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This paper presents an innovative ceramic mould manufacturing technology aimed at improving the driftability of particularly difficult castings, which are characterised by complex geometry and a high tendency to bake/clog the mass in critical areas of the mould (holes, closed casting spaces, corners, sharp edges, variable cross-sections). Traditional ceramic moulds, despite their strength, often create problems during the casting knockout process, leading to casting damage and increased cleaning costs. The new technology is based on the use of a hybrid mould structure, the essence of which is the production of layers in the ceramic mould, in the central zone of the mould, characterised by a significantly reduced final strength, achieved after firing. These layers are made on the basis of an organic binder. As a result, excellent driftability of the castings and effective separation of ceramic residues from the surface of the castings is achieved due to the embedded layer. The special layers can be incorporated over the entire surface or only in the areas where fusion of the casting surface with the ceramic mass occurs. Tests conducted have shown that the developed technology significantly improves the driftability of ceramic moulds, especially for castings with complex geometries, where traditional methods fail. The introduction of this innovation has the potential to be widely applied in various industries where the requirements for precision and quality of castings are very high, such as the aerospace, energy and automotive industries.

A directional solidification experiment was carried out using CMSX-4 superalloy to investigate the effect of the ceramic core on the freckle formation. The results show that the freckle formation exhibits a strong wall-dependence regardless of the shell mold wall or the ceramic core wall. With increasing inner diameter of the ceramic core, the freckle formation on the outer surfaces of the castings is reduced, whereas it is increased on the inner surfaces. The internal freckle defect was found only on the outer convex surfaces of the castings. No freckle appeared on the inner concave surfaces of the castings. With increasing wall-thickness of the ceramic core, the occurrence of the freckle defect on the outer surfaces of the castings is reduced, while the internal freckle defect is increased. The findings in the present study will extend our understanding of the freckle formation and contribute to develop a method to minimize the freckle defect in the directional solidified Ni-based single crystal castings.

Electron-beam casting technology has great potential in obtaining high-quality precision titanium castings due to its good ability to remove inclusions from the metal. In this study, the interfacial reactions of titanium with the face coats of the ceramic mold were investigated using microstructural analysis and microhardness measurement. Refractories—Al2O3, ZrO2, ZrSiO4 and Y2O3 were used as fillers for face coats. The study of the microstructure of cast samples from technically pure titanium showed that the Al2O3 face coat led to the formation of an α-case with a thickness of 300–400 μm. The Y2O3 coating in combination with Al2O3 and ZrO2 stucco ensured the formation of a twice-thin α-case. A combined face coat, which contained 70% ZrO2 + 30% Y2O3 slurry fillers and ZrO2 as stucco, ensured the formation of an α-case up to 200 μm thick. Measurement of microhardness made it possible to determine the nature of the interaction of titanium castings with ceramics and the distribution of gas impurities in the surface layers of the metal. Electron beam processing in combination with electromagnetic stirring leads to the formation of a fine structure in titanium castings. The low overheating of the titanium melt specific for EBCT and the low temperature of the mold contribute to reducing the interaction of titanium with ceramics. The combined face coat showed good technological properties and can be recommended for the production of thin-walled castings from titanium alloys by electron-beam casting technology.

The paper presents the development of an ecofriendly ceramic moulding system for the precision casting of aircraft turbine components from nickel superalloys using water-soluble binders. The motivation was to eliminate hydrolysed ethyl silicate (HES) due to its environmental and occupational hazards. Two water-based binders (K + M)—Keysol (for the primary layer) and Matrixsol (for the backup layers)—were evaluated against the standard HES-based system. A comprehensive comparative analysis was conducted including microstructure, phase composition, wettability, mechanical, thermal, and gas permeability properties. The developed K + M ceramic moulds achieved a bending strength of 12.4 MPa after annealing, average surface roughness (Ra) below 5 µm, and open porosity of 29.1%, indicating excellent strength and permeability. Thermal conductivity increased from 0.3 W/mK to 2.0 W/mK between 22 °C and 1400 °C. The wetting angle of water-based binders was higher (Keysol: ~36°) compared to HES (~5°), resulting in more stable surface morphology. Gas permeability was maintained at 5.6 × 10−9 cm2 at 1100 °C, ensuring effective degassing during casting. The results demonstrate that the K + M system can replace HES in production while improving safety and reducing environmental impact, making it suitable for industrial-scale implementation in the aerospace sector.

