Search Results (97)

The quality of machined marine propellers plays a critical role in underwater propulsion performance. Precision casting is the predominant manufacturing technique; however, deformation of wax models and rough blanks during manufacturing frequently cause deviations in the dimensions of final products and, thus, affect propellers’ performance and service life. Current inspection methods primarily involve using coordinate measuring machines and sampling. This approach is time-consuming, has high labor costs, and cannot monitor manufacturing quality in real-time. This study developed a real-time online automated measurement system containing a high-resolution CITIZEN displacement sensor, a four-degree-of-freedom measurement platform, and programmable logic controller-based motion control technology to enable rapid, automated measurement of blade deformation across the wax model, rough blank, and final product processing stages. The measurement data are transmitted in real time to a cloud database. Tests conducted on a standardized platform and real propeller blades confirmed that the system consistently achieved measurement accuracy to the second decimal place under the continual measurement mode. The system also demonstrated excellent repeatability and stability. Furthermore, the continuous measurement mode outperformed the single-point measurement mode. Overall, the developed system effectively reduces labor requirements, shortens measurement times, and enables real-time monitoring of process variation. These capabilities underscore its strong potential for application in the smart manufacturing and quality control of marine propellers. Full article

Nickel-based single-crystal superalloy turbine blades are typically manufactured via investment casting followed by a well-established heat treatment process, resulting in a uniform microstructure composed of thin γ channels and cubic-shaped γ’. However, the region near the corner of the aerofoil/platform of the blade exhibits a distinct contrast compared to the surrounding area. High-resolution scanning electron microscopy (SEM) reveals significant degradation of the γ and γ’ phases in the dark contrast region. In this area, the γ’ phase no longer maintains its characteristic cubic morphology and appears partially dissolved or even melted. Although the regularity of the γ/γ’ microstructure is disrupted, the region is still composed of irregular-shaped γ and γ’ phases. Based on these microstructural observations, a possible formation mechanism of the abnormal microstructure is discussed. Although the blades are not exposed to conventional creep conditions during casting and heat treatment, residual stress accumulated during casting may be relieved at elevated temperatures during the heat treatment process. The synergistic effect of stress, temperature, and time may contribute to the formation of the observed abnormal microstructure. Full article

Compared with powder metallurgy, centrifugal casting, jet molding, and other technologies, Laser Melting Deposition (LMD) stands out as an advanced additive manufacturing technology that provides substantial advantages in the melt forming of functional gradient materials and composites. However, when high-temperature and high-speed laser energy is applied, the resulting materials are susceptible to porosity, which restricts their extensive use in fatigue-sensitive applications such as turbine engine blades, engine connecting rods, gears, and suspension system components. Since fatigue cracks generally originate near pore defects or at stress concentration points, it is crucial to investigate evaluation methods for pore defects and stress concentration in LMD applications. This study examines the effect of pore defects on stress concentration in LMD-manufactured AlSi10Mg using the crystal plasticity finite element method and proposes a stress concentration coefficient characterization approach that considers pore size, morphology, and location. The simulation results indicate a competitive mechanism between pores and grains, where the larger entity dominates. Regarding the influence of aspect ratio on stress concentration, as the aspect ratio decreases along the stress direction, the stress concentration increases significantly. When pores are just emerging from the surface (s/r = 1), the stress concentration caused by the pore reaches its maximum, posing the highest risk of material failure. To assess the extent to which the aspect ratio, position, and size of pores affect stress concentration, a statistical correlation analysis of these variables was conducted. Full article

Scaling up the production of TiAl turbine wheels for passenger car turbochargers requires the fabrication of thin blades that are similar to those of nickel-based superalloys. To achieve this, the molten metal fillability and impact resistance of thin blades must be improved. In this study, the effects of composition on these properties are predicted using simple laboratory experiments with binary, ternary, and practical alloys and are then verified with actual turbine wheels. The melt fillability of the turbine wheel blade is predicted using the amount of molten metal passing through an Al₂O₃-1%SiO₂ mesh. The binary alloy exhibits the best fillability, which is reduced by the addition of Cr and Si. Charpy impact tests on as-cast materials at 25 and 850 °C show that the addition of Cr and Mn improves the impact resistance, but the addition of Nb, W, Mo and Si reduces it. Therefore, the molten metal fillability and/or impact resistance of practical TiAl alloys containing such additives owing to other requirements are low and require improvement for use in thin-blade turbine wheel applications. Full article

