Showing papers in "Powder Metallurgy in 2008"
TL;DR: The Fe35Mn alloy was found to be essentially austenitic with fine MnO particles aligned along the rolling direction, and it exhibits antiferromagnetic behaviour and its magnetic susceptibility is not altered by plastic deformation, providing an excellent MRI compatibility.
Abstract: An Fe–35 wt-%Mn alloy, aimed to be used as a metallic degradable biomaterial for stent applications, was prepared via a powder metallurgy route. The effects of processing conditions on the microstructure, mechanical properties, magnetic susceptibility and corrosion behaviour were investigated and the results were compared to those of the SS316L alloy, a gold standard for stent applications. The Fe35Mn alloy was found to be essentially austenitic with fine MnO particles aligned along the rolling direction. The alloy is ductile with a strength approaching that of wrought SS316L. It exhibits antiferromagnetic behaviour and its magnetic susceptibility is not altered by plastic deformation, providing an excellent MRI compatibility. Its corrosion rate was evaluated in a modified Hank's solution, and found superior to that of pure iron (slow in vivo degradation rate). In conclusion, the mechanical, magnetic and corrosion characteristics of the Fe35Mn alloy are considered suitable for further development ...
282 citations
TL;DR: In this article, the authors investigated the bulk, dynamic flow and shear properties of four materials and showed that die filling effectiveness correlates well with many powder properties, thus the availability of accurate information about the flow and bulk properties of powders should allow reliable prediction of die filling efficiency, removing any need for the more usual 'trial and error' approach.
Abstract: Understanding powder behaviour during preparation, transfer and filling of dies is important in powder metallurgy since each step influences the quality of the final component. For high productivity and quality during manufacture, it is essential that process and powder characteristics are compatible. This investigation of the bulk, dynamic flow and shear properties of four materials demonstrates that die filling effectiveness correlates well with many powder properties. Thus the availability of accurate information about the flow and bulk properties of powders should allow reliable prediction of die filling efficiency, removing any need for the more usual 'trial and error' approach.
67 citations
TL;DR: Titanium alloys are of great interest for several applications, but their processing and application is often difficult and expensive as mentioned in this paper, which is why metal powder processing permits the reduction of material cost.
Abstract: Titanium alloys are of great interest for several applications, but their processing and application is often difficult and expensive. Metal powder processing permits the reduction of material cost...
62 citations
TL;DR: In this paper, a prealloyed precipitation hardened stainless steel powder with a water-soluble pore former of nearly 100-fold larger size is used to produce a structural foam.
Abstract: Precipitation hardened stainless steel foam is produced using small prealloyed precipitation hardened stainless steel powder with a water soluble pore former of nearly 100-fold larger size. Structural foams with porosities from 40 to 60 vol.% resulted from extraction of the pore former before high temperature sintering. The pore former particle size and leaching parameters are investigated with respect to the resulting structure. The final porosity is directly related to the added fraction of pore former, providing a direct means to control the properties of the sintered structure, even though the pore former is extracted before sintering.
46 citations
TL;DR: In this paper, the results of sintering molybdenum powder to obtain submicron grain size microstructure using microwave energy were reported, achieving densities as high as 98% of theoretical density (TD) with limited grain growth in <5 min.
Abstract: Molybdenum is a refractory metal used for high temperature applications. Sintered molybdenum (Mo) with fine microstructures is desired due to its improved mechanical properties. However, the sintering of Mo is not easily achievable by conventional processes. In this work, the author report the results of sintering molybdenum powder to obtain submicron grain size microstructure using microwave energy. As received Mo powder was agglomerated with a mean agglomerate size of 1˙6 μm, but equivalent surface area based on N2 adsorption suggests an average particle size of 200 nm. Sintering was carried out using the as received powder. Samples with densities as high as 98% of theoretical density (TD) were obtained with limited grain growth in <5 min of sintering time in microwaves, compared to 10–20 h in a conventional process. The highlight of this research is achieving 98%TD in 1 min at 1650°C with a submicron grain size.
