Sigma phase precipitation modelling in a UNS S32760 superduplex stainless steel

  • P. Ferro
  • F. Bonollo
  • G. Timelli


Sigma phase precipitation is known to have detrimental effects on mechanical and corrosion properties
in stainless steels. Accordingly, heat treatments and welding must be performed carefully. For this reason,
computer models which predict the evolution of secondary phases with the temperature are very useful
for a good planning of industrial heat treatments or welding. A semiempirical model, based on the pioneer
work of Wilson and Nilsson, describing the microstructural evolution of UNS S32760 superduplex stainless
steels was developed. The computer model, based on the modified Johnson–Mehl–Avrami-Kolmorgorov (JMAK)
type of equation, uses information from isothermal experiments of sigma-phase transformation and predicts
the transformation kinetics during a cooling process. A good agreement was found between the predicted CCTdiagram
and the experimental tests.