The application of ultra-high-strength steel (UHSS) S960MC in safety-critical sectors is significantly limited by its susceptibility to hydrogen embrittlement (HE). Since welding operations fundamentally alter the optimized microstructure of the base material, understanding the response of welded joints to hydrogen is crucial. This study presents a comparative analysis of S960MC joints fabricated by Tungsten Inert Gas (TIG) and Laser Beam Welding (LBW) to examine how distinct welding thermal cycles influence susceptibility to degradation. Utilizing Slow Strain Rate Testing (SSRT) on electrochemically charged specimens, the research aims to identify the dominant failure pathways. The results demonstrate that TIG welding, characterized by high heat input, produces a softened Heat-Affected Zone (HAZ) that is highly susceptible to Hydrogen-Enhanced Localized Plasticity (HELP). In contrast, the rapid cooling in LBW promotes the formation of a hard martensitic Fusion Zone (FZ), leading to premature and catastrophic brittle failure driven by Hydrogen-Enhanced Decohesion (HEDE) at stresses well below the macroscopic yield strength. Detailed fractographic analysis confirms the synergistic interplay between HELP and HEDE mechanisms, providing critical insights into the structural integrity of UHSS weldments in hydrogen-rich environments.

This study investigates the influence of specific heat input and weld configuration on heat affected zone hardness and residual stress of S960MC high strength steel welds. In total, five types of weld samples were manufactured by Tungsten Inert Gas (TIG) autogenous welding and Metal Active Gas (MAG) butt welding to simulate the effect of increasing heat input and constraining the relative motion of welded parts during the heating and cooling phase. The obtained results show that the highest axial tensile residual stresses with magnitude above 900 MPa, combined with a hardness drop in a range from 13 up to 18%, occur mostly in the sub-critical heat affected zone, making it the critical zone of the weld. Increasing the heat input during welding does not have a simple correlation with generating more residual stresses and the trends obtained on the surface are different from results evaluated at a depth of 0.2 mm. Restraining the relative part motion during the welding affects mostly the tangential residual stresses, causing an increase in their tensile magnitude localized in the middle of the heat-affected zone while almost no influence on the axial residual stress component was recorded.

This study compares the fatigue resistance of two standardized specimen geometries - dog-bone and hourglass-shaped - made from Hardox 450 high-strength steel. Rotating bending fatigue tests evaluated differences in fatigue durability. Strain gauge measurements and the FEM analysis showed hourglass specimens had more uniform stress distribution and lower concentration effects. Fatigue tests revealed an 8 % higher fatigue limit for the hourglass specimens, probably due to the lack of localized stress concentration at the transition between the radius and the cylindrical section. These findings contribute to understanding how standardized specimen geometries influence fatigue performance.

Abstract The quality of components and structures is directly related to degradation processes such as corrosion and fatigue that are concomitant phenomena during their operation. One of the options for increasing the quality of components and structures is the use of appropriate surface coating. In this paper is presented an experimental investigation of the corrosion influence on the fatigue resistance of the carbon steel with coatings based on Ti and Cr nitrides. The experimental work included determination of the chemical composition of the base material, heat treatment, microstructure evaluation, mechanical properties measurement, coating depositions, corrosion test and the fatigue tests by rotation bending of the deposited layers. The corrosion and fatigue tests have shown that the coating provides improvement of the corrosion resistance and that there was no reduction of the fatigue resistance.

This study investigates the microstructural evolution and mechanical property changes in the heat-affected zone (HAZ) of welded S960MC advanced high-strength steel (AHSS). The main objective was to evaluate the influence of welding thermal cycles on the microstructure and mechanical properties of different HAZ subzones, including the subcritical heat-affected zone (SCHAZ), intercritical heat-affected zone (ICHAZ), and fully transformed subzones (FGHAZ, CGHAZ, and FZ). Real welds were performed on 3 mm thick S960MC steel with metal-cored arc welding (MCAW), and thermal cycles specific to each subzone were simulated to study the resulting microstructures. Microhardness and tensile testing were conducted, and microstructural characterization was performed using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and visual light microscopy (VLM). The SCHAZ exhibited carbide precipitation within the martensitic structure, resulting in a mixture of tempered martensite and bainite, with a smooth decrease in microhardness from 330 HV0.5 to 269 HV0.5. The ICHAZ, exposed to temperatures between Ac1 and Ac3, underwent partial austenitization, followed by transformation into a mixture of ferrite, bainite, and martensite, with a significant reduction in microhardness to 234 HV0.5 at its center. The fully transformed subzones showed grain coarsening, with microhardness varying from 284 HV0.5 in the CGHAZ to 319 HV0.5 in the FGHAZ and decreasing to 276 HV0.5 in the fusion zone. The ICHAZ was identified as the most critical subzone, exhibiting the highest susceptibility to mechanical failure.

