Casting Surface Research Articles

Distribution of Fiber-Reinforcement in Thin Concrete Overlays

The spatial distribution and orientation of fibers in concrete materials can be linked with the measured fracture performance of the fiber-reinforced concrete (FRC). For FRC pavements, the improved toughness performance is used for adjusting the structural design and expected service life of the pavement. The prediction of toughness performance and pavement serviceability can be improved with a better characterization of fiber dispersion in the concrete pavement. In this research study, a flowable fibrous concrete (FFC) mixture was developed containing a synthetic macrofiber at a volume fraction higher than found with existing thin concrete pavements. This FFC mixture is anticipated to have greater toughness induced by more fiber alignment in a thinner (5 cm thickness) concrete inlay pavement. Quantification of synthetic fiber dispersion and alignment in the FFC mixture was made using x-ray computed tomography and imaging analyses. The influences of placement technique and proximity of cast or mold surfaces were investigated and found to impact the fiber spatial distribution and orientation. The image analysis revealed that the number of fibers crossing any vertical plane, which increased for FFC placed under directional flow, was directly related to the measured fracture performance. Fibers were verified to have the desired alignment, allowing more fibers to become engaged in crack opening resistance, when the FRC was placed as a thinner pavement layer and therefore resulting in a more cost-effective use of FRC for pavements.

Experimental investigation of CF8 stainless steel impeller quality using PLA-based fused deposition modeling-assisted investment casting

Abstract The conventional Investment Casting (IC) process is extensively used for manufacturing parts with intricate shapes and complex geometries. However, its drawbacks include long cycle times and costly tooling, making it ideal for mass production but inefficient for frequent design changes, small batch production, or customized products. To address these challenges, a novel hybrid method known as Fused Deposition Modeling Assisted Investment Casting (FDMAIC) has been developed. In FDMAIC, the wax pattern is replaced by an FDM-printed pattern, while all other steps follow the conventional IC process. In this study, a semi-open impeller for a centrifugal pump was produced using FDMAIC, with Polylactic Acid (PLA) as the pattern material and CF8 for casting. Dimensional accuracy and surface roughness, key indicators of quality, were evaluated at both the printing and casting stages. Critical dimensions such as outer and inner diameters, shroud and blade thicknesses, and total height were measured, along with surface roughness at the shroud and blade surfaces. In the final cast, maximum dimensional deviation was observed in Outer diameter(−2.408 mm), and minimum dimensional deviation was observed in total height(−0.169 mm). The surface roughness values obtained at the shroud and blade surface of the final cast were 4.64 μm 6.67 μm, respectively. Microstructure and hardness testing were also performed on the FDMAIC impeller to validate the process. The results provide detailed insights into the feasibility of FDMAIC and suggest areas for further improvement.

Influence of the Applied Protective Coating on the Technological Parameters of the Moulding or Core Sand Surface.

An important issue in obtaining a good casting surface without defects in contact with the liquid metal is the use of protective coatings on the surface of the moulding sand forming the mould cavity. Protective coatings are based on highly refractory materials that are finely ground and protect the moulding sand from thermal stresses from the molten metal. An important aspect of obtaining the appropriate properties of the protective coatings used is the method of application. This article presents the results of a quality study of the protective coatings obtained, which were applied by dip and painting with a brush. Four different coatings were applied to mould sand samples prepared on grain matrices with different average grain sizes. During the tests, the viscosity of the protective coatings, their gas-forming capacity, sieve analyses of the grain matrix used, the permeability of the moulding sand with the protective coating and the abrasiveness and adhesion of the protective coatings were determined. The quality of the coating obtained was found to depend on its type, the size of the grain matrix used in the moulding sand and the method of application. The experiments carried out indicate that a comparative study of the available protective coatings can indicate the best solution, taking into account the grain matrix used and the method of application adopted.

