Corrosion Behavior Of High Entropy Alloy Research Articles

Minor tungsten addition enhances corrosive resistance in CoCrFeNi high-entropy alloy at elevated seawater temperature

Most research on the corrosive CoCrFeNi high-entropy alloy (HEA) has mainly modulated element species and atomic concentration recently. However, the corrosive resistance of the passive film in the elevated temperatures environment inevitably need to be extensively explored for application. In this work, the microstructure and corrosion behavior in the elevated temperatures of face-centered cubic (FCC) CoCrFeNiWx (x = 0 and 0.2) HEAs are investigated. The mechanism of passivation layers on the corrosion behavior of HEAs is further discussed for comparison to the alloy of addition tungsten. Through potentiodynamic polarization curves in 3.5 wt% NaCl solution from 25 °C to 70 °C, the addition of tungsten can raise the critical pitting temperature, while maintaining a lower passivation current density and a larger passivation range at the same time. The high resolution X-ray photoelectron spectrometer (HRXPS), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) are all conducted to analyze the passivation composition and chemical reaction of the present alloys detailly. The CoCrFeNiW0.2 HEA exhibits the uniform Cr2O3 layer on the FCC matrix; the proportion of dispersive WO3 layer on the μ phase precipitates form a double-layer passive film under elevated temperature in 3.5 wt% NaCl. It shows that the synergistic effect of the double-layer passive film significantly enhances the pitting and corrosive resistance in this HEA.

Machine learning-assisted prediction and interpretation of electrochemical corrosion behavior in high-entropy alloys

In this study, machine learning (ML) models were successfully employed to predict the short-term electrochemical corrosion behavior of high-entropy alloys (HEAs) based on their chemical compositions. Considering the vast compositional space of HEAs, which restricts the development of corrosion-resistant HEAs, and the lack of non-destructive methods to qualitatively assess their corrosion resistance, this work represents a significant advancement in the field. The “three-step” method was applied to select the optimal feature set from 38 features, and six ML regression models were trained and compared. The eXtreme Gradient Boosting (XGBoost) and Gradient Boosting Decision Tree (GBDT) algorithms demonstrated the highest predictive accuracy (R2 = 81.02 % and 84.64 %, respectively) among the six algorithms. The model’s robust generalization capabilities were confirmed through validation on an additional dataset. Moreover, the interpretability of the model was enhanced by employing two analysis methods, which revealed that pH as an environmental factor, electronegativity difference and average electronegativity as empirical parameters, and the concentrations of Cr and Cu as compositional parameters have the most significant impact on the corrosion resistance of HEAs. The proposed methodology and framework have the potential to optimize alloy composition, facilitating the design and development of new corrosion-resistant HEAs.

Passive film and surface characterization of Alx(CoCrFeNi)100-x (x = 0, 5, 10, 15, 20) high entropy alloys

The current research on the corrosion resistance of high entropy alloys (HEAs), mainly focuses on the influence of element composition and percentage difference. Considering the almost consistent passivation range with different corrosion resistance contributed by element addition, it inevitably exists obvious differences the passive film properties. The effect of passive film on corrosion behavior of HEA is worthy to be investigated in detail. Considering the microstructure transformation detected by electron probe X-ray microanalysis (EPMA) and surface feedback effect measured by approach curve of scanning electrochemical microscopy (SECM), the passivity of Alx(CoCrFeNi)100-x (x = 0–20) HEAs in 0.5 M H2SO4 solution has been investigated by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the passive film is thick and dense at low Al content (5%), which shows excellent corrosion resistance. However, with the increase of Al content, the corrosion resistance of passive film deteriorates gradually. XPS are adopted to detect film composition to explain the reason of film property change. The results suggest that there are more oxidized states of Al and less oxidized states of Cr in the passive film of HEAs with Al addition. The dominate semiconductor characteristics of Alx(CoCrFeNi)100-x with Al addition change from p-type to n-type. All results indicate that the addition of Al has a significantly influence on the composition and properties of passive film on the Alx(CoCrFeNi)100-x alloys surface.

Corrosion behavior of NbxCu0.3Cr2Fe2Ni3Mn2 high-entropy alloys in HNO3 solution

NbxCu0.3Cr2Fe2Ni3Mn2 (x = 0, 0.2, and 0.4; named Nb0, Nb0.2, and Nb0.4, respectively) high-entropy alloys (HEAs) were prepared using arc melting process. The effect of Nb content on the microstructure and corrosion behavior of HEAs in HNO3 solution was studied. Nb0 and Nb0.2 alloys are composed of a single FCC phase, whereas Nb0.4 alloy is composed of FCC + Laves phase. In 10% and 30% HNO3 solutions, the immersion corrosion rate and potentiodynamic polarization corrosion rate of the HEAs showed a trend of first increasing and then decreasing with the increase in Nb content. After 30 days of immersion corrosion, Nb0.4 alloy exhibited the lowest average corrosion rate in 10% and 30% HNO3 solutions, with values of 4.6 × 10−3 and 2.8 × 10−3 mm/yr, respectively. Potentiodynamic polarization corrosion showed that Nb0.4 alloy also had the lowest corrosion current density and average corrosion rate in 10% and 30% HNO3 solutions, with values of 1.74 × 10−5, 5.56 × 10−6 A/cm2 and 0.18, 0.06 mm/yr, respectively. In addition, The Rpo of Nb0.4 alloy are 91 times and 8737 times higher than those of Nb0 alloy, respectively, and has the largest relative thickness of the passivation film. Therefore, Nb0.4 alloy exhibited the best resistance to HNO3 corrosion, mainly because adding Nb reduced the segregation of Cu, thereby weakening the corrosion effect of the primary battery. Meanwhile, Nb could play a stabilizing role in the passivation film of the alloy. The formation of corrosion-resistant Laves phase also correspondingly improved the HNO3 corrosion resistance of the alloy.

