Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS


MATECO Informe resumido

Project ID: 505928
Financiado con arreglo a: FP6-NMP
País: France

Final Report Summary - MATECO (New coatings deposited by PACVD for corrosion protection)

The MATECO project has been designed to develop smart multifunctional coatings based on Si-O-N materials. They have to combine corrosion resistance and tribology, decorative and anti-sticking properties. Developing such a kind of material is only possible if fundamental knowledge on materials and associated coating process is gained. Therefore, the global objectives of this project are:
- to develop, understand and characterise new materials related to the SiOx - SiNx - SiOxNy ternary system;
- to manufacture coatings with these new materials using vapour deposition process;
- to develop, understand and characterise new coatings made with these materials.

More specifically, the project pursued the following individual objectives:

Objective 1: Development and modelling of new materials
Regarding the materials for coatings, the objectives will focus on the increase of fundamental knowledge on:
- the Si - O - N materials and their behaviours concerning properties expected. Models and deep nano-characterisation will be performed;
- the preparation methods of these materials.
A careful attention will be paid on the effect of the gas feed composition on the chemical composition of the coating and its basic mechanical and electrical properties. Indeed, gas feed composition is a crucial parameter for obtaining a coating with the desired chemical composition. As the coatings quality is directly linked to the surface state of the substrate, MATECO project will also focus on the understanding and improvement of substrate surface. The objectives are:
- basic knowledge: to identify the corrosion sources (kind and nature of defect) according to the nature of the substrates
- study on the surface preparation methods: to design suitable surface preparation methods to obtain defect-free coatings.

Objective 2: Study and understanding of vapour deposition process
The process to be studied will be the PACVD. MATECO project proposes to study and develop a new technology, which separates the control of plasma generation (precursor dissociation) from ion bombardment of the growing coating. For this, it is proposed to generate ECR microwave plasma by small sources distributed on the wall of the chamber.

(i) Theoretical understanding:
- to model the production and diffusion of plasma;
- to model the PACVD deposition process;
- to model the cleaning process.
(ii) Study, optimisation and development of process:
- to design a microwave plasma reactor, which produces a plasma density of 1 012 cm-3 at 0.133 Pa;
- to design a low temperature process < 100 degrees Celsius for corrosion protection alone;
- to design a low temperature process < 200 degrees Celsius for corrosion protection and tribology properties;
- to combine two different layer types for wear and corrosion resistance in one production unit, which normally have to be prepared by different processes. This will be disruptive for the cost reduction in deposition and for the increase in quality of the coating;
- to improve the deposition rate of PACVD process up to 7 micometre / h;
- to develop a suitable cleaning process for the reactor and related tools.

Objective 3: Coatings properties
The coatings developed will have to fulfil the following general objectives:
- to obtain homogeneous coating and properties (less than 10 % variation in the whole batch);
- to define the correlation between coating materials and corrosion protection. To achieve this objective, a deep study based upon electrochemical, morphological, and chemical characterisation will be carried out.

Regarding the objectives in terms of properties, coatings developed must have:
- for corrosion protection alone: optical transparency > 80 %, colourless (constant optical transparency from 400 to 900 nm), corrosion protection > 144 h salt spray test, scribe creepage (1 - 2 mm in cyclic testing);
- for adhesion: cross hatch test GT 0 (wet and dry), scratch resistant: no delamination;
- for corrosion and tribology properties: surface hardness > 25 GPa, dry friction coefficient < 0.2, corrosion protection > 96 h salt spray test.

Objective 4: Validation
Validation on the following applications:
- the coated parts have to fulfil the requirements of CRF in terms of mirroring, corrosion and wear resistance for automotive application;
- the coated parts have to fulfil the requirements of EADS regarding wear (fretting and galling), corrosion and anti-sticking properties;
- the coated parts have to fulfil the requirement of HEF in terms of decorative properties and protection of corrosion and wear resistance and protection of electromagnetic shielding metal coatings;
- the coated parts have to fulfil the requirement of TEFAL in terms of anti-sticking an wear protection;
- to maintain the same corrosion resistance of actual used hazardous 'chromium-based or nickel-based...' coating treatments for light alloys components applications with a reduction of industrial coating process cost of about 10 %;
- to prepare sustainable coatings, a life cycle analysis and a socio / economical / health study will be done.

The objectives related to this are:
- to define methods for the recycling of the coating at the end of life;
- to define the economical and environmental impact of such recycling;
- to provide a database on technical, economical and environment analysis of coatings;
- to provide a life cycle analysis of the coatings prepared expecting a lower impact of this coatings.

