Ceramic Mold Research Articles

Alumina-zircon filler based ceramic shell moulds for directionally solidified cast shrouded low pressure turbine blades

Ceramic shell moulds for investment casting of shrouded low-pressure turbine (LPT) blades were prepared by using colloidal silica binder and partial substitution of the zircon filler with fine alumina. Among the two ceramic slurry systems designed, the first slurry system comprised of polymer-free colloidal silica binder, and the second slurry system comprised of polymer-containing colloidal silica binder. The samples prepared from the first slurry system showed higher fired residual strength and self-load sag values (lesser sag resistance). The casting of shrouded LPT blades was carried out at 1525 °C and 1550 °C using CM247LC superalloy. Ceramic shell moulds prepared from the second slurry system, containing 30 wt% of fine alumina filler, yielded aeronautical grade casting (at 1550 °C) of blades with required dimensional accuracy and average surface roughness. Microstructural analysis of the cut surfaces of self-load sag tested samples was carried out to understand the effect of fine alumina substitution on shell characteristics.

Development of a method for manufacturing ceramic tooling for precision casting of blades made of heat-resistant alloys using additive technologies

The technology traditionally used to produce castings of gas turbine engine (GTE) blades involves a large number of alterations, high labor costs due to the large amount of manual labor required, and complex and expensive equipment and tooling. This technology is only suited for large-scale production due to its use of expensive reusable metal molds.The ceramic shell mold for turbine cooled and uncooled blades can be manufactured more quickly and cheaply. This is especially important for fast hardware redesign and reconfiguration.This proposal describes an approach for producing a shell mold including with an internal rod using three-dimensional (3D) printing with refractory ceramic pastes that does not involve a lengthy and time-consuming process of designing and manufacturing forming equipment for the production of castings based on smelted models.

Análisis térmico y comportamiento de desgaste de aleaciones Mg-4Zn-(x)Zr fundidos en molde de cáscara y molde de grafito

El efecto de refinamiento del grano del circonio (Zr) es conocido, sin embargo, la influencia en la cantidad de Zr y su efecto sobre la solidificación y el comportamiento de desgaste de las aleaciones de Mg-Zn modificadas no se han estudiado adecuadamente. Las aleaciones de Mg-4Zn-(x)Zr son aleadas con la adición de 0,5% a 4% en peso de elemento Zr se funden y se vierten en dos moldes de colada diferentes y se realizan análisis térmicos. Se examinaron la microestructura de los productos de colada, el comportamiento de solidificación, las transformaciones de fase, el tamaño de grano, las curvas de análisis térmico y las propiedades de desgaste. La microestructura se modificó mediante la adición de Zr y el tamaño de grano se redujo tanto para los materiales de moldeo de grafito como de cerámica. La máxima resistencia a la tracción se obtuvo añadiendo 1% de Zr (170 MPa) y 4% Zr (105-110 HRB) utilizando un molde de grafito, respectivamente. La máxima resistencia a la tracción a temperatura ambiente se alcanzó en el Mg-4Zn-1Zr, el alargamiento fue del 4,9% y la resistencia a la tracción fue de 138 MPa. El valor máximo de tracción en caliente se obtuvo en las aleaciones con 2% de Zr añadido. La tasa de desgaste de la aleación Mg-4Zn disminuyó al aumentar el elemento Zr hasta un 2% en peso. La adición de más del 2% en peso de Zr provocó un aumento de la microporosidad en la microestructura. Debido a la microporosidad causada por la adición de Zr, la tasa de desgaste se redujo ligeramente.

Ceramic Molding Based on 3D Printing Technology

3D printing technology can also be described as an increase in the manufacture of materials. In the forming process, no traditional machine tools, fixtures and cutting tools are required. Parts models of arbitrary complex shapes can be manufactured quickly and accurately. In the experimental process, small printers are modified in the extrusion part and printed with water-based alumina slurry as ink. The water-based oxide slurry is mainly water medium and contains only a small amount of organic binder. The influence of pH value, solid content, plasticizer, binder, lubricant and dispersant on the fluidity of slurry is studied. The results show that the slurry has the best stability when the amount of dispersant is 0.4 wt%, plasticizer is 1.0 wt%, lubricant is 4.0 wt%, binder is 1.0 wt%.

