Vacuum Casting Research Articles

Comparison of different additive manufacturing patterns on the performance of rapid vacuum casting for mating parts via the Taguchi method

Rapid vacuum casting has been proven to be a successful method in producing high-quality parts in small series. However, a challenge lies in the selection of proper Additive Manufacturing (AM) technologies for the development of a master pattern for the vacuum casting process. Each AM technologies differ from one another in terms of dimensional accuracy, surface finish, cost and lead times. The aim of this study is to investigate the performance of casting mating parts based on different additive manufacturing patterns for small batch. Three types of AM-based patterns: Fused Deposition Modeling (FDM), Stereolithography (SLA) and Multi-Jet Fusion (MJF) were compared. The Taguchi method, Signal to Noise ratio (S/N), Analysis of Variance (ANOVA) and T-test were conducted in determining the optimized parameters. From the findings, curing time is shown to be a significant parameter for dimensional accuracy and surface finish. Dimensional deviation varies in different directions of parts. For surface finish, there was only a slight change from the master pattern whereas the surface roughness of casting parts decreased within the range 0.23% to 2.85%. Tolerance grades for the selected dimensions of the parts were in the permissible range, based on ISO286-1:2010. When using distinct kinds of AM patterns to create replacement components, design tolerance is needed. It was suggested to select AM technology similar to that had been used for the original components. Battery cover was selected as a case study to represent the mating application parts.

Homogeneity analysis of Y-bearing 12Cr ferritic/martensitic steel fabricated by vacuum induction melting and casting

Advanced oxide metallurgy technique was adopted to produce 100-kg Y-bearing 12Cr ferritic/martensitic steel via vacuum induction melting and casting route. Subsequently, nine specimens at top, middle and bottom regions of the sheet were characterized to evaluate the homogeneity of chemical composition, microstructure and mechanical properties. The small vibration of hardness (200–220 HBW), ultimate tensile strength (672–678 MPa), yield strength (468–480 MPa), total elongation (26.2%–30.5%) and Charpy energy at room temperature (98–133 J) and at − 40 °C (12–40 J) demonstrated that mechanical properties’ homogeneity of Y-bearing steel was acceptable although slight Y segregation and inhomogeneous microstructure occurred at the bottom. Furthermore, the effect of Y content on microstructure characteristics and mechanical properties was explained and the comparison of failure mechanism for the dual-phase steel between tensile test (i.e., quasi-static loading) and Charpy test (i.e., dynamic loading) was discussed in detail.

Tensile, impact and fracture toughness properties of banana fibre-reinforced polymer composites

ABSTRACT In this study, fracture toughness test of short banana fibre-reinforced epoxy composites was carried out. The main interest of this study is to incorporate environmentally friendly biodegradable banana fibres in polymer composites to prove the potential of natural fibres. The short fibres from pseudo-stem part of the banana plant were used to prepare composites. The composite samples were prepared using both alkali-treated and untreated banana fibres. Laminates were prepared from vacuum moulding technique. The effects of alkali-treated fibres on untreated were studied. Since polymer composites are used in many structural applications, these materials because of defects which material failure. The better understanding of material behaviour due to crack growth studies on fracture is essential. In this study, banana fibre-reinforced epoxy composites are developed and their mechanical properties such as tensile strength, impact strength and fracture toughness are evaluated. The fibre matrix adhesion and internal surface of the fractured surfaces are studied by using a scanning electron microscope.

INFLUENCE OF METAL OXIDATION AND FEATURES OF VACUUMING ON THE FORMATION AND LOCATION OF NONMETALLIC INCLUSIONS IN LARGE STEEL INGOTS 38ХН3MФA

The article deals with the influence of steel oxidation and features of vacuuming on the processes of formation and distribution of non-metallic inclusions in large ingots and forgings intended for power engineering. It is shown that the distribution of sulfides and oxysulfides across the ingot cross-section is inversely related to each other, due to changes in oxygen and sulfur concentrations during the crystallization of the melt. Under the influence of intensification of degassing process at vacuum casting of ingots at the expense of purging of a jet of metal argon, the formed nonmetallic inclusions had the minimum sizes, more favorable distribution that caused increase in plastic characteristics of the received forgings on the average for 15-20 %

