Electrochemical Corrosion Performance Research Articles

Evaluating the effect of Si and Mg addition on the corrosion performance of gravity-cast Al-12Ce alloys in NaCl solutions

The present investigation assesses the immersion and electrochemical corrosion performance of gravity-cast Al-12Ce and Al-12Ce-X alloys (X = 0.4Mg, 4.0Si, and 4.0Si+0.4Mg, all in wt.%) targeted for diesel engine applications in 0.1M and 3.5wt.% NaCl solutions for the first time. The findings revealed that the Al-12Ce-4Si alloy exhibited highest weight loss (+107%), while Al-12Ce-0.4Mg alloy illustrated the lowest weight loss (-26%) compared to Al-12Ce alloy in both solutions. With increasing exposure time from 0 to 168hours, the open circuit potential (OCP) of the alloys increases, being lower in 3.5wt.% NaCl compared to 0.1M NaCl. Among all the alloys, the Al-12Ce-0.4Mg alloy displayed the lowest double layer capacitance, highest charge transfer resistance, and highest film resistance in both NaCl solutions, indicating its superior corrosion resistance. The current density and electrochemical corrosion rates were the highest for Al-12Ce-4Si alloy and lowest for Al-12Ce-0.4Mg alloy, highlighting the highest corrosion resistance of Al-12Ce-0.4Mg alloy. Corrosion rates of all the alloys were higher in 3.5wt.% NaCl than in aqueous 0.1M NaCl. Cracking and pitting was most severe in Al-12Ce-4Si alloy and least in Al-12Ce-0.4Mg alloy. The α-Al phase adjacent to the CeAlSi2 phase in Al-12Ce-4Si alloy was highly corroded, while the α-Al phase adjacent to Al11Ce3 in Al-12Ce-0.4Mg alloy was less corroded.

High-speed laser-directed energy deposition of crack-free wear-resistant and anti-corrosive Al/Cu bimetal components

ABSTRACT Al/Cu bimetal components (BMCs) possess higher thermal conductivity, better wear resistance and corrosion resistance than Al and Al alloys. It is a big challenging task to fabricate a high-performance Al/Cu BMC by a conventional infrared (IR) laser-directed energy deposition (L-DED) process due to the crack formation and high IR laser reflectivity. A novel high-speed L-DED process was proposed to successfully fabricate a crack-free Al/Cu BMC by controlling the residual stress distribution and brittle intermetallic compounds (IMCs) formation. The damaging effect of the reflective IR laser rays on the laser equipment can also be suppressed. Compared with the Al base metal, the microhardness, wear and electrochemical corrosion performances of the Al/Cu BMC were significantly improved. The residual stress distribution was predicted and measured. The IMC formation mechanism was revealed based on element distributions, the formation energy and the effective heat of formation of each IMC. The study would provide the basis for manufacturing crack-free and high-performance multi-material components in many applications in different industries.

Effects of Laser Oscillation Frequency on the Microstructure and Properties of TiC/Fe‐Based Alloy Composite Coatings

Herein, TiC/Fe‐based alloys are melted and deposited on a 45‐steel substrate by using an oscillating laser with an 8‐shaped trajectory. Four samples are prepared to investigate the phase changes and microstructure characteristics using laser cladding under different oscillation frequencies. The microhardness, wear resistance, and electrochemical corrosion performance on both substrate and coatings are thoroughly evaluated. The results show that with TiC particles uniformly distributed throughout the coatings, the cladded coatings primarily composed of α‐Fe, (Cr, Fe)7C3, M2B (Cr, Fe), and TiC phases contribute to refined grains and enhanced mechanical strength; additionally, an increase in oscillation frequency leads to further grain refinement, which significantly improves the microhardness of coatings; however, higher hardness does not guarantee better wear resistance; the presence of cracks can actually decrease the coating's durability against wear. It is found that the coating with an oscillation frequency of 200 Hz not only achieves the best wear resistance, but also exhibits excellent electrochemical performance.

