The mechanical Properties of an experimental 17%Cr multiphase alloy were studied as function of heat treatment parameters. Containing majoritary ferrite and martensite, this type of steel is applied in tubullars and casings in the off shore oil and gas production, where high corrosion and mechanical resistance are required. Quenching and tempering heat treatments produced different combinations of ferrite, martensite, austenite and precipitates. The as quenched material has 35% of ferrite, martensite and 3.8% of retained austenite. The material quenched and tempered at 500oC has lower austenite (1.2%), and tempered martensite with Nb carbides. The tensile properties were excellent, but the low temperature (-46oC) impact toughness was very small. A high toughness was obtained in the material quenched and tempered at 650oC, with a microstructure of ferrite, tempered martensite and 7.2% of reversed austenite, but the mechanical resistance was under 621 Mpa (90ksi), which is considered too low for the application envisioned. The material tempered at 600oC showed an interesting combination of mechanical resistance and low temperature toughness. The flow stress curves of the material were modelled by Hollomon’s equation and Voce’s equation with correlation coefficients (R2) higher than 0.98.

This work presents a detailed study directed to supermartensitic stainless steels (SMSS) alloyed to nitrogen (UNS S41425) and vanadium (UNS S41427), showing comparison between them by varying their tempering temperature, evaluating the behavior in its mechanical properties, presenting a fractographic and microstructural analysis between these alloys, besides to demonstrate techniques for modeling these strain-hardening results with best coefficients that determine these materials with good predicted values. The Hollomon, Voce and Chaboche models were determined, using an iterative regression method (R2) in order to obtain the best coefficients for each analysis condition. This work concludes by presenting graphic results of the effect of tempering temperature increase on the final mechanical properties, evaluates the differences obtained between these materials and presents an evaluation of the behavior of each coefficient of the models presented separately, showing the best R2 fitting results. With the models determined, it is possible to use the results in this work to perform numerical simulations and meet the needs of the engineering on industry.