Advanced high-strength steels (AHSS) are currently facing a serious challenge from hydrogen embrittlement, which significantly affects their mechanical properties. Problems arise when hydrogen diffuses into the material and accumulates at grain boundaries, inclusions, or microcracks, degrading the material's characteristics. The main objective of the study is to investigate the effects of adding potassium thiocyanate (KSCN) to the sulfuric acid base solution during electrolytic hydrogenation using microalloyed martensitic AHSS grade S960MC. An increase in hydrogen diffusion into the examined material across its full surface is produced by adding thiocyanate ions to the electrolyte. This is the rationale behind the decision to add KSCN to the sulfuric acid base solution. The addition of KSCN to the base environment induced a considerable reduction in fracture strain, and the degradation was attributed to hydrogen buildup at grain boundaries, impurities and microcracks. These steels have an extensive list of applications in the automotive industry and are frequently used in the form of sheets for welding. Therefore, it is important to understand how their mechanical characteristics and behaviour vary in various circumstances, including hydrogen-rich environments.

Heat treatment technology changes all the mechanical properties of metallic materials. The influence of induction hardening, nitriding and boronising on the change in the microhardness, impact toughness, microstructure and coefficient of friction of conventional steels 42CrMo4 and 32CrMo12 has been examined and compared with results obtained in the sintered steels with an increased content of Cu, which were prepared using powder metallurgy technology. Widely used treatments for the examined materials include induction hardening and gas nitriding. This study focuses on comparing those technologies with alternative technologies of boronising. It was found that for powder metallurgy materials, boronising is a much more suitable process than nitriding because after the application of nitriding, the impact toughness dropped to one third of the impact toughness of the base material, while after boronising, the impact toughness remained unchanged. Through boronising, it was possible to achieve the unique possibility of improving the mechanical properties of sintered PM Fe-Cu-C steels and fully replacing the currently used nitriding process. Furthermore, compared to nitriding, it also increases the hardness of the surface layer many times to improve the friction properties and significantly increases the impact toughness.

The heat treatment technology changes all sorts of materials properties. We examined the change of tribological properties of selected powder metallurgy materials and conventional steels, in this article. We used special testing equipment, for measuring the changes of friction coefficient of individual tested materials, before application of the heat treatment and after application of the heat treatment. We tested two types of powder metallurgy steels and two types of conventional steels. The changes in friction coefficient are shown in the table and charts. We used boronising, nitriding and surface hardening as procedures of heat treatment.

Hydrogen embrittlement involves the interaction between hydrogen and the microstructure of metals, which can lead to an alarming loss of mechanical properties. For advanced high-strength (AHS) steel S960MC grade, which finds application in fields ranging from heavy machinery to construction, understanding this phenomenon is important. The material's complex crystalline lattice, carefully engineered to maximize strength, becomes vulnerable in the presence of hydrogen. The sources of hydrogen that can lead to embrittlement of steel are various. From the exposure of steel to hydrogen during production processes to the absorption of hydrogen from the environment. After the absorption of hydrogen into the material, hydrogen atoms diffuse in the microstructure and look for places with high stress concentration (cracks, inclusions, grain boundaries, etc.). In these regions, atomic hydrogen disrupts interatomic bonds, weakening the material and making it susceptible to embrittlement and subsequent complete failure of the component. This research is focused on how the change in current density affects the hydrogen embrittlement of AHS steel S960MC during hydrogenation. It was found that the mechanical properties of steel decrease at a lower current density, but not to the same extent as at a higher current density. Thus, it can be said that the change in current density influences the hydrogen embrittlement of S960MC steel.

Abstract The study explores the influence of hydrogen embrittlement on advanced high-strength steel S960MC, focusing on the role of different hydrogen charging techniques. Hydrogen embrittlement poses a critical challenge in high-strength steels, compromising their structural integrity and limiting their applications in demanding environments. The findings indicate that S960MC steel demonstrates intrinsic resistance to hydrogen embrittlement when exposed to a hydrogen-supersaturated environment without external factors like electric current or elevated temperature. However, cathodic hydrogen charging significantly enhances hydrogen diffusion into the material, leading up to a 60% decrease in ultimate tensile strength. In contrast, immersion hydrogen charging showed a minimal effect on the mechanical properties. Fractographic analysis showed that cathodic charging led to severe embrittlement, characterized by mixed transcrystalline quasi-cleavage, intercrystalline fractures, and extensive secondary cracking. Conversely, immersion charging resulted in negligible embrittlement, with minimal changes in fracture morphology. These results highlight the critical role of hydrogen charging methods in the embrittlement behavior of S960MC steel, emphasizing the substantial impact of cathodic charging on material degradation.

