Metallographic Research Articles

Preparation of enhanced erosive wear resistance SiC-fiber-reinforced SiC ceramic matrix composites integrated with a knit fabric via high temperature crystallization of amorphous Si–C–O–Al fibers

We report the enhanced erosive wear resistance of SiC/SiC CMCs that were integrated with a knit fabric via high-temperature crystallization of relatively inexpensive first-generation (amorphous) fibers of Si–C–O–Al (AM; short for Tyranno™ AM) for use as sliding components. A pyrocarbon (PyC) interface was formed via dip coating in liquid phenolic resin, and matrix densification was achieved by hot pressing at 1900 °C for 1 h at 30 MPa. The PyC-coated AM fibers exhibited low tensile strength values at temperatures below 1600 °C, which increased significantly at 1900 °C (2.68 ± 0.74 GPa). The hot-pressed AM-SiC/SiC CMCs exhibited typical quasi-ductile fracture in a three-point bending test. The erosive wear of the CMCs was investigated using a slurry erosion test, and the associated mechanism was clarified by laser-microscopy-based 3D profiling and scanning-electron-microscopy-based microstructural examination. The matrix of the hot-pressed AM-SiC/SiC CMCs was dense (1.99% porosity), rigidly structured, and hard (27.1 ± 2.91 GPa), enabling the CMCs to outperform conventional SiC/SiC CMCs in terms of slurry erosion resistance.

Mechanical Properties of Cu70Fe30 (at%) Bulk Metastable Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering

The equilibrium‐insoluble Cu and Fe metals with a composition of Cu70Fe30 (at%) are mechanically milled for 20 h, resulting in a metastable single‐phase face‐centered cubic supersaturated solid solution (γS). The alloy powders are consolidated by spark plasma sintering (SPS) at 0.6Tm (622 °C) and 0.7Tm (772 °C), where Tm is the melting point of Cu70Fe30 (1219 °C). Scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and electron backscatter (EBSD) analyses are performed on mechanically alloyed powders and SPS bulk samples. Compressive stress–strain and hardness tests are also conducted on the bulk SPS samples to evaluate the mechanical properties. The metallographic study reveals that the γS phase decomposes into Cu‐rich γ and Fe‐rich α phases after SPS. The 0.6Tm sample exhibits a continuous γ‐network phase surrounding an ultrafine γ + α mixture, causing brittle behavior due to crack propagation during compressive testing. In contrast, the 0.7Tm sample features a discontinuous γ‐network phase, enhancing ductility and resulting in a bimodal grain structure. This sample demonstrates superior mechanical properties, combining excellent strength (1056 MPa) and ductility (23%) due to the coexistence of coarser γ‐network grains (1–2 μm) and ultrafine γ + α grains (200–500 nm).

Improving gel properties of silver carp (Hypophthalmichthys molitrix) myosin with flavonols: Unveiling the advantages of isorhamnetin

This study explores the impact of flavonols (kaempferol, quercetin, kaempferitrin, and isorhamnetin) on the gel properties of myosin derived from silver carp (Hypophthalmichthys molitrix). Before employing a two-stage heating process, myosin samples are pretreated with flavonols, which enhance the structural stability of myosin and aid in the dispersion of myosin molecules. These pretreatments prepare the samples for subsequent thermal processing, where flavonols facilitate myosin unfolding and enhance intermolecular aggregation, thereby improving gel strength. This process also transforms free water within the gel to bound water, significantly increasing the water-holding capacity. Both macroscopic and microscopic rheological analyses suggest that flavonols, particularly isorhamnetin, notably enhance the elasticity and viscosity of myosin during the gelation process. Further, microstructural examinations employing techniques such as small-angle X-ray scattering and micro-computed tomography demonstrate that samples treated with flavonols develop denser and more uniform gel networks. Analytical studies reveal that flavonols, especially methylated derivatives like isorhamnetin, effectively promote gelation through strengthening hydrophobic interactions, disulfide bonds, and ionic interactions among myosin molecules. This research underscores the potential of flavonols as natural additives to enhance the quality and functional properties of surimi products, thereby elevating the processing standards of aquatic products.

