Kurzbeschreibung
(Englisch)
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Coatings are widely used to improve the surface functionality of components. In the engine and transmission industry, they are being increasingly used to improve the performance and lifetime of components. In spite of their importance and relevance, most coating development is based on a trial and error approach. This makes the process of developing new coatings very costly and time consuming. Much of the problem lies in the fact that coatings cannot be meaningfully compared to one another, especially in a small to medium-sized industry setting. A newly developed analysis method that combines simulations with experimental scratch testing, a popular characterization tool, shows considerable promise in providing the much needed quantitative information for coating development. At present, this method is of limited utility because it still needs to be thoroughly tested on various types of coatings with different properties. In addition, the analysis method has to be modified to include real-world effects, such as surace roughness, residual stresses etc. that have up to now been neglected due to the lack of corresponding experimental input. This project creates a platform for an intensive interplay between simulational and experimental groups to achieve: an extension of the up to now 'ideal' scratch-test simulation to real-world conditions by a wide-range simulational and experimental scratch testing on different types of coatings. The outcome will be a new tool to quantitatively characterize and identify coatings by determining their fracture toughness. This identification can be used to address functionality issues in next-generation engines and transmission, such as engines using hydrogen-based fuels and components working under conditions of minimal or even dry lubrication, where the coating will play a critical role in determining system reliability.
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Partner und Internationale Organisationen
(Englisch)
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BE, BG, CH, CZ, DE, DK, EE, ES, FI, FR, GR, HR, HU, IE, IL, IT, LT, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, UK
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Abstract
(Englisch)
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This project aims to improve the characterisation of coatings by providing a more quantitative measurement in form of the fracture toughness to the popular scratch tester. This will especially be useful in determining the functionality of a coating and for optimising it in the developmental stage. The project is based on a novel three-dimensional finite element method. This method, developed recently by one of the project partners, has been used to calculate stresses and strains in the contact of a sliding sphere on a coated surface. This project enhances the utility of the method by thorough testing on various types of coatings with different properties. The project brings together simulational and experimental groups. In the first stage of the project the test procedures and parameters were defined as well as setting up a program of representative coatings for providing a broad set of conditions for the simulational group. In the next stage good quality coatings were prepared on the chosen substrate. In the first instance these substrates were flat. The coatings were then thoroughly analysed by all partners and the results were then transmitted to the simulaitonal group, who then inputted these parameters into their program. An intensive interplay also took place at this point between the various groups to ensure that the parameters were correctly interpreted for the simulations. Very different types of coatings were chosen, prepared and analysed. This included hard coatings, solid lubricant coatings as well coatings on relatively soft substrates. The experimental groups performed a thorough experimental analysis. The Swiss partners in this project were intensively involved in the coating selection, preparation and optimisation as well as analysis of the topograhical and mechanical properties. Other partners in the project performed simulations. Results of the simulations show that it is indeed possible to make predictions about the scratch behaviour. These simulations highlight the importance of Young's modulus, coating thickness, substrate hardness and residual stresses in the coating in relation to surface durability. Values of the coating fracture toughness were obtained for the above coatings. Based on the exchange between the simulational and experimental groups, the simulation procedure was further adapted and optimised. The next steps are to extend the simulation to other coating types as well as to include real-world effects such as coating roughness and to determine whether very thin coatings (less than 1 micron thickness) can also be quantified. Finally, it is planned to adapt the simulations to the already popular scratch testing system. Results at the end of the project suggest that the planned out-come of realizing a new tool to predict behavior adhesion and fracture toughness of the coating in the scratch test can be realized only if materials mechanical properties (coating and substrate) are perfectly well known what is not always the case in a production environnement.
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