Ceramic Mold Research Articles

Effect of Cooling Rate on the Corrosion Behaviour of Zn-Al and Zn-Al-Mg Alloy

Zinc and its alloy is non-ferrous metal often used as anodic material for the corrosion control in industries. The aim of this research is to determine the corrosion behavior of Zn alloy with different cooling rate during casting process. The three zinc alloys used were Zn-0.5Al, Zn-0.5Al-0.1Mg and Zn-0.5Al-0.3Mg. The cooling rates were varied by pouring the melt into the ceramic and steel moulds. Thermal analysis test was conducted to indentify phase reaction and quantify the cooling rate data. Material characterization and electrochemical test were performed on the cast samples by using standard equipment. The results show that the Zn-0.5Al-0.3Mg cast with fast cooling rate had the lowest corrosion rate compare to others. This indicates that the magnesium addition can improve the corrosion resistance of Zn-Al alloy.

Study of magnetic properties and structural and phase transformations in the Co-19 at % Al-6 at % W alloy

The Co-19 at % Al-6 at % W alloy prepared by two methods of melting in an inert atmosphere, namely, by arc melting followed by casting into a water cold copper mold and induction melting followed by casting in a ceramic (Al2O3) mold, has been studied. It was found that the phase composition of the alloy and its magnetic properties depend on the cooling rate of ingot after melting. Samples are ferromagnetic up to 800°C; the specific magnetization equal to σ= 10 emu/g is retained up to ∼700°C. The Curie temperatures of all phases found in the alloy have been determined. It was found that the formation of the Co7W6 phase in the alloy increases the coercive force of the alloy, whereas the saturation magnetization demonstrates a 1.5-fold decrease.

Testing of Implant Prototype of Femoral Component Using Hydraulic Machine ZD40

An article deals with a realization and a statistical evaluation of a pressure test using a hydraulic testing machine ZD 40 in order to determine a strength of a designed implant prototype of a femoral component, more precisely a maximal force F that breaks a material and creates a crack. It is needed to make real testing samples of the new implant prototype of the femoral component for this purpose. Four pieces of testing samples are made in cooperation with the company in Velka Bites. Because of a price and availability in a range of offered cast materials testing samples are made of a bio tolerated cobalt alloy Co-Cr-Mo that is frequently implanted to a live organism. The implant prototype of the femoral component is designed from evaluated CT data of a patient's affected knee-joint (a femur distal part, a proximal tibia part). An individual 3D model of the implant prototype of the femoral component is created on the basis of editing of gained data in software CATIA.The created 3D model is converted to *.stl format with a high resolution. Subsequently, the shell implant of the femoral component (a master model) is made using an additive method FDM (Fused Deposition Modelling). The next production method follows - production of a ceramic mould and casting of the real implant prototype of the femoral component from the bio tolerated cobalt alloy Co-Cr-Mo.

Gel casting of sialon ceramics based on water soluble epoxy resin

A recently developed gel casting system based on water soluble epoxy resin was successfully applied to sialon ceramics. The solids loading could reach 48.9% without any pH adjustment, and all slurries exhibited shear-thinning behaviour. Flexural strengths of sialon ceramic obtained from 44.5vol% slurry were 295.2MPa at room temperature and 281.4MPa at 700°C; the microhardness was 16.5GPa. The net-shape manufacturing of sialon ceramics could benefit from this investigation.

Characterization and modeling of anisotropic SL pattern during investment casting process

Photopolymer-based stereo-lithography (SL) rapid prototyping patterns with honeycomb internal structure reduce lead time and material cost for pattern manufacturing and also minimize ceramic mold residue after pattern removal in investment casting process. However, relatively larger thermal expansion of SL pattern tends to cause ceramic shell cracking during the pattern thermal removal. The anisotropy of SL pattern properties incurs different stress states of ceramic shell depending on the orientation of the honeycomb structure. In this work, a comprehensive thermo-mechanical coupled finite element model was developed to characterize the anisotropy of SL pattern and its effect on stress in investment casting shell molds. An experimental-based thermal degradation material model was developed considering anisotropy of the thermo-mechanical properties of SL pattern. The static analysis of slurry dipping and transient thermo-mechanical analysis of the pattern thermal removal process were performed. Both the pattern and ceramic shell behavior were studied and validated with experimental findings. Facesheet thickness/facesheet-to-core ratio and orientation of honeycomb structure were found to be the key factors to shell stress during pattern firing. Decreased facesheet thickness reduces stress in shell but also increases shell stress sensitivity to anisotropy of SL pattern. The developed tool provides an effective and efficient way to evaluate and optimize the structure of SL pattern for investment casting process.

