Reduction In Hardness Research Articles

Effect of Water on Wear of DLC Coatings in High Temperature and Pressurized Ethanol

The friction and wear characteristics of a-C:H:Si and a-C:H coatings in an ethanol environment at 120 °C and 10 MPa focusing on the effects of water and dissolved oxygen in ethanol were investigated. The friction tests were conducted using an autoclave chamber, with gases (oxygen or nitrogen) and ethanol–water mixtures (0 and 6 vol.%). The wear acceleration of a-C:H:Si took place when it slid in ethanol with 6 vol.% water and pressurized by oxygen, thus the specific wear rate was the highest, approximately 1.8 × 10−7 mm3/Nm. The reason of this wear acceleration was assumed the effect of hardness reduction due to oxidation of the a-C:H:Si, so the O/C ratio by AES and the hardness of topmost surface by AFM nano-scratch were investigated. As a result, the higher O/C ratio showed higher specific wear rate due to the hardness reduction from 13.3 to 6.0 GPa. These findings highlight the role of water and dissolved oxygen in accelerating wear of a-C:H:Si coatings.Graphical abstract

Effect of hot rolling and annealing on microstructure, crystallographic texture, and mechanical properties of Fe11.5 Co20.6 Ni40.7 Cr12.2 Al7.8 Ti7.2 high entropy alloy

The evolution of microstructure and texture during the thermomechanical processing of a Fe-Co-Ni-Cr-Al-Ti dual phase high entropy alloy consists of L12 (γ′) ordered precipitates in the disordered FCC (γ) matrix and its effect on the mechanical properties was investigated. The as-cast alloy was annealed at 1100 °C after 25 % and 50 % hot rolling reduction. The grain size becomes finer, and a considerable amount of annealing twin boundaries (Ʃ3 boundaries) developed in the hot rolling and annealed (HRA) samples. The α-fiber (ND||<110>) texture and twin-related texture components increase after HRA treatment. The mechanical response at room temperature is evaluated employing hardness and uniaxial tensile tests. A significant reduction in hardness, from 448 ± 6 HV to 381 ± 12 HV, is observed in the 50 % hot rolled annealed sample compared to the as-cast sample. Additionally, the yield strength reduced from 779 to 595 MPa with an increment in the ductility from 12.5 to 17.2 % in the as-cast and HR50A samples, respectively. Finally, it has been demonstrated that the increase in coherent twin boundaries and grain size excluding twin boundaries, led to the observed mechanical behavior.

Analysis of the possibilities to increase abrasion resistance of welded joints of Hardox Extreme steel

This paper presents a heat treatment process designed to enhance the abrasion resistance of welded joints of Hardox Extreme steel, which is known for its high hardness (>600 HBW) and tensile strength (>2000 MPa). Despite these properties, the steel's weldability, characterized by a Carbon Equivalent Value (CEV) of 0.70, limits its use in applications like mining machinery where welding is essential. The key challenge in welding martensitic boron steels, such as Hardox Extreme, is the reduction in hardness and abrasion resistance in the heat-affected zone, along with cold cracking due to increased hardenability. This study investigates the abrasion resistance and microstructural properties of welded joints made with submerged arc welding (SAW) under different heat treatment conditions. The developed process achieved a uniform tempered martensite microstructure across all welded zones, increased hardness to over 550 HV in the weld material zone and improved the relative abrasion resistance by 25 % compared to the as-welded state.

Hardness Reduction using Waste Plastic

This study focused on the utilisation of waste plastic as an ion exchanger to reduce water hardness. The three identical glass columns R1, R2, and R3 were used, each containing different types of waste plastic resin, such as styrofoam resin (SR), air bubble plastic resin (AR), or a mixture of both resins (MR), respectively. The plastics underwent a sulfonation process after crushing and sieving; their sulfonation was confirmed using FTIR analysis. For lab-scale experiments, each glass column was filled with sand, gravel, and coconut fiber as supporting media and equipped with a pump and flow-control valves. Groundwater collected from an urban area was passed through the columns at different flow rates and contact times. The process takes place by exchanging the Na+ ions of resins with polluting ions present in hard water. The treatment parameters involved are total hardness, calcium hardness, magnesium hardness, chloride, TDS, and pH. During the treatment process, pH was maintained between 7 and 8.5. All the parameters were tested twice, and the average of the observations was noted. The results showed that the maximum total hardness reduction achieved in reactors R1, R2, and R3 was 63%, 52%, and 58.6%, respectively, at a contact time of 24 h.

