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The article discusses the development of the design of the plasma torch used for welding and surfacing, the relevance of the plasma type of welding, the stages of work necessary to develop this design, modeling the flow of protective and working gas.

Colloidal quantum dot (QD) solids are emerging semiconductors that have been actively explored in fundamental studies of charge transport1 and for applications in optoelectronics2. Forming high-quality QD solids—necessary for device fabrication—requires substitution of the long organic ligands used for synthesis with short ligands that provide increased QD coupling and improved charge transport3. However, in perovskite QDs, the polar solvents used to carry out the ligand exchange decompose the highly ionic perovskites4. Here we report perovskite QD resurfacing to achieve a bipolar shell consisting of an inner anion shell, and an outer shell comprised of cations and polar solvent molecules. The outer shell is electrostatically adsorbed to the negatively charged inner shell. This approach produces strongly confined perovskite QD solids that feature improved carrier mobility (≥0.01 cm2 V−1 s−1) and reduced trap density relative to previously reported low-dimensional perovskites. Blue-emitting QD films exhibit photoluminescence quantum yields exceeding 90%. By exploiting the improved mobility, we have been able to fabricate CsPbBr3 QD-based efficient blue and green light-emitting diodes. Blue devices with reduced trap density have an external quantum efficiency of 12.3%; the green devices achieve an external quantum efficiency of 22%.A solution-based ligand-exchange strategy enables the realization of close-packed quantum dot solid films with near-unity photoluminescence quantum yield and high charge carrier mobility.

The article presents a comprehensive review of key issues and challenges related to enhancing the durability of hot forging tools. It discusses modern strategies aimed at increasing tool life, including modifications to tool materials, heat treatment, surface engineering, tool and die design, die geometry, tribological conditions, and lubrication. The review is based on extensive literature data, including recent publications and the authors’ own research, which has been implemented under industrial conditions at the modern forging facility in Forge Plant “Glinik” (Poland). The study introduces original design and technological solutions, such as an innovative concept for manufacturing forging dies from alloy structural steels with welded impressions, replacing traditional hot-work tool steel dies. It also proposes a zonal hardfacing approach, which involves applying welds with different chemical compositions to specific surface zones of the die impressions, selected according to the dominant wear mechanisms in each zone. General guidelines for selecting hardfacing material compositions are also provided. Additionally, the article presents technological processes for die production and regeneration. The importance and application of computer simulations of forging processes are emphasized, particularly in predicting wear mechanisms and intensity, as well as in optimizing tool and forging geometry.

Friction surfacing (FS) is a solid-state layer deposition process for metallic materials at temperatures below their melting point. While the bonding of the deposited layers to the substrate is proven suitable for coating applications, so far the mechanical properties of additively manufactured stacks have not been systematically investigated. In particular, the effect of successive deposited FS layers, i.e., repetitive thermo-mechanical loading, on the interface properties as well as anisotropy and strength of the deposited stack is unknown. For this purpose, the mechanical properties of FS deposited multi-layer stacks from dissimilar aluminum alloys have been investigated, characterizing layer-to-layer as well as layer-to-substrate bonding interfaces via micro-flat tensile testing. Furthermore, directional dependencies in the stack and failure mechanisms are analyzed. The results show a homogeneous, fine-grained microstructure with average grain sizes between 4.2 and 4.6 μ m within the deposited material. The resulting tensile properties with no significant directional dependency present an ultimate tensile strength between 320 and 326 MPa exceeding the strength of the AA5083 H112 consumable base material. No difference was obtained in terms of layer-to-layer or layer-to-substrate interface strength. Furthermore, homogeneous hardness was observed within the deposited structure, which is in the range of AA5083 base material’s hardness of 91 HV. The results indicate that the FS process in conjunction with the material used is suitable for additively generated structures and highlight the potential of this solid-state layer deposition technology.

