Polymer Binders of Ceramic Nanoparticles for Precision Casting of Nickel-Based Superalloys

This study presents the general characteristics of binders used in precision casting of Nickel-based superalloys. Three groups of binders were described: resins, organic compounds, and materials containing nanoparticles in alcohol or aqueous systems. This study also includes literature reports on materials commonly used and those recently replaced by water-soluble binders, i.e., ethyl silicate (ES) and hydrolysed ethyl silicate (HES). The appearance of new and interesting solutions containing nano-alumina is described, as well as other solutions at the initial stage of scientific research, such as those containing biopolymers, biodegradable polycaprolactone (PCL), or modified starch. Special attention is paid to four binders containing nano-SiO2 intended for the first layers (Ludox AM, Ludox SK) and structural layers (EHT, Remasol) of shell moulds. Their morphology, viscosity, density, reactions, and electrokinetic potential were investigated. The binders were characterized by a high solid-phase content (>28%), viscosity, and density close to that of water (1–2 mPa·s) and good electrokinetic stability. The nanoparticles contained in the binders were approximately spherically shaped with an average particle size of 16–25 nm.

Manufacturing of Al2O3/Ni/Ti Composites Enhanced by Intermetallic Phases

In this study, ceramic–metal composites in the Al2O3/Ti/Ni system were fabricated using the slip casting method. Two series of composites with 15 vol.% metal content and different solid phase contents were obtained and examined. A proper fabrication process allows obtaining composites enhanced by intermetallic phases. The microstructure of the base powders, slurries, and sintered composites was analyzed by scanning electron microscope. Analysis of the sedimentation tendency of slurries was carried out. The phase composition of the sintered samples was examined by X-ray diffraction analysis. A monotonic compression test was used to investigate the mechanical properties of the composites. A fractography investigation was also carried out. The research conducted revealed that the slip casting method allows the obtaining of composites enhanced by intermetallic phases (TiNi, Ni3Ti). The results show the correlation between solid-phase content, microstructure, and mechanical properties of the composites.

Thermoanalytical and dilatometric studies of the Al2O3–Cu–Mo hybrid composite

The present research is focused on the characterization of the composites from Al2O3–Cu–Mo system. The composites were prepared by slip casting method and subsequent sintering of green bodies in a reduced atmosphere. Two series of samples with different volume content of metallic powders were produced in the work: 10 vol% and 15 vol% of metal content with respect to the total solid-phase content. The sintering process of the composites was analyzed in detail. The linear shrinkage of the composites was measured. The shrinkage curves were obtained by dilatometry test in a heating mode. The composites were characterized by DTA/TG analyses and thermal conductivity. The composites were characterized by XRD, SEM, and EDX. The hardness was measured by Vickers hardness tester. Moreover, the Brazilian test was performed to determine the tensile mechanical properties of the composites. Fractography investigation was carried out as well. Dilatometric tests showed that the increase of the metallic phase volume in the ceramic matrix causes a decrease in the starting temperature of densification. Simultaneously, dilatometric experiments indicated that an increasing amount of metallic particles into the ceramic matrix increases the temperature of maximum densification and decreases the total shrinkage of the composites during sintering. The DTA/TG showed the characteristics of the dispersant decomposition to the atmosphere during thermal treatment and increase of mass connected with the oxidation of metals. Fractography results revealed good adhesion between Al2O3 matrix and the metallic phase. The observation allowed to conclude that the Al2O3 matrix surface is characterized by the brittle fracture mechanism.

Simulation Fluidity Test for Semisolid Squeeze Casting

The paper deals with semi solid squeeze casting technology. Fluidity tests were designed for the selected technology. The shape of the test casting was designed in the shape of test bars with different thicknesses and also in the shape of a stepped casting. The thickness of the individual elements was chosen on the basis of a selected / preferred numbers R10 EN STN 17. As a result, the thickness of the elements was 2.0, 2.5, 3.15, 4.0, 5.0 and 6.3 mm. Designed fluidity tests were verified by using ProCast simulation software. The selected process parameters were: operating pressure 80 MPa, mold temperature 200 °C, piston speed 30 mm.s-1. The experimental material was an AlSi7Mg0.3 alloy with a different solid phase content. The initial solid amount were 50, 55 and 60 %. The effect of solidus and liquidus, temperature distribution and pressure was monitored during the evaluation of fluidity.

Blocking compounds on the basis of condensed dispersions for well killing under complicated mining and geological conditions

The article is devoted to the results of laboratory studies of blocking compounds with a condensable solid phase based on calcium. The features of such systems have been revealed and their positive characteristics have been determined. It made it possible to conclude that such systems compounds are promising as blocking compounds for usage in wells with complicated mining and geological conditions (abnormally low reservoir pressures, in reservoirs with complex mineralogical and chemical composition with a high clay content fractions, with a highly fractured bottomhole formation zone, etc.).Based on the data obtained, we have developed blocking compounds with a condensable solid phase (the patent RU 2543003 and the patent RU 2651687), which have high blocking properties (withstand pressure drop up to 20 MPa) and ensure the preservation of reservoir properties (permeability recovery coefficient is more than 95 %) and inhibition of clay minerals swelling. In addition, as a result of studies we have found that for the blocking of productive deposits with a nonuniform permeability (for reservoirs with an average permeability about 1 Darcy) the usage of compounds with a close to stoichiometric ratio of precipitating components with a condensed solid phase content about 11 wt. % is optimal.