Abstract The primary goal of this study was to investigate laboratory techniques for hydrogenating selected steels and to examine the hydrogen embrittlement of steel 1.4104. These processes, which involve hydrogenation and subsequent mechanical testing, are rarely performed in laboratories due to the need for precise, costly equipment and the inherent risks associated with hydrogen’s highly reactive and explosive nature. Various theories have been proposed to explain the mechanisms behind hydrogen embrittlement in steels. These theories attribute material degradation to hydrogen’s interaction with the steel microstructure. However, their applicability is often limited, as they are developed for specific conditions and may not fully describe the phenomenon under different scenarios. This work focused on hydrogenating steel 1.4104 using two distinct methods: immersion and cathodic. The aim was to induce embrittlement and compare the resulting fracture surfaces, particularly after conducting Charpy impact tests, to evaluate the effects of each hydrogenation method.

This research examines the technological processes of applying CrN coating on low-alloy tool steel, focusing on the comparison between hardening-tempering-coating (HTC) and hardening-coating (HC) processes, with an emphasis on energy savings. The study investigates the chemical composition, microstructure, mechanical properties, fractography, residual stress, and corrosion resistance of the coated tool steel. Notably, the results indicate no significant differences in the microstructural, mechanical, and corrosion properties between the HTC and HC processes, suggesting that tempering may be excluded without compromising the quality. This study introduces a novel approach to tool steel coating, which improves energy efficiency while maintaining high-quality outcomes. The findings highlight potential improvements in industrial applications, offering an energy-efficient alternative that does not sacrifice the performance or durability of the tool steel. This advancement could lead to significant improvements in manufacturing efficiency and sustainability.

Binder Jetting technology works on the principle of line injection moulding, using metal powder and liquid binder as input material, which is uniformly applied by print heads to the previous layer using a nozzle. By successively applying each layer, the desired shape of the designed component is obtained. The technology offers a large number of advantages which include the possibility of using any printing powder that may contain functional graded materials. Furthermore, it is a green manufacturing technology where we can reuse unused metal powder in the next printing cycle after following the prescribed process. As a result, we characterize this technology as a near-waste-free production of metal parts. The research aims to analyse the impact of different orientations of printed parts within the workspace on the mechanical properties of the resultant components. Additionally, the study aims to compare these mechanical properties with the specifications recommended by the metal powder manufacturer and findings from previous research studies. Based on the experimental measurements carried out, we can conclude that the influence of the orientation of the parts in the workspace has only a minimal effect on the mechanical properties of the manufactured parts.

The main objective of the work was to describe the laboratory methods suitable for the hydrogenation of free-cutting steels. Furthermore, to study the hydrogen embrittlement of 11SMn30 free-cutting steel. Hydrogenation and subsequent mechanical testing of hydrogenated steel is not a common laboratory method as it requires precise and expensive equipment and is time-consuming and dangerous as hydrogen is highly reactive and explosive. Currently, several theories of hydrogen embrittlement mechanisms of steels describe the causes of material degradation by hydrogen. However, those theories are not universally valid; individual accounts have been developed and describe hydrogen embrittlement only for specific conditions and may fail in their descriptions under others. In this work, the hydrogenation of free-cutting steel 11SMn30 steel by two different methods (immersion and cathodic) was investigated to induce embrittlement and to compare in particular the fracture surfaces after the Charpy impact test. The results reported in this paper indicate that manganese sulphide inclusions are not the main cause of hydrogen embrittlement in free-cutting steels. The effect of manganese sulphide inclusions was attributed only to hydrogen trapping, that generated a high stress causing their decohesion from the matrix.

Re-profiling of hot forging dies is the most common method of die repairing in industry. Due to the surface to core hardness gradient caused by the limited hardenability of the die material, the surface layer after re-profiling possesses lower hardness than the first one, causing decrease of the tool lifetime in means of wear, but also can lead into total failure of the die due to other damaging mechanisms. Performed failure analysis of a hot forging die manufactured from 56NiCrMoV7 which included microstructure analysis, hardness profile, tensile and fatigue tests showed a 31 % decrease of fatigue properties when surface and core material is compared. Based on the experimental results it was calculated, that an optimal preventive action to increase the service life is to perform the re-heat treatment after every 10th re-profiling. The 16th re-profiling is critical; beyond this point, there is a significant risk of total die failure.