Multifunctional liquid metal lattice materials through hybrid design and manufacturing

Multifunctional lattice materials exhibit functionalities beyond conventional load-bearing usage and are usually fabricated by additive manufacturing. This work introduces a new class of functional lattice materials called liquid metal lattice materials. These lattice materials consist of liquid metals and elastomers organized in a core-shell manner. This hybrid design induces a shape memory effect by harnessing the solid-liquid phase transition of liquid metals. Consequently, several remarkable functionalities are achieved such as recoverable energy absorption, tunable rigidity, and reconfigurable behaviors. These liquid metal lattice materials are fabricated by using a hybrid manufacturing approach, which integrates the 3D printing, vacuum casting, and conformal coating techniques. A variety of lattice structures are presented to demonstrate the capability of this hybrid manufacturing method and the functionalities of liquid metal lattice materials. This new class of lattice materials have promising applications in aerospace, robotics, tunable metamaterials, etc.

Hot Deformation Behavior and Processing Map of As-Cast 40CrNiMo Alloy Steel

The as-cast 40CrNiMo alloy steel with uniform microstructure is obtained through vacuum casting by using metal mold. The hot deformation behavior of as-cast 40CrNiMo alloy steel is investigated by isothermal compression tests. The Arrhenius constitutive model and processing maps of as-cast 40CrNiMo alloy steel are constructed. The results indicate that the true stress–strain curves present typical dynamic recovery type under low deformation temperature and high strain rate. With the increases in deformation temperature or the decreases in strain rate, the true stress–strain curves gradually transform to dynamic recrystallization type. Through the analysis of processing maps and microstructures, it can be found that the area of plastic instability increases with the increase in the strain and gradually expands to the region of high deformation temperature and low strain rate. The deformation temperature range of 850-1050 °C and strain rate range of 0.001-0.01 s−1 are recommended as the reasonable hot-working process conditions. Results of this research can provide references for the selection of process parameters in casting–forging combination forming of 40CrNiMo alloy steel.

Additive manufacturing assisted investment casting: A low-cost method to fabricate periodic metallic cellular lattices

Metallic cellular solids are a class of materials known for their high specific mechanical properties, being desirable in applications where a combination of high strength or stiffness and low density are important. These lightweight materials are often stochastic and manufactured by foaming or casting. If regular (periodic) lattice structures are desired, they may be manufactured by metallic additive manufacturing techniques. However, these have characteristic issues, such as un-melted powders, porosity and heterogeneous microstructures. This study reports a novel low-cost route for producing regular lattice structures by an additive manufacturing assisted investment casting technique. Fused filament fabrication is used to produce the lattice structure pattern which is infiltrated with plaster. The pattern is then burnt off and the aluminum is cast in vacuum. In this way we can manufacture non-stochastic metallic lattices having fine struts/ribs (0.6 mm cross-section using a 0.4 mm nozzle) and relative densities down to 0.036. X-ray micro computed tomography (μCT) showed that as-cast A356 Aluminium alloy frameworks have high dimensional tolerances and fine detail control. Frameworks based on units of six connected struts ranging from intruding (auxetic) to protruding (hexagonal) strut angles are studied. Vertical struts are finer than expected, reducing their moment of area which could impact their compressive strength. This new, low cost, route for producing high precision metallic cellular lattices offers an attractive alternative to other additive manufacturing techniques (e.g. selective laser and electron beam melting).

Optimization of vacuum casting process parameters to enhance tensile strength of components using design of experiments approach

Vacuum casting is one of the widely used methods for small-volume production of plastic parts. The main challenge of this method is to choose the optimal working parameters to manufacture plastic parts with better mechanical properties. The conventional vacuum casting (CVC) technology uses gravity to make the casing material to fill the mold cavity, resulting in the yield of the molded components with high tensile strength is relatively low. Vacuum differential pressure casting (VDPC) can overcome this disadvantage since the filling mechanism of the casting material is different from CVC process. In this study, integration of design of experiments approach and the VDPC technique was employed to enhance tensile strength of molded components. It was found that the most important control factor affecting the tensile strength of the fabricated component is the mold cavity temperature, followed by the material mixing time, the differential pressure time, and the mixing chamber inlet valve angle. The optimal process parameters for producing components with better tensile strength are the mold cavity temperature of 35 °C, the material mixing time of 40 s, the differential pressure time of 8 s, and the mixing chamber inlet valve angle of 60 °.

