Effects of Austempering on the Microstructure, Corrosion and Mechanical Properties of AISI 1018 Steel

Abstract

In this study, the effects of austempering on the microstructure, mechanical properties (micro hardness, impact energy and tensile strength) and corrosion behaviours of AISI 1018 low carbon steel were evaluated. The steel specimens were subjected to heat treatment by austenitizing at 830°C, maintained in this condition for 90 min before rapid cooling in a NaNO3 salt bath sustained at 300°C for isothermal transformation for additional 50 min and finally allowed to air cool to room temperature. The as-received and the austempered samples were tested for corrosion in both 0.5M aqueous acidic (HCl) and 0. 5M alkaline (NaOH) media. Microstructural investigation using scanning electron microscope (SEM) reveals transformation from ferrite/pearlite phases to bainite over the austempering process. Interestingly, significant improvements of 15.7% to 95.7% in the various mechanical properties (micro hardness, impact energy and tensile strength) and corrosion resistance in both media were observed.

Impact of Welding Parameters in the Porosity of a Dissimilar Welded Lap Joint of CP800-XPF1000 Steel Weldment by GMAW-P

“…According to the results in Figure 7, the heat input and, with it, the cooling rate led to changes in the solidification mode, which is influenced by the extent of solute partitioning and the phase formation [20]. Specifically, the use of the GMAW-P plays an important role, generating an undercooling that promotes the rapid formation of grains, which tends to be fragmented by the high convection generated in the melt pool due to the high droplet/s transfers, promoting the formation of ferrite (F) and dispersed acicular ferrite (AF) in the weld, as can observed in all samples [21,22]. Trial 1 corresponds to Figure 7a,b, demonstrating the interface with XPF 1000 and CP800, respectively, and shows epitaxial growth from ferritic grains.…”