Effect of Y on solidification microstructure and corrosion resistance of high Mo super austenitic stainless steels

Purpose This study investigates the effect of Y on the microstructure and corrosion resistance of high Mo super austenitic stainless steels. This study aims to provide experimental evidence for the development and application of high-Mo super austenitic stainless steel. Design/methodology/approach High Mo super austenitic stainless steels (SASSs) containing 0, 24, 50 and 93 ppm Y were prepared by vacuum nonconsumable arc melting. Thermodynamic calculations based on the Gulliver-Scheil models, combined with optical microscope, scanning electron microscope, equipped with energy-dispersive spectroscopy, electron backscatter diffraction, X-ray diffractometer, transmission electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy and laser scanning confocal microscopy were used to systematically study the effect of Y on the solidification behavior, microstructure, σ phase precipitation and corrosion resistance of high Mo SASSs. Findings The addition of Y slightly decreased the s phase precipitation temperature and reduced the enrichment of Cr and Mo in the interdendritic residual liquid. Y significantly refined the solidification microstructure and reduced elemental segregation. The σ phase volume fraction, size and continuity decreased significantly with the increase of Y content. In a 3.5 Wt.% NaCl solution, the addition of an appropriate amount of Y reduced the corrosion current density, increased the polarization resistance and reduced pit depth. The test steel with a Y content of 50 ppm showed the best corrosion resistance. Originality/value This study provides insights into the effect and optimum addition content of Y in high Mo super austenitic stainless steels.