Abstract
The nanoindentation technique is widely used to measure the micro-scale mechanical properties of various materials. Herein, the nanoindentation-based micro-mechanical and electrochemical properties of low-carbon steel were investigated after quench hardening and tempering processes. The steel was produced on a laboratory scale and subjected to quench hardening separately in two different media-water and brine (10 wt% NaCl)-and subsequent moderate temperature tempering. Microstructure analysis revealed that the lath martensite phase formed after all heat treatments, having different carbon percentages ranging from 0.26% to 0.58%. A ferrite phase was also observed in the microstructure in three different morphologies, i.e., allotriomorphic ferrite, idiomorphic ferrite, and Widmanstätten ferrite. Nanoindentation analysis showed that the brine quench hardening process provided a maximum twofold improvement in indentation hardness and a 51% improvement in stiffness with a 30% reduction in reduced elastic modulus compared with as-received steel. Electrochemical performance was also evaluated in a 1% HNO3 solution. The water quench-hardened and tempered sample exhibited the highest corrosion resistance, whereas the brine quench-hardened sample exhibited the lowest corrosion resistance among all heat-treated samples.
Highlights
Carbon steels are extensively used in almost every industry, e.g., automotive, aerospace, and aircraft engineering [1], metal processing equipment, nuclear energy, marine energy, chemical processing, fossil fuel power plants, petrochemical processing [2,3], oil refineries, construction, mining, tanks, structures, piping, defense, reactor vessels, and heat-treating fixtures [4]
The following conclusions can be extracted from this work: Microstructures comprising a lath α’ phase with different carbon percentages ranging from 0.26%
To 0.58% and an α phase of different morphologies were achieved after all quench hardening and tempering processes. αal and αid phases were observed in both water and brine quench-hardened samples, and αw and αid phases in brine quench-hardened and tempered samples
Summary
Carbon steels are extensively used in almost every industry, e.g., automotive, aerospace, and aircraft engineering [1], metal processing equipment, nuclear energy, marine energy, chemical processing, fossil fuel power plants, petrochemical processing [2,3], oil refineries, construction, mining, tanks, structures, piping, defense, reactor vessels, and heat-treating fixtures [4]. Various advantages associated with this technique, including statistically rich data sets, easy experiment preparation [17], quasi-non-destructiveness, and the need for only a very small sample size, attract scientists and researchers [18] This technique has been utilized to evaluate the micro-mechanical properties of gaseous, low-temperature-carburized 316L stainless steel [19], the micro-plasticity properties of surface-hardened steels [20], the micro-yield stress profile of nitrided steel [21], multi-layered hardness in ion-irradiated steels [22,23], the mechanical stability of high-carbon steels [24], and the micro-mechanical properties of corrosion products of steel in concrete [25]. Electrochemical analysis was performed in 1 vol% HNO3 to evaluate polarization behavior and corrosion kinetics
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