Accuracy of repaired maxillary dentures from two different repairing techniques: In vitro study

BackgroundDenture fracture is a common problem with acrylic dentures. The fractured denture can be repaired using various techniques such as self-cure acrylic resin acrylic resin and fiber-reinforced acrylic resin. PurposeThe purpose of this study was to compare the accuracy of dentures repaired with self-cure acrylic resin and fiber-reinforced acrylic resin processed using two different techniques (long-cure and microwave processing). Materials and methodsA total of 20 maxillary complete dentures were processed with two techniques; heat (long cycle) processing (10 dentures) and microwave processing (10 dentures). The maxillary cast and denture surface were scanned with Medit intraoral (Medit i700, Medit, South Korea) and STL files were created. Then, the dentures were sectioned at the midline and repaired using self-cure acrylic resin and fiber-reinforced acrylic resin and scanned with Medit intraoral. Finally, adaptation deviations were analyzed from computer software (Geomagic Control X, 3D Systems Inc., USA). The adaptation deviations in each group (long cure and microwave) were compared using an Independent T-test. Two-way ANOVA was done to see whether curing techniques and repairing methods affect the accuracy of repair. A P-value of 0.05 was considered significant. ResultsThe adaptation deviation was slightly higher in the fiber-reinforced acrylic resin group (0.565 ± 0.093) than in the self-cure acrylic resin group (0.536 ± 0.066). However, there was no statistical difference in the adaptation deviations of repaired dentures with self-cure acrylic resin and fiber-reinforced acrylic resin in the long-curing (P-value 0.245) and the microwave (P-value 0.638). Similarly, the adaptation deviation was slightly higher in the long-curing group (0.577 ± 0.075) than in the microwave group (0.524 ± 0.079). However, there was a statistically significant difference in the adaptation deviation of repaired dentures between long-curing and microwave techniques with self-cure acrylic resin (P-value 0.016) but no difference in fiber-reinforced acrylic resin (P-value 0.127). The result of Two-way ANOVA shows that there is no statistically significant interaction between curing techniques (long curing and microwave) and repairing methods (self-cure acrylic resin and fiber-reinforced acrylic resin) for adaptation deviations (P-value 0.646). However, the curing techniques show statistically significant differences (P-value 0.039). ConclusionAcrylic dentures can be repaired with self-cure resin or fiber-reinforced self-cure resin using various processing methods. The accuracy of the denture after repair is unaffected by the repairing method (self-cure acrylic resin and fiber-reinforced acrylic resin) but the accuracy of the denture after repair is affected by the curing techniques (long-curing and microwave). In self-cure resin, the microwave processing showed higher adaptation deviation and less accuracy, whereas the long-curing processing showed lower adaptation deviation and high accuracy.

The Influence of Surface Segregation on the Anodizing of AlSi11Cu2(Fe) Diecastings

A positive segregation is usually formed on the casting surfaces produced by high-pressure die casting (HPDC). In diecast Al-Si-Cu alloy components, this segregation shows a higher content of Si compared to the nominal composition of the alloy and it drastically affects the anodizing response of the casting surface. In the present work, HPDC components were produced by AlSi11Cu2(Fe) alloy, grit-blasted, and then anodized in a sulfuric acid electrolyte at the temperature of -4.5°C. Before the anodizing process, some regions of the casting were also milled, in order to completely remove the surface segregation. Microstructural investigations were carried out on grit-blasted and milled surfaces to characterize the initial substrates before anodizing, and to study their effect on the growth of the anodic layer. Scratch and wear tests were also performed to investigate the surface mechanical properties after anodizing. The results show that the surface segregation and the rough surface present on grit-blasted substrate leads to the formation of a thin and homogeneous anodic layer. On the contrary, a thicker and scalloped oxide film is formed on the milled surfaces. After anodizing, grit-blasted surfaces show lower wear and scratch resistance than milled substrates. The presence of surface segregation prevents the thickening of the anodic layer, negatively affecting the surface wear resistance due to the reduced oxide thickness.

Formation of the iron castings surface during investment casting. Historical background and technological features

Formation of the iron castings surface during investment casting. Historical background and technological features

Influence of Mg Content on Microstructure Coarsening, Molten Pool Size, and Hardness of Laser Remelted Al(-x)-Mg-Sc Alloys.