EFFECT OF C ON THE INTERFACIAL REACTION AND WETTABILITY BETWEEN A Ni-BASED SUPERALLOY AND CERAMIC MOULD

Superalloy components are always produced by the way of investment casing. During investment casting, interfacial reactions may take place and bring about metal contamination and defect formation on the surface of the components. The influence of C content on the interfacial reaction and wettability between a Ni-based superalloy and ceramic mould was investigated by using a sessile drop method. The interfacial morphology and elements distribution were studied by SEM and EPMA. Activities of C, Cr and Al were calculated by using ThermoCalc software. The relationship between interfacial reaction and wettability was discussed. It was found that when C content was higher than 0.1%, activity of C increased greatly and interfacial reaction took place. The wettability varied from non-reactive wetting to reactive wetting. In the reactive wetting systems, sand adhesions appeared and Al and Cr diffused to the ceramic surface.

Electrodialysis Treatment of Aluminoborophosphate Concentrate Solutions in Ultrasonic Field for Precision Casting

There were considered different aspects of ultrasonic application in the process of electrodialysis of aluminoborophosphate concentrate (ABРС) solution for synthesis of binder agent without silica in precision casting of reactive alloys. There was defined that increasing of speed and undergoing degree of electrodialysis in the field of powerful ultrasonic. There was developed corresponding simulation model, offered and realized computer run calculation method of optimal parameters for preparation of activated ABРС binder agent in precision casting. Their use secured effective management of complex physical and chemical process of electrodialysis in the field of ultrasonic. On the base of determined relationships was developed technology of ceramic corundum mold manufacturing on activated ABРС, providing quality increasing of high-duty precision casting from nonferrous alloys.

Reinforced Green Ceramic Shell Mould for Investment Casting Process

The development of thin ceramic shell mould in investment casting process is very crucial as this mould inherited brittle property and highly exposed to the cracking mechanism. The slurry composition produces green (unfired) ceramic shell mould which low in strength and easily crack or fail during wax removal or handling process. By strengthening of this brittle ceramic shell mould via reinforcement technique can enhance the strength of green shell mould body. In this work, the presence of the treated rice husk fibre have toughened the green shell mould by creating mechanical interlocking bonding in shell matrix which contributes to higher modulus rupture value. In fact, SEM observations showed that the addition of fiber to the ceramic body to form a composite shell mould prevent the crack propagation mechanism due to the existence of the matrix-fibre bridging which create the resistance of fiber to pull-out. This directly will increase the strength of green shell mould body. .

Technological properties of ceramic slurries based on aluminium III oxide for ceramic shell moulds fabrication

Technological properties of ceramic slurries based on aluminium III oxide for ceramic shell moulds fabrication

インベストメント及びセラミック鋳型によるNear Net Shape化技術

インベストメント及びセラミック鋳型によるNear Net Shape化技術

Application of Additive Technologies in the Production of Aircraft Engine Parts

The use of rapid prototyping technologies provides a unique opportunity of cost-effective methods of investment casting to create new industrial products, of particular importance is the cost and speed of production. Development and research of rapid prototyping technologies have allowed a new level of optimization and introduction of new technologies into various industries. The essence of investment casting is that to get the castings use a single, accurate non-split, ceramic shell molds, which are produced on single models using liquid molding compounds. Before pouring the melt, a model shape is destroyed by melting, burning, dissolving, or evaporation. To remove residues of the model and hardening, mold is heated to high temperatures. Calcination form before its filling virtually eliminates gas formation and improves occupancy melt. At the stage of pilot production, which is characterized by frequent changes in design, the problem of the rapid production of cast components becomes crucial. This is mainly due to the complexity of manufacturing foundry equipment. The aim of this work is to identify opportunities and evaluate accuracy of the casting size during investment casting using rapid prototyping technology. The work was conducted with the use of cross-cutting design in CAM / CAD / CAE systems. The work has been verified according to the adequacy of the virtual simulation of the casting formation process in the casting simulation ProCAST, in comparison with those obtained castings. The study showed that the use of rapid prototyping technologies with investment casting can significantly reduce the time for making castings, reduce production costs and improve the accuracy of the casting size.

