Abstract
The ternary-based Fe-24Mn-3Cr alloy has superior mechanical properties based on an attractive combination of high strength and ductility, with long-term environmental stability in highly corrosive environments compared to conventional ferritic steel alloys. This study reports that the environmental instability caused by the rapid electrochemical corrosion kinetics on the surface of conventional high Mn-bearing ferrous alloys could be overcome by a combination of high Mn–low Cr-balanced Fe and their synergistic interactions. In contrast to Cr-free Mn-bearing alloys, the high Mn–low Cr-bearing alloy showed comparatively lower corrosion kinetic parameters, without a continuously increasing trend, and higher polarization resistance according to electrochemical polarization and impedance spectroscopy measurements. Moreover, the rate of degradation caused by erosion–corrosion synergistic interaction under erosion–corrosion dynamic flow conditions was the lowest in the high Mn–low Cr-bearing alloy. These surface-inhibiting characteristics of the alloy were attributed primarily to the formation of a bilayer scale structure consisting of inner α-Fe2−xCrxO3/outer FexMn3−xO4 on the surface.
Highlights
In comparison with rare, noble, and expensive elements, Fe and Mn are the 4th and 12th most abundant elements in the earth’s crust, respectively, and a ferrous alloy containing high quantities of Mn was developed under the name of Hadfield steel in the late nineteenth century[1]
With the advent of high Mn-bearing ferrous alloys with a face-centered cubic (FCC) structure at room temperature, they have attracted considerable attention owing to their superior mechanical properties of strength ductility compared to the conventional ferritic steel alloys[2]
Our work demonstrates that a combination of a more active element in larger quantities and nobler elements in smaller quantities in ferrous alloys enables the development of stronger, tougher, and more commercially available alloys with superior resistance to both static corrosion and flowing erosion–corrosion
Summary
Noble, and expensive elements, Fe and Mn are the 4th and 12th most abundant elements in the earth’s crust, respectively, and a ferrous alloy containing high quantities of Mn was developed under the name of Hadfield steel in the late nineteenth century[1]. API X70 was more vulnerable to erosion–corrosion than H_Mn. The other noticeable feature was that the contribution of EC to VT was comparatively higher in the Mn-bearing alloy samples.
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