Molecular dynamics mechanism of incorporating ZnO with varying particle sizes into ECTFE coatings and its impact on corrosion resistance

A composite coating of zinc oxide/chlorotrifluoroethylene copolymer (ZnO/ECTFE) was prepared on the surface of carbon steel via electrostatic spraying and heat treatment at 260 ℃. The influence of ZnO particle size variations on the anticorrosive properties of ECTFE coating was investigated by characterizing the microstructure, adhesion, hydrophilic/hydrophobic properties, electrochemical corrosion performance, as well as the dynamics simulation analysis on water molecule and chloride ions diffusion in the coating. The results show that the ECTFE coating incorporated with 100nm ZnO has the highest surface roughness (Roughness coefficient Ra = 30.6nm), the most robust adhesion (Bonding pull-out strength = 5.22MPa), and the lowest corrosion current density after a 90-day immersion (Icorr,90d = 4.05 × 10⁻⁸ A∙cm⁻²). These improvements represent an increase of 81.67% and 59.9% compared to the pure copolymer coating (Icorr,90d = 2.21 × 10⁻⁷ A∙cm⁻²) and the coating incorporated with 200nm ZnO (Icorr,90d = 1.01 × 10⁻⁷ A∙cm⁻²), respectively. This phenomenon can be attributed to the addition of small-sized ZnO, which enhances the density of the coating, induces a hydrophobic transition on its surface, strengthens the double electric layer effect, thereby improving its resistance against water molecule and chloride ions diffusion and ultimately enhances the corrosion resistance.

Effect of temperature on the electrochemical corrosion behavior of X52 pipeline steel in NS4 simulated solution

In this study, the electrochemical corrosion performance of both the base material and welded joint of X52 pipeline steel was analyzed at various temperatures (room temperature-RT, 30 °C, 50 °C, and 80 °C) using microscopic characterization techniques and electrochemical methods in a simulated soil solution (NS4). Additionally, the influence of temperatures on the electrochemical corrosion behavior of the X52 pipeline steel base material and welded joint was examined. The findings indicate that the open circuit potential (Eocp) of the base material and welded joint shifts in the negative direction with increasing temperature. The corrosion current density increased from 30.7 to 110.2 μA∕cm2 and from 19.5 to 100.2 μA∕cm2, respectively, while the polarization resistance dropped from 637.3 to 272.6 Ω•cm2 and from 961.3 to 360.7 Ω•cm2. Notably, anodic dissolution controls the corrosion process of the base material and welded joint of X52 pipeline steel at room temperature. Furthermore, the charge transfer resistance (Rt) of the base material and welded joint gradually decreases with increasing temperature, and the corrosion process transforms into cathodic diffusion control. Additionally, the welded joint of X52 pipeline steel exhibits superior corrosion resistance to that of the base material at the same temperature.

Microstructure, mechanical behavior, and cavitation erosion-corrosion resistance of the BCC/B2 strengthened FeNiCrMoAl-based multi-principal element alloys

The influence of disordered and ordered body-centered cubic (BCC-β and B2-β′) secondary phases on the mechanical properties and cavitation erosion-corrosion (CE-C) behavior of BCC/B2 strengthened FeNiCrMoAl-based multi-principal element alloy (MPEA) was systematically investigated. An increased β/β′ phases content enhanced the MPEAs’ strengths while maintaining good ductility. However, this increases also led to a higher proportion of loosely bound Al2O3 within the passivation film, resulting in a slight reduction in electrochemical corrosion performance. Remarkably, in a NaCl solution, the increased β/β′ phases significantly improved the MPEAs’ resistance to CE-C, attributed to the outstanding corrosion resistance and mechanical properties which could withstand elastic strain damage and plastic deformation.

