Search Results (42)

In this paper, based on the Weibull Inverse Power Law, we present a methodology to determine the following: (1) the failure percentiles, referred to as the P–S–N field, of an S–N curve for a 42CrMo4 steel material exhibiting bilinear ($s_1 \mathrm{and} s_2)$ behavior (e.g., a competence failure mode); (2) the Weibull family that characterizes the entire bilinear behavior; and (3) the zero-vibration test plan that meets the required vibration reliability index of $R\left(t\right)=0.97$ with a reliability confidence level of $CL=0.75$. From the application, based on the formulated normal–Weibull relationship, we determine the failure percentiles for the normal (one, two, and three) sigma levels, as well as those failure percentiles corresponding to the capability ($Cp$) and ability ($Cpk$) indices. Finally, we present the formulation to determine the $R\left(t\right)$ index and the $CL$ level associated with each normal percentile, along with their numerical values. Full article

The growing antibiotic resistance of microorganisms causing postoperative infections following orthopedic surgeries underscores the urgent need for localized antiseptic and lavage delivery systems to enhance infection control. This study evaluates the in vitro effectiveness of antiseptic and lavage solutions—including polyhexanide, povidone–iodine, low-concentrated hypochlorite, Ringer’s solution, and saline—against Staphylococcus epidermidis, Staphylococcus aureus MRSA, Cutibacterium acnes, Corynebacterium amycolatum, Pseudomonas aeruginosa, and Candida albicans. Using microplate models (Minimum Inhibitory Concentration, Minimum Biofilm Eradication Concentration, and Biofilm-Oriented Antiseptic Test assays), flow-based models (Bioflux system), and surfaces relevant to orthopedic implants (e.g., stainless steel disks/screws, Co-Cr-Mo, Ti-Al-Nb orthopedic alloys, and ultra-high-molecular-weight polyethylene), as well as a bio-nano-cellulose scaffold representing tissue, we assessed the solutions’ activity. The cytotoxicity of the solutions was evaluated using osteoblast and keratinocyte cell lines, with additional in vivo insights gained through the Galleria mellonella larval model. The results show that polyhexanide-based solutions outperformed povidone–iodine in biofilm eradication in most tests applied, particularly on complex surfaces, whereas iodine demonstrated higher cytotoxicity in applied in vitro and in vivo tests. Low-concentration hypochlorite solutions exhibited minimal antibiofilm activity but also showed no cytotoxicity in cell line and G. mellonella larval models. These findings highlight the importance of careful antiseptic selection and rinsing protocols to balance infection control efficacy with tissue compatibility in orthopedic applications. Full article

Aluminum-modified plasma nitriding was developed in this research by the addition of a few FeAl particles around samples of 42CrMo middle carbon alloy steel during plasma nitriding. The goal of this study was to enhance nitriding efficiency and the combined performance of the steel. The research results show that nitriding efficiency was greatly enhanced, by about 6 times, with the effective hardening layer rising from 224 μm to 1246 μm compared with traditional plasma nitriding at 520 °C/4 h. More importantly, the compound layer increased just a little bit, from 11.64 μm to 14.32 μm, which remarkably reduced the ratio of the compound layer’s thickness to the effective hardening layer’s thickness, thus being quite beneficial to decreasing the brittleness level, making the brittleness level decrease from Level 4 to Level 1. Also, extremely high surface hardness and excellent wear resistance were obtained by aluminum-modified plasma nitriding due to the formation of hard phases of AlN and FeAl in the nitrided layer, with the surface hardness rising from 755 HV_0.025 to 1251 HV_0.025 and the wear rate reducing from 8.15 × 10⁻⁵ g·N⁻¹·m⁻¹ to 4.07 × 10⁻⁵ g·N⁻¹·m⁻¹. In other words, compared with traditional plasma nitriding, wear resistance was enhanced by two times after aluminum-modified plasma nitriding. Therefore, this study can provide comprehensive insights into the surface characteristics and combined performance of aluminum-modified plasma nitriding layers. Full article