High-entropy alloys are novel metallic materials distinguished by very special mechanical and chemical properties that are superior to classical alloys, attracting high global interest for the study and development thereof for different applications. This work presents the creation and characterisation of an FeMoTaTiZr high-entropy alloy composed of chemical constituents with relatively low biotoxicity for human use, suitable for medical tools such as surgical scissors, blades, or other cutting tools. The alloy microstructure is dendritic in an as-cast state. The chemical composition of the FeMoTaTiZr alloy micro-zone revealed that the dendrites especially contain Mo and Ta, while the inter-dendritic matrix contains a mixture of Ti, Fe, and Zr. The structural characterisation of the alloy, carried out via X-ray diffraction, shows that the main phases formed in the FeMoTaTiZr matrix are fcc (Ti₇Zr₃)_0.2 and hcp Ti₂Fe after annealing at 900 °C for 2 h, followed by water quenching. After a second heat treatment performed at 900 °C for 15 h in an argon atmosphere followed by argon flow quenching, the homogeneity of the alloy was improved, and a new compound like Fe_3.2Mo_2.1, Mo_0.93Zr_0.07, and Zr(MoO₄)₂ appeared. The microhardness increased over 6% after this heat treatment, from 694 to 800 HV_0.5, but after the second annealing and quenching, the hardness decreased to 730 HV_0.5. Additionally, a Lactate Dehydrogenase (LDH) cytotoxicity assay was performed. Mesenchymal stem cells proliferated on the new FeMoTaTiZr alloy to a confluence of 80–90% within 10 days of analysis in wells where the cells were cultured on and in the presence of the alloy. When using normal human fibroblasts (NHF), both in wells with cells cultured on metal alloys and in those without alloys, an increase in LDH activity was observed. Therefore, it can be considered that certain cytolysis phenomena (cytotoxicity) occurred because of the more intense proliferation of this cell line due to the overcrowding of the culture surface with cells. Full article

This study evaluates the perfection of the crystal structure of single-crystal turbine blade castings made from the CMSX-4 nickel superalloy. The analysis included primary and secondary crystal orientation measurements using the Ω-scan method and the novel OD-EFG X-ray diffractometer. The selected microstructural parameters of the single crystals were also analyzed, including the assessment of stereological parameters and the degree of porosity. A creep test was performed according to standard procedures and under conditions simulating real operational environments. The model single-crystal turbine blades were manufactured using the Bridgman–Stockbarger method, with variable withdrawal rates of 1 and 3 mm/min. Heat treatment of the single-crystal castings involved solution treatment followed by double aging. The evaluation of structural perfection was carried out in three states: as-cast, after solution heat treatment, and after double aging. The crystallographic orientation of the blades was determined on both the airfoil and the root part. The study determined how crystallographic orientation and microstructural parameters influence the creep resistance of the castings. It was found that in the as-cast condition, the greatest influence on high creep strength has a small deviation of the primary and constant value of secondary crystal orientation along the height of the blade casting. After heat treatment, the highest creep resistance was obtained for the blade manufactured at a withdrawal rate at 1 mm/min. Full article

Organic semiconductor materials are interesting due to their application in various organic electronics devices. [1]benzothieno[3,2-b][1]benzothiophene (BTBT) is a widely used building block for the creation of such materials. In this work, three novel solution-processable regioisomeric derivatives of BTBT—2,7-bis(3-octylthiophene-2-yl)BTBT (1), 2,7-bis(4-octylthiophene-2-yl)BTBT (2), and 2,7-bis(5-octylthiophene-2-yl)BTBT (3)—were synthesized and investigated. Their optoelectronic properties were characterized experimentally by ultraviolet–visible and fluorescence spectroscopy, time-resolved fluorimetry, and cyclic voltammetry and studied theoretically by Time-Dependent Density Functional Theory calculations. Their thermal properties were investigated by a thermogravimetric analysis, differential scanning calorimetry, polarizing optical microscopy, and in situ small-/wide-angle X-ray scattering measurements. It was shown that the introduction of alkyl substituents at different positions (3, 4, or 5) of thiophene moieties attached to a BTBT fragment significantly influences the optoelectronic properties, thermal stability, and phase behavior of the materials. Thin films of each compound were obtained by drop-casting, spin-coating and doctor blade techniques and used as active layers for organic field-effect transistors. All the OFETs exhibited p-channel characteristics under ambient conditions, while compound 3 showed the best electrical performance with a charge carrier mobility up to 1.1 cm²·V⁻¹s⁻¹ and current on/off ratio above 10⁷. Full article