Influence of nano graphene filler on hardness, impact strength and density of glass epoxy composites

AbstractThis study investigates the effects of graphene reinforcement on the hardness and impact strength of glass epoxy composites. Four different materials were examined: pure epoxy (EP), glass epoxy (GE), glass epoxy with 1 wt.% graphene (GE1), and glass epoxy with 2 wt.% graphene (GE2). The results show that the incorporation of graphene significantly enhances the hardness of the composites. Pure epoxy (EP) exhibited a Shore D hardness of 60 and an impact strength of 0.09 J/m2. The glass epoxy (GE) showed a reduction in hardness to 56 but an increased impact strength of 0.15 J/m2 due to the inclusion of 33 wt.% glass fiber. Further addition of graphene in GE1 and GE2 led to notable improvements in hardness, reaching 68 and 74 Shore D, respectively. However, the impact strength displayed a decrease with the inclusion of graphene, with GE1 and GE2 showing values of 0.13 and 0.11 J/m2, respectively. When transitioning from pure epoxy (EP) to glass epoxy (GE), there is a 6.67% decrease in hardness, while the impact strength increases by 66.67%. Introducing 1 wt.% of graphene to the glass epoxy (GE1) results in a 21.43% increase in hardness but a 13.33% decrease in impact strength. Further adding 2 wt.% of graphene (GE2) leads to an additional 8.82% increase in hardness, though the impact strength decreases by 15.38%. X‐ray diffraction (XRD) analysis has revealed nano graphene presence and distribution, while fractography has revealed its effectiveness in enhancing interfacial adhesion and toughening mechanisms. Furthermore, XRD identifies potential changes in crystallinity or phase composition induced by nano graphene incorporation, further elucidating the composite's structure and properties. The study highlights the novel and significant trade‐offs encountered in optimizing the mechanical properties of epoxy‐based composites by incorporating graphene and glass fiber.

Weakening of olivine by hydrogen implantation: Results of nano-indentation tests and some applications to planetary materials

Sticking of the dust grains is a critical step in planet formation. To investigate the solar wind effect on the dust mechanical properties, we conducted hydrogen implantation experiments (using beam energies of 10 keV, 20 keV and 50 keV) on olivine single crystals and determined the elastic modulus and the hardness as a function of depth by nano-indentation tests. The near surface regions of the samples (to ∼600 nm) show a substantial decrease in both hardness (up to ∼85%) and modulus (up to ∼74%), indicating a large degree of mechanical weakening. The depth extent of the weakened region increases with implantation energy while the degree of weakening decreases with implantation energy. TEM (transmission electron microscopy) observations of the samples show that the depth where damaged region occurs increases with the implantation energy used. The results are interpreted based on the physics of ion-solid interaction during implantation. According to our results, we expect that olivine-like dust exposed to solar wind would display a similar mechanical weakening in the surface (∼ 74% reduction in elastic modulus, ∼ 85% reduction in hardness). Mechanical weakening by solar wind implantation would enhance the sticking of the dust in the disk if dust have been effectively exposed to the solar wind. The present results are also applied to interpret observations of some planetary materials.

Influence of fracturing fluids on shale matrix permeability and micro-mechanical properties after chemical interactions

Geochemical interactions between shale and hydraulic fracture fluids (HFFs), principally mineral dissolution and precipitation, can result in alteration of matrix permeability and tendency of proppant embedment, ultimately impacting hydrocarbon migration through the shale formation. This study aimed to quantify changes of core permeability and micromechanical properties after shale-HFF chemical interactions. Extent of chemical alteration of the solid phase was characterized by synchrotron X-ray fluorescence mapping, micro-computed tomography, and scanning electron microscopy. Post-reaction brine was evaluated for elemental concentrations. Both low-carbonate and high-carbonate shale exhibited carbonate dissolution, an iron oxidation zone, and barite precipitates partially infilling secondary porosity. These reactions were more obvious in the high-carbonate shale but extended further into the low-carbonate shale. Pulse-decay permeability measurements generally revealed increase in permeability after reactions, whereas hardness and modulus reduction were observed only in reaction zones of high carbonate shale. Inevitable heterogeneity of natural shale samples resulted in large deviations in hydromechanical measurements both on the core scale and on the microscale.

Nitrogen Gas-Assisted Extrusion for Improving the Physical Quality of Pea Protein-Enriched Corn Puffs with a Wide Range of Protein Contents.