Constitutive analysis and dynamic recrystallization behavior of as-cast 40CrNiMo alloy steel during isothermal compression

Casting-forging combination forming process is an advanced manufacturing technique which is applicable to manufacture the parts with both complex shape and high performance. As a fundamental research of casting-forging combination forming process, as-cast 40CrNiMo alloy steel is obtained through vacuum casting by using metal mold. The isothermal compression tests of as-cast 40CrNiMo alloy steel are implemented on a Gleeble-3800 thermal simulation machine at deformation temperatures of 800, 900, 1000 and 1100 ℃, with strain rates of 0.001, 0.01, 0.1, 1 and 10 s−1. The results indicate that the true stress-strain curves present typical dynamic recovery type under low deformation temperature and high strain rate. With the increases of deformation temperature or the decreases of strain rate, the true stress-strain curves gradually transform to dynamic recrystallization type. The Arrhenius-type constitutive equation with Zener–Hollomon parameter is determined for constitutive analysis. The kinetic model and kinematic model of dynamic recrystallization are deduced to describe the dynamic recrystallization behavior.

Synthesis and evaluation of high dispersed nanocarbon/Al composite material by vacuum casting

Synthesis and evaluation of high dispersed nanocarbon/Al composite material by vacuum casting

Multifactor optimization for development of hybrid aluminium matrix composites

The present study aims to multi factor optimization for preparation of aluminum matrix composites (AMC) by reinforcement of SiC/ Al2O3/ Al2O3+ SiC particles having dual particle size (DPS) and triplicate particle size (TPS) based upon signal to noise (S/N) ratio analysis. In this work the amalgamation of fused deposition modelling (FDM) and vacuum moulding (V-process) assisted stir casting (SC) has been employed for the development of AMC. The process parameters under investigation are: particle size (DPS/ TPS); reinforcement type (Al2O3/ SiC/ Al2O3+ SiC); vacuum pressure (VP) (300-400 mm of Hg); moulding sand grit size (American foundry society (AFS) No. 50-70); vibration time (VT) (4-6 sec) and reinforcement proportion/composition (5/7.5/10 by wt.%). The S/N ratio based upon the wear performance (pin-on disc tester), micro hardness (HV) and dimensional accuracy/deviation (Δt) has been evaluated by using Minitab-17 software which further acts as input for multifactor optimization. The best parametric setting proposed for multi objective/factor optimization is: DPS of Al2O3+ SiC reinforcement at 350 mm of Hg VP with 50 AFS No. sand grain size, 4sec VT and 10% composition/proportion. The results of analysis of variance (ANOVA) highlight that particle size (with 18.49% contribution) and reinforcement type (with 42.13% contribution) have significant influence on multi factor optimization for the development of AMC. Confirmatory experiments have been performed which shows that the proposed amalgamation of FDM and V-process assisted SC can be successfully applied for enhancing the performance of AMC. Finally the X-chart and R-chart have been plotted at the proposed settings, which highlights that amalgamation process is controlled and useful for mass/ batch production.

Effect of Heat Treatment Conditions on the Mechanical Properties and Machinability of Ti15SnxCu Alloys

Abstract In the current work, the microstructure, mechanical properties and machinability of Ti15SnxCu alloys (x = 0 to 2 wt. %) were investigated. The alloy was prepared by the vacuum arc remelting and casting route and then thermally processed by solutionizing at 1000 °C for 2 hours, followed by water quenching. By controlling the heat-treated condition and Cu content, the highest bending strength and modulus were obtained from three-point bending testing. The increases were mainly caused by the strengthening effects of the formation of crystallites with fine grain size and nano-Ti2Cu precipitate phase. In addition, nano-Ti2Cu precipitation was caused by crack initiation and propagation, which reduced the ductility and improved the machinability of Ti15Sn2Cu alloy.