Electrodeposition fabrication of corrosion−resistant Ni–based composite film on surface of Cu: Role of conductive YSZ and non−conductive Si3N4 nanoparticles

The Cu materials are playing an irreplaceable role in modern marine facilities, while one major issue affecting their service life is corrosion attack caused by external erosion of chloride ions, which leads to the quickly structural deterioration and reduced durability. To solve this obstinate issue, the corrosion−resistant Ni−based composite films with conductive Yttria–stabilized zirconia (YSZ, 2.5–15 g/L) and non−conductive Si3N4 (2.5–15 g/L) reinforcing phases were composite–electrodeposited on Cu substrate in direct current (DC) mode. It was believed that the electrical differences of incorporated nanoparticles have a significant impact on nucleation and growth behaviors during electrodeposition, which further altered the structure and property of Ni−based composite films. Therefore, the emphasis of this study was to establish the correlation between obtained structure, electrochemical, and immersion corrosion performances at different incorporation levels of YSZ/Si3N4 nanoparticles. The results demonstrate that by increasing the total doping contents, the Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) measurements exhibited an initial increase followed by a subsequent decrease on co−deposition dynamics, which was related to the dominant impact of conductive YSZ nanoparticle at electrocrystallization process. Meanwhile, the moderate incorporation level of 15 g/L offered effective control over structural compactness through dispersion−strengthening and grain−refining, and the same ratio of YSZ/Si3N4 nanoparticles further maximized the improvement degree of microhardness, electrochemical passivation, and immersion stability of resulting films. Besides, the corrosion current density (jcorr) of Ni−YSZ−Si3N4 composite coating under optimum condition of 15 g/L was two orders of magnitude smaller than that of Cu substrate after long−term immersion test, and the corresponding polarization resistance (Rp) also increased by 8.6 times. Overall, these substantial alterations obtained provide effective guideline for the design and preparation of corrosion−resistant Ni−based composite coating, which is beneficial to prolonging the service life of Cu components in saline environments.

Effect of Tempering Temperature on the Aqueous Corrosion Resistance of 9Cr Series Heat-Resistant Steel

In this investigation, the aqueous corrosion resistance of 9Cr series heat-resistant steel during tempering was investigated. Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrometer (EDS) were used to analyze the effect of tempering temperature on the microstructure and precipitation behavior of precipitates. The heat-resisting steel was heated to 1150 °C for 1 h, and then tempered at different temperatures between 680 °C and 760 °C for 2 h. The microstructure of the heat-resistant steel after tempering was composed of lath-tempered martensite and fine precipitates. The hardness decreased with increasing tempering temperature, ranging from HBW 261 to HBW 193. The aqueous corrosion resistance improved as the tempering temperatures increased from 680 °C to 720 °C but deteriorated at higher temperatures, such as 760 °C, which was obtained by an electrochemical corrosion performance test. The aqueous corrosion resistance was affected by the decrease in dislocation density and the decrease in Cr solution in the tempered martensite. With the increase in the tempering temperature, the aqueous corrosion potential first increases and then decreases, the self-corrosion current density first decreases and then increases, and the polarization resistance first increases and then decreases. Furthermore, the increase in corrosion resistance is attributed to the reduction in dislocation density and chromium depletion in the martensitic structure as the tempering temperature approaches 720 °C. This paper reveals the effect of tempering temperature on the corrosion resistance of 9Cr series heat-resistant steel, which is a further exploration of a known phenomenon.

Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating by temperature field-assisted laser cladding

The CrMnFeCoNi high entropy alloy coatings were prepared on the surface of Q345 steel using a temperature field-assisted laser cladding process, and the effects of the applied temperature field on the cladding coatings were studied. The microstructures and corrosion morphologies of the coatings were observed, and the elemental distribution, hardness, effective elastic modulus, electrochemical corrosion performance, and corrosion products of different coatings were analyzed. The results show that the porosity of the HEA coatings prepared with a temperature field is reduced to below 50 % of the initial level. The microstructure of the coating changed, with the nanoindentation hardness of the coating increasing by up to 0.55 GPa, enhancing the mechanical properties. Among all the coatings, the coating prepared at 250 °C temperature field exhibited the best corrosion resistance, with corrosion potential and current density of −0.27 V and 0.15 μA/cm2, respectively, improving the corrosion potential by 0.1 V and reducing the current density by 1.08 μA/cm2 compared to the sample prepared at room temperature. After incorporating the temperature field, the stability of the passive film on the coating during corrosion improved, and the nucleation rate of pitting decreased. Therefore, incorporating an appropriate temperature field during laser cladding can effectively enhance the overall performance of the CrMnFeCoNi HEA coating.