Investigations leading to high-quality surfaces and optimized properties in laser remelted Al-Mg-Sc alloys remain scarce. Laser surface remelting (LSR) has been used for the final treatment of these alloys processed through additive manufacturing. However, the direct microstructure responses of the treated cast surfaces have not yet been investigated. In the present research, Al-3, 5, and 10 wt %-Mg-0.1 wt %-Sc alloys plates were processed using LSR to study the effects of local melting and rapid solidification. The morphology of the α-Al phase, microstructure coarsening, and hardness were mapped from the bottom to the top of the molten pools, varying with local Mg content and laser heat input (2.5 J/mm, 5 J/mm, and 10 J/mm). This study aimed to create a comprehensive map of the microstructures, hardness, and molten pool sizes under various conditions. The findings may help to optimize these alloys through understanding laser processing parameters. Methods used included CALPHAD computations, optical microscopy, SEM, EDS, image analysis, hardness tests, and heat flow models. The results obtained showed α-Al cell growth with bands in all alloys with hardness changes correlating with cell spacing and heat input. Higher Mg content resulted in more refined cells and a higher fraction of bands. Increased Mg content decreased the thermal diffusivity and enthalpy of melting, enlarging the molten pool size. Hardness increased with decreasing heat input and higher Mg content in the tested alloys, especially in the Al-10 wt %-Mg-0.1 wt %-Sc alloy as the heat input was varied.

Comparison and evaluation of the cast iron castings surface using different types of foundries sands

This study investigates and compared various properties of high-quality foundry sands on the surface quality of castings, whose cores are produced using the col-box method. Methods such as the measurement of flushable fraction, sieve analysis, electron and optical microscopy, pH and electrical conductivity measurements were used to monitor the physico-chemical properties of silica and non-silica sands. 5 core mixtures were prepared from individual sands by adding 1.6 % of organic binder based on phenol-formaldehyde formed from resin and hardener using an MR100 mixer. The produced cores were placed in moulds made of a uniform bentonite mixture and cast (15 test castings). In all the tested sand samples, the dust content was visible at a 300× magnification, but the share of flushable content is not exceeded 3 %, which is one of the fundamental conditions for moulding. All the tested sands are heat resistant at 1600 °C and had a low flushable fraction in the range 0.05–0.3 %. The results indicate that the occurrence of surface defects in high-quality foundry sands is not related to the flushable fraction content, to the average grain size value d50, to the electrical conductivity, to the shape of the sand grains and to the flexural strength. The surface roughness is related to the average grain size, to the grain shape and to the flexural strength.

Self-assembled rectorite films with remarkable mechanical performance: preparation, structural characterization, and properties

Cohesive flexible rectorite clay films with good mechanical performance were prepared by a simple casting method through the self-assembly of exfoliated natural clay from aqueous dispersions. The multi-layered microstructure of the films consisted of continuous layers of aligned clay platelets parallel to the casting surface. Layers overlap randomly in the lateral direction (plane) and join vertically in an irregular manner by edge-to-face cross-linkages (bridging) to form coherent multi-layered nanostructured films with platelet-void microstructure. The films with the highest mechanical properties had thicknesses below 30 µm. Overall films from rectorite clay with monovalent interlayer content exhibited a higher experimental tensile strength ranging up to 44 MPa and Young’s modulus up to 56 GPa. The corresponding experimental values for films with divalent interlayer cations were 23 MPa for strength and 25 GPa for modulus. The highest experimental values for strength and modulus for neat Na–Ca–rectorite films were 25 MPa and 50 GPa respectively. These two mechanical property values of the best rectorite-based clay films compare favorably with values featured by polymer films typically used for packaging applications.