The purpose of the study was to ascertain the corrosion resistance in Hanks’ solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating thickness as well as the correlated effect of the metallic sublayer type and defects present in DLC films on corrosion propagation were discussed. The results obtained were compared with findings on the adhesion of DLC to the steel substrate. The synthesis of carbon thin films with Cr and Ti adhesive sublayers was performed using a combined DC and a high-power-impulse vacuum-arc process. Evaluation of the corrosion resistance was carried out by means of potentiodynamic polarisation tests and scanning electron microscopy. Adhesive properties of the sublayer/DLC coating systems were measured using a scratch tester. It was found that systems with Ti sublayers were less susceptible to the corrosion processes, particularly to pitting. The best anti-corrosion properties were obtained by merging Ti with a DLC coating with a thickness equal to 0.5 μm. The protective properties of the Cr/DLC systems were independent of the carbon coating thickness. On the other hand, the DLC coatings with the Cr sublayer showed better adhesion to the substrate. Full article

Arc welded 316 stainless steel coatings with flux-cored wires are very promising for marine service environments due to their low cost, high efficiency, and satisfactory performance, while they suffers from Cr dilution during the preparation process. Herein, based on the consideration of increasing the Cr content and ensuring the same value of the Cr/Ni equivalence ratio (Cr_eq/Ni_eq), 316-modified flux-cored wires, 316F (19Cr-12Ni-3Mo) and 316G (22Cr-14Ni-3Mo), were designed under the guidance of a Schaeffler diagram for the improvement of the electrochemical and mechanical properties of 316 stainless steel coatings. The designed flux-cored wires were welded into a three-layer cladding by the tungsten inert gas welding (TIG) process, and the microstructure, corrosion resistance, and mechanical properties of the claddings were investigated. The results showed that 316F and 316G consist of γ-Fe (austenite) and a small portion of δ-Fe (ferrite) as the Cr_eq/Ni_eq is approximately 1.5. However, due to the higher value of the equivalent Cr content (ECC), 316G has an additional intermetallic phase (σ), which precipitates as a strengthening phase at grain boundaries, significantly increasing the tensile and yield strength of 316G but reducing its plasticity. In addition, the corrosion current density (i_corr) and pitting potential (E_b) for 316G are 0.20447 μA·cm⁻² and 0.634 V, respectively, while the values for 316F are 0.32117 μA·cm⁻² and 0.603 V, respectively, indicating that 316G has better anti-corrosion performance. Full article

Fe-Mn-Cr-Ni alloys like Citomangan, delivered in the form of powders, tubular wires, and coated electrodes, are intended for welding deposition operations to create wear-resistant layers. Their main characteristic is their high capacity for surface mechanical work-hardening under high shock loads, along with high toughness and wear resistance. In order to increase the resistance to cavitation erosion, hardfacing of Duplex stainless steel X2CrNiMoN22-5-3 with Citomangan alloy was performed using a new welding technique, namely one that uses a universal TIG source adapted for manual welding with a coated electrode in pulsed current. Cavitation tests were conducted in accordance with the requirements of ASTM G32—2016 standard. Comparing the characteristic cavitation erosion parameters of the manganese austenitic layer, deposited by this new welding technique, with those of the reference steel, highlights an 8–11 times increase in its resistance to cavitation erosion. Metallographic investigations by optical microscopy and scanning electron microscopy (SEM), as well as hardness measurements, were carried out to understand the cavitation phenomena. Full article

In connection with the growing importance of the efficiency and reliability of tools in industrial sectors, our research represents a key step in the effort to optimize production processes and increase their service life in real conditions. The study deals with the comparison of the tribological properties of three tool steels, two of which were produced by the powder metallurgy method—ASP2017 and ASP2055—and the last tool steel underwent the conventional production method—X153CrMoV12. The samples were mechanically machined with the finishing technology of turning and, finally, heat treated (Q + T). The study focused on the evaluation of hardness, resulting microstructure, wear resistance, and coefficient of friction (COF). The ball-on-disc method was chosen as part of the COF and wear resistance test. The tribological test took place at room temperature with dry friction to accelerate surface wear. The pressing material was a hardened steel ball G40 (DIN 100Cr6). Measurements were performed at loads of 10 N, 6 N, and 2 N and turning radii of 13 mm, 18 mm, and 23 mm, which represents a peripheral speed of 0.34, 0.47, and 0.60 m/s. The duration of the measurement for each sample was 20 min. The results showed that the COF of powder steels showed almost the same values, while a significant difference occurred with the increase of the radius rotation in the case of conventional steel. The results within the friction mechanism showed two types of wear, namely, adhesive and abrasive wear, depending on the Q + T process. From a tribological point of view in terms of wear, it was possible to state that the material ASP2055 after Q + T showed the lowest rate of wear of all the tested steels. Full article

