Study regarding the influence of the material quality on the cavitation erosion resistance of soft martensitic stainless steels used for the casting of hydraulic turbines parts

摘要

During their operation, the components of hydraulic equipment are exposed both to special mechanical and technological loads and to the corrosive action of the working environment, which affect the normal functioning of the machinery. After decades of activity, hydro turbines from Romania hydropower plants, respectively their components have been subjected to vast refurbishment processes. On these occasions, frequently cavitation erosion has been found on the surfaces of Kaplan and Francis turbine blades. The stainless steel grade X3CrNiMol3-4 (1.4313), alloyed with chromium, nickel and molybdenum and presenting a martensitic structure with a low content ferrite is widely used for the casting of Kaplan blades and Francis runners designed to equip Romanian power plants. In this paper, the authors realized a comparative study regarding the cavitation resistance of several samples of soft martensitic stainless steel type 13-4, having different compositions and microstructures. The material samples were taken from cast components used in five Romanian hydropower plants. The results obtained may be used to support the refurbishment program for hydraulic turbines set on Romanian rivers.