Results of experimental testing of the shot peened steel C55 specimens are presented in this paper.The aim was to establish behaviour of the compressive residual stresses induced by the shot peening at elevated temperatures; namely their stability in terms of temperature and time.Experimental work included verification of the tested material chemical composition, heat treatment (austenitization at 820 °C ± 5 °C for 30 minutes, cooling in the Durixol V70 oil at 20 °C ± 5 °C, high tempering at 450 °C ± 5 °C for 120 minutes, followed by cooling in air), tensile tests according to EN 10002-1 standard, hardness (HRC) measurements, shot peening with parameters Almen intensity 12A and coverage of 100 %, at the incidence angle close to 90° with respect to the specimen surface.The residual stresses state was evaluated by the X-ray diffraction measurement.It was concluded that the elevated temperature of 130 °C and after exposure of 100, 500 and 1000 hours, did not cause a significant decrease in compressive residual stresses.

Abstract. Recent years have seen a lot of research on modern steels with higher yield strengths. The study investigates the microstructure and mechanical properties of two different welding techniques - gas metal arc (GMA) and laser beam (LB). The result of this study showed a significant softening effect in the heat-affected zone (HAZ) for both welding techniques, the GMA and LB, resulting from formation of a coarse-grained microstructure during welding. The findings of this study increased understanding and added to the body of knowledge in the rapidly growing field of GMA and LB welding processes of HSLA steels.

In the case of 3D printing of polymer matrix composites, the most widespread material is nylon. Improper storage of nylon results in moisture absorption, which in the case of Fused Filament Fabrication affects the print quality due to uncontrolled deposition of the material into the structure. The uncontrolled deposition results in printing imperfections which the authors faced during the preparation process of specimens for the articles. The imperfections negatively affect the resulting mechanical properties. It has been shown that modification of the nozzle temperature is one of the options which could solve the issue of improperly stored materials printing. The specimens did not report any apparent printing defects. However, the modification of the nozzle temperature affects the joint quality between the individual laminas. The results showed that the quality improved heating of the printing bed. To identify the effect of the printing parameters modifications, the authors carried out a tensile test to compare the tensile properties of a) specimens printed from properly stored material at default printing parameters and b) specimens printed from improperly stored material with modified printing parameters. According to the results, these series reported different fracture patterns. On the other hand, the tensile strength values were comparable.

This study deals with the research on the impact of the construction of a tire-building drum on the selected parameters of a passenger tire. The introductory part of the study deals with a comprehensive analysis of the production process and factors that affect the quality of the final tire product during production. The content of this analysis is also the naming of problematic parts and their subsequent influence on the resulting parameters of a passenger tire. The core of the study is an optimization design for improving the construction of the tire-building drum. The world-renowned TRIZ methodology was applied to achieve the desired improvement results. Using the TRIZ methodology, the technical system was analysed, identified problematic parts, and defined the technical and physical contradictions and proposed possibilities for their removal. The systematic approach to the solution of the task has generated options for the right solution and possible optimization by reducing the weight of individual parts of the tire-building drum. During analysis, simulations of the deformation and total stress will be available before and after optimization. The work's conclusion describes the results of the simulation and the development process for the experimental testing possibilities of the optimized equipment. The study output is also a systematic procedure for testing the technical system, which can help designers design and optimize some parts of similar technical systems.

This paper deals with changes in selected properties of composite material and surface degradation after exposure to an acidic environment. A carbon fiber-reinforced composite (CFRP) produced from prepregs was tested. The weight change, micro-hardness, and surface degradation of the CFRP composite made of cured pre-impregnated laminates were evaluated in this study. Material consisting of a DT121R epoxy resin matrix with high reactivity and high viscosity, with two reinforcing carbon fabrics layers, is characterized by a low value of tensile strength. Evaluation of changes in the material properties was performed before and after exposure to specific environmental conditions, which are achieved by using a chemical solution of 15% H2SO4 at various temperatures. Subsequently, the effect of 15% H2SO4 at various temperatures on the material properties was monitored. The specimens were immersed in the solution for up to 3 and 6 weeks at the temperatures of 23°C, 40°C, and 60°C. It was found out, that the degradation of the composite material is conditioned by the aging of the epoxy resin (matrix). Carbon fibers (reinforcement) are relatively stable. The weight change, micro-hardness, and surface quality depend on the time of exposure to acidic solution and temperature. The micro-hardness tests show a significant influence on exposure time. The biggest changes in weight change and surface quality of the CFRP composite were observed after exposure at the temperature of 60°C.