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1937 |
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Tuesday, May 04, 2010, Olivia Room 11:20 AM Hard Chrome Replacement |
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Microstructures of metallic NiCrBSi coatings manufactured via hybrid plasma spray process |
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Nicolas Serres* / INSA de Strasbourg, France Françoise Hlawka / INSA de Strasbourg, France Sophie Costil/ LERMPS - UTBM, France Cécile Langlade/ LERMPS - UTBM, France Frédérique Machi/ IREPA LASER , France |
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Electrodeposited hard chromium plating is generally used to produce hard and wear-resistant coatings. However, plating baths contain hexavalent chromium, which has adverse health and environmental effects and is more and more forbidden by the European regulation. That is the reason why some coating alternatives are nowadays studied. Thermal spraying is already used in industry, but results are not always satisfactory for reasons of porosity and microstructures. In this study, atmospheric plasma spraying (APS) and in situ laser irradiation by diode laser processes were combined to modify structural characteristics of NiCrBSi coatings. The microstructure evolution was studied, with the analysis of chemical composition, microhardness, and residual stresses. Results show that in situ laser remelting induces: (i) the growth of a dendritic structure which strongly decreases the porosity of as-sprayed coatings, (ii) no phase transition after laser treatment. Several technical parameters were investigated, especially the laser energy density, in order to establish the better configuration to obtain coatings without solidification cracking, one of the major defects that can occur during solidification of metallic alloys. At least, the new studied process appears to be a possible alternative to hard chromium plating, in order to protect mechanical parts. Keywords: Plasma-laser hybrid process, Microstructures, NiCrBSi, thick coatings |