Rosdi Ibrahim

Solvent Debinding of Inconel 718 Fabricated via Metal Injection Molding

The demand for components manufactured by Metal Injection Molding (MIM) has been increased due to a diverse range of applications on the high temperature mechanical properties and corrosion/oxidation resistance. Super alloy utilize the inherent physical properties of heat-resisting alloy based on iron-nickel, or cobalt specifically high purity and fine particle size distributions, which can enhance sintering and maximize the density of the final component. The development of super alloy Inconel 718 (IN718) using MIM is discussed. IN718 powder with binder formulation consists of polyethylene (PE) / palm stearin (PS) were mixed homogeneously and injected to produce green compacts. The binders then were removed through solvent extraction process from various heating temperature and duration of time. The binder removal was quantified by weight loss measurements and the evolution of pore structure for the debound specimens was observed using scanning electron microscope (SEM). Result shows that complete extraction of PS from the green parts can be concluded during 60 °C of heating and 6 hours of immersion in heptane.

Analysis of the Rheological Behavior and Stability of Inconel 718 Powder Injection Molding (PIM) Feedstock

In PIM process, the molding stage is a critical step for the fabrication of sound parts without cracks and distortions. So, this step requires specific rheological behavior. Rheological analysis can be made to quantify the stability of the PIM feedstock during molding process. In this study, an experimental rheological study has been performed to evaluate the influence of palm stearin on the rheological behavior and stability of Inconel 718 powder injection molding (PIM) feedstock. The effects of shear rate and temperature were investigated via capillary rheometer method. The viscosity and shear rate of the feedstock were measured at various range of temperature and shear rate across the L/D = 1 capillary rheometer. The results show that the formulation binder system PSPE 7030 is the best feedstock to be injection molded because it has moderate value of flow sensitivity index, lower value for flow activation energy and higher value for mold ability index. Besides that, the increasing of PS content in the binder system has found reduce viscosity and value of flow activation energy and increase value of mold ability index of feedstock.

The Effect of Sintering Temperature on Physical Properties of Sintered Inconel 718 for Potential Aerospace Industry Application

The most demanding high temperature application requires nickel-based super alloys, named Inconel 718 (IN718) is a precipitation hardenable nickel chromium alloy containing significant amount of iron, niobium and molybdenum along with lesser amounts of aluminium and titanium. The development of IN718 for metal injection molding was already proposed to provide increased resistance to distortion during and prior to debinding. This paper reports on the effects of sintering temperature on physical and mechanical properties of IN718 alloy. IN718 powder (60 vol%) with binder formulation (40 vol%) consists of polyethylene (PE) and palm stearin (PS) were mixed homogeneously and injected to produce green compacts. The binders then was removed and sintered at 1100 °C and 1200 °C for 8 h respectively. During sintering, the debound part is heated, which is allowing densification of the powder into a dense solid followed by elimination of pores. The sample sintered in vacuum condition at atmosphere 10-5 mbar whereby samples sintered at 1100 °C, show the density of 6.806 g/cm3 compared to samples sintered at 1200 °C is 8.186 g/cm3. Super alloy sintered at 1200 °C exhibited better densification rate with lower porosity. The preliminary results indicate that super alloy can be used in the MIM fabrication of nickel based super alloys to produce high-density sintered parts.

Effect of Sintering Conditions on Mechanical Properties and Microstructure of Titanium Alloy Produced by Metal Injection Moulding (MIM)

Metal Injection Moulding (MIM) is an efficient method for high volume production of complex shape components from powders. The purpose of this study is to determine the sintering condition of titanium alloy (Ti6Al4V) tensile shape sample. In high temperature, Ti6Al4V will react with oxygen to form of titanium oxide (TiO2) which present a problem during sintering thus affected the mechanical properties and microstructure. This reaction can be avoided either by introducing argon gases or in vacuum condition. Ti6Al4V with binder formulation consist of polyethylene (PE), paraffin wax (PW), stearic acid (SA) and palm oil derivatives; palm stearin (PS) were mixed homogenously and injected to produce green compact. The binders then are removed and sintered at 1100 °C for 8 h. During sintering, the debound part is heated, thus allowing densification of the powder into a dense solid with the elimination of pores. It was expected that the impurity gas in argon had strong effects on aspects of the densification and properties. Samples of PE/PS formulation with argon added to the sintering atmosphere, experience density of 4.375g/cm3 and tensile strength stated at 1000.100MPa compared to samples in vacuum condition which do not show any significant increment with density of 3.943g/cm3 and tensile strength at 325.976MPa. PE/PW/SA samples of vacuum condition also show no improvement in sintered properties. However with additional argon flow the density can reach until 4.359g /cm3 and 940.823MPa of tensile strength. Ti-alloy sintered in argon exhibited better densification rate than in vacuum with high strength, better elongation and lower porosity. In argon, the powder particles became interconnected signifying densification was achieved due of non-reactive properties of inert gases that prevent undesirable chemical reactions from taking place.