Investigation of the influence of softening modifiers on the knockout of investment castings

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.

Complex reaction behaviour of ceramic mould with the molten AZ91 alloy during investment casting

The effects of different pouring temperatures on the reaction behaviour of the ceramic shell with the molten Mg-9%Al-1%Zn-0.4%Mn (all are in wt-%) (AZ91) alloy during investment casting were studied. The scanning electron microscopy (SEM) micrographs with energy dispersive spectroscopy (EDS) analysis illustrated a complex interaction behaviour of the alloy with the mould components at various pouring temperatures. The MgO + MgAl2O4 compounds were formed on the surface of investment cast alloy at the pouring temperature of 600°C. With increasing the temperature to 650°C, the MgO compounds with the Al2O3 particles were observed at the interface of metal/mould. The Al2O3 particles were the main compound on the surface of alloy at the pouring temperature of 700°C. The formation of Al2O3 particles instead of the MgO compounds on the surface was related to the increase of magnesium evaporation by enhancement of the pouring temperature and also diffusion of Al2O3 particles from the ceramic shell to the surface of the alloy.

Effect of Pouring Temperature and Heating of Ceramic Shells Mould on Projection of Thin Wall Castings

One of the research directions of this study is to determine the possibility of making precise, thin-walled castings from selected iron alloys. The scope of research work is aimed at determining the applicability of the casting process of selected iron alloys with the technology of wax pattern, for making precise castings with a wall thickness of less than 3 mm. The article presents the results of tests carried out for experimental castings with the shape of steps, characterized by different wall thicknesses: 1 mm, 5 mm, 10 mm, 25 mm. The castings were made of LH14, Gs42crMo4, L35H7MP2, LH26N9, 316L cast steel, and a new alloy marked “0”. The metal was smelted in an induction furnace with a capacity of 150 kg. The technology of ceramic shell mould used in the plant was used to make the experimental castings. Ceramic shell moulds were heated in a chamber furnace at a fixed temperature. The time of annealing the ceramic mould was constant in a ceramic form. The following parameters were variable during the tests: iron alloy, pouring temperature, and annealing temperature of the ceramic shell mould.

Image data analysis of high resolution μCT data for the characterization of pore orientation and pore space interconnectivity in freeze cast ceramics

Unidirectional and non-unidirectional freeze cast SiOC monoliths were characterized by means of digital image processing. For this purpose a novel method of pore segmentation in complex dendritic pore morphologies was developed. For the first time, the proposed method made it possible to perform an extensive geometrical and structural pore space characterization and analysis on single pore level. The orientation of the primary dendritic channels was obtained from high resolution μCT images. Based on the mean directional vector distribution, the pore space was segmented. As a result, 95% (unidirectional) and 88% (non-unidirectional) of the original binary pore volume could be allocated to individual pores. The pore interconnectivity could be derived from this segmented pore space. It has been shown that the degree of interconnectivity between pores of the same orientation is higher than between pores of different orientation. This could be the reason for peculiar wicking behavior in non-unidirectional samples.

A new FTIR method for estimating the firing temperature of ceramic bronze-casting moulds from early China

Intricate ceramic bronze-casting moulds are among the most significant archaeological remains found at Bronze Age metallurgical workshops in China. Firing temperature was presumably one of the most important technical factors in mould making. However, it has proven difficult to determine the firing temperatures of excavated moulds using existing analytical methods. This study establishes an innovative new method for using Fourier-transform infrared spectroscopy (FTIR) to estimate the firing temperature of clay-containing remains. The method is based on the finding that the infrared absorptivity of fired clay minerals, measured at the Si–O–Si stretching resonance band, is negatively correlated with firing temperature. Moulds and mould cores dating to the Early Shang period (sixteenth to fourteenth century BCE) are found to have been fired at extremely low temperatures—as low as 200–300 °C in many instances. These results provide critical new data for understanding the metallurgical technology of ancient China.