Laser-based powder bed fusion of metals (PBF-LB/M) is a widely applied additive manufacturing technique. Thus, PBF-LB/M represents a potential candidate for the processing of quenched and tempered (Q&T) steels such as 42CrMo4 (AISI 4140), as these steels are often considered as the material of choice for complex components, e.g., in the toolmaking industry. However, due to the presence of process-induced defects, achieving a high quality of the resulting parts remains challenging in PBF-LB/M. Therefore, an extensive quality inspection, e.g., using process monitoring systems or downstream by destructive or non-destructive testing (NDT) methods, is essential. Since conventionally used downstream methods, e.g., X-ray computed tomography, are time-consuming and cost-intensive, micromagnetic NDT measurements represent an alternative for ferromagnetic materials such as 42CrMo4. In this context, 42CrMo4 samples were manufactured by PBF-LB/M with different process parameters and analyzed using a widely established micromagnetic measurement system in order to investigate potential relations between micromagnetic properties and porosity. Using multiple regression modeling, relations between the PBF-LB/M process parameters and six selected micromagnetic variables and relations between the process parameters and the porosity were assessed. The results presented reveal first insights into the use of micromagnetic NDT measurements for porosity assessment and process parameter optimization in PBF-LB/M-processed components. Full article

In this study, the effect of niobium addition and a specific preheating process on the microstructure and tensile properties of 52CrMoV4 steel used in leaf springs was investigated. Flat and leaf spring materials were used to accomplish this aim. The flat materials under investigation were kept in a furnace for 90 min at 900 °C. A homogeneous microstructure was aimed for with the use of this pre-annealing heat treatment in addition to the standard process before rolling used to create NbC. Leaf spring production was carried out with flat materials that possessed various Nb contents, with or without pre-heating. Grain size measurement and tensile tests were performed on the flat and leaf springs. Additionally, scanning electron microscopy images were captured from the fractured surfaces after the tensile tests were carried out. The current study highlights the importance of Nb addition as an alloying element and the effect of the selected pre-annealing process in optimizing the grain structure and enhancing the tensile properties of leaf springs. The leaf spring with a Nb ratio of 0.0376 that was pre-annealed exhibited a finer grain structure (G = 11.3), greater tensile properties (YS = 1550 N/mm² and UTS = 1688.6 N/mm²), and deeper tear valleys and larger dimples, indicating higher energy consumption during fracturing, according to the SEM images produced, in contrast with the other materials studied. Full article

In order to enhance the comprehensive performance of plasma nitrided heavy load components used in corrosive environments, post-oxidation was conducted under different conditions after plasma nitriding 42CrMo4 steel at 500 °C for 5 h. The results show that an oxide film composed of Fe₃O₄ and Fe₂O₃ was formed above the compound layer, resulting in a significant increase in corrosion resistance; the self-corrosion potential was greatly increased from −658.72 mV to −429.23 mV. Meanwhile, it needs to be emphasized that the characteristics of the plasma nitriding layer could be effectively adjusted as expected by post-oxidation. The compound layer thickness decreased from 9.41 μm to 3.62 μm by post-oxidation at 400 °C for 2 h, while the thickness of the effective hardening layer increased from 300 μm to 378 μm. Due to the expected change in the characteristics of the plasma nitriding layer, post-oxidation could simultaneously improve the toughness, hardness, and wear resistance of the samples; the brittleness level decreased from Grade 4 to Grade 1; the surface hardness increased from 765 HV_0.05 to 825 HV_0.05; and the wear rate decreased from 3 × 10⁻⁵ g·m⁻¹·N⁻¹ to 1.19 × 10⁻⁵ g·m⁻¹·N⁻¹, illustrating that the wear resistance was greatly improved. Full article

Experiments with changes in motion geometry can provide valuable data for engineering and development purposes, allowing a better understanding of the influence of tribological factors on the performance and service life of joints. The presented subject article focused on the experimental investigation of the influence of the geometry of the movement of the friction process on the change in the tribological properties of 30CrNiMo8 steel. The friction process was carried out without the use of a lubricant in contact with a steel ball of G40 material with a diameter of 4.76 mm. The steel ball performed two types of movement on the surface of the experimental material. The first method used was ball on disc, in which the ball moved reciprocally in an oval direction at an angle of 180° on a circumferential length of 35 mm at a speed of 5 mm/s. The second method consists of the same input parameters of the measurement, with the difference that the path along which the ball moved had a linear character. The load during the experiment was set at a constant value of 50 N with 1000 repetitions. The results show that with the ball on disc method, there was an increase in wear by 147% compared to the linear test method, which was approximately a coefficient of increase in wear of 2.468. EDS analysis pointed to the occurrence of oxidative wear that affected the resulting COF values, which were lower by 8% when using the ball on disc method due to a more uniform distribution of O and C on the surface of the friction groove where these elements acted as solid microlubricants. With the ball on disc method, defects in the form of microcracks occurred, which affected the reduction in the values of the depth of the affected area of microhardness. Full article

