Modified Ni equivalent for evaluating hydrogen susceptibility of Cr-Ni based austenitic stainless steels

Abstract

In Cr-Ni austenitic stainless steels, Ni equivalent is an important indicator of austenite stability, and thereby, the resistance to hydrogen embrittlement. Although N is often added to Cr-Ni austenitic stainless steels as a strengthening element, its contribution to Ni equivalent has not been satisfactorily taken into account. Based on an up-to-date thermodynamic database, the existing Ni equivalents are reassessed, and a modified Ni equivalent is suggested to accurately consider the N effect on austenite stability. The newly suggested Ni equivalent equal to 27 is proposed to be the lower limit for the applications in hydrogen environment. (C) 2016 Elsevier B.V. All rights reserved.