Effects of Alloying Elements on Sigma Phase Precipitation in Duplex Stainless Steel (1) - Modelling of Effects of Chromium, Molybdenum and Tungsten on Sigma Phase Growth Rate in Super Duplex Stainless Steel -

The modelling of the precipitation and growth behaviour of the sigma phase in super duplex stainless steel was investigated to clarify the quantitative effects of chemistry. The alloying elements of Cr and Mo useful for improving of corrosion resistance can promote sigma phase precipitation but that phase does not always grow rapidly. Therefore it is meaningful to clarify the effect of alloying elements on the kinetics of sigma phase growth to improve the trade-off relation between the corrosion resistance and avoiding harmful phase precipitation. A physical model regarding sigma phase growth rate as a function of temperature and the parameters regarding the amount of allying elements in the steel was suggested on the basis of the traditional nucleation theory during isothermal heating process. It was confirmed that the physical model suggested in this work explains the experimental results of the effects of temperature and alloying elements of CR, MO and Won the growth rate of the sigma phase.