Static, dynamic and fatigue characteristics of the pipeline API 5L X52 steel after sandblasting

The influence of sandblasting on a surface notched pipeline with API 5L X52 steel is studied. The purpose of this study is to evaluate the mechanical characteristics of material in both directions of pipeline (longitudinal (L) and transverse (T)). Specimens were taken from a pipeline and material damage was made by projecting corundum particles (aluminium oxide). It has been shown that the sandblasting has little affect on the yield stress and ultimate strength. Erosion of surface layers, under the sand impacting, improves the material lifetime and elongation at fracture. The fracture toughness of sandblasted material manifests differently in both L and T directions. In order to justify these evolutions, a microstructural study was carried out. The observation of damage mode and distribution of residual stress under the notch tip show that the material hardening, the notch radius and the compressive stress play an important role in stabilizing the mechanical properties of material.