TC10 - Lecture 1
Hydrogen assisted cracking paths in cold drawn pearlitic steel wires for wind turbine structures: Resembling Mantegna’s Dead Christ Perspective
Wind turbines are key elements in the field of renewable energies. The main subject of this lecture is related to anisotropic hydrogen embrittlement and hydrogen-assisted cracking paths of cold drawn pearlitic steel wires for wind turbine structures and foundations. It is seen that progressive cold drawing in pearlitc steel (to manufacture prestressing steel wires) produces a preferential orientation of pearlitic colonies and ferrite/cementite lamellae, thus inducing strength anisotropy in the steel and mixed mode propagation. While in the rolled eutectoid steel (not cold drawn) the pearlitic microstructure is randomly oriented and the crack progresses in hydrogen by breaking the ferrite/cementite lamellae, in the most heavily drawn steels the pearlitic microstructure is fully oriented and the predominant mechanism of hydrogen assisted cracking is the delamination (or even decohesion) at the ferrite/cementite interface, as a clear consequence of the microstructural and strength anisotropy induced by heavy drawing. Heavily drawn pearlitic steels exhibit in their hydrogen assisted cracking paths (HACP) evidence of strongly anisotropic behaviour with a marked deflection angle of 90º. This resembles Mantegna’s Dead Christ Perspective (MDCP) painting with is relevant and innovative change of point of view in the Dead Christ (90º rotated from the traditional painting perspectives) with his body axis perpendicular to the canvas (foreshortening perspective).