44 citations
TL;DR: In this paper, the evolution of design principles and better evaluation of the impact of cleanliness has led to an evolution of metallurgy (grades and microstructure) and processes.
Abstract: Industrial production of critical parts in aero engine by PM is now more than 30 years old. During this period, evolution of design principles and better evaluation of the impact of cleanliness has led to an evolution of metallurgy (grades and microstructure) and processes. The basis of this evolution will be presented and illustrated by examples taken from companies worldwide.
37 citations
TL;DR: A coupled numerical analysis of the filling, packing and cooling stages of powder injection molding (PIM) has been implemented in this paper, where Finite Element Method/finite difference method methodologies were used in the filling and packing stages while Boundary Element Method (BEM) was used for the cooling stage.
Abstract: A coupled numerical analysis of the filling, packing and cooling stages of powder injection moulding (PIM) has been implemented. Finite element method/finite difference method methodologies were used in the filling and packing stages while Boundary Element Method (BEM) was used for the cooling stage. Using these methodologies, a numerical simulation program for the injection moulding process of PIM parts, PIMSolver was developed by taking into account the peculiar rheological behaviour of powder–binder mixtures. Specifically, the apparent slip phenomena at the mould wall and the yield stress were incorporated into the above analysis. The coupled analysis among the filling, packing and cooling stages was performed because the viscosity and slip phenomena of powder–binder mixture highly depend on temperature. In order to evaluate the significance of the coupled analysis and slip phenomena, several PIM experiments were performed using 316L stainless steel powders dispersed in a paraffin wax–polypropylene binder system. Using the examples of a U-shaped test specimen and an electronic package part, the importance of coupled numerical analysis for PIM parts and the significance of slip dependency of temperature during the coupled analysis were demonstrated.
28 citations
TL;DR: A metal injection molding technique for the production of aluminium alloy components is described in this paper, where a part is formed by injection moulding a mixture of alloy 6061 and 2 wt-%Sn with a resin consisting of stearic acid, palm oil wax and high density polyethylene.
Abstract: A metal injection moulding technique for the production of aluminium alloy components is described. A part is formed by injection moulding a mixture of alloy 6061 and 2 wt-%Sn with a resin consisting of stearic acid, palm oil wax and high density polyethylene. The resin is removed by a combination of solvent and thermal processing. The parts are then sintered in a nitrogen atmosphere to a density of 97%. Sacrificial magnesium blocks which act as an oxygen and moisture getter are placed in the vicinity of the parts during sintering. This ensures surface integrity. Aluminium nitride forms throughout the part, which provides structural rigidity and dimensional stability and limits grain growth. After artificial aging, the tensile strength is 300 MPa. The technique allows the production of small complicated shapes and provides an additional means to manufacture aluminium components for a wide variety of applications.
27 citations
TL;DR: In this article, a PM manufacturing route with mechanical alloying as a crucial step has allowed significant improvement of both oxidation resistance and mechanical properties via micro-alloying additions including nano-dispersed second phase oxide particles.
Abstract: Molybdenum base silicide alloys exhibit promising oxidation resistance in addition to the inherent high temperature strength of refractory metals. However, alloys with sufficient oxidation resistance are effectively brittle up to temperatures above 816°C (1500°F). Recent progress in alloy and process development, utilising a PM manufacturing route with mechanical alloying as a crucial step, has allowed significant improvement of both oxidation resistance and mechanical properties via micro-alloying additions including nano-dispersed second phase oxide particles.
26 citations
TL;DR: In this paper, the consolidation behavior of reinforced metal matrix composite powders during cold uniaxial compaction in a rigid die was studied using modified Cooper-Eaton equation.
