Search Results (311)

A novel stainless steel with high Mn and Mo content (much higher than traditional stainless steel), designated CH241SS, was developed as a potential replacement for Cr-Mo-V alloy steel in the cold forging applications of precision industry. Through carbon reduction in an environmentally friendly manner and a two-stage heat treatment process, the hardness of as-cast CH241 was tailored from HRC 37 to HRC 29, thereby meeting the industrial specifications of cold-forged steel (≤HRC 30). X-ray diffraction analysis of the as-cast microstructure revealed the presence of a small amount of ferrite, martensite, austenite, and alloy carbides. After heat treatment, CH241 exhibited a dual-phase microstructure consisting of ferrite and martensite with dispersed Cr(Ni-Mo) alloy carbides. The CH241 alloy demonstrated excellent high-temperature stability. No noticeable softening occurred after 72 h for the second-stage heat treatment. Based on the mechanical and room-temperature tensile fatigue properties of CH241-F (forging material) and CH241-ST (soft-tough heat treatment), it was demonstrated that the CH241 stainless steel was superior to the traditional stainless steel 4xx in terms of strength and fatigue life. Therefore, CH241 stainless steel can be introduced into cold forging and can be used in precision fatigue application. The relevant data include composition design and heat treatment properties. This study is an important milestone in assisting the upgrading of the vehicle and aerospace industries. Full article

This study focuses on S32654 super austenitic stainless steel (SASS) and systematically characterizes the morphology of the sigma (σ) phase and the segregation behavior of alloying elements in its as-cast microstructure. High-temperature confocal scanning laser microscopy (HT-CSLM) was employed to investigate the effect of the rare earth element yttrium (Y) on the solidification microstructure and σ phase precipitation behavior of SASS. The results show that the microstructure of SASS consists of austenite dendrites and interdendritic eutectoid structures. The eutectoid structures mainly comprise the σ phase and the γ₂ phase, exhibiting lamellar or honeycomb-like morphologies. Regarding elemental distribution, molybdenum displays a “concave” distribution pattern within the dendrites, with lower concentrations at the center and higher concentrations at the sides; when Mo locally exceeds beyond a certain threshold, it easily induces the formation of eutectoid structures. Mo is the most significant segregating element, with a segregation ratio as high as 1.69. The formation mechanism of the σ phase is attributed to the solid-state phase transformation of austenite (γ → γ₂ + σ). In the late stages of solidification, the concentration of chromium and Mo in the residual liquid phase increases, and due to insufficient diffusion, there are significant compositional differences between the interdendritic regions and the matrix. The enriched Cr and Mo cause the interdendritic austenite to become supersaturated, leading to solid-state phase transformation during subsequent cooling, thereby promoting σ phase precipitation. The overall phase transformation process can be summarized as L → L + γ → γ → γ + γ₂ + σ. Y microalloying has a significant influence on the solidification process. The addition of Y increases the nucleation temperature of austenite, raises nucleation density, and refines the solidification microstructure. However, Y addition also leads to an increased amount of eutectoid structures. This is primarily because Y broadens the solidification temperature range of the alloy and prolongs grain growth perio, which aggravates the microsegregation of elements such as Cr and Mo. Moreover, Y raises the initial precipitation temperature of the σ phase and enhances atomic diffusion during solidification, further promoting σ phase precipitation during the subsequent eutectoid transformation. Full article

This study investigates the effect of boron carbide (B₄C) ceramic reinforcement on the microstructural, mechanical, electrical, and electrochemical properties of CoCrMo, Ti, and 17-4 PH alloys produced via powder metallurgy for potential biomedical applications. A systematic experimental design was employed, incorporating varying B₄C contents into each matrix through mechanical alloying, cold pressing, and vacuum sintering. The microstructural integrity and dispersion of B₄C were examined using scanning electron microscopy. The performance of the materials was evaluated using several methods, including Vickers hardness, pin-on-disk wear testing, ultrasonic elastic modulus measurements, electrical conductivity, and electrochemical assessments (potentiodynamic polarization and EIS). This study’s findings demonstrated that B₄C significantly enhanced the hardness and wear resistance of all alloys, especially Ti- and CoCrMo-based systems. However, an inverse correlation was observed between B₄C content and corrosion resistance, especially in 17-4 PH matrices. Ti-5B₄C was identified as the most balanced composition, exhibiting high wear resistance, low corrosion rate and elastic modulus values approaching those of human bone. Weibull analysis validated the consistency and reliability of key performance metrics. The results show that adding B₄C can change the properties of biomedical alloys, offering engineering advantages for B₄C-reinforced biomedical implants. Ti-B₄C composites exhibit considerable potential for application in advanced implant technologies. Full article

