Abstrakt

Influences of the rate and of the direction of plastic deformation on the corrosion behaviour of compressed iron-based alloys

Pierre-Yves Girardin, Adrien Frigerio, Patrice Berthod

After having been subjected to intense stresses metallic alloys can be partially or totally affected by a permanent geometric change. The resulting much higher dislocations densities may lead to severe microstructure disorder inducing possibly changes in the surface reactivity of the piece, after or not machining. It is thus interesting to specify the effects of plastic deformation on the local corrosion resistance of metallic alloys, by taking into consideration the local orientation of the surface with respect to the deformation tensor. In this work two metallic alloys, pure polycrystalline iron and a ternary Fe-10Ni-18Cr alloy, both (re-)melted and (re-)solidified in the same conditions were cut, uni-axially deformed and tested in corrosion in a sulphuric solution, by applying the Stern-Geary, Tafel and cyclic polarizationmethods, to highlight the links of dependence of parameters as open circuit potential, polarization resistance, corrosion current densities and passivation characteristics, on the amplitude and direction of mechanical plastic deformation. Some tendencies obviously exists, notably concerning the corrosion resistance in the active state for iron or some of the passivation characteristics, but the variation observed in many cases remain not well established. The microstructure texture is suspected to superpose its influence on the deformation one.