Abstract: The consolidation behaviour of particulate reinforced metal matrix composite powders during cold uniaxial compaction in a rigid die was studied. Al–SiC powder mixtures with varying SiC particle size, ranging from nanoscale (50 nm) to microscale (40 µm), at different volume fractions up to 30% were used. Based on the experimental results, the effect of the reinforcement particles on the densification mechanisms, i.e. particle rearrangement and plastic deformation, was studied using modified Cooper–Eaton equation. It was found that by increasing the reinforcement volume fraction or decreasing its size, the contribution of particle rearrangement on the densification increases while the plastic deformation becomes restricted. In fact, when percolation network of the ultrafine reinforcement particles is formed, the rearrangement could be the dominant mechanism of consolidation. It was also shown that at tap condition and at the early stage of compaction where the particle rearrangement is dominant, the...
26 citations
TL;DR: In this article, the sintering behavior of elemental powders of Fe and Al was investigated at various heating rates (0˙5−10°C min−1).
Abstract: The sintering behaviour of elemental powders of Fe and Al was investigated at various heating rates (0˙5–10°C min–1). It was found that the formation of porous FeAl material was accompanied by the volume expansion during the formation of the intermediate phase Fe2Al5. The final pore structure of porous FeAl material depends strongly on the heating rate; the higher the heating rate, the higher the volume expansion and the larger the porosity and the maximum pore size. It has been found that the pore structures produced with different heating rates experienced different formation routes.
TL;DR: In this paper, the possibility of replacing a conventional MIM superalloy feedstock (particle size <20 μm) by a mixture of powders with different particle size ranges, to tailor the flow properties, was investigated.
Abstract: One of the most important stages in the metal injection moulding (MIM) process is feedstock fabrication, since the rheological properties of the feedstock are of crucial importance in the injection moulding step. In the present work, the possibility of replacing a conventional MIM superalloy feedstock (particle size <20 μm) by a mixture of powders with different particle size ranges, to tailor the flow properties, was investigated. Five Inconel 718 feedstocks were prepared with the same binder (HDPE–paraffin wax–stearic acid) and different mixes of four spherical gas atomised powder fractions (<22; 16–45; 45–63; 65–212 μm). The rheological characteristics and processability of each feedstock were evaluated with a capillary rheometer to determine flow index, yield stress and activation energy.
TL;DR: In this article, the design issues related to PIM for the fabrication of thin walled, high aspect ratio geometries were investigated using the state-of-the-art computer aided engineering design tool, PIMSolver.
Abstract: Powder injection moulding (PIM) is a net fabrication technique that combines the complex shape forming ability of plastic injection moulding, the precision of die casting, and the material selection flexibility of powder metallurgy. For this study, the design issues related to PIM for the fabrication of thin walled, high aspect ratio geometries were investigated. These types of geometries are typical to the field of microtechnology based electro chemical, mechanical and biological systems, which are multiscale (sizes in at least two or more different length scale regimes) fluidic devices working on the principle of heat and mass transfer through embedded micro- and nanoscale features. Stainless steel was the material chosen for the investigations because of its high temperature resistivity and chemical inertness necessary for typical microfluidic applications. The investigations for the study were performed using the state of the art computer aided engineering design tool, PIMSolver. The effect of...
TL;DR: In this article, a master decomposition curve (MDC) was formulated based on the intrinsic kinetics of polymer pyrolysis and the Kissinger method was used to estimate the activation energy from thermogravimetric analysis.
Abstract: Polymer burnout (pyrolysis or delubrication) is a crucial step in sintering die compacted powders. To systematically analyse and design the thermal delubrication step, the master decomposition curve (MDC) has been formulated based on the intrinsic kinetics of polymer pyrolysis. The Kissinger method was used to estimate the activation energy from thermogravimetric analysis (TGA) experiments. The activation energy of poly(ethylene-co-vinyl acetate) (EVA) was determined and an MDC analysis was performed to map the weight loss of the polymer as a function of time and temperature. The developed MDC was used to investigate the effects of powder chemistry, powder shape, and particle size of 316L stainless steel on the decomposition behaviour of EVA. The activation energies for decomposition of EVA decreased in the presence of gas and water atomised 316L stainless steel powders, indicative of a catalytic effect. This effect was more pronounced for the first decomposition step suggesting the possible role ...