A novel processing route of producing CrFeNiMo, Co_0.5CrFeNiMo, and Al_0.5CrFeNiMo high-entropy alloy coatings was proposed in this work. Pre-alloyed HEAs were consolidated by spark plasma sintering (SPS) in order to fabricate electrodes for electrospark deposition (ESD) coatings on carbon steel substrates. Investigations were performed to observe aspects such as phase composition and stability, contamination level, homogeneity, elemental distribution, and microstructural integrity. The results indicated phase stability and lower porosity when increasing the SPS temperature by 50 °C for all cases, with tetragonal distortion related to the HEAs’ severe lattice distortion core effect. The coating surface analysis indicated that a continuous and compact coating was obtained, correlated with the ESD layering count, but microfissures were present after 6 layers were applied due to the reduced ductility combined with rapid cooling under Ar atmosphere. The chemical integrity of both the sintered samples and the coatings was preserved during the processing, revealing a uniform elemental distribution with no contaminations or impurities present. The results indicated successful HEA sintering and deposition, highlighting the potential of the combined SPS-ESD process for high-performance material fabrication with possible applications in aggressive environments. Full article

H13 steel, a widely used material in hot work tooling, faces premature failure due to insufficient hardness and wear resistance. To address this limitation, Mo₂FeB₂ cermet coatings were fabricated on H13 alloy steel via plasma spray welding, and subsequently quenched at 850 °C, 1000 °C, and 1150 °C. The effects of the quenching temperature on the microstructure and wear resistance were investigated using optical microscopy (OM) for cross-sectional morphology, scanning electron microscopy (SEM) for microstructural and wear surface analyses, energy-dispersive spectroscopy (EDS) for elemental composition analysis, and X-ray diffraction (XRD) for phase identification. The coating primarily consisted of α-Fe, Mo₂FeB₂, (Mo,Fe,Cr)₃B₂, and Fe₂₃(B,C)₆ phases. Increasing the temperature to 1150 °C increased the Mo₂FeB₂ hard phase and elevated microhardness by 32.04% (from 827 HV_0.5 to 1092 HV_0.5). Wear resistance improved by 46.38% (mass loss reduced from 6.9 mg to 3.7 mg). The main wear mechanism was identified as abrasive wear due to the spalling of hard phase particles. These results demonstrate that optimizing quenching temperature enhances the hardness and wear resistance in Mo₂FeB₂ coatings, offering a viable strategy to extend H13 steel service life in high-temperature industrial applications. Full article

22MnCrNiMo steel, a high-strength low-alloy material, is primarily used in the production of mooring chains for offshore oil platforms, offshore wind turbines, and ships. The application of additive manufacturing technology allows for the direct fabrication of seamless mooring chains. This paper investigates the selective laser melting (SLM) process parameters for 22MnCrNiMo mooring chain steel, analyzing the effects of different process parameters on the microstructure, phase composition, and mechanical properties of the steel. The experimental results demonstrate that under the laser parameters of 200 W laser power, 800 mm/s scanning speed, 30 μm layer thickness, and 110 μm scanning spacing, the SLM-formed parts exhibit the best comprehensive mechanical properties, with a microhardness of 513.2 HV0.5, a tensile strength of 1223 MPa, a yield strength of 1114 MPa, an elongation of 8.5%, and an impact energy of 127 J. This study reveals the microstructure evolution and the mechanism of enhanced mechanical properties in SLM-fabricated 22MnCrNiMo steel, providing a new approach for the preparation of high-performance mooring chains using 22MnCrNiMo steel. Full article