Mitigating adverse effects of Cu-containing intrauterine devices using a highly biocompatible Cu[sbnd]5Fe alloy

Copper-containing intrauterine devices (Cu-IUD) are adopted by worldwide women for contraception with the advantages of long-term effectiveness, reversibility and affordability. However, adverse effects occur in the initial implantation stage of Cu-IUD in uterine because of the burst release of Cu2+. To minimize the burst release, in this study, we designed a series of Cu–Fe alloys with 0.5 wt%, 1 wt% and 5 wt% Fe and also further produced ultrafine grained (UFG) structure for these alloys via equal-channel angular pressing. The microstructures and properties of the coarse grained (CG) Cu, CG Cu–Fe alloys and UFG Cu–Fe alloys were systematically investigated, including grain structure and phase compositions, metallic ions release behavior, electrochemical corrosion performance, and in vitro cytotoxicity. With careful comparison and selection, we chose the CG Cu–5Fe and UFG Cu–5Fe for in vivo tests using rat model, including tissue biocompatibility, in vivo corrosion behavior, and contraceptive effectiveness. Moreover, the corrosion mechanism of the Cu–5Fe alloy and its improved biocompatibility was discussed. Both CG and UFG Cu–5Fe alloys exhibited dramatic suppression of Cu2+ release in simulated uterine fluid for the long-term immersion process. The in vivo tissue compatibility was significantly improved with both CG and UFG Cu–5Fe alloys implanted in the rats’ uterine while the high contraceptive efficacy was well maintained. Due to the superior biocompatibility, the CG and UFG Cu–5Fe alloys can be the promising candidate material for Cu-IUD. Statement of significanceA highly biocompatible Cu–Fe alloy was designed and fabricated for Cu-containing intrauterine devices (Cu-IUD). With 5 wt% Fe, the burst release of Cu2+ is inhibited due to the formed galvanic cell of Cu and Fe, resulting in earlier release of Fe3+. As Fe is the most abundant essential trace element of human body, it can mitigate the toxic effects of Cu2+, thus significantly improving both in vitro cell compatibility and in vivo tissue compatibility. More importantly, the Cu–5Fe alloy exhibits 100 % contraceptive efficiency as the CG Cu, but with greatly reduced adverse effects to the uterus tissues. An advanced Cu-IUD can be developed using Cu–Fe alloys.

Corrosion resistance of pressure/pressureless sintered cemented carbides with/without graphene oxide in NaOH solution

The electrochemical corrosion performance of WC-Co hard alloy was studied under pressure/pressureless sintering and conditions with/without graphene oxide added. Three electrochemical testing methods were used to evaluate the corrosion behavior: open circuit potential, electrochemical impedance spectroscopy, and dynamic potential polarization. The corrosion resistance of the alloy was compared using three parameters of corrosion potential, corrosion current density, and total impedance. The corrosion mechanism was studied by observing the surface morphology of corroded alloy using scanning electron microscopy and analyzing the surface corrosion products using X-ray photoelectron spectroscopy. The results showed that pseudo-passivation phenomenon appeared in the potentiodynamic polarization curve of the hard alloy in the sodium hydroxide solution. The corrosion behavior was mainly controlled by anodic dissolution, with the dissolution of WC phase being greater than that of Co phase. The corrosion resistant properties of the pressure sintered cemented carbide are higher than that of the pressure-less sintered cemented carbide respectively in NaOH solution, mainly because pressure increases the grain size and decreases the grain boundaries of cemented carbide, which can be regarded as the dislocation wall between grains and normally attacked by the serious corrosion preferentially.

