Corrosion resistance of W600 hot work tool steel in artificial rainwater and 3.5 % NaCl solution

This paper studied the corrosion resistance of W600 tool steel in artificial rainwater and 3.5 % NaCl solution. The equilibrium phase diagram was determined from the material’s chemical composition, with calculations and thermodynamic simulations carried out using Thermo-Calc software, enabling accurate prediction of stable phases as a function of temperature and composition. According to the obtained projections, the solidification and precipitation of individual phases at characteristic temperatures was read. Following the completion of the electrochemical measurements, insight into the corrosion behavior of the tested sample was provided. Electrochemical tests showed a decrease in charge transfer resistance and an increased corrosion rate in the 3.5 % NaCl solution, indicating inadequate resistance in a chloride-containing solution, attributed to the formation of a thin oxide layer caused by the attack of chloride ions from the solution. Metallographic analysis confirmed the occurrence of slowly progressing pitting corrosion in chloride solution, while no significant changes were observed after testing in artificial rainwater. The lower rate of pitting corrosion was attributed to the martensitic microstructure with fine needle-like morphology with uniformly distributed carbides in the W600 tool steel. Such investigations are essential for understanding material behavior in aggressive environments and for reliably predicting its durability in real applications.