A total of 0.3%C-Cr-Mo-V steel, a high-strength alloy steel widely used in rocket motor housings, suspension systems in high-performance vehicles, etc., is noted due to its high strength-to-weight ratio. However, its high carbon equivalent (CE > 1%) makes it challenging to weld, as it is prone to brittle martensitic formation, which increases the risk of cracking and embrittlement. The present paper focuses on enhancing the microstructure and mechanical properties of 0.3% C-Cr-Mo-V steel by gas tungsten arc welded (GTAW) joints, utilizing post-weld heat treatment and cooling strategies (PWHTCS). A systematic experimental approach was employed to ensure a defect-free weld through dye penetrant testing (DPT) and X-ray radiography techniques. Subsequently, test specimens were extracted from the welded sections and subjected to PWHT protocols, including hardening, tempering, and rapid quenching using air and oil cooling (AC and OC, respectively) mediums. Results show that OC has enhanced tensile strength and hardness while simultaneously maintaining and improving ductility, ensuring a well-balanced combination of strength and toughness. Fractography analysis revealed ductile fracture in AC samples, whereas OC weldments exhibited a mixed ductile–brittle fracture mode. Thus, the findings demonstrate the critical role of PWHTCS, with OC, as an effective method for achieving enhanced mechanical performance and microstructural stability in high-integrity applications. Full article

Metallic implants in radiotherapy patients alter dose distributions due to their high density and unique composition, potentially compromising treatment precision. This study evaluates the effects of three metallic materials, Co-Cr-Mo alloy, titanium alloy, and stainless steel, on dose distribution across four radiotherapy modalities: 6 MV photons, 15 MeV electrons, 170 MeV protons, and very-high-energy electrons (100 and 150 MeV). Monte Carlo simulations in the TOol for PArticle Simulations Monte Carlo (TOPAS MC) generated percentage depth dose curves and dose profiles, with dosage data standardized to a reference point and uncertainties addressed via error propagation. Results revealed that the Co-Cr-Mo alloy produced the most significant alterations. For instance, at 100 MeV Very High Electron Energy (VHEE), the dose at a 15 cm depth was 34.57% lower than in water; 6 MV photons showed a 15.16% reduction, and the proton Bragg peak shifted 9.5 cm closer to the source. These pronounced changes along the central beam axis affected dose distributions anterior and posterior to the metal. A prostate cancer simulation further demonstrated considerable dose reduction with deeply embedded metallic implants. The findings underscore the critical impact of implant properties on radiotherapy dose distributions, emphasizing the need to integrate these factors into clinical protocols to improve dosimetric accuracy and treatment safety. Full article

Al-Cr-N ternary coatings were deposited on the surface of Cr12MoV alloy tool steel via multiarc ion plating technology. The microstructure and mechanical and tribological properties of these coatings were systematically characterized, analyzed, and compared with those of the uncoated substrate specimens. The results indicated that under optimal conditions, Al70Cr30 alloy was effectively ionized, leading to the formation of AlN and CrN phases between Al ions, Cr ions, and nitrogen atoms. These phases were uniformly distributed within the coating, forming an ordered lattice structure. At a bias voltage of −60 V, the deposited Al-Cr-N coating exhibited a uniform and smooth morphology. However, because of the inherent characteristics of arc deposition, droplets and craters were observed on the coating surface as a result of sputtering and back-sputtering effects. The average nanohardness of the Al-Cr-N ternary coating reached 23.8 ± 3.1 GPa, while the coefficient of friction stabilized at approximately 0.7 during the wear process, compared with around 0.8 for the uncoated Cr12MoV substrate. Compared with the uncoated Cr12MoV substrate, the Al-Cr-N coating demonstrated significantly enhanced hardness and wear resistance, thereby effectively improving the performance of Cr12MoV alloy tool steel. Full article