Microstructures, high-temperature tribological and electrochemical mechanisms of FeCoNiCrAl high-entropy alloy coating prepared by laser cladding on a copper alloy: Combined TEM and DFT calculation

Two layers of FeCoNiCrAl coatings were prepared on copper (Cu) alloys substrates in this paper in order to improve the wear and corrosion performance of Cu alloys and to reduce the dilution of Cu in the laser cladding (LC) process. The microstructures, phase composition, microhardness, and crystal structure of the resulting coatings were analyzed, and their high-temperature tribological and electrochemical properties were tested. The results show that the surface of the HEA coatings still consists of a single-phase body-centered cubic (BCC) with low Cu content, and no generation of a second phase was observed. Compared with the substrate, the FeCoNiCrAl HEA coatings have better wear resistance, with oxidative wear and slight adhesive wear as the wear mechanism at 250 ℃. In addition, the FeCoNiCrAl HEA coating showed better electrochemical corrosion performance in 3.5 wt% NaCl solution. The corrosion mechanism is that the dense oxide layers inhibit the erosion of Cl- and high reaction barriers slow down electrochemical reactions.

The electrochemical corrosion performance of aluminum alloys grade 6082-T6 weld repair

This research investigated the corrosion behavior of standard current metal inert gas weld repair for 6082-T6 aluminum alloy using ER5356 filler metal. The new and repaired (NW and RW) welds were studied. The welds comprised the weld metal (WM), the heat affected zone (HAZ) (solid solution and softened zones), and the base metal (BM). The study focused on investigating electrochemical corrosion using polarization and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solutions, especially in HAZ, including metallurgical and mechanical examinations. The BM containing an α-Al matrix with Al(Fe,Mn)Si and Mg2Si phases exhibited the maximum hardness (70–104 HV0.1). The WM hardness decreased (67–76 HV0.1) with the α-Al, β-Mg3Al2, and Mg2Si phases. Despite having comparable phases to BM, HAZs showed lower hardness (Solid HAZ: 70–82 HV0.1) due to more intermetallic phases. The RW’s softened HAZ revealed the minimum hardness (52–63 HV0.1) compared to that of the NW (55–70 HV0.1). Besides, the tensile strength of the RW (179.7 MPa) was also lower than that of the NW (174.4 MPa) because of the reheating effect. The electrochemical corrosion results indicated that the BM exhibited the maximum corrosion resistance (the lowest corrosion current density (icorr), the highest corrosion potential (Ecorr), and the charge transfer resistance (Rct)), followed by the HAZ and the WM, respectively. The softened HAZ demonstrated better corrosion resistance than the solid solution HAZ. Conversely, the over-aging effect reduced the softened zone’s pitting corrosion resistance (Ep) compared to the solid solution zone. The RW exhibited inferior corrosion resistance compared to the NW due to increased intermetallic phases, which was consistent with the mechanical results. However, the RW’s softened HAZ corrosion characteristics were inconsistent with its mechanical properties; its hardness and tensile strength were the lowest, but its corrosion resistance was not. Pitting corrosion was observed on the weld surfaces using the SEM.

Mechanical and Corrosion Properties of Super Austenitic Stainless Steel Joint for Double‐Sided Synchronous TIP TIG Arc Butt Welding

Super austenitic stainless steel 254SMO (254SMO SASS) plates are joined by double‐sided double‐arc synchronous TIP TIG butt welding (DSSTTABW) using ER NiCrMo3 wire, and the micro‐structure, mechanical and corrosion properties of 254SMO SASS joints are investigated subsequently. Results show that solidification grain boundary and solidification sub‐grain boundary can be observed in fusion zone. A small amount of σ phase precipitates in the weld, while χ phase is found in the transition zone, but no solidification crack occurs in weld and heat affected zone (HAZ). 254SMO SASS joint has higher micro‐hardness and lower tensile strength and elongation compared to base metal. During transverse tensile process, 254SMO SASS joints fail in the weld zone in a ductile mode. Electrochemical corrosion performance tests indicate that 254SMO SASS joint achieve equivalent pitting corrosion resistance and similar passive mechanism to base metal in 3.5 wt% NaCl solution. The passivation film on the surface of both joint and base metal display as n‐p semi‐conductive character, but the film stability of 254SMO joint surface is slightly poorer compared to base material. The surface passivation film of 254SMO joint primarily consists of oxides of Fe, Cr, and Mo before potentiodynamic polarization, while hydroxides of Fe and Cr are also observed after polarization.