TL;DR: In this article, gas atomised and water atomised nickel base superalloy powders having compositions close to standard Nimonic 90 were MIM processed and sintered in a PADS (plasma assisted debinding and sintering) reactor under argon at 1280-1310°C.
Abstract: Gas atomised and water atomised nickel base superalloy powders having compositions close to standard Nimonic 90 were MIM processed and sintered in a PADS (plasma assisted debinding and sintering) reactor under argon at 1280–1310°C. A single, integrated debinding–sintering cycle of just under 10 h consistently yielded parts of >98% density that did not require hipping to achieve mechanical properties typical of heat treated wrought Nimonic 90 components. The best overall results were attained with the water atomised material sintered at lower temperatures. These results are particularly relevant to the development of turbine components for the automotive and aerospace industries.
TL;DR: In this paper, the microstructural improvement of such an alloy system, so that it can provide a potential candidate material to be used as KEP, having sufficient penetration depth.
Abstract: Tungsten heavy alloys (WHA) such as W–Ni–Cu and W–Ni–Fe are usually used as kinetic energy penetrators (KEP). However, the amount of penetration of these alloys is not sufficient due to their mushrooming effect that occurs as they impact their targets. On the other hand, KEP made of depleted uranium (DU) in spite of their excellent penetrating properties are not a very good substitute for WHA due to their environmental problems. Therefore, in order to increase the penetration depth of WHA penetrators, a new brand of WHA namely W–Ni–Mn alloys have been developed. The present paper deals with the microstructural improvement of such an alloy system, so that it can provide a potential candidate material to be used as KEP, having sufficient penetration depth. For developing this material, various ratios of Mn/Ni powder were mixed with 90 wt-% pure tungsten powder before compaction and sintering in order to investigate the amount of solubility of W in Ni–Mn matrix. In addition to study the effect of thi...
TL;DR: In this paper, the compressibility of prealloyed steel powders with total alloying ∼2·0% was investigated using equation P=P 0exp (−Kp11), where P is the porosity at pressure p; P 0 is apparent porosity; K and n are parameters related to morphology and plasticity of powder particles.
Abstract: The compressibility of metal powders depends on many factors, including morphological and mechanical properties of particles. Alloying elements increasing ferrite solid solution strengthening can influence the compressibility of prealloyed steel powders. The contribution deals with compressibility of Fe–Mn–Cr–[Mo–Ni] prealloyed and premixed powders with total alloying ∼2·0%. Quantification of powders compaction was performed using equation P=P 0exp (−Kp11); proposed by Parilak et al. (1994), where P is the porosity at pressure p; P 0 is apparent porosity; K and n are parameters related to morphology and plasticity of powder particles. The equation enables to study the compressibility in relation to geometry and mechanical properties of powder particles, through development of K and n parameters on pressing pressure p. The tested powders exhibited low varieties in the density at pressing pressures higher than ∼400 MPa, but some differences were identified during the first stage of compaction, at pr...
TL;DR: In this paper, a slip band model is proposed to explain void formation in polyethyleneglycol (PEG) and polymethylmethacrylate (PMMA) binders with stearic acid as a lubricant.