Mechanical alloying of bronze with aluminum and nickel: Impact on corrosion resistance and hardness

The effect of alloying bronze with aluminum (Al) and nickel (Ni) on hardness and corrosion resistance is examined in this work. Bronze alloys were manufactured in vacuum induction melting (VIM) using 99.9 % pure copper as the main component. High-purity tin, aluminum, and nickel were added. This study examined the corrosion behavior of an Al and Ni-modified bronze alloy in a 3.5 % NaCl solution using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The corrosion resistance of the alloys was assessed, with findings indicating that Ni-bronze had the best corrosion resistance—nearly twice as much as bronze. Microstructural examinations and Rockwell hardness testing further revealed that nickel-bronze had the highest hardness values, owing to strong nickel intermetallic phases formed. This thorough analysis highlights how Ni-bronze alloys perform better in challenging conditions, which qualifies them for uses needing strong mechanical durability and resistance to corrosion.

Enhancing microstructural properties of copper-based composite castings through microwave-assisted reinforcement with MWCNT

An emerging advancement in the field of metallic materials casting is the in-situ microwave casting of metallic materials. To achieve this, the microwave heating process is applied within the applicator cavity, working on the principles of hybrid microwave heating (MHH). This process involves melting the charge, pouring it into an in-situ container, and subsequently solidifying the melted charge. The electromagnetic and thermal properties of the charge influence the interactions between the microwave energy and the material, as well as the melting behavior induced by the microwaves. As for the solidification process, this is also controlled by a cooling condition within the applicator. The present study aims to outline an in-situ casting process for copper-based composite castings fabricated within a multimode cavity, utilizing 900 W at 2.45 GHz. The quality of the developed in-situ cast was assessed by analyzing its characteristics. A microstructural examination revealed that the composite castings exhibited a homogeneous and dense structure. Scanning electron microscopy (SEM) and Energy-dispersive spectroscopy (EDS) analysis was conducted across the casting. The XRD pattern confirmed the presence of major peaks of copper in the composite castings, along with the presence of oxide phases such as Cu64O. Also, the micro indentation hardness of the Cu + 1.5%MWCNT casts was found to be 1.23 times higher than that of microwave-processed pure copper.

Analysis of GTAW and FCAW Welding in Impact Testing in Steel Micro Structures

Welded joints, which encompass the criteria of welding base metal connections in the material, welding speed, material quality, and material toughness, are an integral aspect of tank construction. Steel material joints frequently fail during the Gas Tungsten Arc Welding (GTAW) and Flux Cored Arc Welding (FCAW) welding procedures because air droplets become trapped in the steel material during the welding process. Finding the primary reasons for welding failures is the goal of this study. Impact and microstructure testing are used in the welding research method on SS400 steel. The FCAW welding process uses E71T-1C (Kobe) Electrodes Steel Familiarc AWS A5.2 E71T-1C) at varying currents of 80 A (Root), 100 A (Filler), and 120 A (Capping), against SS400 steel plate material with a thickness of 10 mm x 200 mm x 200 mm in V Buut seams Joints. The GTAW ER 70 SG (Familiarc Filler/Rods TG-S51T) Electrode classification allows for 90 A (Root), 110 A (Filler), and 120 A (Capping). Plate 1 has a value of 36.3 kJ/inch in the heat input calculation findings at the three section sites, while Plate 2 has the highest value of 61 kJ/inch. In the meantime, FCAW plate 2 has an impact strength value of 142.1 J, and plate 1 has an average hit in the test results at each of the three places of the specimen, according to the impact test findings. Three welding parameter points were used to record the findings of the metallographic testing's microstructure observations. plates 1 and 2 on the capping, filler, and root. being aware of the areas in the welded junction between plates 1 and 2 that are impacted by heat in the microstructure. Because of the material's strong heat input, which makes the steel brittle and promotes the formation of pearlite rather than ferrite, plate 2 has the highest value in the impact test

Electrochemical and microstructural characterization of a precipitation hardened 17-4 steel in different environments

In this study, an in-depth electrochemical characterization of a precipitation hardened 17-4 stainless steel (SS17-4PH) was carried out in combined acidic, alkaline, and chloride environments. The characterizations were carried out through polarization-EIS analysis, Mott-Schottky analysis to characterize the semiconducting properties of the thin oxide films, and a post-mortem scanning electron microscopy (SEM-EDX) analysis to reveal the morphologies after anodic polarization. The electrochemical measurements revealed that the corrosion rate of SS17-4PH samples in acidic-chloride solutions is higher than the sample polarized in only NaCl or NaOH solution. From the Mott Schottky results, the straight lines with a positive slope obtained for the steel samples in different test media show that there is no change in the semi-conducting properties of the passive film. For samples polarized in acidic-chloride medium, the microstructural examination revealed the formation of a foot-like pit and zig-zag degradation structure. This was attributed to the presence of acid in the test media, and the deposition of corrosion products on the sample surface.

