THE EFFECT OF MICROSTRUCTURAL CHANGES ON THE CORROSION PROPERTIES OF 310S AUSTENITIC STAINLESS STEEL AFTER THERMOMECHANICAL TREATMENT

In this study, microstructural changes and their effect on corrosion properties of 310s austenitic stainless steel during thermomechanical treatment were investigated.

The cold rolling process was performed with a 90% reduction in thickness. The samples were then annealed at 750, 850, 950, and 1050 °C for 10 minutes. The microstructure of the samples was examined by an optical microscope. Electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed in 3.5 wt. % NaCl to investigate the corrosion properties of the samples.

The results showed that the cold rolling process reduces the grain size and converts the austenite phase to strain-induced αʹ-martensite. Subsequently, a reverse transformation of αʹ-martensite to austenite occurs due to the annealing. Increasing the annealing temperature also causes grain growth and an increase in the average grain size. Corrosion resistance improved by reduction in grain size. Annealing at 750 °C also increased the corrosion resistance from 26800 to 38950 Ω.cm2 compared to the un-annealed sample. Reverse transformation is one of the main factors in this increase in corrosion resistance. While increasing the annealing temperature leads to grain growth and a decrease in corrosion resistance. So that the amount of corrosion resistance in the annealed sample at 1050 °C is reduced to 5400 Ω.cm2.