Abstract: Mixtures of 94 wt-% tungsten carbide (WC) and 6 wt-% cobalt (Co) powders with different particle sizes have been formed with binders composed of polyethyleneglycol (PEG) and polymethylmethacrylate (PMMA), in some cases with the addition of stearic acid (SA) as a lubricant. The presence of voids has had to be invoked to explain why, when the same moulding conditions were used, the as moulded and as leached densities varied with binder composition and in some cases, why the former were lower than expected from the proportions of binder components and solids used to prepare the feedstocks. For a given nominal binder content (vol.-%), calculated on the assumption of zero voidage, and using constant moulding conditions, it appears that the actual voidage tended to decrease as PMMA progressively replaced PEG, and to increase as SA was introduced to replace PEG. The former change to the binder composition should, with constant binder content and moulding conditions, increase the apparent viscosity of the feedstock, while the latter should reduce it. A slip band model is postulated which allows flow behaviour and void formation to be explained qualitatively. This is further developed in Part 2 of this paper. Data from previous studies using PEG/PMMA binders with stainless steel powders are included as these can now be given a qualitative explanation with the slip band model.
TL;DR: In this article, a floating die shear plate was used to explore the effect of density and normal stress on the friction between compact and tool set surfaces. But the results also suggest that the friction coefficient during ejection will be lower than that during compaction; at very high contact stresses, there is a likelihood that the lubrication regime will break down leading to galling.
Abstract: The development of a floating die shear plate apparatus and its use to explore lubrication mechanisms (both admixed and die wall) and to assess the effectiveness of lubrication under a wide range of both compaction and normal loading conditions are described. The equipment allows the independent exploration of the effect of density and normal stress on the friction between compact and tool set surface. Tests were carried out using DistaloyAE, a zirconia target surface and Kenolube as lubricant (added or applied). A friction correlation that includes both density and normal stress effects and that reduces in response to both of these parameters was found. The results also suggest that the friction coefficient during ejection will be lower than that during compaction; at very high contact stresses, there is a likelihood that the lubrication regime will break down leading to galling. With regard to the friction mechanism, surface analysis using EDX did not detect the presence of lubricant on the comp...
TL;DR: In this article, elemental tungsten powder was mechanically milled by planetary mill for 100 h. Particles were thinned down to nanometre scale and the shape of the milled powders was flat cylindrical with average diameter and length 12.5 and 46.5 nm respectively.
Abstract: Elemental tungsten powder was mechanically milled by planetary mill for 100 h. Particles were thinned down to nanometre scale. The shape of the milled powders was flat cylindrical with average diameter and length 12˙5 and 46˙5 nm respectively. The corresponding crystallite size obtained by X-ray diffraction (XRD) was 26˙96 nm. The results obtained by XRD and small angle X-ray scattering were well supported by transmission electron microscopy and high resolution transmission electron microscopy results. The maximum shrinkage of the compact has been observed at ∼1500 K, which has been used as a guideline for sintering experiments. The powders sintered at 1773 K have resulted in 96% relative density.
TL;DR: In this paper, the effects of preheating treatment on the morphology of powders were studied using X-ray diffraction (XRD) and SEM, and the results indicated that the powders are uniform in size and the size and morphology of particles changed with pre-heating schedules.
Abstract: Ultrafine ilmenite CoTiO3 powders were prepared with sol–gel method. The effects of preheating treatment on the morphology of powders were studied using X-ray diffraction (XRD) and SEM. The powders were characterised as an antiferromagnetic material in crystallography and as a ceramic pigment in chromaticity. The XRD analysis revealed that single phase ilmenite CoTiO3 powders were obtained by calcining at 700°C for 3 h with and without preheating and were of vivid blue green colour and of average particle sizes of 42˙5, 41˙9 and 45˙2 nm for non-preheated and preheated powders at 300 and 400°C respectively. The calculated c/a ratio increased from 2˙7440 to 2˙7455 and 2˙7474 with increasing preheating temperature. The SEM analysis indicated that the powders were uniform in size and the size and morphology of particles changed with preheating schedules. The powders were of luminance factor of Y=19˙77 and chromaticity coordinate value of x=0˙2765 and y0˙3600.
