Corrosion Fatigue Behaviors Of Fracturing Pump Steels In Hydrochloric Acid

By using a cantilever beam reversed bending and corrosion fatigue testing machine,the corrosion fatigue behaviors of fracturing pump steels in hydrochloric acid wereinvestigated. Besides, corrosion fatigue influence factors, morphology and mechanismswere also studied, providing a theoretical basis for a reasonable selection of high strengthsteels for Fracturing Pump.Corrosion fatigue life of25Cr2Ni4MoV and30CrNi2MoV steels decreased withincreasing cyclic stress and also with increasing concentration of the hydrochloric.Besides, corrosion fatigue life is more vulnerable to magnitude of the cyclic stress than theconcentration of the hydrochloric acid, the concentration of hydrochloric acid had lessimpact on the life of a certain concentration range. Smaller prior austenite grain sizewould get a higher corrosion fatigue life.There are cracks parallel to the fractures on the surfaces of25Cr2Ni4MoV and30CrNi2MoV steels, second cracks and branches on the fractures too. Cracks wereoriginated from pitting. The morphology showed the corrosion fatigue crack propagationwas typical intergranular cracking. The corrosion fatigue mechanism was selectivedissolution of slip bands due to its higher electrochemical potential to matrix under theinteraction of cyclic stress and corrosion environment.Based on the slip bands selective dissolution model, to improve corrosion fatigue lifeof the fracturing pump in hydrochloric acid solution, the following advises were suggested:first, reasonable designing of the fracturing pump structure to reducing in the process ofthe degree of stress concentration; second, refining the grain size of high-strength steels toget higher mechanical properties or selecting more higher mechanical properties strengthsteels.