The paper considers the problem of laboriousness of cleaning and knocking out investment casting castings from ceramic molds material. The influence of softening modifiers on the structure and residual strength of ceramic samples was analyzed. A magnesium sulfide and copper chloride were selected for the study because of their temperature of destruction, which is in the range of the calcination temperature of the ceramic shells and the temperature of pouring the mold with liquid metal. For comparative studies of particle size distribution after exposure to shock loading the samples were formed from ceramic suspension with introduction of 1.5 and 3 wt.% of softening modifiers. Fractures of ceramics were examined using a two-beam electron scanning microscope “Versa 3D”. It was shown that the use of copper chloride as a softening modifier in the composition of ceramics is facilitate the process of knockout the mold of investment casting.

Film cooling is an important cooling method to decrease the turbine blade surface temperature, and its average cooling efficiency is mainly dependent on the cooling structures of internal passageways and the shapes of film cooling holes. Compared with standard cylindrical film cooling holes, abnormal film cooling holes have higher average cooling efficiency. But it is difficult to manufacture these holes using traditional machining methods. In this paper, a novel process was developed to fabricate turbine blades with abnormal film cooling holes by combining stereolithography (SL) technology with gelcasting technology. To decrease the drying shrinkage, the freeze-drying technique was applied to treat the wet ceramic casting mold green body surrounded by the SL mold, and the proper sintering process parameters were determined for lowering the sintered shrinkage. Finally, the integral ceramic casting mold was obtained, and a turbine blade with converging–diverging film cooling holes was rapidly cast to verify the feasibility of the proposed process.

The properties of light alloy castings are strongly affected by their inclusion content, particularly double oxide film defects (bifilms), which not only decrease the tensile and fatigue properties, but also increase their scatter. Recent research has suggested that oxide film defects may alter with time, as the air inside the bifilm would react with the surrounding melt, while the hydrogen dissolved in the melt could diffuse into the bifilm cavity to form hydrogen porosity. The mechanical properties of the casting were shown to be significantly dependent upon the new morphology of its entrained bifilms. In this work, the Weibull moduli of the tensile properties of three Al castings, all expected to contain oxide films of, approximately, the same amount were compared. The first casting was poured into a resin-bonded sand mould while the second and third castings were poured into ceramic moulds with the mould for the third casting being preheated prior to pouring. The results of mechanical property analysis and electron microscopy examination suggested a considerable influence of the type of the mould and the solidification time on the morphology of bifilms and by implication, on the reliability and reproducibility of the tensile properties.

Metal confined ceramic hollow ball composite was prepared by low pressure casting impregnation molding process. Because the ceramic hollow ball is fully constrained by metal in the circumference and radial direction, and takes into account high hardness of ceramic and strength and toughness of metal, it has a strong back strength and energy absorption effect and excellent impact resistance when it is penetrated by projectiles. The protection test of metal confined ceramic hollow ball composite material was carried out by using 14.5mm ballistic gun and firing 14.5mm perforating projectile. The test results show that the average protection coefficient of metal confined ceramic hollow ball composite structure is 1.53, and the damage area of metal confined ceramic hollow ball composite is small, and it has great advantages in resistance to multiple bullets.

Conventional metal (sand) casting requires solid patterns consisting of two halves (cope and drag) prepared to remove the pattern. The approach is simple but leads to numerous steps and mismatch errors. Also, sand, a porous material, is very sensitive to vibration and susceptible to cracks and breakage. This research presents a novel approach for investment metal casting, where a water-soluble material is used for pattern generation using material extrusion additive manufacturing (AM). As a proof of concept, a semi-complex non-prismatic geometry with various dimensional features is physically realized using this soluble pattern casting (SPC) technique. The pattern is designed and 3D printed out of a water-soluble acrylonitrile butadiene styrene (ABS) thermoplastic using an indigenously fabricated screw extrusion–based AM setup. A ceramic mould is created from plaster of Paris (PoP) around the soluble pattern, generating the mould cavity on further dissolution. A heated water bath with added turbulence via solid vibrations assisted the dissolution process. The final geometry is realized by firing the mould cavity followed by metal pouring. Various geometrical features and intricate details, such as layer lines, are satisfactorily replicated from the 3D-printed pattern to the final metal casting. The dimensional accuracy and surface finish are analysed along the process, starting from the printed pattern to the ceramic mould cavity and the final metal cast part. The presented method has applications in investment casting (IC) industries as it can help significantly reduce the lead time and provide excellent dimensional conformance and geometrical replication from the pattern to cast.

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.