The aim of this study was to investigate cutting force when milling 40 × 13 stainless steel samples obtained via electron-beam surfacing. The samples were obtained by surfacing the wire made from the martensitic 40 × 13 stainless steel. The microstructure of the samples and the hardness are discussed in the present study. Emphasis is placed on the study of cutting forces when handling the samples. The structure of the samples obtained by electron-beam surfacing consisted of tempered martensite. The average hardness of the samples was similar to the hardness obtained after quenching and tempering the samples—576 HV for horizontally printed workpieces and 525 HV for vertically printed workpieces. High-speed milling, high-efficiency milling, and conventional milling have been proven to be suitable for handling such workpieces. This study shows that an increase in milling width leads to a gradual decrease in specific cutting force. As the milling depth increases, the specific cutting force decreases intensively at first but then more slowly with time. Machining the workpieces made of the martensitic stainless steel and produced by electron-beam surfacing requires the use of purely carbide mills with a diameter of at least 12 mm. Using a high-speed steel as a tool material results in the rapid failure of the tool. The cutting conditions during the investigation allowed for a decrease in the temperature of the cutting edge, cutting force, and the low-rigid end mill bending. Therefore, this study has made it possible to select modes that allow for a reduction in the vibration of the lathe-fixture-tool-part system.

The up to date industry tends to introduce additive technologies in all fields of production, since their use furthers manufacturing of sufficiently qualitative products in a quite quick and economical way.As a consequence, it is still a topical issue how to control quality of the output products.The paper reports on a numerical model of thermal processes in a substrate plate and in a product while depositing.Temperature distribution patterns and a penetration form of a substrate plate are considered for the entire process of deposition.

In the present research, the friction surfacing process has been used to deposit a wear-resistant and fully bonded AA7075 coating on an AA6082 substrate. Taguchi L9 orthogonal array was used to design the experiments and to study the effects of process parameters, such as the AA7075 consumable rod rotational speed (1000, 1200, and 1400 rpm), transverse speed (140, 160, and 180 mm/min), and consumable rod diameter (18, 20 and 22 mm), on the bond strength and wear resistance of the deposited coatings. The Taguchi gray relational analysis technique was employed to optimize the process parameters. A ram tensile test, dry sliding wear test, and microhardness test were employed to study the coatings’ bond strength, wear resistance, and hardness, respectively. The Taguchi gray relational analysis demonstrated that the optimal parametric setting included a rotational speed of 1000 rpm, a transverse speed of 180 mm/min, and a consumable rod diameter of 20 mm, which resulted in a hard coating with a bond strength of 128.54 MPa and 46.38% wear resistance compared to the AA 6082 substrate. The analysis of variance results indicate that the rotational speed contributes the most to the coating’s wear resistance and bond strength, followed by the transverse speed and consumable rod diameter. Moreover, the ductile failure mode was observed in the coatings during the ram tensile test, and the coatings exhibited adhesion, followed by the abrasion type of wear mechanism during wear testing.

The dilution rate of surfacing layers and the quality of weld forming are important factors affecting the quality of surfacing layers in open-arc surfacing. They are determined by the interaction of various surfacing parameters. In this paper, the response surface method is used to optimize the process parameters of open-arc surfacing welding. Mathematical models of the surfacing current, surfacing voltage, surfacing speed, dilution rate and weld residual height were established, and the reliability of the models was verified by variance analysis. By performing an analysis of the perturbation diagram and response surface diagram, the influence law of each influencing factor on the response value was obtained. The parameters of surfacing welding were optimized by setting optimization targets, and the experimental results of optimized parameters were compared with the predicted results. The optimized surfacing parameters were tested by grinding roller surfacing repair. The experimental results show that the quality of the grinding roller can meet the repair requirements. This shows that the model can be used to guide the surface repair of rollers and is of great significance to ensure the surface-repair quality of rollers.

Surfacing reinforcement in its various options leads to a decrease in the hardness of the base metal of heat strengthened steel 65G and does not affect the HRC value of the bead formed by the electrode for abrasive resistant surfacing.

The paper presents the influence of chemical compositions and structure of the deposited metal on its hardness and wear resistance in abrasive-shock conditions. Metal Was deposited by the arc powder wire automatic welding. The studies have shown that increasing nikel contain to 0.65% in the surfaced steel and cobalt additive while reducing carbon contain to 0.17-0.23%, provides martensite and former austenite grain size disintegration. In consequence of multivariate correlation analysis, it was determined dependence to the hardness of the deposited layer and the wear resistance of the mass fraction of the elements included in the flux-cored wires of the system Fe-C-Si-Mn-Cr-Mo-Ni-V-Co. Obtained dependences could be used in predicting hardness and wear resistance of the deposited metal while changing welding metal chemical composition.