Effect of open die forging and cooling rate on the precipitation of secondary phases and corrosion properties of a cast UNS S32760 super duplex stainless steel

Abstract

This study investigates the effect of hot plastic deformation on the precipitation kinetics of secondary phases in cast UNS S32760 super duplex stainless steel (SDSS). Due to their dual-phase morphology and composition, the SDSS are characterized by a favourable compromise between corrosion resistance and mechanical properties. However, during thermomechanical processing, the precipitation of intermetallic phases such as sigma, chi and chromium nitrides can occur, potentially affecting their overall performance. This research focuses on evaluating the effect of open-die forging on the precipitation of secondary phases in cast UNS S32760 during continuous cooling. Hot forging simulations are performed at a temperature of 1100 °C followed by different cooling rates. Microstructural analysis, phase amounts quantification and corrosion tests are employed to quantify and investigate the effect of secondary phases on mechanical and corrosion properties. The results reveal a significantly higher degree of sensitization in samples subjected to hot plastic deformation. The findings provide new valuable insights on the existing knowledge gap about the interplay between hot plastic deformation, secondary phase precipitation kinetics and the corrosion behaviour of super duplex stainless steels, contributing to the understanding of their performance in demanding chloride-rich environments.

Keywords

• Super duplex stainless steel
• Open die forging
• Sensitization
• Secondary phase precipitation
• Continuous cooling
• Dynamic recrystallization