Implémentation de méthodes d'intelligence artificielle pour le contrôle du procédé de projection thermique

Depuis sa création, la projection thermique ne cesse d étendre son champ d application en raison de ses potentialités à projeter des matériaux bien différents (métallique, céramique, plastique,...) sous des formes bien différentes aussi (poudre, fil, suspension, solution,...). Plusieurs types de procédés ont été développés afin de satisfaire les applications industrielles, par exemple, le procédé HVOF (High Velocity Oxygen Fuel), le procédé APS (Atmospheric Plasma Spraying), le procédé VLPPS (Very Low Pressure Plasma Spray). Parmi ces procédés, le procédé APS est aujourd hui bien implanté dans l industrie et en laboratoire réussissant à élaborer des revêtements de bonne qualité à coût intéressant. Néanmoins, cette technologie pâtit des incidences des instabilités du procédé sur la qualité du produit obtenu et souffre d un manque de compréhension des relations entre les paramètres opératoires et les caractéristiques des particules en vol.Pour rappel, pendant la projection APS, les phénomènes d instabilité du pied d arc, d érosion des électrodes, d instabilité des paramètres opératoires ne peuvent pas être complètement éliminés. Et, il est encore aujourd hui difficile de mesurer et de bien contrôler ces paramètres.Compte tenu des progrès réalisés sur les moyens de diagnostic qui peuvent être utilisés en milieu hostile (comme dans le cas de la projection APS), un contrôle efficace de ce procédé en boucle fermée peut être maintenant envisagé et requiert le développement d un système expert qui se compose des réseaux de neurones artificiels et de logique floue. Les réseaux de neurones artificiels sont développés dans plusieurs domaines d application et aussi maintenant au cas de la projection thermique. La logique floue quant à elle est une extension de la logique booléenne basée sur la théorie mathématique des ensembles flous. Nous nous sommes intéressés dans ce travail à bâtir le modèle de contrôle en ligne du procédé de projection basé sur des éléments d Intelligence Artificielle et à construire un émulateur qui reproduise aussi fidèlement que possible le comportement dynamique du procédé.Since its creation, the thermal spraying continuously expands its application scope because of its potential to project very different materials (metal, ceramic, plastic ...) as well as different forms (powder, wire, suspension, solution ...). Several types of methods have been developed to meet industrial applications, for example, the process HVOF (High Velocity Oxygen Fuel), the process APS (Atmospheric Plasma Spraying), the process VLPPS (Very Low Pressure Plasma Spray). Among these methods, the APS process is now well established in the industry and laboratory for successfully developing coatings with good quality but low cost. However, this technology suffers from the instability effect of the process on the obtained product quality and endures a lack of understanding of the relationship between the operating parameters and the characteristics of in-flight particles.As a reminder, during the projection APS, the arc foot instability phenomena, the electrode erosion, the instability of the operating parameters cannot be completely eliminated. Further, it is still difficult to measure and control these parameters well. With the developing technology of diagnostic tools that can be used in a hostile environment (as in the case of APS process), an effective control of APS process in closed-loop can be considered and requires the development of an expert system consisting of artificial neural networks and fuzzy logic controlling. The artificial neural networks have been developed in several application fields and now also to plasma spraying process. Fuzzy logic controlling is an extension of Boolean logic based on the mathematical theory of fuzzy sets.We are interested in this work to build an on-line control model for the APS process based on the elements of artificial intelligence and to build an emulator that replicates as closely as possible the dynamic behavior of the process. Further, the artificial neural networks will be combined with the emulator for constituting a big system who can monitor the process and also can automatically carry out modification action. The system then will be tested off-line, the time response will be discussed.BELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

Suspension plasma spraying on finely structured coatings

International audienc

Latest Developments in Suspension and Liquid Precursor Thermal Spraying

International audienceThe interest to manufacture onto large surfaces thick (i.e., 10-20 lm, average thickness) finely structured or nanostructured layers is increasingly growing since the past 10 years. This explains the interest for suspension thermal spraying (STS) and solution precursor thermal spraying (SPTS), both allowing manufacturing finely structured layers of thicknesses varying between a few micrometers up to a few hundreds of micrometers. STS aims at processing a suspension of sub-micrometer-sized or even nanometer- sized solid particles dispersed in a liquid phase. The liquid phase permits the injection of particles in the thermal flow (i.e., due to their size, a carrier gas cannot play this role). SPTS aims at processing a solution of precursors under the same conditions. Upon evaporation of the liquid phase, the precursor concentration increases until precipitation, pyrolysis, and melting of small droplets occur. Compared to conventional thermal spray routes, STS and SPTS are by far more complex because fragmentation and vaporization of the liquid control the coating build-up mechanisms. Numerous studies are still necessary to reach a better understanding of the involved phenomena and to further develop the technology, among which are injection systems, suspension and solution optimizations, spray kinematics, etc. This review presents some recent developments and our present knowledge in this field together with the available tools implemented to characterize the plasma-liquid interaction and the coating formation

Suspension and solution plasma spraying

International audienc

Pore network architecture in plasma sprayed ceramic coatings

International audienceA combination of two techniques was implemented to quantify the morphology and the connectivity of the complex pore-crack network architecture of thermal sprayed coatings: image analysis coupled to stereological protocols permits to quantify the coating porous morphology, that is to say the porosity level (with a discrimination between globular pores and cracks), the orientation and the linear density of cracks; electrochemical impedance spectroscopy permits to quantify the pore connectivity (the open porosity level). These techniques were applied to characterize the pore structure of grey alumina (Al(2)O(3-)13TiO(2)) coatings and Yttria-Partially Stabilized Zirconia (Y-PSZ) Thermal Barrier Coatings (TBCs), respectively manufactured implementing air plasma spraying and hybrid plasma spraying (which combines plasma spraying and in situ laser remelting)

Recent developments in plasma spraying

EditorialInternational audienc

Quantifying thermal spray coating architecture by stereological protocols : Part I. A historical perspective

This article presents, from a historical perspective, some stereological protocols of the first order. Such protocols can be implemented to quantify statistically the architecture of thermal spray coatings and their relevant features (pores, lamellas, etc.). A forthcoming Part II of this article will address some key points to implement, from a practical point of view, such protocols