Electrochemical dissolution behavior of Inconel 718 alloy in NaNO3 solution: A comparison between wrought and cast

Cast IN718 and wrought IN718 are highly capable materials for blisks in aeroengines, owing to their high-temperature capabilities. Understanding their anodic electrochemical behavior is crucial for electrochemical machining (ECM) applications. In this study, electrochemical tests and ECM experiments were conducted on both cast IN718 and wrought IN718 alloys in a 10 wt% NaNO3 solution to explore their passivation-related behaviors and interface structures. The investigation included analysis via open circuit potential, polarization curve, and electrochemical impedance spectroscopy (EIS). Results indicate that compared to wrought IN718, the passive layer formed on cast IN718 surfaces contains numerous pores, rendering the corrosion resistance of cast IN718 less challenging in the 10 wt% NaNO3 environment. Additionally, X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of the passive layer. The analysis revealed that the passive layer on both cast and wrought IN718 surfaces primarily consisted of NiO, Ni(OH)2, Cr2O3, CrO3, Fe3O4, α-FeOOH, γ-Fe2O3, Fe2O3, NbO, Nb2O5, MoO2, and MoO3. Notably, the passive layer on cast IN718 was richer in NiO and lacked Cr2O3 and MoO3, which supports its porous and loose structures. Furthermore, ECM experiments were conducted at various current densities (1, 4, 8, and 15 A·cm−2) to identify the dissolution morphology. The results revealed several pitting pits on the machined surface of cast IN718 at low current densities, with lower surface roughness compared to wrought IN718. Conversely, for wrought IN718, the presence of needle-like structures dispersed on the machined surface improved substantially as the current density increased, significantly influencing surface quality.

Analyzing the synergistic effects of hard ceramic TiB2 and rare earth oxide La2O3 on mechanical behaviour, wear resistance, and residual stress of AA6061-T6 hybrid composite fabricated via ultrasonic-assisted stir casting

This investigation involves the fabrication of an aluminium metal matrix composite using AA6061-T6 alloy as the matrix, incorporating 2 wt% of hard ceramic (TiB2, 14 μm particle size) and 0.5 wt% of rare earth oxide (La2O3, 40–50 nm particle size) reinforcement powders through ultrasonic assisted stir casting. The study examines the microstructure, residual stress, and mechanical properties alongside performing pin-on-disk wear tests. Taguchi's optimization and ANOVA are used to optimize the wear rate of the composite using three control parameters: Load, Sliding Distance, and Sliding Speed. Results from optical micrography and field emission scanning electron microscopy (FESEM) with energy-dispersive spectrometer (EDS) analysis confirm the uniform distribution of TiB2 and La2O3 particles within the AA6061-T6 volume when ultrasonic stirring is employed. The composite's microhardness is found to increase by 25.15 %, and its tensile strength by 31.32 % compared to the base alloy due to a higher dislocation density. ANOVA highlights Load as the primary influencer, contributing 69.54 %, followed by Sliding Distance (17.45 %) and Sliding Speed (12.56 %). The optimal parameters for minimizing wear rate are found to be Load (20 N), Sliding Distance (1500 m), and Sliding Speed (2.5 m/s). Scanning Electron Microscope (SEM) images of worn surfaces reveal various mechanisms such as abrasion, delamination, and adhesion, with abrasion being the dominant mechanism. Residual stress increases with the addition of TiB2 and La2O3 particles in the matrix, showing transitions from tensile to compressive stress from the inner to the outer surface of the composite casting.

Critical Challenges in the Anodizing Process of Aluminium–Silicon Cast Alloys—A Review

The microstructure of the substrate plays a crucial role in the anodizing process. Anodizing cast aluminum alloys is quite challenging due to the higher levels of alloying elements present compared to pure aluminum. Elements such as silicon, iron, and copper significantly impact the growth and quality of the anodic layer. Additionally, anodizing parameters such as electrolyte composition, current density, and temperature are critical in determining the morphology and thickness of the anodic film. The casting process, surface condition, and post-treatment also affect the properties of the anodic layer. Optimizing these parameters is essential to achieve a durable and high-quality anodic layer. This work aims to provide a comprehensive understanding of the various factors affecting the anodizing of cast aluminum alloys and the properties of the anodic layer, including its thickness, corrosion resistance, and wear resistance.

SLGA-YOLO: A Lightweight Castings Surface Defect Detection Method Based on Fusion-Enhanced Attention Mechanism and Self-Architecture.