Precision Cutting of Ceramics with Milling Tool of Single Crystalline Diamond

Micro milling tools made of Single Crystalline Diamond (SCD) have been developed to machine micro dies and molds made of ceramics. The milling tools of a cylindrical SCD having many sharp cutting edges are fabricated 3-dimensionally by scanning a laser beam. Flat shape of binder-less tungsten carbide mold was cut with the developed milling tool to evaluate the tool wears and its life. Some micro aspheric molds of tungsten carbide were cut with the milling tool at a rotational speed of 50,000 min-1. The ceramic molds were cut in the ductile mode. By cutting with the milling tool, the form accuracy obtained was about 100 nm P–V and the surface roughness 8 nm Rz.

Electrochemical Tests in Stainless Steel Surgical Implants

In the present work the corrosion resistance of stainless steels was evaluated following the specifications of ASTM F-745 standards. The specimens were obtained by two methods, the conventional process of investment casting and countergravity low pressure casting. Cyclic polarization tests were performed according to ASTM F 2129, using a conventional three-electrode cell, with Pt as a counter electrode and saturated calomel as a reference electrode. The experiments were performed at (37 ± 1) °C and, before starting the test, the electrolyte was purged with N2 gas for 15minutes. As electrolyte, a solution of 0.9% NaCl was used (pH≈7), the open circuit potential (OCP) was monitored for 1 hour and then the potentiodynamic scanning started in the anodic direction, at a speed of 0.167mV/s, from a potential of 100mV below the OCP. The sweep was reversed after passing the threshold of current density at a value hundred times greater than the current density of pitting. Measurements of electrochemical impedance spectroscopy were performed after one hour of exposure of the specimens to OCPs performed in a frequency range from 100kHz to 1 mHz and potential amplitude of ± 10mV. The microstructure of the samples was analyzed before and after testing using optical microscopy. The results indicated that the samples in general exhibit crack corrosion, and in some cases the occurrence of pitting corrosion was observed. Also, the capacity values were within the range corresponding to the electric double layer and the charge transfer resistance increased on the specimens obtained by conventional casting in ceramic mold.

Evolution of Metallographic Parameters during Horizontal Unidirectional Solidification of Zn-Sn Alloys

In the present research the horizontal directional solidification of Zn-Sn alloys (Zn-4wt.%Sn, Zn-6wt.%Sn, Zn-10wt.%Sn and Zn-30wt.%Sn) was carried out by extracting heat in two opposite directions. For this purpose, ceramic molds, a muffle, a horizontal furnace with two heat extraction systems at the ends, a measurement, acquisition and recording temperature system, eight K-type thermocouples and an electronic recorder were used. The main parameters involved in the columnar-to-equiaxed transition, CET, were: the moment of start and end of solidification at each position under consideration, cooling rates, the average temperature gradients and critical temperature gradients at the CET. Also, metallographic parameters evolution (secondary dendritic arm spacing) was analyzed in function of the position in the sample and correlated with thermal parameters. The values of the critical thermal gradients for each composition were 0.01°C/cm (right side) and 0.23°C/cm (left side) for Zn-4wt%Sn, 0.25°C/cm (right side) and 0.41°C/cm (left side) for Zn-6wt%Sn, 1.4°C/cm (right side) and 1.7°C/cm (left side) for Zn-10wt%Sn and -0.05°C/cm (right side) and 0.15°C/cm (left side) for Zn-30wt%Sn.