Objective: The increasing number of aging patients with total hip arthroplasties (THA) causes an increased incidence of periprosthetic fractures (PPF). The study aimed to evaluate the impacts of two different materials in the same-sized cemented stems on PPF in bone models. Methods: This study compared the maximum rotational torque leading to PPF when stems made of cobalt–chromium–molybdenum (Co–Cr–Mo) alloy and stainless use steel (SUS) were implanted using simulated bone models (Sawbones, 3403). The maximum destruction torque was compared statistically for each material (Co–Cr–Mo alloy vs. SUS stainless steel) in this model, and fracture patterns were examined. Results: The PPF occurred with a spiral propagation from the proximal femur towards the diaphysis, with breakage occurring near the distal end of the stem. There were no significant differences in the destruction torque values between the Co–Cr–Mo alloy (103.0 ± 14.9 Nm) and SUS (98.7 ± 15.1 Nm) samples (p = 0.575). The fractures using the bone models exhibited similar patterns in all specimens, resembling clinical PPF fracture types clinically, specifically Vancouver classification B2. Conclusions: The comparison of the maximum destruction torques of the Co–Cr–Mo alloy and SUS cemented stems in simulating PPF showed no significant differences. The results suggest that the materials of the cemented stems might not significantly affect the occurrence of PPF in THA. Full article

Nano-precipitates play a vital role in the development of ultra-high strength steels (UHSSs). In recent decades, the B2-NiAl phase, which forms highly coherent interfaces with the BCC-Fe matrix, has attracted significant attention for enhancing the strength of UHSSs. However, direct experimental investigation of alloying elements—specifically their atomic distribution and the resulting effects on the interfacial bonding strength of nano-precipitates—remains challenging. This study uses density functional theory (DFT)-based first-principles calculations to investigate the role of alloying elements in modifying interfacial characteristics. Six elements—Al, Ni, Co, Cr, Mo, and C—are introduced at various occupation sites within the coherent interface model to calculate the formation energy. The predicted preferential distribution of solid-solution atoms aligns well with experimental findings. Stable configurations of alloying segregation are selected for first-principles rigid tensile fracture tests along the <001> direction. Electronic structure analysis reveals that Co, Cr, and Mo segregation enhances interface strength due to solute-induced high charge density and the preservation of bonding characteristics of bulk phases at the interface. The results offer valuable insights and practical guidance for developing novel ultrahigh-strength structural steels strengthened by B2-NiAl. Full article

Martensitic stainless steel (MSS) is widely used in several parts of automobiles where high strength, hardness, and corrosion resistance are required. However, the metastability of retained austenite can transform into martensite under severe deformation, adversely affecting material properties. Cryogenic treatments (CTs) have been extensively employed in iron-based alloys for fastener application due to their advantageous effect. This study explores the heat treatment processes applied to 13Cr-2Ni-2Mo martensitic stainless steel (MSS), including austenitizing, cryogenic treatment, and tempering cycles. Cryogenic treatment at (−150 °C) for varying durations, followed by tempering at 200 °C for 2 h, and the impact of post-cryogenic tempering at 200 °C for different tempering duration on the microstructure and mechanical properties were evaluated. Experimental results indicate that the sample quenched at 1040 °C for 2 h (CHT) contains lath martensite, retained austenite, δ-ferrite, and undissolved carbide precipitation. Compared to as-quenched samples, hardness decreased by 5.04%, 7.24%, and 7.32% after tempering for 2 h, 5 h, and 10 h, respectively. Extending cryogenic durations to 2 h, 12 h, and 20 h promoted nucleation of a mixture of M₃C and M₂₃C₆ small globular carbides (SGCs) and grain refinement but resulted in hardness reductions of 5.04%, 5.32%, and 8.36%, respectively. The reduction in hardness is primarily attributed to a decrease in solid solution strengthening and promoted carbide coarsening. Full article