Parametric analysis of tribological for gear materials behaviour and mechanical study of cobalt metal powder filled Al-7075 alloy composites

The research article presents the results obtained from the tribological behavior and mechanical characterization of Co metal powder (0–2 wt%) reinforced Al7075 alloys composites for gear materials fabricated via high vacuum casting method. The wear experiments are conducted on the multi specimen tester in lubrication condition. The specimen of fabricated composite is used as new developed material in automotive industry for fabricating of gear. Important variation in behaviour of these materials is possible as a result of cobalt particulate filler introduction. The hardness (151.2–196 HV), flexural strength (341–498.2 MPa), compressive strength (290–490 MPa), tensile strength (235–394 MPa) and impact strength (20–65.5 J) of particulate reinforced alloy composites are showing improved in mechanical characteristics with the increased in cobalt metal powder from 0 wt% to 2.0 wt% respectively. The result of experiment that the cobalt metal powder particulate composites exhibited a minimum the wear rate compared to base alloy and the wear resistance of composite improves it. Finally, the results were investigated that the analysis of microstructure, mechanical and wear behaviour of cobalt metal powder filled Al7075 alloy composite.

Excellence of Al-metal matrix composite fabricated by gas injection bottom pouring vacuum stir casting process

The present study has envisaged an advance technique, gas injection bottom pouring vacuum stir casting process, for the casting of metal matrix composite (MMCs). This process has been eliminated several manual processing steps of conventional stir casting hence concerns about the workers’ safety and its bottom pouring mechanism & vacuum mould chamber improve the properties of the fabricated MMC. An Al/(10wt% Al2O3) MMC has been fabricated by the proposed technique and characterized for the mechanical and microstructural properties. An experimental plan based on Taguchi L16 orthogonal array has also been used to investigate the factors affecting the wear behaviour. The fabricated Al-MMC has a density of 2.65 gm/cc, micro-hardness of 73.3 HV, tensile strength of 220 MPa and wear rate of 0.0137736 mm3/m, implying in substantial improvements from the matrix Al-alloy. A comparative study with the available literature has been carried out to investigate the possibilities of the proposed method in today’s manufacturing world. The results concluded that the fabricated MMC has significantly enhanced the properties of MMCs when compared to the existing casting techniques. From the results of present study, it has been suggested to employ the process in industrial & allied applications and especially in the research institutes where the researchers are not very skilled for the casting operations.

Determining Thermal Conductivity of Small Molecule Amorphous Drugs with Modulated Differential Scanning Calorimetry and Vacuum Molding Sample Preparation.

Thermal conductivity is a material specific property, which influences many aspects of pharmaceutical development, such as processing, modelling, analysis, and the development of novel formulation approaches. We have presented a method to measure thermal conductivity of small molecule organic glasses, based on a vacuum molding sample preparation technique combined with modulated differential scanning calorimetry. The method is applied to the two amorphous model compounds indomethacin and celecoxib. The measured values of below 0.2 W/m °C indicate very low thermal conductivity of the amorphous compounds, within the range of organic liquids and low conducting polymers.

Mechanical and dry sliding wear behaviour of B4C and rice husk ash reinfroced Al 7075 alloy hybrid composite for armors application by using taguchi techniques

These research works investigate, the mechanical and dry sliding behaviour of AA7075-B4C-rice husk ash (RHA) hybrid alloy composite. The specimens of AA7075 with 0, 2, 4, 6, 8 wt% of B4C mixed with 0, 2, 4, 6 and 8 wt% rice husk ash (RHA) are prepared using high vacuum casting machining to study the dry sliding wear behaviour at room temperature. The surface study is used to characterize the fabricated hybrid AA7075 composites. The mechanical behaviour, hardness, flexural tests are conducted using respective ASTM standards. The maximum hardness of 128 HV is obtained for AA7075-8 wt% B4C – 8 wt% rice husk ash (RHA) hybrid composite. The maximum tensile, compressive and flexural strength obtained to be 270 MPa, 570 MPa and 480 MPa respectively, at 8 wt% B4C – 8 wt% of RHA. RHA and B4C particles improved the wear resistance of hybrid composites and decreased the damage on the worn surface. The obtained results are also optimized and observed that addition of 8 wt% B4C – 8 wt% of RHA have reduced wear rate of composite greatly even with increasing sliding velocity and the applied load. Thus, the wear resistance of composite improves at 8 wt% B4C – 8 wt% of RHA.

