Evaluation of cobalt free coatings as hardfacing material candidates in sodium-cooled fast reactor and effect of oxygen in sodium on the tribological behaviour
Den-Service de la Corrosion et du Comportement des Matériaux dans leur Environnement (SCCME), CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
2 Den-Service d'Etudes Analytiques et de Réactivtiés des Surfaces (SEARS), CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
3 Den-Service de Recherches Métallurgiques Appliquées (SRMA), CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
4 EDF R&D, Département Matériaux et Mécanique des Composants, Les Renardières, 77818 Moret Loing Orvanne, France
5 FRAMATOME, DTIML, 10 rue Juliette Récamier, 69006 Lyon, France
* e-mail: firstname.lastname@example.org
Received in final form: 20 May 2019
Accepted: 2 August 2019
Published online: 5 November 2019
The feedback produced by operating Sodium-cooled Fast Reactors (SFRs) has shown the importance of material tribological properties. Where galling or adhesive wear cannot be allowed, hardfacing alloys, known to be galling-resistant coatings, are usually applied on rubbing surfaces. The most used coating is the cobalt-base alloy named Stellite 6® because of its outstanding friction and wear behaviour. Nevertheless, cobalt is an element which activates in the reactor leading to complex management of safety during reactor maintenance and mainly decommissioning. As a consequence, a collaborative work between CEA, EDF and FRAMATOME has been launched for selecting promising cobalt-free hardfacing alloys for the 600 MWe Sodium-cooled Fast breeder reactor project named ASTRID. Several nickel-base alloys have been selected from literature review then deposited by Plasma Transferred Arc or Laser Cladding on 17Cr austenitic stainless steel 316L(N) according to RCC-MRx Code (AFCEN Code). Among the numerous properties required for qualifying their use as hardfacing alloys in SFR, good corrosion behaviour and good friction and wear behaviour in sodium are essential. First results on these properties are shown in this article. Firstly, the corrosion behaviour of all coatings was evaluated through exposure tests in purified sodium for 5000 h at 400 °C. All coatings showed an acceptable corrosion behaviour in sodium. Finally, the friction and wear properties of one alloy candidate, NiCrBSi alloy, were studied in sodium in a dedicated designed facility. The influence of the oxygen concentration in sodium on the friction and wear properties was evaluated.
© F. Rouillard et al., published by EDP Sciences, 2019
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