Blowing agent-assisted extrusion cooking is a novel processing technique that can alter the expansion of extruded snacks and, thus, enhance their physical appeal, such as texture. However, to this day, this technique has only been studied for ingredients with limited protein contents (<30%). In this study, protein-enriched snacks were extruded using nitrogen gas as a blowing agent at a wide protein range (0-50%) to better explore the potential of this technique in manufacturing high-protein snacks. The results showed that, with nitrogen gas injection, extrudate radial expansion was significantly (p < 0.05) improved at 10% and 40% protein, while extrudate density was significantly reduced at 30% and 50% protein. Nitrogen gas-injected extrudates, especially at 50% protein, exhibited improvements in texture, including a reduction in hardness and an increase in crispness. Collectively, this study showed the promising potential of nitrogen gas-assisted extrusion in improving the physical appeal of innovative healthy snacks at a high protein level (i.e., 50%).

The Effect of Lactiplantibacillus plantarum SHY130 and Konjac Glucomannan on the Physicochemical, Antioxidant, and Sensory Properties of Stirred Yogurt.

The impact of konjac glucomannan (KGM)-based synbiotics on yogurt quality is not well understood. This study investigated the effects of a synbiotic mixture of KGM and the selected probiotic Lactiplantibacillus plantarum SHY130 on the physicochemical, antioxidant, and sensory properties of yogurt. The results showed that KGM significantly promoted the growth of Lactiplantibacillus plantarum SHY130. The synbiotics dramatically enhanced the count of lactic acid bacteria in yogurt during the 14 days of storage. Texture analysis indicated that the synbiotic supplement had no impact on springiness and cohesiveness but resulted in notable reductions in hardness, gumminess, and chewiness. The synbiotics did not significantly affect the water-holding capacity and syneresis. While the synbiotics initially decreased yogurt viscosity, it increased with storage time. Furthermore, the synbiotics significantly improved the yogurt's antioxidant capacity. Additionally, the supplementation of the synbiotics did not adversely affect sensory properties, although the synbiotics containing 0.02% KGM negatively impacted overall acceptability. Overall, these findings elucidate the effects of KGM-based synbiotics on yogurt quality, providing a foundation for developing novel synbiotic yogurt products.

Material compatibility of epoxies exposed to repeated low temperature vaporized hydrogen peroxide sterilization

ABSTRACT Through technological advancements, medical devices have evolved in their designs and have become more complex in both their design and materials of construction. Medical grade biocompatible epoxies are widely used in reusable medical devices. Choosing an epoxy that maintains its performance characteristics when subjected to repeated sterilization throughout the reusable medical device’s lifespan is a known challenge for medical device manufacturers. This study evaluated the material compatibility of seven cured 2-part and 1-part epoxies used in medical devices following exposure to 100 cycles in a low temperature vaporized hydrogen peroxide sterilizer. Six of the seven epoxies tested were found to be compatible with vaporized hydrogen peroxide sterilization based on qualitative, hardness and weight measurements conducted post exposure to 100 VHP cycles. The epoxies deemed to be compatible displayed no visual signs of physical defects, minimal reduction in hardness (≤2%) and total weight gain (≤2.9%). One of the epoxy samples did not maintain its texture and exhibited 17% loss in hardness post exposure to 100 VHP sterilization cycles and was found to be incompatible with the low temperature vaporized hydrogen peroxide process. This study verifies the need for material compatibility evaluations of epoxies prior to designing and developing a medical device while keeping in mind the application, lifecycle and intended use of medical devices.

Laser Powder Bed Fusion and Heat Treatment of the Martensitic Age‐Hardenable Steel (1.2709)

The primary objective of this study is to clarify the fundamental question of whether, in principle, it is possible to dispense with a prior solution annealing process in favor of a direct aging heat treatment for specimens of maraging stainless steel grade X3NiCoMoTi18‐9‐5 (1.2709) produced by laser powder bed fusion (LPBF). The waiver of a solution annealing process would significantly increase the process efficiency and thus support a sustainable and resource‐friendly production of such components. Therefore, the hardness, microstructure, and the present phases of specimens in as‐built + aged condition (AB + A) and solution‐annealed + aged (SOL + A) are examined during this study. Initially, an extended parameter study is performed using a Renishaw AM 250 LPBF system equipped with a pulsed mode laser system to achieve the highest possible apparent density. As test specimens, small cubes are produced for parameter study and are analyzed for porosity by means of optical microscopy. To investigate the relationship between microstructure and hardness in different material states, one series of specimens is aged directly after LPBF processing in the as‐built state (AB + A). For comparison, the other series was solution annealed at 820 °C for 60 min, quenched in water and then aged (SOL + A). A maximum hardness value of 614 HV1.0 is achieved for specimen aged at 490 °C for 120 min in as built condition (AB + A), while 624 HV1.0 was measured for specimen aged at 490 °C for 180 min in conventionally solution annealed + aged (SOL + A) condition. Significant austenite reversion is not observed at aging temperature of 490 °C in both cases. Aging of specimens at temperatures of 540 and 600 °C resulted in reduction of specimen hardness due to higher percentage of austenite reversion. No significant difference between the hardness values of AB + A and SOL + A specimens is observed. It can therefore be concluded that, in principle, conventional solution annealing and ageing can be dispensed with in favor of direct aging. However, as the results are based on small sized specimens, further investigations into the scalability are needed.