Evaluation of hardness and density properties of sintered Inconel 718 using palm oil-based binder

This paper investigates the effect of palm oil-based binder on hardness and density of sintered Inconel718. Palm stearin (PS) is the palm oil derivative, which has been formulated and evaluated as possible alternative binder system. The variety of PS contents can be an advantage during debinding process as it can be removed gradually to maintain the shape of the debound part. At different heating temperatures, each binder contents melts, leaving different impurities. The remaining impurities help to form capillary holes for the removal of the binder material. The PS binder system is compared with conventional binder system based on the physical and mechanical properties of Inconel718 sintered parts. It was found that the PS binder systems proved to enhance the properties and improve the microstructure behaviour. Result shows that the sintered properties from palm oil binder system can be achieved in accordance to the Metal Powder Industries Federation standard.

The effect of impurities elements on titanium alloy (Ti-6Al-4V) MIM sintered part properties

The titanium alloys (Ti-6Al-4V) compact were fabricated by Metal Injection Molding (MIM). However, the real challenge of MIM processing for titanium alloy is its affinity to be contaminated by interstitial light elements such as oxygen and carbon which could degrade the mechanical properties of sintered titanium alloy such as its tensile strength and ductility. The sintering temperature effect on carbon and oxygen content that affects its physical and mechanical properties of the sintered titanium alloy was studied. The titanium MIM brown specimen was sintered at four different sintering temperatures which are 1100 °C, 1150 °C, 1200 °C and 1250 °C for 4 hours under furnace control atmosphere. The experimental result indicated that the specimen which has been made from 100% gas atomized powder have a relative density of 92.2 % - 97.6 %, the range of porosity percent around 2.38 %-3.84 %. Ultimate tensile strength of 873.11 MPa - 1007.19 MPa and ductility percent in range of 1.89 %-3.46 %. The titanium alloy MIM specimen which was sintered at 1150 °C contained 0.145 % of carbon and 0.143 % of oxygen possess the highest value of density and tensile strength, with value of 4.344 gcm−3 and 1007.2 MPa respectively. Meanwhile, the titanium alloy MIM specimen which was sintered at 1200 °C contains 0.130 % of carbon and 0.127 % of oxygen, has the highest percentage of ductility with 3.46 %. The carbon content level increased as the sintering temperature increased due to decomposition of high molecule weight of residue binder system which could not be eliminated during solvent extraction debinding process and sintered at low temperature. Contrarily, the oxygen content level indicates a decrease as the sintering temperature increased. Briefly, the sintering temperature could influence the physical and mechanical properties of titanium alloy MIM sintered specimen as it influences the oxygen and carbon content level in the alloys.The titanium alloys (Ti-6Al-4V) compact were fabricated by Metal Injection Molding (MIM). However, the real challenge of MIM processing for titanium alloy is its affinity to be contaminated by interstitial light elements such as oxygen and carbon which could degrade the mechanical properties of sintered titanium alloy such as its tensile strength and ductility. The sintering temperature effect on carbon and oxygen content that affects its physical and mechanical properties of the sintered titanium alloy was studied. The titanium MIM brown specimen was sintered at four different sintering temperatures which are 1100 °C, 1150 °C, 1200 °C and 1250 °C for 4 hours under furnace control atmosphere. The experimental result indicated that the specimen which has been made from 100% gas atomized powder have a relative density of 92.2 % - 97.6 %, the range of porosity percent around 2.38 %-3.84 %. Ultimate tensile strength of 873.11 MPa - 1007.19 MPa and ductility percent in range of 1.89 %-3.46 %. The titanium allo...

