Enhanced mechanical and corrosion properties of super duplex stainless steel obtained by powder metallurgy host isostatic pressing (PM-HIP)

Abstract

This work explores the impact of the microstructure on the corrosion resistance and the mechanical behaviour of S32505, a super duplex stainless steel (SDSS) produced by powder metallurgy hot isostatic pressing (PM-HIP). The results demonstrate that by the appropriate selection of hot isostatic pressing (HIP) and annealing conditions, improved mechanical and corrosion behaviour are achieved, compared to those of an equivalent forged SDSS (S32750). The fine and isotropic microstructure of PM-HIP SDSS, free of inclusions, σ phase or Cr₂N precipitates explain their outstanding impact behaviour and their mechanical strength and ductility more than 15% above the values obtained with the forged SDSS. Despite having a pitting resistance equivalent number lower than forged SDSS, the PM-HIP SDSS grade shows similar or higher pitting and crevice corrosion resistance. The feasibility of obtaining PM-HIP SDSS with suitable microstructure and properties, integrating solution annealing and quenching in an ultra-rapid quenching HIP unit, has also been demonstrated.