EFFECT OF RARE EARTH METALS ON CAVITATION AND CORROSION RESISTANCE OF 07KH19N11M3 WELD OVERLAY COATINGS

This study examines the influence of microalloying with rare-earth metals (yttrium and its compounds) on the cavitation-corrosion resistance of deposited 07KH19N11M3 austenitic stainless steel, widely used in pump equipment for nuclear power plant cooling systems. Weld overlays were produced by manual arc welding with electrodes featuring a fluoride-calcium coating modified by rare-earth metal additives and tested under conditions simulating high-velocity cooling water flow (15…25 m/s, 42 °C) combined with cavitation and electrochemical loading. Electrochemical analysis using potentiodynamic polarization revealed that microalloying with rare-earth metals reduces corrosion current density and corrosion rate by more than threefold compared to the baseline deposited metal, indicating enhanced stability of the passive film under cavitation conditions. Microstructural characterization showed a reduction in δ-ferrite content, refinement of the dendritic structure, and formation of a more uniform fine-grained austenitic matrix. The secondary dendrite arm spacing (SDAS) decreased from approximately 368 to 212…227 μm, while the number and size of non-metallic inclusions were reduced by more than threefold. Regression analysis identified yttrium and molybdenum as key factors governing corrosion resistance and austenitic grain size. An optimal yttrium microalloying range (0.002…0.003 mass%) was established, ensuring minimal corrosion rate and maximum structural improvement. These findings confirm the effectiveness of rare-earth metal additions in enhancing the operational reliability of 07KH19N11M3 weld overlays under combined cavitation–corrosion conditions.