Influence of GH4169 addition on cracking control, microstructure and mechanical properties of GH4169/K465 composite material manufactured by selective laser melting

In the process of additive manufacturing, K465 nickel-based superalloy tends to form a eutectic structure with a low melting point. Subsequently, rapid cooling leads to the formation of significant residual tensile stress. This tensile stress makes the prepared sample susceptible to cracking. The research explored the susceptibility to cracking of the alloy material and analyzed the microstructure and properties of GH4169/K465 alloy obtained. The generation of cracks can be managed by decreasing the concentration of Al and Ti elements. The microstructure of GH4169/K465 alloy consists of a matrix phase γ, a white Laves precipitated phase, and spherical particle precipitated phase NbTi4. The mechanical properties of samples 1GH1K, 7GH5K, and 3GH1K were analyzed. The results indicated an elongation exceeding 20 %, a tensile strength exceeding 1000 MPa, and a reduction in hardness from 329 HV to 285 HV. The powder mixing process has been demonstrated to effectively address the shortcomings of individual materials by combining the strengths of different alloy materials to produce a hybrid material with excellent comprehensive performance.

The development of B/Cr co-doped DLC coating by FCVA deposition system and its tribological properties at 300 °C

The diamond-like carbon (DLC) coating prepared using filtered cathodic arc deposition (FCVA) lost its promising wear resistance under high temperatures. Element-doped DLC coatings have been investigated to suppress carbon oxidation reaction and subsequently enhance the wear resistance in high-temperature environments. Previous research clarified the excellent tribological properties of boron-doped DLC (B-DLC) but identified challenge such as arc discharge extinguishment and coating declamation (under high-temperature friction test). In this study, the introduction of Argon gas (10 sccm) during the deposition process stabilized stable arc discharge, resulting in high hardness and deposition rate. Moreover, a chromium interlayer and varying concentration of Cr dopant (0.5 %, 1.0 %, 3.0 % at.) were added to B-DLC to develop a stable, co-doped DLC with low friction and high wear resistance. Raman spectroscopy and nano-indentation revealed an increase in the disordered carbon structure and reduction in hardness and Young's Modulus with Cr doping. Macroscopic ball-on-disk friction test, showed 1 % Cr-doped B-DLC (a-C:B:Cr1) coating exhibited super low friction (avg. coefficient 0.02) and a low specific wear rate (<5.0 × 10−6 mm3/Nm). Raman spectroscopy indicated that the transferred graphite-like tribo-film onto the surface of Si3N4 counterparts contributed to stable low friction. Additionally, XPS analysis on the DLC coatings' wear track suggested the rich BB bond might contribute to its high wear resistance. This successful improvement on element-doped DLC prepared by FCVA provided valuable insights for further exploration of DLC coating applied to various working situations.

Colloidal and thermal properties of poly(hydroxyethyl caprolactone acrylate‐co‐methyl methacrylate)‐g‐pullulan latex obtained by seeded semi‐batch emulsion polymerization