Beneficial role of short-term aging on creep performance of cold-worked Ti-added 14Cr–15Ni stainless steel

The initial microstructure of cold-worked Ti-added 14Cr–15Ni stainless steel was modified through short-term aging and its influence on creep properties has been investigated at a test temperature of 973 K and two stress levels of 150 and 175 MPa. The improvement in rupture life of the condition comprising of post-aging was nominal at 175 MPa, but enhanced more than two times at 150 MPa when compared to the condition which comprised of prior cold work alone. Microstructural examination after creep testing showed that though M23C6 type of precipitates was prominent in both conditions, their size distribution varied with respect to processing condition (viz., one with prior cold work and another comprising of prior cold work followed by aging) as well as applied stress. Retention of cold work-induced dislocation structures aided by secondary TiC precipitates in the aged condition enhanced the rupture life at 150 MPa. Extensive recovery of the dislocation substructure was observed in the unaged condition tested at the same stress level. The size distribution of the dimples observed from the fractographs could be correlated with the extent of creep-induced cavitation. This work describes how the two preprocessing conditions influence the nucleation of M23C6 and secondary TiC precipitates during creep deformation.Graphical

The effect of post-bond heat treatment on microstructure and mechanical properties of a two-step heating transient liquid-phase bonding IN738LC

ABSTRACT This study evaluated the bonding of a Ni-based superalloy, Inconel 738LC, using two-step heating and conventional TLP bonding techniques using a foil of BNi-2 filler alloy with a thickness of 70 μm. The bonds were processed. The first step at 1160 °C for 1 min and the second step at 1120 °C for different isothermal solidification times (50, 65, 80, and 95 minutes), and the conventional TLP process at 1120 °C for 80 min. It was inferred from the results of microstructural examinations that the joints contained eutectic product constituents that formed an athermal solidified zone (ASZ) during the bonding time of 50 min. It was also found that 80 min was required to complete isothermal solidification in the two-step TLP bonding employed in this study, whereas isothermal solidification was incomplete in conventional TLP for 80 min. The time necessary to complete the isothermal solidification was lowered using two-step TLP bonding. The microstructure after being subjected to a two-stage postbond heat treatment, becomes close to the base metals. As a result, homogenizing microstructure forms throughout the joint. The heat-treated sample contained a much greater amount of the γ′ phase generated at the bond location, resulting in increased shear strength and hardness of the bond.

Development and Quality Enhancement of Fried Fish Cake Prototype with Transglutaminase, Trehalose, and Herbal Oil for Room Temperature Distribution.

This study focuses on developing a fried fish cake prototype with improved quality and extended shelf-life, enabling room-temperature distribution through an innovative high-temperature and high-process retort method. Surimi-based products typically necessitate cold storage and a refrigerated distribution system, affecting their physical properties and flavor while escalating costs. By incorporating Transglutaminase (TGase), trehalose, and herbal oils, and optimizing the heating process using the response surface methodology, this research addresses challenges related to changes in physical properties, color, and off-flavors during high-temperature and high-pressure treatment. The addition of 0.37% ACTIVA-K TGase significantly enhanced gel strength by promoting protein cross-linking, while 0.75% trehalose improved color stability by suppressing browning, thus enhancing visual appeal. A 0.1% concentration of bay oil effectively enhanced the flavor profile by masking undesirable odors without compromising the sensory quality. Optimized processing conditions maximized DPPH radical scavenging activity, whiteness, and gel strength, ensuring superior product quality and safety. Nutritional analysis confirmed a balanced composition of moisture, protein, essential amino acids, and minerals, in accordance with Korean national standards for acid values. Microstructural examination revealed a uniform network structure, contributing to excellent texture and sensory evaluations. Shelf-life predictions indicated a storage duration of approximately 19 months, surpassing commercially available products and offering a competitive edge. This novel approach allows surimi-based products to be stored and distributed at room temperature, while also providing the potential for increased profitability.