Preparation and Electrochemical Corrosion Performance of Plasma-Sprayed NiMoCrFeW Coatings

Preparation and Electrochemical Corrosion Performance of Plasma-Sprayed NiMoCrFeW Coatings

The semi-continuous (Mg,Al)2Ca second phase on Mg-Al-Ca-Mn alloys as an efficient anti-corrosion anode for Mg-air batteries

Developing high anti-corrosion and good discharge properties of magnesium based alloys for Mg-air batteries is still in challenge. In this work, a series of Mg-Al-Ca-Mn (AMX) alloys are prepared, and the second phases on AMX alloys are adjusting by varying the Al content. The AMX alloys with 3 wt% Al (denoted as AMX311) exhibits the excellent anti-corrosion behavior with a corrosion current density of 85.7 μA cm−2 and a low corrosion rate (4.1±0.21 mm y−1) in the 3.5 wt% NaCl solution. Furthermore, AMX311 shows lower hydrogen evolution volume (20.9±1 ml/cm2) and weight loss (5.8±0.3 mg) compared to other contrast samples. The outstanding electrochemical corrosion performance of AMX311 is attributed to the Al-rich oxide film which slowing corrosion at the initial stage and the formation of semi-continuous (Mg,Al)2Ca phase which can acts as a physical barrier to prevent the electrolyte from further corroding the magnesium matrix. Moreover, the AMX311 exhibits the highest discharge voltage (-1.471 V) and a peak specific energy of 1684.7±30.0 mW h g−1 at 20 mA/cm2, due to its superior corrosion resistance and reduced chunk effect. This work provides a good guide for designing advanced Mg-based alloys and an excellent insight into the effect of second phase on the corrosion and discharge performance of Mg-air batteries anode materials.

Analysis of electrochemical corrosion performance of 316L stainless steel fabricated and textured by selective laser melting

Textured surfaces were used to increase the electrochemical corrosion resistance of the laser powder bed fusion, corrosion performance, DC corrosion and electrochemical impedance spectroscopy techniques were examined. Corrosion resistance could be optimized as a result of changing the surface energy on modified surfaces and eliminating selective laser melting (SLM)-induced morphological discontinuities. The corrosion resistance of optimum textured surfaces is higher than that of forged samples. Results close to texture-free surface performance were obtained on surfaces where texture density reached maximum. Increasing texture weakened the corrosion resistance. Thus the best corrosion resistance; icorr = 156 nA/cm2 with Ecorr = −327 mV observed at 5CR. Material losses are 49.40 mpy × 10−3 for 5CR, 63.48 mpy × 10−3 for 5SQ, 382.60 mpy × 10−3 for 15CR, 63.33 mpy × 10−3 for 15SQ, 394.6 mpy × 10−3 for 25CR and 174.80 mpy × 10−3 for 25SQ, respectively. The highest performance in terms of material losses was found to be 5CR. No significant change in the context of texture geometry was observed in the SEM images. According to quantitative evaluation in electrochemical corrosion tests, the differences are quite close to each other.

