Abstract
It is commonly known that precipitation of secondary phase in non-ferrous alloys will affect the mechanical properties of them. But due to the nature of dual-phase low-alloy high-carbon steel and its high potential of precipitation of cementite, there is limited study on tailoring the mechanical and corrosion properties of this grade of steel by controlling the precipitation of different phases. Predicting and controlling precipitation behaviour on this grade of steel is of great importance towards producing more advanced applications using this low-cost alloy. In this study the new concept of selective-precipitation process for controlling the mechanical and corrosion behaviour of dual-phase low-alloy high-carbon steel has been introduced. We have investigated the precipitation of different phases using in-situ observation ultra-high temperature confocal scanning laser microscopy, image analyser – ImageJ, scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and electron probe microanalysis (EPMA). Volume fraction of each phase including retained austenite, martensite and precipitated phases was determined by X-ray diffraction (XRD), electrochemical corrosion test by Tafel extrapolation method and hardness performance by nanoindentation hardness measurement. The experimental results demonstrated that, by controlling the precipitations inside the matrix and at grain boundaries through heat treatment, we can increase the hardness of steel from 7.81 GPa to 11.4 GPa. Also, corrosion resistance of steel at different condition has been investigated. This new approach will open new possibility of using this low-cost steel for high performance applications.
Highlights
It is commonly known that precipitation of secondary phase in non-ferrous alloys will affect the mechanical properties of them
Population and size of secondary phase precipitations can strikingly influence the corrosion resistance and hardness properties of high-carbon steels. It is very likely for manganese sulphide (MnS) precipitations to be generated during solidification process of steel, due to very low solubility between S and Fe elements at room temperature[12]. Other inclusions formations such as MnC formation in the steel is considerably unavoidable as the C content in high-carbon steel is relatively high, this can cause Mn and C to form manganese carbide (MnC) that mainly corresponds to different temperature, activity and diffusivity of C
In the current work we have investigated the influence of selective-precipitation process under different heat treatment condition
Summary
It is commonly known that precipitation of secondary phase in non-ferrous alloys will affect the mechanical properties of them. Population and size of secondary phase precipitations can strikingly influence the corrosion resistance and hardness properties of high-carbon steels It is very likely for MnS precipitations to be generated during solidification process of steel, due to very low solubility between S and Fe elements at room temperature[12]. Other inclusions formations such as MnC formation in the steel is considerably unavoidable as the C content in high-carbon steel is relatively high, this can cause Mn and C to form manganese carbide (MnC) that mainly corresponds to different temperature, activity and diffusivity of C. By changing the population and size of formed MnS, Fe3C and MnC inclusions through different heat treatment approach, high-carbon low-alloy steel with the same composition but different hardness and corrosion properties has been produced. Each phase volume percentage – retained austenite, martensite, MnS and MnC inclusions, was resolved by X-ray diffraction (XRD), electrochemical measurements by Tafel extrapolation method and hardness properties by nanoindentation hardness test
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