Combined numerical and experimental approach of the impact-sliding wear of a stainless steel in a nuclear reactor

In nuclear power plants, tubes and guides of the rod cluster control assemblies undergo impacts at low contact pressures, which lead to a specific wear of the contact surfaces. The aim of this paper is to propose a first explanation of this particular wear with the help of finite element simulations and experimental observations. In a first part, we present some experimental observations, obtained using a tribometer specially designed for this application by AREVA NP, which allows to reproduce the wear scars in the same environment and with equivalent loading conditions. In a second part, we detail the numerical model. More specifically, we consider that the impact-sliding process can be modelled by a scratching process of a double-layered material (stainless steel recovered by a friction film) with a rigid spherical asperity. The mechanical behaviour of these materials comes from instrumented nanoidentation tests and the geometric parameters are deduced from experimental observations. From both the numerical results and the experimental observations, a wear mechanism is then proposed. Finally, we conclude on the capability of finite element analysis to improve the understanding of specific wear phenomena when it is combined to experimental results.