A novel wear-resistant and corrosion-resistant Mo2NiB2–Ni cermet coating prepared using fast hot pressing sintering

A new fast hot pressing (FHP) sintering method was used to prepare Mo2NiB2–Ni cermet coating to solve the problems of small scale and high energy consumption in the production. The synthetic phase and microstructure of the Mo2NiB2–Ni cermet coating were studied, and friction and wear as well as electrochemical corrosion performance were also tested. The results indicated that the Mo2NiB2–Ni cermet coating was composed of two phases, the Mo2NiB2 hard phase and the Ni metal-bonded phase. A metallurgical bond interface resembling interlocking teeth was formed between the Mo2NiB2–Ni cermet coating and the stainless steel substrate, thereby enhancing the bonding strength of the interface. Compared with the Mo2FeB2–Fe cermet coating, the Mo2NiB2–Ni cermet coating had certain wear resistance and excellent corrosion resistance. The high hardness of the Mo2NiB2 hard phase, the low mutual solubility between the Ni metal-bonded phase and the Si3N4 balls, and the generated mechanical mixing layer reduced the friction coefficient and the adhesive wear, which improved the wear resistance. The higher open circuit potential and the formation of the passivation film during the corrosion process enhanced the corrosion resistance of the Mo2NiB2–Ni cermet coating.

CORROSION EVALUATION OF LPBF-MANUFACTURED DUPLEX STAINLESS STEEL

In this study, the effect of as built and heat-treated additively manufactured 2507 super duplex stainless steel (SDSS) on electrochemical corrosion performance was examined. The corrosion was studied by Tafel polarization and electrochemical impedance spectroscopy (EIS) methods in a 3.5% NaCl solution. For this purpose, the as-built and heat-treated printed samples (solution annealed and stress-relieved) were examined by LOM/SEM and X-ray diffraction to evaluate the phase changes of steel at different processing stages. The correlation between corrosion resistance, structure, and heat treatment was assessed. As a result of the very fast cooling rate of the LPBF process, SDSS reveals ferrite as the major phase in the printed samples. To enhance the corrosion resistance of LPBF-produced duplex stainless steel, it's crucial to balance its two-phase structure and minimize residual stresses. The ferrite grains are elongated in the build direction, with some austenite precipitation along the grain boundaries or as Widmanstatten laths. The stress-relieved and as-printed SDSS exhibits reduced corrosion characteristics by around 20% compared to the solution-annealed SDSS, according to anodic polarization curves. Based on EIS results, the solution-annealed SDSS revealed an almost double increase in corrosion resistance (based on charge transfer resistance values) compared to the as-printed and stress-relieved conditions.

Enhancement mechanisms of self-lubricating Ti3SiC2 ceramic doping in CoCrFeNi high-entropy alloy via high-speed laser cladding: Tribology and electrochemical corrosion

High-entropy alloys (HEAs) are renowned for their superior mechanical properties and corrosion resistance, positioning them as promising materials in the realm of wear and corrosion-resistant applications. In this study, CoCrFeNi HEA coatings were fabricated utilizing the high-speed laser cladding (HLC), and the effects of adding Ti3SiC2 self-lubricating phase on the microstructure, wear resistance, and electrochemical corrosion performance of CoCrFeNi HEA coatings was investigated. The results show that CoCrFeNi HEA coatings synthesized via HLC exhibit an impressively low dilution rate of <0.1 %, while concurrently ensuring a robust metallurgical bond with the substrate. CoCrFeNi coating has an FCC simple solid solution structure. Upon the addition of Ti3SiC2, the composite structure comprises FCC, Ti3SiC2, and TiC phases. The friction coefficients (COFs) of CoCrFeNi coating and the coatings with 3, 6, and 9 at.% Ti3SiC2 content are 0.684, 0.628, 0.429, and 0.426, respectively. Predominantly, the wear mechanisms observed encompass abrasive wear, adhesive wear, and oxidative wear. Intriguingly, when the Ti3SiC2 content reaches 6 at.%, a contiguous self-lubricating layer forms within the wear track, leading to a notable reduction in COF and a marked enhancement in wear resistance. In electrochemical corrosion evaluations, the coatings demonstrated polarization resistances of 11,400, 9923, 9654, and 6125 Ω·cm2, respectively. While Ti3SiC2 exhibits commendable passivation capabilities, an elevated Ti3SiC2 content can expedite corrosion processes by fostering a potential difference battery formation on the coating surface.