Effect of Elemental Partitioning on Pitting Resistance of High Nitrogen Duplex Stainless Steels

摘要

The present paper describes an investigation on highly alloyed duplex stainless steels with nitrogen concentrations varying in the range 0.31-0.44%. The distribution of alloying elements obtained in the electron microprobe (EPMA) was compared with predictions obtained by the thermodynamic computer program Thermo-Calc. Based on calculated and measured chemical composition of the two phases, pitting resistance equivalent (PRE) values were calculated. The critical pitting temperature (CPT) was determined and related to the PRE of the weakest phase, which turned out to be ferrite in the present case. Thermo-Calc proved to be capable of predicting PRE-values as a function of temperature in ferrite and austenite, thereby offering a means of balancing the partitioning of alloying elements between ferrite and austenite. This reduces the number of laboratory melts when developing duplex stainless steels.