Sliding wear performance of graphite reinforced AA6061 alloy composites for rotor drum/disk application

This research work reports sliding wear performance of graphite reinforced AA6061 alloy composites for rotor drum/disk application in automobiles. The solid lubricant i.e. graphite-particulates of varying weight percentage (0–10 wt%) was used to reinforce AA6061 alloy, fabricated via high vacuum casting method. The sliding wear was simulated experimentally using Taguchi techniques on Pin-on-Disk tribo-tester, with operating conditions viz. applied load (15–55 N), sliding speed (0.5–2.5 m/s) and sliding distance (200–1000 m). Results show improvement in wear resistance of alloy due to the lubricating effect of graphite. Additionally, 7.5 wt% 6061/Gr alloy composite shows superior wear resistance performance under experimental conditions. Surface morphological studies of worn-out surfaces are carried using scanning electron microscope (SEM), in-order-to understand hidden surface wear mechanisms.

The SEM Metallography Analysis of Vacuum Cast ZhS6K Superalloy Turbine Blade after Various Working Hours

A vacuum cast Ni-base superalloy ZhS6K is used for the production of turbine blades whose are working in the hot section of turbine in former USSR DV-2 jet engine. The usual working temperature for this kind of alloy is designed for 800/1050°C. Turbine blades with protective alitized layer made from this alloy were evaluated at the starting stage, then after 600, 1000, 1500 and 2000 hours of regular working. The SEM methods of quantitative metallography were used for structural characteristics evaluation. The microstructural analysis shows increasing of the medium distance of secondary dendrite arms D, what is related to chemical changes in dendritic structure, and the intermetallic strengthening gamma prime phase coarse and turn into spherical shape what leads to decreasing of dislocation and precipitation strengthening mechanism and further decreasing of hot temperature properties of the alloy. The method used at quantitative evaluation and techniques of colour optical microscopy and SEM is useful when microstructure degradation of superalloys has occurred.

Aqueous Corrosion Behavior of Cast CoCrFeMnNi Alloy

CoCrFeMnNi high-entropy alloy demonstrates good mechanical properties and can be further strengthened by thermomechanical processes. A sample alloy prepared by vacuum casting in a graphite mold was further investigated for its corrosion resistance. One-millimeter thin strips of cast alloy were used to investigate its corrosion behavior at room temperature. Linear potentiodynamic tests of the alloy in sodium chloride solution confirmed uniform corrosion property comparable to stainless steel AISI 304. However, a positive cyclic hysteresis loop indicated susceptibility to pitting corrosion. In sodium hydroxide solution, metastable pit formation was observed, while sulfuric acid solution passivated the alloy. In both cases, the alloy did not show any spontaneous pitting tendency.

Filling mechanism for prototype parts produced by vacuum differential pressure casting technology

Vacuum casting (VC) is the most economical production process for producing small numbers of prototype parts under vacuum conditions. The filling of the casting material in the conventional VC process only depends on the gravity. Thus, some defects of the cast part are observed. In this study, differential pressure (DP) VC was proposed to reduce the filling time and improve the quality of cast parts. In this study, the filling mechanisms in both horizontal and vertical directions were investigated theoretically and experimentally. The actual filling situations of the acrylonitrile butadiene styrene resin in both the horizontal and vertical directions are similar to the simulation results. The relationship of the filling time for DP time, sprue diameters, and mold cavity capacities was investigated. The filling time can be estimated in terms of DP time, sprue diameter, and mold cavity capacity.