A novel multicomponent micro-alloyed magnesium for orthopaedic applications: a microstructural, mechanical, degradation and bioactivity study

ABSTRACT The current study focuses on development of magnesium based micro-alloy with the composition of Mg–0.5Zn–0.15Ca–0.1Mn–0.1Sn–0.1Ag–0.2Ce–0.2Sr using casting method. Microstructural examinations conducted using optical microscopy and scanning electron microscopy (SEM) unveiled a uniform grain distribution in the alloy with minimal intermetallic content, corroborated by X-ray diffraction (XRD) analysis matching the magnesium peak precisely. Tensile testing indicated that the solution strengthening process boosted the alloy’s required yield strength and stiffness, while enhancing magnesium’s ductility up to 19.07% elongation. Electrochemical tests demonstrated an outstanding corrosion resistance rate of 0.91 mm/year, supported by Nyquist plots indicating passivation behaviour and film formation. The pH variations revealed an initial spike to 8.13 within the first 24 hours, gradually declining thereafter. The bioactivity assessment of the developed alloy showcased the formation of near-stoichiometric apatite layers on the alloy surface, confirming its potential as a suitable orthopaedic implant material.

Microstructure Evolution of Super304H Steel Used in a Service Power Station Boiler.

The microstructure and structure of a Super304H superheater steel pipe after 47,000 h were analyzed by metallographic microscope, scanning electron microscope (SEM), and EDS, and its mechanical properties were measured by hardness meter. The results show that the austenitic grains appear on the outer wall of Super304H steel pipe after service, while the SEM and metallographic microscope tests show that the outer wall particles are coarse. There is an obvious corrosion layer on the outer surface, and the thickness of the corrosion layer on the windward surface is significantly higher than that on the leeward surface. The inner surface is refined and the hardness of the material is significantly increased; the outer surface, the inner surface, and the center all grow abnormally. In this case, the room temperature tensile strength and impact performance of the rough crystal area of the outer wall of the Super304H steel pipe are reduced and fracture along the crystal. Supervision should be strengthened to eliminate the safety risks caused by the abnormal growth of the outer wall austenite grain. The results of crystal phase microscopy show that the main structure of the material still maintains the basic structure of austenitic steel, and particle aggregation mainly occurs in the sub-inner layer of the inner and outer surface. Compared with the lee surface, the middle body structure is basically the same, but whether the thickness of the corrosion layer on the inner surface or the outer surface increases, the deformation degree of the deformation layer is greater. The hardness measurement finds that the hardness of the corrosion layer is caused by the increase in Super304H steel surface stress. In case of pipe explosion accident, the highest chance of pipe explosion here should be closely observed.

Anisotropy of acoustic properties in thin-sheet rolled low-carbon manganese steel

Thin-sheet rolled low-carbon manganese steel 09G2S with a thickness of 0,8 mm which has strong property anisotropy due to texture and residual stresses, was experimentally studied using SH-wave with horizontal polarization and zero-order symmetric Lamb wave mode. The velocities of elastic wave propagation along the sheet were analyzed as their direction and polarization varied relative to the rolling direction in the range of angles from 0 to 180 degrees. The excitation and reception of normal waves in the sheet were carried out by piezoelectric transducers with dry point contact, providing tangential force application. The results of the research on the anisotropy of acoustic properties, X-ray structural analysis of residual stresses and inverse pole figures, and metallographic studies were obtained.

Utilization of the oil-contaminated soil as a sustainable resource in rural road construction and rehabilitation in oil-producing countries