AbstractIn this study, the influence that the monomer composition of hydroxyethyl caprolactone acrylate/methyl methacrylate (HECLA/MMA) has on the properties of the latex films, including contact angle, thermogravimetric analysis, and mechanical properties was evaluated. The polymerization process to obtain small particle sizes, good colloidal stability, and polymer films was optimized through the use of pullulan (Pull) and different ratios of HECLA and MMA. The results revealed a substantial impact of the monomer composition and polymerization processes on the particle size and latex film properties. The use of seed latex obtained in situ reduces particle size and particle size distribution. Additionally, it was observed that the contact angle of the polymer films increased as the concentration of HECLA increased. Furthermore, the water absorption of the polymer films exhibited a decreasing trend after reaching an 80/20 monomer composition of HECLA/MMA. An increase in HECLA contents in the recipe showed a reduction in tensile strength, elastic modulus, hardness, and elongation at break. Conversely, higher HECLA contents contributed to improving the thermal properties of the polymer films. Finally, the optimal ratio of HECLA/MMA to improve the thermal degradation and tensile mechanical properties of the polymer film was 50/50 wt%. The results found in this work allow additional data for producing poly(HECLA‐co‐MMA)‐g‐Pull latexes by manipulating the ratios of HECLA and MMA, which can create new potential applications in various industrial settings for a wide range of polysaccharides.Highlights Poly(HECLA‐co‐MMA)‐g‐Pull with different ratios of HECLA/MMA were successfully obtained. The use of Pull after molar mass reduction had a significant effect on colloidal stability. A reduction in tensile strength and elongation at break was obtained by increasing the amount of HECLA. Thermal stability of the latex films showed a direct relationship with the content of HECLA. Poly(HECLA‐co‐MMA)‐g‐Pull latexes can be used in agricultural applications.

Enhancing the quality of highland barley noodles by Lactobacillus plantarum pre-fermentation: Insights into its underlying mechanism

To improve highland barley noodles (HBNs) quality, the highland barley flour (HBF) was pre-fermented by Lactobacillus plantarum in this study. The changes in the quality of HBNs, the hydration properties and microstructure of the dietary fiber (DF), and the conformation and cross-linking of the protein in HBNs were measured. With the extension of pre-fermentation time (0–4 h), the overall acceptance of HBNs increased from 7.83 to 8.27, along with a 5.9% reduction in hardness and a 4.5% increase in springiness of HBNs. Meanwhile, confocal laser scanning microscopy (CLSM) revealed that the physical structure of the DF gradually disintegrated, which caused a significant (p < 0.05) decrease in its water retention capacity. In addition, spectral analysis showed a continual increase (from 19.62% to 30.15%) in β-turn content of the protein. The content of the free sulfhydryl group and sodium dodecyl sulfate extractable protein (SDSEP) decreased by 18.1% and 4.12%, respectively. However, with the further extension of pre-fermentation time (6–8 h), the degradation in HBNs sensory quality occurred, accompanied by a significant (p < 0.05) decrease in pH (5.95–5.01). These findings suggested that a moderate duration (4 h) of HBF pre-fermentation could effectively improve the quality of HBNs.

Novel photocatalysis-assisted mechanical polishing of laser cladding cobalt-based alloy using TiO2 nanoparticles

This paper presents a novel photocatalysis-assisted mechanical polishing method for cobalt-based alloy cladding layers using TiO2 nanoparticles. By leveraging the active oxygen species generated by the photocatalyst under illuminated conditions, surface oxidation reactions on cobalt-based alloys are initiated, thereby enhancing material removal efficiency. The underlying principles of photocatalytic oxidation are elucidated, particularly the promotion of oxidation by •OH when it interacts with the metal surface, leading to the formation of a CoO oxide film on the cladding layer surface and a subsequent reduction in surface hardness. An experimental platform was established, and research findings identified an etching time of 60 min and a TiO2 concentration of 10 wt% as optimal process parameters. Comparative analysis with pure mechanical polishing and chemical mechanical polishing revealed that photocatalysis-assisted mechanical polishing yielded superior surface roughness of 60 nm and a material removal rate of 63.8 μm/min.

Influence of bottled salad dressings on the development of enamel erosion in the presence or absence of salivary pellicle – An in vitro study

