Effect of Contact Stress on Fretting Corrosion Behavior of Alloy 690 Tube Exposed to Simulated Secondary Water

Abstract

Flow-induced vibration is unavoidable in the steam generator, so the wear of heat transfer tubes can’t be ignored. It is essential to evaluate the fretting wear damage of the heat exchanger tube. In this paper, the high frequency fretting wear tests of Alloy 690 tubes/405 stainless steel plate were carried out in the dynamic water loop experimental device, simulated the secondary water (285°C, 10.5 MPa). Changing the contact stress is realized by applying a range of normal forces. As the contact stress increased, the wear volume increased, and the material removal increased the contact area and wear depth. The wear coefficients of Alloy 690 tubes were found to be intensely dependent on the contact stress. The damage mechanisms of Alloy 690 tube were mainly delamination and abrasive wear, and accompanied by material oxidation in the fretting process. The oxide type of wear debris mainly consisted of (Ni, Fe) (Fe, Cr)2O4 and Fe3O4. The profile shape of wear scar was dependent on the action of the wear particles. When the contact stress is minor, the debris was easy to escape from the interface, and the typical profile shapes were U-shaped. As the contact stress increased, the elastic deformation of the contact material increased, followed by adhesion and delamination in the contact area.