The project was structured into six Work packages (WPs), as follows:

WP 1: Understanding and optimisation of the surface properties of substrate materials - surface engineering
WP 1 concerned the understanding and the optimisation of the surface properties of substrate materials. According to the DOW document, the three main objectives related to this part were:
- to identify the corrosion sources (kind and nature of defects) of the substrates selected by the different partners;
- to improve the surface preparation (by mechanical and plasma means) before PACVD for corrosion protection purpose;
- to correlate the experimental results with the theoretical analysis of the substrates.

WP 2: Understanding and optimisation of PACVD process
The partners in this WP were complementary, such that they have covered all the scientific and technical aspects involved in WP 2. At the end of the project, all tasks are finished, and all of them with successful results. In particular, the development of a reactor cleaning process represents a challenge, since, until now, no satisfactorily and friendly processes were available at the industrial level.

In WP 2, two theses were finished and successfully defended at the very end of MATECO project. A solution to the key problem of reactor cleaning at industrial level has been proposed and patented and some of the scientific results obtained in WP 2 have already been presented in various conferences or published in international journals.

WP 3: Materials for corrosion resistance coating
WP3 has allowed a good understanding of the plasma deposited coatings performance in terms of corrosion protection. In particular, it has been found that SiOx coatings are better than SiOxNy ones in corrosion protection. On the other hand, coatings deposited in this project are very homogeneous and smooth. Finally, it has been well understood that to get nitrogen included in a SiN environment it is necessary to start from N containing monomers, with the eventual addition of NH3, more than N2.

WP 4: Coating understanding, architecture and characterisation
Multifunctionnal coatings have been elaborated and characterised in the WP4. 2 coatings families were defined. On one side, SiOx coatings have been found to be very efficient for corrosion protection. This coating can be deposited alone for optical application because of its high optical properties. The main difficulty with this solution concerns the deposition of high thickness to prevent coloration by light interference. This solution was not retained as it is not considered to be economically viable to protect metal coatings on plastic parts which necessitate low deposition rate to keep low the deposition temperature.

SiOx coatings were also combined with low surface energy top coatings. These top coatings were obtained by addition of fluorine to the coatings. The functional characterisation of these coatings have allowed to evidence that low surface energy is not the only characteristic to consider for 'easy to clean' applications. One might also consider micro-roughness and chemical inertia which can affect the ETC in the chosen application. The scratch resistance necessary for the ETC application is estimated to be insufficient, the low surface energy coatings are not hard enough.

On the other side, SiCHN coatings were combined with top DLC coatings. The SiCHN base layers demonstrate the possibility to bring corrosion protection. The addition of DLC on SiCHN coatings was possible and showed good adhesion between the two layers. SiCHN was chosen instead of SiOx despite its lower corrosion protection efficiency, because adhesion of DLC on SiOx was not possible and because SiCHN has higher intrinsic mechanical properties.

Such coatings were deposited on three kinds of real parts concerned by mechanical applications and have shown the interest of such solution compared to the state of the art. The characterisations carried out in this WP have allowed understanding the mechanism for corrosion protection of such coatings. It was also shown that the behaviour of the base layer in term of corrosion protection could be affected in some case by the deposition of the top layer. This explains the better behaviour of the combination of SiCHN with DLC compared to classical industrial DLC solutions.

WP 5: Life cycle analysis and socio / economical / health impact
The refinement of the data collected has allowed finding more accurate results. The work related to coating removal was carried out, using a plasma technology and was based on results issued from the reactor cleaning in WP2.

WP 6: Validation of the coating studied
The coatings deposited by partners contains some species like oxygen and carbon based materials which gives strong connexions with carbonised food and obviously does not fulfil TEFAL requirement for 'easy to clean' applications. DLC based coatings have been tried for few samples for iron applications, results are promising but it would need much more trials and more conditions in order to find the best compromise.

The sliding properties were rather good but many other tests should be done to pursue this investigation. CRF evaluated the developed coatings taking into consideration corrosion resistance and tribological behaviour. The coatings developed in the project presented in CRF application an efficient corrosion protection, but the tribological properties were not completely satisfactory. In fact, the tested coating applied to shim components in the engine valve train system, presented a delamination and a complete removing after the test in the contact area. The promising results related to the friction torque in the coupling shim-camshaft for the MATECO coating, in comparison with the actual treatment, push on to proceed with further investigation and development in the coating deposition to reach the necessary adhesion. For HEF, it has appeared that despite the excellent corrosion protection efficiency of SiOx coatings and their high optical transparency, the deposition of such coatings for decorative application on plastic parts is not economically viable. The deposition of SiCHN coatings for the protection of silver coatings has given good results. The coatings are coloured, but this is not a problem for the protection of electromagnetic shielding silver coatings. The coatings on gas spring rods carried out in WP4 have shown a real breakthrough compared to the state of the art related to corrosion protection by vacuum deposited coatings. The progress achieved is reinforced by the fact that tribology properties brought by DLC allow increasing further the interest of such PACVD coatings compared to classical corrosion protective coatings.

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Christophe HEAU
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