Achieving sustainable, cleaner production (CP) is essential for reducing industrial waste and conserving natural resources, especially in rapid industrialization. One of the significant environmental challenges is the remediation and effective utilization of contaminated soils. While substantial research has been conducted on coarse-grained contaminated soils, a critical knowledge gap exists regarding the impact of oil contamination on the stabilization and long-term performance of fine-grained soils. This knowledge gap is especially evident when assessing soil performance over extended periods (e.g., 365 days). This study addresses this gap by investigating both the macro- and microstructural behavior of oil-contaminated fine-grained soils under different stabilization conditions and extended curing durations. Our research introduces an innovative approach to utilizing oil-contaminated fine-grained soils resulting from pipeline leaks as sustainable materials for soil stabilization. This method mitigates environmental hazards and promotes resource conservation by converting waste into cleaner construction materials. A comprehensive series of laboratory tests—including compaction, unconfined compressive strength (UCS), durability, California bearing ratio (CBR), mineralogical analysis, and microstructural examinations—was performed to evaluate soils with varying oil concentrations (4%, 7%, and 10%) and different cement contents (0%, 3%, 6%, and 9%). Results showed that the sample containing 4% oil and 9% cement exhibited the highest durability after six wet-dry (W-D) cycles, with durability 7.3 times greater than that of non-stabilized samples. Higher cement contents also significantly improved crack resistance, corresponding with durability findings. Long-term curing (365 days) increased UCS by 6.4%–8.5% in soils with 9% cement, highlighting the importance of extended curing for stabilizing oil-contaminated fine-grained soils. The microstructural analysis confirmed the formation of Calcium-Silicate-Hydrate (C-S-H), which is crucial for enhancing soil strength. These findings demonstrate the viability of this waste utilization strategy for future pavement stabilization, offering a cleaner production method that supports environmental sustainability and efficient resource management. The study provides a cost-effective solution for infrastructure projects by repurposing oil-contaminated soils as valuable construction materials by recycling industrial byproducts.

Experimentation and FE analysis of low carbon steel-based laser welded tailored blanks in case of single point incremental forming

This study explores the formability of laser-welded tailored blanks in the context of single-point incremental forming (SPIF), a flexible and dieless manufacturing process. Two approaches, variation in materials and thicknesses, were used to fabricate tailor-welded blanks (TWB) with CRCA and DD steel sheets. The quality of the weld was evaluated by metallographic studies and tensile tests. The ductility of the welded joint was reduced by 81%, and the hardness was increased by 133% compared to the base metal. SPIF was employed using a hemispherical tool to form a ‘D’ shape geometry on fabricated TWBs. Fracture was observed only at the weld line, irrespective of thickness and material combination in the TWB. The forming height achieved from the SPIF of TWBs was reduced by 24% and 34% for both differences in thickness and material when compared to their corresponding base metals. Finite Element simulations were performed in Abaqus software using a dynamic explicit approach employing von Mises and Hill48 yield functions. Further, the FE model was validated by comparing the thickness and surface major/minor strains at the same forming height as observed from the experiments. Reduced formability and no weld line movement were the main observations made in this study, and the same was manifested by the FE simulation.

In-situ alloying of a Zr-based bulk metallic glass composite via powder-fed laser additive manufacturing and pure elemental blend

This study investigates the feasibility of synthesizing a ZrCuAlNb bulk metallic glass composite through in-situ alloying of pure elemental powder blend using powder-fed laser-directed energy deposition. The process parameters are carefully optimized and multiple laser remelting is applied to address the chemical inhomogeneity and elemental micro-segregation. A detailed microstructural examination confirms the successful discovery and development of an amorphous-crystalline composite structure.

Examination of Microstructure, Mechanical Properties, and Fatigue Strength in a Wire Arc Additively Manufactured Material Comprising Dissimilar Materials: AISI 316L Stainless Steel and Carbon Steel

This study provides a comprehensive investigation into the microstructure, hardness, tensile strength, and bending fatigue behavior of a Wire Arc Additively Manufactured (WAAM) component composed of dissimilar materials—Carbon Steel (CS) and 316L stainless steel. Microscopic analysis reveals distinct microstructural characteristics, such as equiaxed ferrite grains in WAAM CS and a coarse columnar structure with delta-ferrite phases in WAAM 316L. A macroscopic phase map indicates a predominantly Body-Centered Cubic (BCC) structure near the interphase, suggesting element migration between CS and 316L due to high heat input. Higher magnification scans highlight martensitic structures on both sides of the interphase, with the CS side exhibiting larger grain sizes. Hardness assessment along the built direction shows a peak hardness of 407 HV near the interphase on the 316L side, contrasting with the CS side's average interphase hardness of 316 HV due to larger grain sizes. The yield strength of both WAAM CS and WAAM dissimilar material was consistently measured at 392 MPa. In comparison, WAAM 316L exhibited a slightly lower yield strength of 359 MPa. Notably, WAAM 316L demonstrated the highest tensile strength among the materials, reaching 656 MPa. Meanwhile, WAAM CS displayed a robust tensile strength of 503 MPa, and the WAAM dissimilar material exhibited a yield strength of 520 MPa. In terms of elongation, WAAM CS and WAAM 316L showcased values of 44.9% and 49.6%, respectively. On the other hand, WAAM dissimilar material exhibited a somewhat lower elongation of 20.4%, suggesting a different mechanical behavior in terms of ductility. Bending fatigue tests on WAAM 316L, WAAM CS, and the dissimilar material reveal a fatigue limit of approximately 225 MPa for WAAM 316L, 210 MPa for WAAM CS, and approximately 210 MPa for the dissimilar material. In the low-cycle and medium-cycle regimes, the dissimilar material exhibits slightly superior fatigue strength, potentially due to its marginally higher static strength. Notably, consistent fractures on the CS side during fatigue tests underscore a recurring behavior in the dissimilar material.

