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Courville-sur-Eure, France

Rolland G.,MINES ParisTech Center of materials | Rolland G.,Metalor Technologies SAS | Sallamand P.,University of Burgundy | Guipont V.,MINES ParisTech Center of materials | And 3 more authors.
Journal of Thermal Spray Technology | Year: 2012

This work demonstrated the feasibility of cold spray for the achievement of industrial electrical contacts to be used in contactors and circuit breakers. This resulted from the study of cold spray conditions when applied to two types of silver-based particulate composites. Starting materials, primarily powder characteristics and addition content, and spraying conditions were optimized from thorough studies of microstructures and mechanical properties of the cold-sprayed composites. These involve x-ray microtomography and transmission electron microscopy in particular, in addition to tensile tests. Moreover, thermomechanical laser testing of series of cold-sprayed microstructures was successfully developed to investigate into damage mechanisms in coatings. The whole led to a novel phenomenological approach to damage in cold-sprayed materials. Durability tests of the best coatings were carried out using industrial facilities. Cold-sprayed contacts compared more than well with those from conventional powder metallurgy (P/M), which opens a new and cost-attractive production route for electrical contacts. © 2012 ASM International. Source


Rolland G.,MINES ParisTech Center of materials | Rolland G.,Metalor Technologies SAS | Sallamand P.,University of Burgundy | Guipont V.,MINES ParisTech Center of materials | And 3 more authors.
Surface and Coatings Technology | Year: 2011

Ag-Ni composite coatings were achieved using the cold spray process. In this work, two blends were sprayed to lead to coatings with different mechanical properties, which corresponded to either a fine or a coarse microstructure. These coatings were studied using SEM and X-ray microtomography (XMT) to determine the best coating quality through characterization of particle-to-particle bonding. The fine microstructure showed better properties than the coarse microstructure.To avoid time-consuming characterization techniques such as SEM and XMT, an innovative laser characterization test was developed. The principle of this test is based on the thermal shock-induced by a laser pulse at the surface of the coating. Thus, particle interfaces were stressed and cracking damage could occur. SEM observation of cross-sections and top views was carried out to rank the coatings as a function of the generated damage. The influence of heat treatments was also studied.To enhance the approach, thermomechanical simulations have been performed on a real meshed microstructure. The influence of layering effect in the cold spray was shown to be detrimental due to local concentrated stresses. © 2011 Elsevier B.V. Source

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