Synthesis and Tribological Properties of Bio-Inspired Nacre-Like Composites

Ceramic materials possessing the properties of high-strength and rigidity are widely used in industry. The shell nacre has a layered structure containing both macroscopic and microscopic levels and is equipped with superior qualities regarding hardness and strength. Therefore, the ceramic composites with a nacre-like layered structure have the potential to be utilized as sliding bearings employed in the harsh conditions of wells. For the purpose of this paper, a porous Al2O3 ceramics skeleton with nanometer powder is prepared using the freeze-casting method. Then the porous ceramic skeleton is filled with polymer polymethyl methacrylate (PMMA) through mass polymerization to produce a bionic Al2O3/PMMA composite with a lamellar structure. The properties of the prepared composite are determined by the analysis of micro-hardness, fracture toughness, friction coefficient, wear scar diameter, and the morphology of the worn surface. Consequent results indicate that elevation in the A12O3 powder, which acts as the initial solid phase content, prompts the ceramic slurry to exhibit an increase in viscosity and a gradual decrease in the pore size of the ceramic skeleton. The prepared layered Al2O3/PMMA composite possesses high fracture toughness, which closely resembles that of Al, is approximately four times that of the matrix of the Al2O3 ceramics and 16 times that of the PMMA. Three kinds of composites containing different solid phase content are subjected to testing involving lubrication by water-based drilling fluid to determine the friction coefficient of each. The results indicate that an increased load leads to a decreased friction coefficient while the impact of speed is not evident. Under dry conditions, the friction coefficient of three different composites tested, declines with elevated load and speed. With the use of water-based drilling fluid as lubrication, the wear scar diameter increases at higher speed, while dry conditions denote increased load. Abrasive wear is determined to be the principal form of erosion of layered Al2O3/PMMA composites.

Influence of the Al2O3 Solid Phase on the Kinetics of Binding Ceramic Moulds

The investigation results of the kinetics of binding ceramic moulds, in dependence on the solid phase content in the liquid ceramic slurries being 67, 68 and 69% - respectively, made on the basis of the aqueous binding agents Ludox AM and SK. The ultrasonic method was used for assessing the kinetics of strengthening of the multilayer ceramic mould. Due to this method, it is possible to determine the ceramic mould strength at individual stages of its production. Currently self-supporting moulds, which must have the relevant strength during pouring with liquid metal, are mainly produced. A few various factors influence this mould strength. One of them is the ceramic slurry viscosity, which influences a thickness of individual layers deposited on the wax model in the investment casting technology. Depositing of layers causes increasing the total mould thickness. Therefore, it is important to determine the drying time of each deposited layer in order to prevent the mould cracking due to insufficient drying of layers and thus the weakening of the multilayer mould structure.

Impact of Plate Diameter and Sample Height on the Determined Pre-Compaction Value

The objective of the paper was to verify previously obtained results of research on the impact of the plate diameter on the determined value of pre-compaction stress of soil (NG) with a wider selection of dimensions of samples. Tests were carried out on samples with a diameter (D) of 100 mm and heights (H) of 30, 50 or 100 mm produced from the soil material (M) or collected (NNS) from subsoil with the granulation group of: silt loam, loam, sandy loam, sandy clay loam. The following soil properties were determined: granulation type, density of the solid phase, content of humus and calcium carbonate, reaction, plastic and liquid limit. Properties of samples were described with moisture, dry density of solid particles, porosity of aeration, degree of plasticity and saturation. Samples were loaded with plates of varied diameters. The NG value was calculated with the method of searching for the crossing point of tangents with the secondary stress curve and the virgin stresses curve (a traditional method). It was stated that the plate diameter (d) and sample height (H) do not influence the measurement results when the relation d/D is within 0.5 ≤ d/D ≤ 0.8 and the ratio D/H equals 2. It is possible to omit the condition d/D in a situation when soil is low cohesive and its degree of moisture is ca. 0.41-0.44.

Fabrication of ZrO2-Ti Composites by Slip Casting Method

Slip casting is one of the most popular shaping method in ceramic technology which allows producing a large number of elements in small period of time. This shaping technique gives a possibility to fabricate ceramic or composite materials such as ZrO2-Ti. Ti with its properties (low density, high melting point, high-temperature strength, good corrosion resistance and others) combine with ZrO2 (high flexure strength, high compression resistance and very high KIC) can be considered for different applications as constructional and functional materials. For the preparation of such composite nanometric zirconium oxide powder stabilized by 3 mol% Y2O3 and micrometric titanium powder were used. Water-based slurries with 35, 40, 45 and 50 vol.% solid phase content were prepared with 3, 10 and 15 vol.% addition of titanium powder. Zeta potential and pH of prepared slurries were considered. The pH changes were tested as a function of Ti content. The viscosity of the prepared slurries was measured. The sedimentation tests for selected slurries were performed. The casting rate for slurry of 35% solid phase with 10 vol.% Ti was examined. These measurements showed good stability of slurries. With the increasing of the solid phase concentration the density of the green bodies increased. However, the increase of the content of Ti powder reduced the density of green body samples. For selected samples the SEM observations was carried out. Composites produced by slip casting were characterized by a homogenous distribution of Ti particles in the ZrO2 matrix.

Technological Properties of SiC-Based Ceramic Slurries for Manufacturing Investment Casting Shell Moulds

In this work technological properties of ceramic slurries based on silicon carbide were characterized. Silicon carbide and poly(vinyl alcohol) in an amount 6%, 10% and 15 wt. % as a solution were added to prepare the ceramic slurries. Solid phase content in ceramic slurries was 62, 5 wt.%. Plate weight test, pH, density, viscosity (measured by the Zhan 4# cup) and dynamic viscosity were investigated. Dipping test on wax model was done to measure adhesive properties. Characterization of SiC fillers powder was made by determination of grain size, density, chemical composition, Zeta potential and by use of scanning electron microscopy. Obtained results of ceramic slurries based on SiC meet standard specification in industrial investment casting and its properties are very promising for future application in investment casting of superalloys.