Contact fatigue is the main failure model for bearing systems in steel rolling mills. Characterizing the degree of contact fatigue damage is important for predicting its operating life. In this paper, the X-ray diffraction method (XRD) is used to measure the residual stress state and the diffraction peak width (FWHM, full width at half maximum) of six samples with different degrees of contact fatigue failure. The results show that surface residual stress values increased by more than 70% compared with the original state, while the diffraction peak width values decreased by more than 7% and were strongly correlated with the degree of contact fatigue damage. The XRD measurement of the bearing inner ring enables the characterization of the evolution of the residual stress state and grain distortion due to damage development. FWHM values may be considered an indicator for predicting the degree of contact fatigue. Full article

The composition of the filler electrodes, as well as the shielding gases, has a strong impact on the static and dynamic properties of welded joints in HSLA steels. The content of Cr, Ni, and Mo, along with the shielding gases, helps maintain the hardness values in the HAZ of HSLA steels welded using the GMAW process, resulting in a positive impact on the fatigue life of the joints. Maintaining fatigue properties in the regions of the heat-affected zone is crucial. The increase in the size of the HAZ, coupled with microstructural changes, leads to a reduction in the hardness values in this region, contributing to a decrease in the fatigue life of welded joints. In this study, the effects of using different filler electrodes and shielding gases on the fatigue properties of welded joints in LNE 600 steel with a thickness of 4.75 mm, welded using the GMAW process, were evaluated. It was possible to observe a reduction in the hardness values in the HAZ region and a similar static resistance behavior for all evaluated conditions, except for the ER70S-6 electrode with 5% O₂ gas, where the fatigue life showed better results with the application of the ER120S-G electrode. Full article

This research was devoted to unveiling the strain rate sensitivity (SRS) of G18NiCrMo3-6 cast steel in tension/compression asymmetry. For that purpose, detailed mechanical characterization tests were conducted providing a process window covering quasi-static and medium strain rate regimes (0.001, 0.1, 10 [s⁻¹]) in tension and compression states. Through this experimental effort, the SRS of the material could be extracted by a function of strain and the strain rate which enabled us to create a mathematical expression to easily be implemented as a state variable for constitutive material modeling. Finally, a pressure- and rate-dependent constitutive material model on the basis of the Cocks’89 yield locus definition was created using a subroutine (UMAT) file and the material parameters were verified with respect to the experimental data. The UMAT file also takes into account the tension/compression asymmetry in yielding to handle the effect of the porous media plasticity concept. The predictions of the proposed material model are in line with the experimental outputs. Full article

Degradation of industrial machinery through wear can be mitigated with the deposition of protective coatings to reduce maintenance costs and prolong their service lifespans. Electroless nickel-based composite coatings is one possible method used to provide this protection. The addition of Tribaloy (CoMoCrSi alloy) particles has been found to produce composite coatings with high toughness. In this work, electroless Ni-P-Tribaloy composite coatings were plated on AISI 1018 steel substrates and subjected to low-stress abrasion tests following ASTM G65 standards to investigate the abrasion of the coating. The test was performed at 10 revolution increments, with a 45 N applied load, until coating failure was observed and the measured abrasion was reported as volume loss. The two Ni-P-Tribaloy coating samples lasted for 90 and 100 revolutions, exhibiting a wear rate of 0.170 mm³ per revolution, compared to 0.135 mm³ per revolution for the Ni-P coatings. The abrasive wear mechanism in the Ni-P-Tribaloy coating was found to be plowing of the matrix around the Tribaloy particles, followed by the removal of the particles once they are protruding, which subsequently contributes to the three-body wear of the coating. The particle removal was accelerated at the coating particle-matrix interface. It is concluded that the size of the Tribaloy is a major factor, and we recommend that further studies be carried out using finer particles to improve the wear resistance of the Ni-P-Tribaloy coating. Full article