This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

Role of nitrogen on the corrosion behavior of austenitic stainless steels

A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications

Electrochemical investigation of the influence of nitrogen alloying on pitting corrosion of austenitic stainless steels

The influence of nitrogen on the passivation of stainless steels

Nitrogen, probably in an uncharged form, is enriched on the metal side of the metal film interface after passivation of the number 30 alloy. Molybdenum is probably present in the oxide film, but is depleted compared with the bulk alloy and shows no obvious association with nitrogen. The improvement of passivity by alloying with nitrogen probably results from segregation of nitrogen to the metal surface during preferential dissolution of metal atoms, rather than from its incorporation into an oxide film.

Surface Enrichment of Nitrogen during Passivation of a Highly Resistant Stainless Steel

Surface enrichment of nitrogen during passivation of a highly resistant stainless steel

Nitrogen additions of 0.45 to 0.5 wt % to an austenitic stainless steel containing about 22 Cr, 20 Ni and 6 Mo (all wt %) dramatically enhance its resistance to localized corrosion. The electrochemical behavior of this alloy has been studied as a function of chloride ion concentration and temperature. Also, its corrosion resistance has been compared with that of a similar commercial alloy with normal residual nitrogen of only 0.04 wt %. Compositional analyses of the passivated surface of the high nitrogen alloy show an enrichment nitrogen at the metal-passive film interface, with a binding energy similar to that of the bulk nitrogen on the fully sputtered surface. The role of nitrogen in enhancing the corrosion resistance is discussed in light of the above results and some recent concepts on passivity.

R. Bandy

Papers

Surface Enrichment of Nitrogen during Passivation of a Highly Resistant Stainless Steel

Surface enrichment of nitrogen during passivation of a highly resistant stainless steel

Role of nitrogen in improving resistance to localized corrosion in austenitic stainless steels. [22 Cr-20 Ni-6 Mo]