The high-temperature performance of 10CrNi2Mo3Cu2V steel is critically governed by the distribution of Cu-rich phases. This study systematically investigated the evolution of solute redistribution, Cu-rich phase precipitation, microstructural transformations, and mechanical properties in 10CrNi2Mo3Cu2V alloy under varying aging temperatures. Advanced characterization techniques, including atom probe tomography (APT) and transmission electron microscopy (TEM), were employed to analyze microstructural features and phase formation in both as-built and heat-treated specimens. The key findings reveal that copper atom segregation initiates at a tempering temperature of 350 °C. Upon increasing the temperature to 450 °C, extensive precipitation of nanoscale copper clusters is observed. Temperatures exceeding 450 °C trigger the formation of ε-Cu phases, which undergo subsequent coarsening. Notably, these copper clusters and Cu-rich precipitates act as dislocation pinning sites, promoting crack nucleation and propagation, thereby markedly degrading the alloy’s impact energy absorption capacity. The critical diameter for Orowan mechanism-governed strengthening by Cu-rich phases is determined to be ~6 nm, while the average diameter of matrix-penetrating Cu-rich particles is approximately 1.46 nm. Quantitative analysis demonstrated that the combined contributions of the Orowan bypass mechanism and particle-cutting mechanism yield a strength enhancement of ~219 MPa, which exhibits excellent agreement with experimentally measured strength increments. These results provide critical insights into the interplay between microstructural evolution and mechanical degradation in precipitation-strengthened steels under thermal exposure. Full article

This study explores the enhancement of antimicrobial and biomedical properties in Fe-based bulk metallic glasses (BMGs) through the addition of Ag. Fe_55-xCr₂₀Mo₅P₁₃C₇Ag_x (x = 0, 1, 2, 3 at.%) master alloy ingots were synthesized by the induction melting technique and industrial-grade raw materials, the master alloy ingots were prepared as bulk metallic glasses (referred to as Ag0, Ag1, Ag2, and Ag3) by the water-cooled copper-mold suction casting technique, and their glass-forming ability, corrosion resistance, biocompatibility, and antimicrobial properties were systematically investigated. The results indicate that the glass forming ability (GFA) decreased with increasing Ag content, reducing the critical diameter for fully amorphous formation from 2.0 mm for Ag0 to 1.0 mm for Ag3. Electrochemical tests in Hank’s solution revealed the superior corrosion resistance of the Fe-based BMGs as compared with conventional 316 L stainless steel (316L SS) and Ti6Al4V alloy (TC4), with Ag3 demonstrating the lowest corrosion current density and the most stable passivation. Biocompatibility assessments, including fibroblast cell viability and adhesion tests, showed enhanced cellular activity and morphology on Fe-based BMG surfaces as compared with 316L SS and TC4, with minimal harmful ion release. Antimicrobial tests against E. coli and S. aureus revealed significantly improved performance with the Ag addition, achieving bacterial inhibition rates of up to 87.5% and 86.7%, respectively, attributed to Ag⁺-induced reactive oxygen species (ROS) production. With their excellent corrosion resistance, biocompatibility, and antimicrobial activity, the present Ag-containing Fe-based BMGs, particularly Ag3, are promising candidates for next-generation biomedical implants. Full article

The hot deformation behavior of 4Cr16MoCu martensitic stainless steel alloyed with 1% Cu was investigated through hot compression tests at temperatures ranging from 900 to 1150 °C and strain rates of 0.001 to 1 s⁻¹. The addition of Cu is strategically employed to synergistically enhance precipitation hardening and corrosion resistance, yet its complex interplay with hot deformation mechanisms remains poorly understood, demanding systematic investigation. The results revealed a narrow forging temperature range and significant strain rate sensitivity, with deformation resistance increasing markedly at higher strain rates. An Arrhenius constitutive model incorporating a seventh-degree polynomial for strain compensation was developed to describe the flow stress dependence on deformation temperature and strain rate. The model demonstrated high accuracy, with a correlation coefficient (R²) of 0.9917 and an average absolute relative error (AARE) of 3.8%, providing a reliable theoretical foundation for practical production applications. Furthermore, a hot processing map was constructed based on the dynamic material model (DMM), and the optimal hot working parameters were determined through microstructural analysis: an initial forging temperature of 1125 °C, a final forging temperature of 980 °C, and a strain rate of 0.1 s⁻¹. These conditions resulted in a fine and uniform grain structure, while strain rates above 0.18 s⁻¹ were identified as unfavorable due to the risk of uneven deformation. Full article