Étude des composantes mécanique et métallurgique dans la liaison revêtement-substrat obtenue par projection dynamique par gaz froid pour les systèmes «Aluminium/Polyamide6,6» et «Titane/TA6V»

Abstract : Cold Spray consists in the high-speed spray of powder particles onto a target; namely the substrate. Their adhesion and accumulation leads to a more or less dense coating to be used in the automotive, the biomedical… areas. The first stage of coating results from a powder to substrate contact. Bonding is due to mechanical anchoring and, depending on the involved materials, to metallurgical interaction. This study helps to rule on these two components. For this, two systems, which promote either mechanical or metallurgical mechanism separately, are selected. Mechanical anchoring is studied through polymer metallization using of aluminum for spraying onto polyamide 6,6. Metallurgical bonding is studied using titanium onto Ti-6Al-4V. Before studying the bonding mechanisms, the spraying process is investigated using many process parameters and materials properties (temperature, particle size…). Advanced tools are employed to determine impact conditions; i.e. particle velocity by DPV2000, substrate temperature by infrared thermography and particle temperature by numerical calculation. Mechanical anchoring onto the polymer is described through the analysis of elementary particle impacts and through 2D (micrograph sections) and 3D (laminography) study of interface roughness. The porosity gradient is also quantified. Metallurgical bonding is studied by TEM. Before that, a finite element simulation is used to go into the phenomenology of the impact and to quantify the local deformation and temperature at the interface. The simulated particle morphology is compared to those observed in real spraying conditions. Lastly, deposit adhesion is assessed by pull-off testing and the fractured surface is observed. The influence of the substrate surface morphology is exhibited using sand-blasting and laser structuring pretreatments.
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Damien Giraud. Étude des composantes mécanique et métallurgique dans la liaison revêtement-substrat obtenue par projection dynamique par gaz froid pour les systèmes «Aluminium/Polyamide6,6» et «Titane/TA6V». Matériaux. Ecole Nationale Supérieure des Mines de Paris, 2014. Français. ⟨NNT : 2014ENMP0018⟩. ⟨pastel-01073679⟩

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