Microstructure, Corrosion Resistance, and Hardness of Simulated Heat-Affected Zone of Duplex UNS S32205 and Superduplex UNS S32750 Stainless Steels.

Thermal simulation is an interesting method to reproduce different regions of the heat-affected zone (HAZ) in specimens with dimensions proper to perform microstructural investigations, corrosion resistance and mechanical tests. In this work, different regions of the HAZ of duplex UNS S32205 and superduplex UNS S32750 stainless steels were reproduced using a Gleeble machine. For each material, thermal cycles with peak temperatures of 800, 1000, 1200 and 1350 °C were reproduced in order to evaluate the microstructure, pitting resistance, hardness and microhardness of the phases. It was found that the critical pitting temperature (CPT) was reduced in specimens processed with a peak temperature of 1350 °C in comparison with the base metals, while with peak temperatures of 800 and 1000 °C there was an increase in the CPT. Secondary austenite precipitation was identified in specimens with peak temperatures 800 and 1000 °C, but this phase did not impar the pitting resistance. Intense chromium nitrides precipitation and increase in the ferrite phase content were the main microstructural changes observed with peak temperature 1350 °C. The duplex steel undergone higher ferritization than the superduplex. The CPT was reduced with the chromium nitride precipitation, but the microhardness of the ferrite was not affected by these particles. [ABSTRACT FROM AUTHOR]