A large-sized backward-curved fan with high shape difficulty was designed, and fan performance was roughly predicted from computational fluid dynamics. Three gating systems of aluminum sand casting were designed to fabricate the fan. The flow pattern and solidification process of molten metal were analyzed by casting simulation. Three types were applied: bottom-up with four gates, bottom-up with ten gates, and top-down with a feeder. The simulation results of the bottom-up with four gates show that a large temperature loss occurs while molten metal flows into thin blades, and there is a temperature range below the liquidus temperature. Due to nonuniform temperature distribution, the solidification pattern is also not uniform. The bottom-up with ten gates shows almost similar flow and solidification patterns but has the effect of slightly reducing the temperature loss of molten metal. The top-down type has a much smaller temperature loss, while molten metal flows into the mold cavity compared to the bottom-up type and has a directional solidification pattern. As the feeder also acts as a riser to compensate for the shrinkage of the thick part, the simulation results regarding porosities are also significantly reduced. The fan cast as a top-down type has soundness without any unfilled parts. Full article

To address the frequent cleaning requirements of casting molds in bridge tower construction, a wall-climbing cleaning robot based on negative pressure adsorption is designed to safely and efficiently replace manual labor for cleaning tasks. The primary focus of this paper is the establishment of a theoretical model for negative pressure adsorption, along with an analysis of potential adhesion hazards. Initially, the robot’s chassis was designed, followed by the development of a theoretical model for the rotational-flow suction unit that incorporates two critical parameters: the number of blades and their thickness. This model was validated through computational fluid dynamics (CFD) and experimental methods. The findings indicate that, with fewer blades, an increase in blade quantity significantly improves the distribution of nonlinear velocity in the z-plane, resulting in a substantial enhancement of suction force up to a certain limit. As the number of blades increases, the thickness of the blades primarily influences the volume of air within the rotating domain, thereby affecting the suction force; thinner blades are preferable. Moreover, this study reveals that square suction units provide greater suction force compared to circular ones, attributable to their superior negative pressure effect and larger adsorption area. The most critical adhesion risk identified is leakage at the edges of the suction unit. Full article

This article presents the results of testing the suitability of X-ray computed tomography for the quality control of the casting moulds used for producing turbine blades. The research was focused on the analysis of cross-sectional images, spatial models and the porosity of moulds using a Phoenix L 450 microtomograph. The research material consisted of samples from three mixtures of ceramic materials and binders intended for producing casting moulds using the lost wax method. Various configurations of filling materials (Molochite and quartz flours) and binder (Remasol, Ludox PX 30 and hydrolysed ethyl silicate) mixtures were considered. X-ray computed tomography enabled the detection of a number of defects in the ceramic mass related to the distribution of mass components, porosity concentration and defects resulting from the specificity of the mould production. It was found that casting mould quality control on cross-sectional tomographic images is faster and as accurate as the analysis of three-dimensional models and allows for the detection of a whole range of ceramic defects, but the usefulness of the images is greatest only when the cross-sections are taken at an appropriate angle relative to the object being examined. Full article

During the production of single-crystal superalloy blades, a kind of channel-type defect, named “quasi-freckle”, was found on the casting surface, which is similar to typical freckles in macroscopic appearance but different in microstructure. In the as-cast microstructure of the quasi-freckle channels, the γ/γ’ eutectic is significantly accumulated and can be dissolved during the solution heat treatment. Since no disoriented grains were detected, the quasi-freckles have a basically identical crystal orientation with the matrix. The quasi-freckle channels actually appear as thermosolutal convection traces in the directional solidification process of single-crystal casting. Because the convection was not strong enough to break dendrite arms, the single-crystal consistency of the castings was not destroyed. However, with the deterioration of the solidification condition and the increase in solutal convection, quasi-freckles often develop into typical freckle defects. Full article

