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3737 |
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Novel in-situ thermal gradient heat treatment during cold spray
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Yassine Zeralli* / MINES ParisTech- Centre des Matériaux/C2PCompetence Center for spray Processing, CNRS UMR 7633, France Gilles Rolland / MINES ParisTech- Centre des Matériaux/C2PCompetence Center for spray Processing, CNRS UMR 7633, BP 87, 91003 , France Michel Jeandin/ MINES ParisTech- Centre des Matériaux/C2PCompetence Center for spray Processing, CNRS UMR 7633, BP 87, 91003, France Frédéric Rambaud / Metalor Technologies France SAS, Rue des Aquées, 28190 , France Christine Bourda/ Metalor Technologies France SAS, Rue des Aquées, 28190 , France |
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Cold spray can substitute for several coating processes for various applications, due to a high efficiency coupled with high properties for the sprayed product. During the impact with the substrate, the particles undergo plastic deformation which results in adhesion. In addition, plastic deformation coupled to particle build-up generates residual stresses into the deposit. These stresses give the deposit certain desired properties such as resistance to crack propagation. However, these stresses can be detrimental for the coating/substrate bond strength and may lead to decohesion of the deposits. Consequently, subsequent thermal annealing is generally needed to release them. In this study, an innovative in-situ heat treatment was developed to lead to a coating which combined the advantages of both untreated and heat-treated cold-sprayed deposit. For this purpose, a specific ceramic device was designed for thermal insulation and heat storage below the substrate when spraying. In-situ heat-treating at the spraying stage could thus be controlled to result in a gradient of mechanical properties into the deposit. This gradient was exhibited through in-depth coating hardness profiles, in particular. Operating conditions, including ceramic characteristics in the device, were optimized using thermal modeling coupled with series of spraying tests using thermocouples. This innovative heat treatment was applied to the achievement of cold-sprayed electrical contacts. Mechanical and electrical subsequent severe cyclic tests ascertained the beneficial effect of in-situ heat-treating on lifetime. |