ОСОБЕННОСТИ ИСПОЛЬЗОВАНИЯ ОРГАНИЧЕСКИХ ИЛИ ВОДНЫХ СВЯЗУЮЩИХ НА ОСНОВЕ ОКСИДОВ ЭЛЕМЕНТОВ III ИЛИ IV ГРУПП ПРИ ИЗГОТОВЛЕНИИ КЕРАМИЧЕСКИХ ФОРМ ДЛЯ ЛИТЬЯ ОТЛИВОК ИЗ ХИМИЧЕСКИ АКТИВНЫХ СПЛАВОВ (обзор)

The article considers the experience of using organic and aqueous binders based on silicon or aluminum oxides in the manufacturing of ceramic casting molds, and tendencies of world manufacturers in this industry to improve the quality, accuracy and operational reliability of cast products, especially critical parts made of titanium, intermetallic and heat-resistant alloys obtained by investment casting. The paper gives information on the results of studying physical and mechanical properties of ceramic molds and defect zone of the outer surface of castings made of various alloys.

КЕРАМИЧЕСКИЕ ЛИТЕЙНЫЕ ФОРМЫ ИЗ ПАМЯТНИКА КРУГЛАЯ ДОЛИНА В ПРИМОРЬЕ: ОПЫТ МЕЖДИСЦИПЛИНАРНОГО ИССЛЕДОВАНИЯ

The article presents an interdisciplinary study of casting molds as one of the kinds of old technical (“metalworking”) ceramics. The material of the study is ceramic molds (47 whole and fragmented samples) unearthed at the Kruglaya Dolina settlement in the central Primorye region. The molds and other objects of technical ceramics (crucibles, nozzle) were found in destroyed, non-stratified cultural deposits and connected with the remains of bronze-casting workshops complex which was dated supposedly to the Bohai state period, 698-926. The study aimed (1) to examine the morphological and technological characteristics of the molds, and (2) to detect traces of alloys at the working surfaces of the molds. The study employed methods of binocular microscopy and laboratory refiring testing for (1), and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), portable X-Ray fluorescence spectroscopy (pXRF) for (2). The analyzed ceramic molds were intended for the casting of semi-spherical buttons, several kinds of pendants, rosette-shaped openwork ornaments. Original bronze items which could be cast in these molds were not found at Kruglaya Dolina. According to the data on the morphological variability of the molds together with the results of the examination of the ceramic pastes technology, one can suppose that the casting molds were produced by different craftsmen or different workshops. SEM-EDS and pXRF analyses detected the traces of bronze alloys at 15 mold samples with carbonized working surfaces. Chemical elements - metals - lead (Pb), tin (Sn), and copper (Cu) are traced in various combinations at various samples. In some cases together with metals arsenic (As) is detected. The interpretation of these results follows methodological recommendations based on the published data of experimental research. The presence of certain elements can be stated, and their relative concentrations in the spectrum composition can be evaluated. However, it is necessary to take into account that the amounts of certain elements in the spectrum do not correspond to their amounts in the original alloy composition. Therefore, qualitative characteristics of the alloys can be determined, but not quantitative ones. According to the results, the three-component alloys containing copper, tin, and lead are recognized certainly. The tin-copper non-lead alloy and the “pure copper” alloy are supposed in some cases. Previous investigations on the old bronzes chemical compositions in southern Russian Far East revealed that three-component alloys (lead-tin-copper) containing arsenic had been used widely during the Bohai state period. Tin-copper and “pure copper” alloys were known at that time as well. It seems to be likely that the casting molds from the Kruglaya Dolina site are dated to the Bohai state period. Further researches of this site's bronze-casting workshops complex remains will focus on other categories of technical ceramics.

Литейная форма для производства проушного бронзового топора позднекротовской (черноозерской) культуры