COMPUTER MODELING FOR THE VISUALIZATION AND GEOMETRIC RECONSTRUCTION OF ARTEFACTS FROM THE CASTING WORKSHOP IN GRZYBIANY

The casting workshop in Grzybiany is one of the most important archaeological sites in regards to casting technology from the Bronze and Early Iron Ages. During the “Grzybiany. Osada nadjeziorna z epoki brązu i zelaza” [Grzybiany. Lakeside settlement from the Bronze and Early Iron Ages] research, the structure of casting moulds was analyzed as well as the chemical composition and microstructure of one of the more-interesting metal artefacts found within the workshop. Based on this, geometric visualization was performed with the help of computer-modeling methods. For scientific, experimental, and educational purposes, reconstruction of a zoomorphic pendant was performed using the lost-wax method. Wax models injected into a matrix were used, along with fired ceramic (gypsum) moulds and a specially prepared modeling alloy that corresponds to the original material. In this way, a true replica of the original was obtained: technologically, structurally and chemically. Studies of production technology of the casting workshop dated back to the Bronze and Early Iron Age help to increase the knowledge of the mould-preparing technology and the alloys used. Modern tools and computer programs aid in the research of old technologies and help disseminate the results.

Ceramic crucibles and moulds

Ceramic crucibles and moulds

Corrosion in 316L Porous Prostheses Obtained by Gelcasting

Gelcasting (GC) process, usually used for ceramic moulding, is adapted for producing spongy or porous metal osteosynthesis components destined to bone void filling. The main objective of the interconnected porosity is to improve the osteoconductive of metal matrix by ingrowth of bone. Further, porosity reduces metal density and Young module, which causes bone resorption, leading to implant failure, phenomenon known as stress shielding. The employed GC is based on the formulation of AISI 316L stainless steel powder suspension in an aqueous solution of organic polymers. This suspension is cast into porous ceramic shells, like those used in lost wax technique, wherein the polymer crosslinking is induced by heating. The shells, containing the resulting hydrogel–metal composite, are subjected to thermal cycle in order to dry, burn the organic phase, sinter the metal particles at 1200°C, and cool down to room temperature under dry hydrogen permanent flow. The susceptibility to corrosion of 50-60% porous pieces was analyzed. The results indicated that the lower relation between the open porosity and the total porosity, the lower the corrosion rate.

Effects of Activated Charcoal on Dewaxing Time in Microwave Hybrid Heating

High energy consumption, mould cracking and wax contaminations are the major problems during dewaxing process in investment casting. On the other hand, low loss factor of most mould materials and some pattern waxes make direct microwave heating them slow. In this research, activated charcoal was added to the ceramic mould in order to improve microwave absorption and reduce dewaxing time. A modified domestic microwave oven was used as a test rig. The activated charcoal was added to the back-up stucco from 0 to 30% by weight. The microwave heating tests were carried out from 5 to 20minutes. The dielectric properties of the green mould and the wax were measured using a co-axial dielectric end probe. It was found that the loss factor of the wax is low, and the higher the percentage of activated charcoal added into the mould, the better the dielectric loss factor and the lower the dewaxing time. Adding 25% activated charcoal in the mould causes about 40% decrease in dewaxing time. This also improved energy saving and makes the process more sustainable.

High-refractory corundum molds based on a silica-free binder

We have proposed a process for the fabrication of high-refractory (up to 2000°C) ceramic monoxide corundum molds for investment casting using a silica-free binder. This approach is most effective in fabricating ceramic shell molds for complex-shape investment casting using highly alloyed steels, refractory metals, and high-temperature and titanium alloys.

The Influence of the Method of Mould Filling on the Quality of Castings Made of EN AC-44000 or EN AC-46200 Alloy

Abstract The performed examinations concerning the process of filling the plaster ceramic moulds with aluminium alloys allowed to assess the influence of various methods of introducing the metal into the mould cavity on the macro- and microstructure of the obtained experimental castings. The comparison was performed for castings with graded wall thickness made either of EN AC-44000 alloy or of EN AC-46000 alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the Vacumetal technology), or by counter-gravity casting. It was found that the silicon crystals grow in size with an increase in wall thickness due to the slower cooling and solidification of castings