

New family of hard protective and tribological coatings. A modern approach in this topic is the preparation of nanocomposites and/or multilayer coatings combining and exceeding the properties of the two phases integrating the film. FUNCOAT will carry out the preparation of new families of composite (e.g. TiN/Si3N4 and other, DLC) thin films and C-based coatings. The control of the nanostructure of this nanocomposite film, using PVD (magnetron sputtering or cathodic arc) or plasma techniques is a crucial problem that will require an input from WP.A and WP.B.
Scaling up of the deposition process of coatings on flat and 3D substrates. This activity addresses an important scientific and technological problem as it is the up-scaling of deposition processes for the treatment of 3D substrates where “line of sight” methods cannot be used. This is especially critical to deposit homogeneous coatings on small cavities, such as micro-manufacturing tools for surface pattern replication. Conditions for a successful deposition of these complex films, i.e. thickness homogeneity In the micron range, good adhesion with no delamination, and compatibility with metal substrates have to be achieved, even working in batches, with a lot of specimens.
Chemical, structural and mechanical characterization of functionalised surfaces at room and high temperatures.
A common place in the study of mechanical coatings is the existence of a strong interplay between the mechanical properties of the coatings (hardness, friction and wear resistance) and their chemical, structural and microstructural characteristics. Surface analytical techniques (XPS, AES, XANES, Micro-Raman) and electron and proximity microscopies (HRTEM, SEM, AFM/STM) with good and in-depth spatial resolution are to be used. As output of activity C3, a detailed description of macroscopic mechanical and tribological properties will be done, based on the micro and nanostructure of the coatings.
Corrosion and oxidation behaviour under extreme conditions: This activity is devoted to the optimisation of coatings for surface protection against corrosion under extreme conditions. The idea is to evaluate the behaviour of the coatings under conditions as close as possible to those found under real operation. As output of activity C4, a detailed characterisation of the protective properties of coatings will be carried out to identify the failure mechanisms either in aggressive electrolytes or at high temperatures, assessing the long term durability of materials under service conditions.

The internal relationship between the activities/tasks with themselves and with other Work Packages is described in the following picture.

Diagrama WPC