This article presents a ceramic casting mold for producing socketed bronze axe, found in the burial of the Late Krotovo (Cherno-Ozerye) caster at the Sopka-2/5 burial ground located in the Baraba forest-steppe. The mold included the fragments of two halves, aligned along the dividing line. A part of working chamber with cavities for fastening the core has survived. The mold was made of a mixture of clay, fine calibrated sand, and organic matter. The axe had an L-shape, rhomboid crosssection of the working part, and round socket with straight upper edge. The working chamber shows traces of thermal impact from repeated use. It could have become destroyed during its use and was placed in the grave as a replacement for a whole object, as a necessary tool of a caster. This type of axe is considered to be imported for the Late Krotovo (Cherno-Ozerye) culture, manifesting the Andronovo (Fedorovo) influence. Thus, socketed axes which significantly changed the capacity of the syncretic culture, should be added to previously identified set of bronze objects introduced into autochthonous Krotovo environment by the carriers of the Andronovo (Fedorovo) culture, who migrated from the west. This set also includes daggers of the Srubno-Andronovo type and bracelets with spiral ends. In the meantime, a casting mold for producing axes from the Late Krotovo burial is indisputable proof that such axes were manufactured by the local casters. There was a large amount of metal implements accompanying the deceased caster, and the presence of weapons (dagger and celt axe) indicated his privileged position. Apparently, the Late Krotovo (Cherno-Ozerye) society had a large property differentiation, and casters might have had a special status.

Technology and Design of Intelligent Casting and The Drying Line for Sanitary Ceramics

Firstly, the social production demand of sanitary ceramic intelligent manufacturing mold drying line is described. Secondly, the technological process of intelligent manufacturing mould drying for sanitary ceramics was analyzed, and the overall design scheme and implementation method of intelligent manufacturing mould drying line were put forward. Again the key equipment of intelligent manufacturing die drying line is analyzed and explained again, its structural characteristics, functions and characteristics are introduced, and its working principle is explained in detail. Finally, the feasibility and superiority of intelligent mould drying for sanitary ceramics were proved.

Technology of slip casting of celsian-slavsonite ceramics

The article considers the slip casting technology of celsian-slavsonite ceramics with the ratio of raw materials to obtain crystalline phases of ВаAl2Si2O8: SrAl2Si2O8 – 25:75. The manufacture technology of product proceeded in two stages. The first stage of synthesis was performed in a muffle furnace at a rate of temperature of 15 deg / min at a maximum firing temperature of 1200 °C with a holding time of 2 hours. Then the synthesized ceramics were grinded for 10 minutes. The second stage was to obtain a slip with the addition of surfactants (DOLAPIX PC 67). The finished slip was poured into a plaster mold. Drying of the green sample was carried out in an oven at a temperature up to 110 °C for 3 hours. Firing of the dried sample was carried out in a muffle furnace at a rate of set temperature of 15 deg / min, at a maximum firing temperature of 1250 °C for 2 hours. The fired materials were subjected to machining. The obtained data indicate that, the best sample was fired at a temperature of 1250 ° C and had the following properties: dielectric constant — 9.4, water absorption — 5.9 %, open porosity — 14.4 %, apparent density — 2.42 g/cm3, flexural strength — 19 MPa.

Interaction of Titanium with Ceramic Molds in the Conditions of Electron Beam Casting Technology

Interaction of Titanium with Ceramic Molds in the Conditions of Electron Beam Casting Technology

Computational and experimental study of lattice structured patterns for casting process

PurposeThe quality of lost foam casted engineering components is directly influenced by the characteristics of the respective ceramic shell mold (CSM) and hence casting pattern. In this present work, rapid prototyping (RP) was used to fabricate the lattice structured patterns (LSPs) to reduce the defects and cracks in CSM during the heating stage.Design/methodology/approachThe quality of the LSPs was accessed by measuring the dimensional accuracy. Further, the thermal stress in the CSM during the heating of porosity varied LSPs was analyzed using ANSYS software package 16.0. The Ni-alloy casting was fabricated by using the designed LSP and compared with its respective CAD model to access its quality.FindingsThe obtained results revealed that the Wigner–Seitz LSPs retained high accuracy and minimized the stress for defect-free CSM. Also, the thermal stress generated in the CSM depends upon the porosity coefficient of the LSP. Hence the interplay with porosity coefficient of LSPs leads to the formation of defect free CSM and hence high quality casting.Originality/valueRP was used to develop LSPs and investigated the dependency of unit cell parameters on the accuracy of the final casting.

Dry sliding wear of a Ni-based superalloy as a function of the aging time.