TL;DR: A slip band model for powder injection molding (PIM) feedstocks has been proposed in this article, which allows flow behaviour and void formation to be explained qualitatively, i.e. by a slip band mechanism.
Abstract: Flow and deformation of powder injection moulding (PIM) feedstocks are considered to occur in similar ways to those observed in materials containing substantial amounts of clay and water, i.e. by a slip band mechanism. A slip band model for PIM feedstocks has been postulated, which allows flow behaviour and void formation to be explained qualitatively. For feedstocks, the slip bands are assumed to be layers of mobile liquid, which, for polyethyleneglycol/polymethylmethacrylate (PEG/PMMA) binders, are considered to be mainly PEG. It is proposed that some of the slip band liquid is drawn from between the randomly densely packed particles between slip bands to form voids. It is considered for given moulding conditions that increasing the apparent viscosity of a feedstock, by decreasing the volume fraction of binder in slip bands, reduces voidage. This can be achieved by increasing the nominal powder loading of a feedstock and/or increasing the effectiveness of the PMMA in holding the particles togeth...
TL;DR: The identification and assessment of the effects of Engineered Nanoparticles on Human and Environmental Health research project funded by the German Federal Ministry of Education and Research (BMBF) has been set up to address these issues as discussed by the authors.
Abstract: Little research has to date been done to evaluate the impact of nanoparticles on the environment and humans, despite their use in products such as cosmetics, paint and tyres. Experience with other emerging technologies has shown that they are only accepted by society if possible health effects are analysed and published at an early stage of development. INOS, the Identification and Assessment of the Effects of Engineered Nanoparticles on Human and Environmental Health research project funded by the German Federal Ministry of Education and Research (BMBF), has been set up to address these issues. Some initial results of the project are briefly described.
TL;DR: In this paper, the effect of mechanical alloying on the microstructure of elemental powder and the properties of as-sintered alloy has been investigated by X-ray diffraction (XRD), scan electronic microscopy (SEM), density measurement and bending test.
Abstract: Ni3Al intermetallics have been successfully made from mechanically alloyed powder with nominal compositions Ni75Al25 (at.%) by spark plasma sintering (SPS). The effect of mechanical alloying on the microstructure of elemental powder and the properties of as-sintered alloy has been investigated by X-ray diffraction (XRD), scan electronic microscopy (SEM), density measurement and bending test. The results show that the mechanical alloying (MA) refines the grain of particles. It suggests that during subsequent sintering processes the high energy powder enhanced by MA needs lower sintering temperature than mixture powder to gain single phase Ni3Al compacts. Under the same sintering conditions, density and strength of Ni3Al compacts increase with milling time initially and then began to decrease with prolong of milling time under the interaction of grain refinement and more defects involved by MA. Sintering temperature has significant influence on the purity of Ni3Al in the compacts fabricated by react...
TL;DR: In this article, the influence of Mo and Cr additions to improve the microstructure homogeneity and mechanical properties of sintered Ni-containing powder metallurgy (PM) steels was examined.
Abstract: Ni rich/C lean ferrite and austenite are frequently found in the microstructure of sintered Ni containing powder metallurgy (PM) steels. These Ni rich areas are soft and prone to fracture during mechanical testing. To improve the microstructure homogeneity and mechanical properties, the influences of Mo and Cr additions were examined. The results showed that when Mo or Cr containing prealloyed powders were used as the base powder, more homogeneous microstructures and improved mechanical properties were attained. With the use of the Thermo-Calc software, the results of thermodynamic analysis indicated that these improvements were attributed to the reduction of the repulsion effect between Ni and C and thus the elimination of the soft Ni rich ferrite and austenite.
TL;DR: Porous titanium implants with large size and complex shape were successfully fabricated by a novel near net forming process, gelcasting, and the effects of processing parameters on the viscosity of the implant.
Abstract: Porous titanium implants with large size and complex shape were successfully fabricated by a novel near net forming process, gelcasting, and the effects of processing parameters on the viscosity of...