Effect of Using Different Compositions and PU Foam Template to Produce Cobalt Chromium Molybdenum (CoCrMo) Foams

Slurry dipping is a simple and popular method of producing porous and interconnected foams using a metallic slurry. The advantage of the network-like metal foams is it exhibits a natural bone-like structure which enables ingrowth of bone cells and blood vessels. The aim of the present study was to investigate the effect of using difference composition and scaffold to produce Cobalt Chromium Molybdenum (CoCrMo) foams. The CoCrMo slurry was prepared by using different composition of CoCrMo powder which was 60wt%, 65wt% and 70wt%. Also two different types of scaffold were used in this study. The CoCrMo slurry was produced by mixing CoCrMo powder with Polyethylene Glycol (PEG), Carboxyl Methyl Cellulose (CMC) and distilled water. Then, polyurathane foam template was dipped in CoCrMo slurry and dried at room temperature. Sintering process was running by vacuum furnace at high temperature, 1200°C. The CoCrMo foam was characterized by using a Scanning Electron Microscopy (SEM) analysis. The physical properties of CoCrMo foam was analyzed by porosity and bulk density test that was Archimedes method. From the study it was expected that the composition of metallic slurry play important roles to produce a CoCrMo foam. In order to orthopaedics application to apply in cancellous bone, highest value of porosity from PU foams type (a) was most suitable result to use. This is due to the value of porosity that generate that was 65.2%.

Physical Properties of 316L Stainless Steel (SS316L) Foam with Different Composition by Using Compaction Method

Nowadays, the 316L stainless steel metal foams (SS316L) have acknowledged important attention in various fields and are required to be used as engineering materials including heat exchange, sound absorption, filtration and others. So, in this study the production of SS316L foams using different composition through compaction method by using a starch powder as space holder was studied. The range of selected composition of SS316L that obtained is between 50 wt% to 60 wt% while the remaining percentages are space holder and binder. The SS316L compact is prepared by mixing SS316L alloy powder, starch powder, and Polyethylene Glycol (PEG). Then, the mixture is compact into a mould under 8 tonnes of controlled pressure using hydraulic press machine. This is later sintered in a vacuum furnace. The sintered SS316L foams were characterised using a Scanning Electron Microscopy (SEM) analysis. Then, the physical properties of SS316L foam was also analysed by Archimedes method that includes porosity and bulk density test. As a result, the sample with 60 wt% were produced a good and finer pores and struts. Meanwhile, for that sample the percentage of porosity and bulk density are 0.19% and 7.44 g/cm3, respectively.

Towards an aerogel-based coating for aerospace applications: reconstituting aerogel particles via spray drying

Silica aerogel is an ultralight and highly porous nano-structured ceramic with its thermal conductivity being the lowest than any solids. Although aerogels possess fascinating physical properties, innovative solutions to tackle todays problems were limited due to their relative high manufacturing cost in comparison to conventional materials. Recently, some producers have brought forward quality aerogels at competitive costs, and thereby opening a panoply of applied research in this field. In this paper, the feasibility of spray-drying silica aerogel to tailor its granulometric property is studied for thermal spraying, a novel application of aerogels that is never tried before in the academic arena. Aerogel-based slurries with yttria stabilised zirconia as a secondary ceramic were prepared and spray-dried according to modified T aguchi experimental design in order to appreciate the effect of both the slurry formulation and drying conditions such as the solid content, the ratio of yttria stabilised zirconia:aerogel added, the amount of dispersant and binder, inlet temperature, atomisation pressure and feeding rate on the median particle size of the resulting spray-dried powder. The latter was found to be affected by all the aforementioned independent variables at different degree of significance and inclination. Based on the derived relationships, an optimised condition to achieve maximum median particle size was then predicted.

Development and Characterization of SS316L Foam Prepared by Powder Metallurgy Route

Open cell foams, made on the basis of polyurethane foams replication method are well known and had been widely used since decades. The advantage of the network-like metal foams is it exhibits a natural bone-like structure which enables ingrowth of bone cells and blood vessels. The aim of the present study is to develop SS316L foam with an open cell structure by using powder metallurgy routes via foam replication method. The SS316L slurry was produced by mixing SS316L powder with Polyethylene Glycol (PEG), Methylcellulose (CMC) and distilled water. The composition of the SS316L powder in the slurry was varied from 40 to 60 wt. %. Then, polymeric foam template was impregnated in SS316L slurry and dried at room temperature. Sintering was carried out in a high temperature vacuum furnace at 1300°C. The microstructure of the SS316L foam produced was observed by Scanning Electron Microscope (SEM) and the elemental analysis was carried by Energy Dispersive X-ray (EDX). It was found that pore size are within 200-400μm and the average pore size is 293μ. The detected elements in the SS316L foam were C, Al, Ca, O, Cr, Fe, Mo, Ni and Si.