Evaluation of the effects of cold rolling parameters and aging treatment for improving the strength and ductility of 13–8Mo stainless steel

Abstract

In this paper, the design of experiment technique was used to investigate the effect of cold rolling and aging treatment on the mechanical properties and microstructure of 13-8Mo stainless steel. For this purpose, the parameters of cold rolling percentage, aging temperature and aging time have been selected as variables to investigate their effect on the hardness, tensile strength, area reduction percentage and elongation. Microstructural evolutions have also been examined using the optical and scanning electron microscopy (SEM), as well as EDS analysis. The results showed that the maximum volume fraction of precipitates (2.1%) has been obtained after 86% cold rolling and aging at 500 °C for 4 hours. Moreover, the volume fraction of precipitates and the martensite phase were reduced to 0.7% and 64% respectively, after 73% cold rolling and aging at 600 °C for 4 hours. In this condition, the reversed austenite and Cr 23 C 6 carbide were formed in addition to NiAl. The optimal values of the parameters for simultaneous improvement of strength and ductility were obtained at the aging temperature of 535 °C, aging time of 4 hours and after 76% cold rolling. Moreover, the values of hardness, tensile strength, area reduction percentage and elongation at optimal conditions were predicted to be 395 HV, 1267 MPa, 24.5% and 9.4%, respectively. The validation experiments at optimal conditions indicated that the predicted values were in good agreement with the experimental results. • Finding the optimal values of the cold rolling and aging parameters for improving the strength and ductility of 13-8Mo stainless steel. • Estimating the regression models for tensile strength, hardness, area reduction percentage and elongation of 13-8Mo stainless steel using the cold rolling and aging parameters. • Finding a relationship between the mechanical properties and microstructure of 13-8Mo stainless steel after cold rolling and aging treatment.