Effect of alloying elements (Mn, Ti, and Mo) on the corrosion behavior of FeCoNiCr-based high entropy alloy in supercritical water

The effect of alloying elements, Mn, Ti, and Mo, on the corrosion behavior of FeCoNiCr-based high entropy alloy (HEA) in supercritical water was investigated. The corrosion resistance of the HEA was enhanced by adding Mo while reduced with the addition of Ti and Mn. The segregation of Ti and Mo resulted in the formation of oxide films that were both structurally and chemically heterogeneous. Grain boundaries accelerated the diffusion rate of Mn, leading to the formation of MnCr2O4 oxide scales decorated with Mn2O3 particles. In addition, the governing mechanisms of alloying elements on the corrosion behavior of HEAs were also discussed.

Mechanical and Corrosion Behavior of Zr-Doped High-Entropy Alloy from CoCrFeMoNi System.

The aim of the paper is to study the Zr addition effect on the mechanical properties and corrosion behavior of a high-entropy alloy from the CoCrFeMoNi system. This alloy was designed to be used for components in the geothermal industry that are exposed to high temperature and corrosion. Two alloys, one Zr-free (named Sample 1) and another one doped with 0.71 wt.% Zr (named Sample 2), were obtained in a vacuum arc remelting equipment from high-purity granular raw materials. Microstructural characterization and quantitative analysis by SEM and EDS were performed. The Young modulus values for the experimental alloys were calculated on the basis of a three-point bending test. Corrosion behavior was estimated by linear polarization test and by electrochemical impedance spectroscopy. The addition of Zr resulted in a decrease in the value of the Young modulus but also in a decrease in corrosion resistance. The beneficial effect of Zr on the microstructure was the grain refinement, and this ensured a good deoxidation of the alloy.

Corrosion Behavior of High Entropy Alloys and Their Application in the Nuclear Industry—An Overview

With multiple principal components, high entropy alloys (HEAs) have aroused great interest due to their unique microstructures and outstanding properties. Recently, the corrosion behavior of HEAs has become a scientific hotspot in the area of material science and engineering, and HEAs can exhibit good protection against corrosive environments. A comprehensive understanding of the corrosion mechanism of HEAs is important for further design of HEAs with better performance. This paper reviews the corrosion properties and mechanisms of HEAs (mainly Cantor alloy and its variants) in various environments. More crucially, this paper is focused on the influences of composition and microstructure on the evolution of the corrosion process, especially passive film stability and localized corrosion resistance. The corrosion behavior of HEAs as structural materials in nuclear industry applications is emphasized. Finally, based on this review, the possible perspectives for scientific research and engineering applications of HEAs are proposed.

Corrosion Behavior of CoCrFeMnNi High-Entropy Alloys (HEAs) Under Aqueous Acidic Conditions

The corrosion behavior of high-entropy alloys (HEAs) from the CoCrFeMnNi family was evaluated in CO2 containing 3.5 weight percent sodium chloride (NaCl) at pH 4 and temperature of 40°C by electrochemical and immersion methods. Their corrosion parameters were compared to those of Hastelloy® C276 (UNS N10276) and stainless steel 316L (UNS 31600). Corrosion rates were determined by weight loss analysis and corrosion current methods for each of the alloys. During immersion testing experiments, HEA-1 (high Cr content) had the lowest corrosion rate and HEA-8 (no Cr content) underwent metal dissolution and exhibited the highest corrosion rate. On the other hand, after potentiodynamic polarization measurements, significant pitting corrosion was developed on the surface of all the alloys except HEA-8 and C276, where scanning electron microscopy (SEM) analyses depicted general corrosion. HEA-6 exhibited the lowest corrosion rate while HEA-2 had the highest. Scanning electron microscopy (SEM) analyses of the corroded surfaces after electrochemical testing revealed that HEA-8 underwent general corrosion while the rest of HEAs and stainless steel 316L underwent pitting corrosion. X-ray diffraction (XRD) on immersion testing samples revealed the presence of oxide-rich phases in formed corrosion products of HEA-8.

Alloying and Processing Effects on the Aqueous Corrosion Behavior of High-Entropy Alloys

The effects of metallurgical factors on the aqueous corrosion behavior of high-entropy alloys (HEAs) are reviewed in this article. Alloying (e.g., Al and Cu) and processing (e.g., heat treatments) effects on the aqueous corrosion behavior of HEAs, including passive film formation, galvanic corrosion, and pitting corrosion, are discussed in detail. Corrosion rates of HEAs are calculated using electrochemical measurements and the weight-loss method. Available experimental corrosion data of HEAs in two common solutions [sulfuric acid (0.5 M H2SO4) and salt water (3.5 weight percent, wt.%, NaCl)], such as the corrosion potential (Ecorr), corrosion current density (icorr), pitting potential (Epit), and passive region (ΔE), are summarized and compared with conventional corrosion-resistant alloys. Possible directions of future work on the corrosion behavior of HEAs are suggested.