BackgroundAcidic beverages are believed to elevate the risk of enamel surface erosion. In addition to the intake of soft drinks, the increased consumption of salad dressings has been linked to a higher prevalence of dental erosion. Therefore, the current study aimed to investigate the influence of bottled salad dressings on the development of enamel erosion in the presence or absence of pellicle through in vitro experiment. MethodsPreliminary pH and calcium analyses of solutions were performed. Highest pH and calcium content was found for sandwich spread i.e., 4.69 and 55.4 mg/100 g grams, respectively. Eighty tooth specimens (measuring 4 × 4 × 3 mm) were prepared from extracted human premolars and randomly assigned to four groups (group 1: orange juice; group 2: eggless plain mayonnaise; group 3: sandwich spread; and group 4: thousand island dressing) with 20 samples in each group. Ten tooth specimens from each group were immersed in 20 ml of the respective solutions for 5 min (control group). The remaining ten tooth specimens from each group were submerged in 5 mL saliva vials for 3 min to facilitate salivary pellicle formation before being immersed in their respective solutions for 5 min (saliva-covered group). Pre and post-experimental assessments of enamel roughness and hardness were conducted using a surface roughness tester and Knoop Hardness indenter, respectively. ResultsOverall, enamel roughness was notably elevated in the control group, with the eggless plain mayonnaise (0.52 ± 0.38) and thousand island dressing groups (0.57 ± 0.29) showing a significant increase in surface roughness post-test (p = 0.05). Nevertheless, there was no significant difference in the enamel roughness between the groups. On the other hand, regardless of the presence/absence of the salivary pellicle, a marked decrease in enamel hardness was observed among all groups except for group 3 (sandwich spread) with a mean score of 311.5 ± 82.6 (p < 0.05). ConclusionA significant increase in surface roughness and reduction in enamel hardness was observed with salad dressings. However, in vitro formed salivary pellicle showed a protective effect against tooth erosion.

Effect of Dietary Simulating Solvents on the CAD-CAM Provisional Restorative Materials' Microhardness and Color Stability Properties: An in vitro Study.

This in vitro study investigated the effects of dietary solvents on the microhardness and color stability of CAD/CAM provisional restorations compared to conventional materials. Disc-shaped specimens (n=200) were fabricated from self-cured acrylic resin, two 3D-printing resins (FormLabs, NextDent), and a milled material (TelioCAD). Randomization assigned specimens (n=10/group) to immersion solutions: artificial saliva, citric acid, heptane, coffee, and tea. Microhardness and color stability were evaluated. One-way and three-way ANOVA with Tukey's post hoc test analyzed the data. Dietary solvents significantly reduced the surface microhardness of all tested materials (p<0.05). Unpolished surfaces exhibited greater color changes compared to polished ones (p<0.05) across all materials. Coffee and tea induced the most substantial reductions in hardness and the most significant color alterations (p<0.05), whereas saliva and citric acid had minimal effects. Milled provisional restorations exhibited superior hardness and color stability. Dietary solvents significantly affected material properties over time, highlighting the importance of material selection for clinical applications.

Impact of electron beam welding on the microstructure of PM2000 ODS steel

This work investigated the impact of electron beam (EB) welding, using various traverse speeds of the electron beam (1200–2200 mm/min), on the microstructure of PM2000 ODS steel which was characterized using analytical electron microscopy and microhardness. The different heat inputs during welding explored in this study (72–39 J/mm), related to the traverse speed used, correlated with small differences in the widths of the fusion zone. Only minor differences in local microstructures and hardness of the fusion zones were detected amongst the four butt welds produced. The fusion zone is characterized by large columnar grains in the ferritic matrix, together with a coarsened Y-Al-O particle distribution and a reduction in its particle number density as compared to the base material. There is also a sharp border between the fusion zone and base material, with the joint showing little evidence of a heat-affected zone. These changes in microstructure during welding led to a hardness reduction of ∼30 % in the fusion zone of the welds with respect to the base material.

Understanding the effect of cathodic reaction on corrosion-enhanced erosion in sand-entraining electrolyte

In this study, the pure erosion behaviour of pure iron and its erosion-corrosion behaviour under different anodic polarization currents were investigated in various cathodic reactions (oxygen reduction, hydrogen ion reduction, and water reduction) using a cylindrical stirring system. The corrosion-enhanced erosion (C-E) rates were determined for each condition. The results revealed that pure iron displayed similar pure erosion behaviour across all three cathodic reactions. When the cathodic reactions involve hydrogen ion reduction or water reduction, the erosion-corrosion of pure iron manifested as uniform damage, with the reduction in hardness being the main cause of the C-E in this case. Conversely, in the case of oxygen reduction reaction as the cathodic reaction, the erosion-corrosion presented as pitting damage, with the reduction in hardness resulting from localized concentration of anodic current and the formation of easily worn protruding flaky iron structures at the edges of the pits as the main mechanism of the C-E. Moreover, linear and exponential relationships were found between the C-E rate and the anodic current density for uniform damage and pitting damage, respectively. Finally, the concept of surface equivalent hardness was proposed, along with the establishment of a mathematical model for surface equivalent hardness based on the relationships between the C-E rate and the anodic current density. Utilizing the surface equivalent hardness enables the evaluation of the erosion rate on material surfaces considering the coupled effect.