Advancing characterization of VOC diffusion in indoor fabrics: A dual-porosity modeling approach

Volatile organic compounds (VOCs) are major chemical pollutants in indoor air. Indoor fabrics, such as curtains, carpets, sofas, and clothes, strongly adsorb VOCs due to their high loading rates and large specific surface areas. The desorption of VOCs from these fabrics can act as a secondary source, worsening indoor air pollution and prolonging its effects. The diffusion coefficient is a key parameter that determines the source-sink properties of fabrics. In this study, the VOC diffusion characteristics in fabrics were investigated through microstructural examination, mass transfer analysis, and environmental chamber experiments. Yarn and fiber gaps were identified as dual mass transfer channels within the fabrics and were represented using two distinct fractal models. A dual-porosity medium (DPM) model, based on these fractal representations, was developed to predict the VOC diffusion coefficients in indoor fabrics and was validated via experiments under various environmental conditions and fabric-VOC combinations. The results highlight the significant impact of fabric structure and composition on VOC adsorption and emission dynamics. The validated DPM model provides a comprehensive approach to predicting VOC diffusion in fabrics, providing a more accurate method for assessing indoor air quality and fabric-mediated human exposure.

Effect of Al2O3-SiO2 mass ratio and sintering temperature on the properties of water-soluble salt-based ceramic cores formed by binder jetting

Binder Jetting (BJ) technology, known for its cost-effectiveness and efficiency, is widely used for the rapid fabrication of complex ceramic cores. However, fabricating high-strength and water-soluble ceramic cores via BJ technology is particularly challenging due to the balance between mechanical properties and water solubility. In this work, BJ technology was employed to fabricate high-strength and water-soluble salt-based ceramic cores (SCC) regulated synergistically by Al2O3 and SiO2. The effects of the mass ratio of Al2O3 to SiO2 (A/S) and sintering temperature on the properties of Na2CO3-based samples were investigated, with detailed analyses of the regulation mechanism through thermodynamic, kinetic, and microstructural examinations. The results indicated that when A/S was 1:4, the bending strength of samples sintered at 760 °C for 60 min reached up to 62.38 MPa with good water collapsibility. Thermodynamic and kinetic analyses revealed that the formation of Na2SiO3 was prioritized over NaAlO2, and the content of Na2SiO3 as well as the proportion of liquid phase increased with the decrease of A/S and the increase of sintering temperature, resulting in the increase of sample density, as confirmed by microstructure analyses, which was the main strengthening mechanism of samples. Ultimately, complex-structure SCC samples were successfully fabricated. This study provides an insightful method for fabricating high-strength and water-soluble ceramic cores, with significant potential applications in the casting industry.

Metastable pitting corrosion behavior of the Incoloy 825 liner of metallurgically clad pipe in simulated oilfield produced water

This study investigates the metastable pitting corrosion behavior and passive film characteristics of metallurgically clad pipe (MCP) 825 within simulated oilfield produced water. Electrochemical testing and microstructural examination were employed to assess the corrosion behavior. The results revealed a narrowing of the passivation region and an increased frequency of metastable pitting nucleation. These phenomena are attributed to the enlarged grain size and the proliferation of precipitate phases within the MCP 825. X-ray photoelectron spectroscopy analysis unveiled a decreased fraction of Cr3+ and Fe3+ ox in the passive film. Additionally, an elevated concentration of vacancies and a rapid vacancy diffusion rate were observed, leading to diminished defect performance as indicated by Mott-Schottky (M − S) and electrochemical impedance spectroscopy (EIS) results.