The current investigation focuses on the viscosity, coating weight, and surface characteristics of lost foam casting coatings, examining the effects of blade shape, stirring speed, and stirring time. A systematic analysis was conducted to determine how different stirring speeds and durations influenced coating weight and viscosity. The results indicate that the blade shape has a considerable impact on the uniformity and efficacy of the coating, with some designs being far more effective in reaching the optimal viscosity and coating weight through uniformly distributed mixing. Results were consistently obtained when stirring at 800–1200 rpm. It was demonstrated that while stirring speed significantly impacts coating deposition, it has small effect on viscosity. A stirring time of 30 min was found optimal for stabilizing coating weight and viscosity without significant variations. Drying at room temperature produced smoother surfaces with fewer cracks, whereas higher drying temperatures (50 °C) were associated with increased surface roughness and cracking. Crack analysis after drying revealed that coatings mixed with the tri-blade had the lowest tendency to crack, demonstrating its superior capability for even and thorough mixing. Full article

This paper presents the results of an analysis of resistance to hydrogen embrittlement and offers solutions and technologies for manufacturing castings of components for critical applications, such as blades for gas turbine engines (GTEs). The values of the technological parameters for directional crystallization (DC) are determined, allowing the production of castings with a regular dendritic structure of the crystallization front in the range of 10 to 12 mm/min and a temperature gradient at the crystallization front in the range of 165–175 °C/cm. The technological process of making GTE blades has been improved by using a scheme for obtaining disposable models of complex profile castings with the use of 3D printing for the manufacture of ceramic molds. The ceramic mold is obtained through an environmentally friendly technology using water-based binders. Short-term tensile testing of the samples in gaseous hydrogen revealed high hydrogen resistance of the CM-88 alloy produced by directed crystallization technology: the relative elongation in hydrogen at a pressure of 30 MPa increased from 2% for the commercial alloy to 8% for the experimental single-crystal alloy. Full article

With the increasing demand for high-performance leisure boat propellers, this study explores the development of high-strength aluminum alloy propellers using the low-pressure die-casting (LPDC) process. In Part I of the study, we identified the optimal alloy compositions for Al-6Zn-2Mg-1.5Cu propellers and highlighted the challenges of hot tearing at the junction between the hub and blades. In this continuation, we developed a coupled thermal fluid stress analysis model using ProCAST software to optimize the LPDC process. By adjusting casting parameters such as the melt supply temperature, initial mold temperature, and curvature radius between the hub and blades, we minimized hot tearing and other casting defects. The results were validated through simulations and practical applications, showing significant improvements in the quality and structural integrity of the propellers. Non-destructive testing using X-ray CT confirmed the reduction in internal defects, demonstrating the effectiveness of the simulation-based approach for alloy design and process optimization. Full article

The TNM alloy, a β_o-phase-containing TiAl alloy, has been withdrawn from use as a last-stage turbine blade in commercial jet engines as it suffered frequent impact fractures in service, raising doubts regarding the necessity of the β_o-phase in practical TiAl alloys. Here, we evaluate the practical properties required for jet engine blades for various TiAl alloys and investigate the effects of the β_o-phase thereupon. First, we explore the influence of the β_o-phase content on the impact resistance and machinability for forged Ti–43.5Al–xCr and cast Ti–46.0Al–xCr alloys; the properties deteriorate significantly at increasing β_o-phase contents. Subsequently, two practical TiAl alloys—TNM alloy and TiAl4822—were prepared with and without the β_o-phase by varying the heat treatment temperature for the former and the Cr concentration for the latter. In addition to impact resistance and machinability, the creep strength is significantly reduced by the presence of the β_o-phase. Overall, these findings suggest that the β_o-phase is an undesirable phase in practical TiAl alloys, especially those used for jet engine blades, because, although the disordered β-phase is soft at high temperatures, it changes to significantly more brittle and harder β_o-phase after cooling. Full article