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2018-06-29 - Colloque/Présentation - poster - Anglais - 1 page(s)

Montagne Alex, Mughal Zeeshan, Bonin Luiza , Sebastiani Marco, Bemporad Edoardo, Vitry Véronique , Iost Alain, Staia Mariana, "Residual stresses in electroless nickel coatings" in SMT32 - 32nd International Conference on Surface Modification Technologies, San Sebastian, Espagne, 2018

  • Codes CREF : Mécanique appliquée générale (DI2100), Résistance et comportement des matériaux (DI2110)
  • Unités de recherche UMONS : Métallurgie (F601)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Ingénierie des matériaux (CRIM)
Texte intégral :

Abstract(s) :

(Anglais) Electroless nickel coatings are widely used in industry as a substitute for hard chromium due to environmental and regulatory concerns, as well as their excellent wear and corrosion resistance. The study of residual stresses is of utmost importance for the understanding of the mechanical behavior of the coatings under mechanical stresses. For example, the residual stresses in coatings can limit the propagation of cracks and thus increase the apparent toughness if they are compressive stresses. Moreover, high stresses near the interface coating / substrate can lead to buckling or delamination of the film. In this study we propose the evaluation of the residual stresses in NiB coatings. Two samples have been considered, one as-deposited and a second one subjected to a heat treatment. The experimental approach chosen here is based on incremental Focused Ion Beam (FIB) milling. A pillar is machined in the coating and as the material is removed, the pillar relaxes. SEM micrographs are taken at different milling depths and finally the strain relaxation is analyzed trough digital image correlation. Mechanical properties, hardness and elastic modulus, have been explored by means of nanoindentation performed on both the top surface and cross-section. Results show that there are small residual stresses in both treated and untreated samples. Moreover, it is shown that the residual stresses are distributed within a small length scale, having different intensity and sign. Larger pillars show almost no strain relaxation, which indicates a mutual annihilation between local residual stresses.