Corrosion Resistant Boron-Modified Ferritic and Austenitic Stainless Steels Designed by CALPHAD

Recently, it has been reported that the wear resistance of different stainless steel grades can be substantially improved by addition of boron as alloying element, however, with a trade-off in the corrosion resistance. In this work, CALPHAD method was employed to design a ferritic and an austenitic stainless steel modified with 1 wt pct B with high corrosion resistance. The designed alloys were produced by conventional casting in graphite mold and characterized by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM). Structural characterization revealed that the target microstructures composed of ferrite and austenite matrixes with hard borides were successfully achieved. Their corrosion resistance was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in synthetic seawater and compared to conventional 316 L stainless steel. It was shown that designing the chemical composition of the alloys’ matrixes is the key to obtain corrosion resistant boron-modified stainless steels.