Behavior of constitutive models from slow strain rate test of maraging 300 and 350 steels performed in several environmental conditions

Maraging steels are ultra-high mechanical strength steels based on Ni-Co-Mo-Ti with extra low carbon content (< 0.03%). This steel family belongs to a strategic group of materials with multiple applications, including pressure vessels, aeronautic and aerospace components, and sportive equipment. Thus, the knowledge of stress strain curves behavior performed at slow strain rate tensile tests (SSRT) is very interesting for processing, manufacturing and service from these high-performance alloys. In this work, SSRT tests were performed in maraging 300 and 350 steels in solution treatment and aged conditions (783 K for 6 h). Additionally, the hydrogen embrittlement was evaluated in SSRT performed by cathodic potential applied at −1.2 VSCE in 3.5% NaCl solution. Therefore, an analysis by environmental test was performed by obtention of stress and ductility comparative parameters. The hydrogen diffusion in alpha iron was studied using an electrochemical permeation transfer function. Similarly, a study was performed with Hollomon and Voce constitutive models to describe the strain-hardening behavior of these alloys. There is a lack of information in the literature, the use of these models is very interesting to these alloys in order to describe the mechanical behavior of maraging steels. In this work the experimental values were fitted using an iterative regression method of R2, which provided values close to the unit. The fitting by Voce model provided more accurate predictions at large strain-hardening behavior when compared with Hollomon’s model. The constants values obtained from Voce’s model were evaluated in all treatment conditions establishing a correlation with changes in work hardening. Voce is distinguished from Hollomon in that it allows more precise adjustments of the constants, and this allows a better description of the experimental values obtained from aging and environmental analysis. Finally, the work concludes by presenting an analysis of the behavior of the coefficients under different test conditions studied and correlates the values obtained with the fractographic analysis, demonstrating the models can be used with good accuracy to describe the plastic deformation response of high strength values on maraging 300 and 350 steels.