Castings' surface-defect detection is a crucial machine vision-based automation technology. This paper proposes a fusion-enhanced attention mechanism and efficient self-architecture lightweight YOLO (SLGA-YOLO) to overcome the existing target detection algorithms' poor computational efficiency and low defect-detection accuracy. We used the SlimNeck module to improve the neck module and reduce redundant information interference. The integration of simplified attention module (SimAM) and Large Separable Kernel Attention (LSKA) fusion strengthens the attention mechanism, improving the detection performance, while significantly reducing computational complexity and memory usage. To enhance the generalization ability of the model's feature extraction, we replaced part of the basic convolutional blocks with the self-designed GhostConvML (GCML) module, based on the addition of p2 detection. We also constructed the Alpha-EIoU loss function to accelerate model convergence. The experimental results demonstrate that the enhanced algorithm increases the average detection accuracy (mAP@0.5) by 3% and the average detection accuracy (mAP@0.5:0.95) by 1.6% in the castings' surface defects dataset.

Dynamic evolution of residual stress upon manufacturing Al-based diesel engine diaphragm

Abstract As a thin-walled complex structure, the manufacturing of Al-based diesel engine diaphragms involves casting and heat treatment. Residual stress is introduced during the uneven temperature field in casting and heat treatment, as well as the plastic deformation and cutting heat during mechanical processing. This research investigates the evolution and accumulation models of residual stress in casting and heat treatment for Al-based diesel engine diaphragms using ProCAST and ABAQUS software, combining with the experimental tests. To mitigate residual stress, the optimal parameter combination for casting temperature, knockout temperature, and mold preheating temperature in casting process is explored. The results indicate that the knockout temperature has the most significant influence on casting residual stress, and mold preheating is beneficial for reducing residual stress. Despite improvements, some internal stress concentration areas persist on the knockout casting surface. Furthermore, T6 heat treatment proves to be effective in eliminating more than 50% of the residual stress.

Analysis of Fragmentation Phenomenon of Composite Layers of Fe-TiC Type Obtained “in situ” in Steel Casting

A method for fabrication of a composite layer on the surface of a steel casting using coating containing TiC substrates was presented. The reaction of the synthesis of the ceramic phase was based on the SHS method (Self-propagating High-temperature Synthesis) and was triggered by the heat of molten steel. High hardness titanium carbide ceramic phases were obtained, which strengthened the base material improving its performance properties presented in this article. Microstructural examinations carried out by light microscopy (LM) on the in-situ produced composite layers showed that the layers were the products of reaction of the TiC synthesis – the phenomenon called “fragmentation” by the authors of study. The examinations carried out by scanning electron microscopy (SEM) have revealed the presence of spheroidal precipitated and free of impurities. The presence of titanium carbide was twofold increase in hardness in the area of the composite layer as compared to the base alloy which was carbon cast steel.

Study of mechanical properties of the YL113 die casting surface and middle layer

The YL113 die casting surface and middle layer are separated by machining and densities, porosities and mechanical properties of the YL113 die casting surface and middle layer are measured. Results show that the densities and mechanical properties of the total YL113 die casts are in between those of the YL113 die casting surface and middle layer and are identical to those of the YL113 die casting middle layer. The porosities of the die casting surface layer are smaller and fewer and its densities are bigger and mechanical properties are better than those of the middle layer. Effects of different die casting process parameters on the surface layer and the middle layer of die casting are different, of whom effects of the casting pressure and the biscuit thickness on them are most obvious. The densities and mechanical properties of the surface layers and the middle layers of die castings increase with increasing the casting pressures and the biscuit thicknesses. In addition, the effects of densities on the mechanical properties of the die casting middle layers are more obvious than those of the die casting surface layer.

Unveiling the origin of severe hot cracking susceptibility in Al-Li alloys

This work reports a new mechanism for the severe hot cracking susceptibility (HCS) of cast Al-Li alloys. In contrast to the narrow vulnerable solidification temperature range increasing cracking resistance, alloys with high Li content or solute content, which are supposed to show lower HCS, instead exhibit anomalously high HCS. Results reveal that this phenomenon arises from a variety of Li-rich inclusions distributed in the interdendritic paths, including Li2O, LiAlO2, Li2CO3 and LiH. These particles can form spontaneously with O2, CO2 and H2O during solidification, deteriorating the interfacial bonding capacity. Meanwhile, the occupation of refilling channels for residual liquid increases the potential risk of microcrack initiation. These unfavorable factors promote the rapid propagation of cracks from the casting surface inward, which eventually leads to catastrophic fractures.

