Cavitation erosion - corrosion behaviour of ASTM A27 runner steel in natural river water

27th IAHR Symposium on Hydraulic Machinery and Systems

Tôn-Thât, L.^1

Institut de Recherche d'Hydro-Québec Expertises - Mécanique, Métallurgie et Hydroéolien, 1800 boulevard Lionel-Boulet, Varennes

QC

J3X1S1, Canada^1

关键词: Cavitation erosion-corrosion;    Corrosion parameters;    Damaging mechanism;    Degradation parameter;    Deleterious effects;    Material removal mechanisms;    Resistance properties;    Synergistic effect;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/5/052021/pdf
DOI  :  10.1088/1755-1315/22/5/052021

来源: IOP

【 摘 要 】

Cavitation erosion is still one of the most important degradation modes in hydraulic turbine runners. Part of researches in this field focuses on finding new materials, coatings and surface treatments to improve the resistance properties of runners to this phenomenon. However, only few studies are focused on the deleterious effect of the environment. Actually, in some cases a synergistic effect between cavitation erosion mechanisms and corrosion kinetics can establish and increase erosion rate. In the present study, the cavitation erosion-corrosion behaviour of ASTM A27 steel in natural river water is investigated. This paper state the approach which has been used to enlighten the synergy between both phenomena. For this, a 20 kHz vibratory test according ASTM G32 standard is coupled to an electrochemical cell to be able to follow the different corrosion parameters during the tests to get evidence of the damaging mechanism. Moreover, mass losses have been followed during the exposure time. The classical degradation parameters (cumulative weight loss and erosion rate) are determined. Furthermore, a particular effort has been implemented to determine the evolution of surface damages in terms of pitting, surface cracking, material removal and surface corrosion. For this, scanning electron microscopy has been used to link the microstructure to the material removal mechanisms.