TL;DR: In this paper, the authors describe a series of tests that use an instrumented die, unconfined compression of a cylinder, three point bending and Brazilian disc test to explore the elastic modulus and tensile failure in powder compacts.
Abstract: The paper describes a series of tests that use an instrumented die, unconfined compression of a cylinder, three point bending and Brazilian disc test to explore the elastic modulus and tensile failure in powder compacts. Through the use of common powders test methods are benchmarked against each other. The results show that modulus data from the instrumented die does not depend on data reduction method, however it does exhibit the influence of die dilation at high pressures, made evident in a reduction in modulus at higher density levels. Modulus data from the unconfined compression of a cylindrical compact lead to a lower level of modulus in comparison with the instrumented die test, due principally to the removal of confining and frictional effects at the die wall. Modulus data obtained from three point bending are again lower than that obtained from the unconfined compression test. At this time, this is attributed to the anisotropy within the compact and the relationship between sample compress...
TL;DR: In this paper, the effect of a 1 − 3% manganese addition and of molybdenum carrier grades on sintered and sinter hardened properties of prealloyed Fe −3Cr −0·5Mo steel with low carbon content was investigated.
Abstract: Chromium, manganese and molybdenum exhibit a high hardening effect, especially with carbon, and therefore offer a considerable potential for powder metallurgy production of sintered and sinter hardened highly stressed precision steel parts. The object of the investigation was to study the effect of a 1–3% manganese addition and of manganese carrier grades on as sintered and as sinter hardened properties of prealloyed Fe–3Cr–0·5Mo steel with low carbon content. The sintering of the samples was carried out at 1250°C in cracked ammonia with a dew point −30°C at the cooling rate of 0·06°C s−1, and sinter hardening at the mean cooling rate 0·3°C s−1. The tensile, bending and impact strength, hardness and microstructures of the steels were determined and analysed. The highest values of the mechanical properties were obtained for alloys with 2% manganese added as medium carbon ferromanganese, in both the sintered and sinter hardened state. Heterogeneous microstructures rate, containing martensite, baini...
TL;DR: In this paper, a new manufacturing route via powder presintering and direct hot extrusion is presented, which enabled manufacturing of Fe based metal matrix composites with up to 30% of fused tungsten carbide (FTC, WC/W2C) or titanium carbide(TiC).
Abstract: Materials with high resistance against abrasive wear are of high interest for many tool applications, e.g. in mining industry. These materials usually contain a large amount of hard ceramic phases embedded in a metallic matrix and can only be manufactured by powder metallurgy, most often via hot isostatic pressing. Here a new manufacturing route via powder presintering and direct hot extrusion is presented, which enabled manufacturing of Fe based metal matrix composites with up to 30% of fused tungsten carbide (FTC, WC/W2C) or titanium carbide (TiC). The matrixes chosen are hot and cold work tool steels. The manufacturing process is elucidated and microstructures formed are presented. The microstructure–property relation of the new Fe based MMC is discussed.
TL;DR: In this article, the effect of multi-stage thermal control on the debinding rate was investigated through experiments and the relationship among viscous force, capillary force and pressure force for different working conditions was discussed in details.
Abstract: In metal injection moulding, the quality of the products depends highly on an effective and suitable debinding process. The improvement of the debinding process thus becomes one of the most important topics in metal injection moulding research. To increase the binder debinding rate and decrease the defects of the products, it is essential to understand the influence of thermal control on the debinding process. The present paper aims to investigate the effect of multisteps thermal control on the debinding rate through experiments. Different from previous researches in which single binder is usually adopted, multicomponents binder is used to reflect the real manufacturing situations in industry. The relationship among viscous force, capillary force and pressure force for different working conditions is discussed in details. Experimental results show that the debinding rate and the final debinding fraction are dominated by particle size in the compact rather than that in the wick. For thick compact w...