Sliding Indentation Behaviour of x 65 Hydrogenated Steel Grade

Abstract

The paper presents an experimental research on non-hydrogenated and hydrogenated X 65 steel samples. The steel was obtained from a continuous casting slab, this grade being used in petroleum industry. The hydrogen has an embrittlement action on the steel and reduces its mechanical properties. In time the hydrogen diffuses to the surface, so its concentration is higher into the superficial layer than the one into the material bulk. In the paper this action is appreciated by a sliding indentation test. It was found that low indentation forces generate smaller trace widths as the hydrogenation duration increase, due to the hydrogen into the superficial layer. For big indentation forces, the trace widths are bigger than the above ones caused by a lower hardness. The decrease of hardness is due to the lower hydrogen concentration in the bulk and the deeper extent of the plastic deformations. This aspect is confirmed by the value of a parameter defined in this paper