Formation mechanism of the microstructural heterogeneity in a die-cast Al-Mg-Si alloy and its effect on mechanical properties

Al-Mg-Si series alloys fabricated by high pressure die casting (HPDC) have a broad application prospect in the production of large-scale and thin-walled die-castings. However, the die-cast Al-Mg-Si series alloys usually exhibit obvious microstructural heterogeneity. This study investigated the microstructural heterogeneity of the die-cast Al-7 Mg-3Si alloy along the thickness direction, and the corresponding formation mechanism was verified. In this study, the die-cast sample can be divided into four distinct regions (R1 ∼ R4) from the surface to the center in turn according to the area fraction of the primary α-Al. Two aspects were considered to be the main reasons for the formation of microstructural heterogeneity. On the one hand, the externally solidified crystals (ESCs) preferentially formed in the shot sleeve and aggregated in the casting center. On the other hand, the cooling rates were quite different in each region, leading to different solidification behaviors. Based on the combination of the microstructural observation and calculated cooling rates, a physical model has been proposed to describe the formation mechanism of the microstructural heterogeneity. The heterogeneous microstructure of the die-cast sample resulted in the inhomogeneity of mechanical properties along the thickness direction. The R2 exhibited the highest micro-hardness than the other regions because of its highest amount of eutectics. Moreover, the casting surface with fine grains (R1) is conducive to improving the EL, whereas the center (R4) showed the lowest tensile properties due to the existence of ESCs and porosity band.

Improving the Abrasion Resistance of Nodular Cast Iron Castings by Remelting Their Surfaces by Laser Beam.

This paper presents the results of research conducted in the field of the technology of surface hardening of castings from unalloyed and low-alloy nodular cast iron using the laser remelting method. The range of studies included macro- and microhardness measurements using Rockwell and Vickers methods as well as metallographic microscopic examinations using a scanning electron microscope. Moreover, abrasive wear resistance tests were performed using the pin-on-disk method in the friction pair of nodular cast iron-SiC abrasive paper and the reciprocating method in the friction pair of nodular cast iron-unalloyed steel. Analysis of the test results shows that the casting surface layer remelting by laser for unalloyed nodular cast iron results in a greater improvement in its resistance to abrasive wear in the metal-mineral system, as compared to low-alloy cast iron. Additionally, carrying out the laser hardening treatment of the surface layer made of the tested grades of nodular cast iron is justified only if the tribological system of the cooperating working parts and allowable dimensional changes during their operation are known.

Relationships Between Macrostructure and Microstructure in Lamellar Graphite Iron Castings

AbstractSpherical sheet steel molds filled with gray iron melts of varying chemical compositions and metallurgical conditions were air-cooled until solid, followed directly by austempering to preserve the austenite grain structure. The castings were studied using a combination of cooling curves and quantitative metallography, in order to clarify control of the austenite grain structure and its impact on the local microstructure. A novel method utilizing fast Fourier transform provided visual overview of macroscopic trends in the scale of the flake graphite structure. Castings inoculated with Sr-containing ferrosilicon featured finer eutectic cell structure but coarser equiaxed structure of austenite, emphasizing that melt treatments applied to control the graphite structure may have unintended effects on the austenite grain structure. In most non-inoculated castings, the microstructure was banded, with alternating layers of coarse and fine flake graphite with distance from the casting surface. The extent of the columnar zone of austenite grains showed no correlation with the graphite structure nor the volume fraction of dendrites. The volume-to-surface ratio of dendrites was more uniform in the columnar zone, but increased toward the center in the equiaxed zone. The casting with the highest carbon equivalent (4.34), featured zones containing finer dendrites and graphite. These zones appear to be gaps in the early solidification structure which filled later by secondary dendritic growth from surrounding austenite. This highlights that high carbon equivalent may lead to poor dendrite coherency which can make the microstructure less uniform and less predictable.