AbstractFrom the present work, the wear behavior of aged Ni-based superalloy was analyzed under dry sliding conditions. Such alloy was melted in a vacuum induction furnace and cast into a ceramic mold. Then the alloy was solubilized at 1080°C for 4 hours and then aged at 760°C for 4, 8, 16, 24, 48, 72 and 150 hours. The alloy was characterized as-cast and also in the heat-treated conditions by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical characterization included just Vickers hardness and wear resistance under dry sliding conditions by a block on ring configuration according to the ASTM G77 standard. Wear tests were undertaken for 2000 m at a speed of 0.7 ms-1 at two different loads (25 and 78 N). The worn samples were analyzed by an optical profiler to determine the wear volume and by SEM to analyze the worn surface and the microstructure below the worn surface. The main findings indicate the formation of an oxide layer mainly formed by Cr and Ni during sliding. The thickness of such a layer is about 10 μm for short aging times and about 5 μm for longer aging times. For this load, the wear resistance was 50% higher for the shorter aging times than that for the longer aging times. This behavior is described in terms of the thickness of the protecting layer, and on the availability of chromium to form such a layer since it forms Cr23C6 at long aging times. On the other hand, for a load of 78 N the wear behavior is in agreement with hardness. Wear resistance increases with aging time due to the higher precipitation of prime gamma phase.

Effect of Chopped ZrO2 Fiber Content on the Microstructure and Properties of CaO-Based Integral Ceramic Mold.

A chopped ZrO2 fiber (ZrO2 (f)) reinforced CaO-based integral ceramic mold was successfully fabricated by stereolithography (SLA) and tert-butyl alcohol (TBA)-based gel-casting, and the effect of chopped ZrO2 (f) content on properties of the ceramic mold was investigated. The results show that the ZrO2 (f) content had a significant effect on the viscosity of CaO-based ceramic slurry, which directly affects the filling ability of slurry in complex structures of the integral mold. The tiny structures of the ceramic mold cannot be filled completely with a ZrO2 (f) content exceeding 3 vol %. The sample fabricated with 3 vol % fiber content showed a harmonious microstructure and exhibited an excellent comprehensive performance with 25 °C bending strength of 22.88 MPa, an 1200 °C bending strength of 15.74 MPa, a 1200 °C deflection of 0.86 mm, and a sintering shrinkage of 0.40%, which can meet the requirements of casting very well.

Characteristics of interfacial reactions between Ti-6Al-4V alloy and ZrO2 ceramic mold

The interfacial reaction between Ti-6Al-4V alloy and ZrO2 ceramic mold with zirconia sol binder was investigated by keeping the 12 g alloy melt in a vacuum induction furnace for 15 s. The microstructures, element distribution and phase constitution of the interface were identified by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the whole interface reaction layer can be divided into three regions: metal penetration layer, transition layer, and hardened layer according to the structure morphology, which has the characteristics of severe metal penetration, finer lamellar, and coarse oxygen-rich α phase, respectively. The erosion of the alloy melt on the ceramic mold promotes the decomposition of zirconia, which leads to the increase of local Zr concentration, greatly increasing the activity coefficient of Ti, aggravating the occurrence of interfacial reaction. Thus, the interfacial reaction shows the characteristics of chain reaction. When the oxygen released by the dissolution of zirconia exceeds the local solid solubility, it precipitates in the form of bubbles, resulting in blowholes at the interface. The result also indicates that the zirconia mold with zirconia sol binder is not suitable for pouring heavy titanium alloy castings.

Manufacture of Ceramic Molds and Cores from Inorganic Materials Using Permanent

The paper describes the technology for the manufacture of ceramic molds and cores from inorganic materials using permanent masters. A technique for reinforcing molds and cores using ceramic tubes is proposed. The effect of pulse currents of different power on the slurry has been studied. In the experimental part, the performed experiments and the data obtained are described. In contrast to the conventional Show-process based on ethyl silicate binder (basic option), the technology developed for the manufacture of ceramic molds from inorganic materials ensures improving the quality and economic and environmental efficiency of investment castings. The quality improvement is determined by improved physical and mechanical characteristics of ceramic molds and the stable ceramic cracking. The improvement in environmental indicators is ensured by using safe inorganic molding materials and eliminating the solvent burning. Improving economic indicators is determined by reducing power consumption for calcining ceramic molds, casting defects, and molding material costs. Thus, the technology developed allows improving the quality of investment castings manufactured for the country’s oil and gas complex.