Showing papers in "Powder Metallurgy in 2006"
TL;DR: In this paper, a small particle size changes the response during sintering, requiring lower reaction times, resulting in lower wear-resilience and lower power consumption of tungsten powders.
Abstract: Nanoscale tungsten powders promise access to very hard, strong and wear resistant materials via the press–sinter route. A small particle size changes the response during sintering, requiring lower ...
38 citations
TL;DR: Experimental investigations on millimetre wave sintering of copper and mixed elemental metal powder compacts in the system iron-copper-carbon have been performed in nitrogen atmosphere as discussed by the authors.
Abstract: Experimental investigations on millimetre wave sintering of copper and mixed elemental metal powder compacts in the system iron–copper–carbon have been performed in nitrogen atmosphere. Therefore, ...
33 citations
TL;DR: In this article, a multicomponent Cu-based metal powder, which consisted of a mixture of Cu, 10Sn and 8·4P powder, was developed for direct metal laser sintering (DMLS).
Abstract: Recent advances in direct metal laser sintering (DMLS) have improved this technique considerably; however, it still remains limited in terms of material versatility and controllability of laser processing. In the present work, a multicomponent Cu based metal powder, which consisted of a mixture of Cu, Cu–10Sn and Cu–8·4P powder, was developed for DMLS. Sound sintering activities and high densification response were obtained by optimising the powder characteristics and manipulating the processing conditions. Investigations on the microstructural evolution in the laser sintered powder show that liquid phase sintering with partial or complete melting of the binder (Cu–10Sn), but non-melting of the cores of structural metal (Cu) acts as the feasible mechanism of particle bonding. The additive phosphorus acts as a fluxing agent to protect the Cu particles from oxidation and shows a concentration along grain boundaries owing to the low solubility of P in Cu and the short thermal cycle of laser sintering...
32 citations
TL;DR: In this paper, an Ag-SiC composite was brazed to Ti alloy using an interlayer of Ag-Cu-Ti alloy, Ti and C mixed powder, which provided good reinforcement and alleviation of the joint thermal stress.
Abstract: Cf–SiC composite was brazed to Ti alloy using an interlayer of Ag–Cu–Ti alloy, Ti and C mixed powder. Microstructure and shear strengths of the brazed joint at both room temperature and 500°C were investigated. The performed joints have dense bonding layers reinforced by in situ synthesised TiCx from reaction of C and Ti in the bonding layers. In situ synthesised TiCx provides good reinforcement and alleviation of the joint thermal stress, resulting in an increase in strengths of brazed joints at both room temperature and elevated temperature.
28 citations
TL;DR: In this article, an instrumented die was used to investigate the behavior of metal powders during cold (ambienttemperature) and warm (up to 140°C) compaction.
Abstract: An instrumented die was used to investigate the behaviour of metal powders during cold (ambienttemperature) and warm (up to 140°C) compaction. This instrument enables simultaneousmeasurement of density, die wall friction coefficient, the triaxial stresses acting on the powderduring the course of compaction and ejection pressure. Commercial iron, titanium, aluminium,316L stainless steel (SS) and aluminium–silicon powders were employed for investigation. Theresults demonstrated the advantages of powder preheating on the compaction behaviour of metalpowders concerning green density, dimensional changes, frictional behaviour, ejectioncharacteristics and compactibility. However, the outlines also determined that the response ofthe non-ferrous powders to powder preheating is somehow different from those of the ferrouspowders. In this context, the behaviour of prealloy aluminium–silicon powders during compactionwas found of particular interest, as their compactibility is strongly affected by powder prehe...
25 citations
TL;DR: The objective of the present study was to investigate high velocity compaction of titanium powder and to prepare a dense composite biomaterial of titanium and hydroxyapatite with the purpose of forming dental components with improved early healing properties.
Abstract: The objective of the present study was to investigate high velocity compaction of titanium powder and to prepare a dense composite biomaterial of titanium and hydroxyapatite with the purpose of forming dental components with improved early healing properties. A high purity titanium powder was compacted using high velocity compaction to study the density distribution. Then, a titanium–hydroxyapatite composite was prepared by mixing titanium powders and hydroxyapatite grains. Dental implant components were formed from the high velocity compacted specimens, exposing the hydroxyapatite grains at the component surface. The green density reached more than 98·5% after more than one impact. The composite was heated to 500°C, enough to bind the titanium grains, but to avoid observable reactions. Compacted pure titanium could be sintered to full density. The heated composite material reached 99% density, no reaction was observed between titanium and hydroxyapatite, and the composite material could be formed...
23 citations
TL;DR: In this paper, a novel route was investigated for the preparation of metal injection molding (MIM) titanium alloys by TiH2 powder, and it can be known from the analysis of thermodynamics and kinetics of dehydrogenation reaction that decomposition occurs when hydrogen partial pressure is ∼10−2 Pa at 300°C.
Abstract: A novel route was investigated for the preparation of metal injection moulding (MIM) titanium alloys by TiH2 powder. It can be known from the analysis of thermodynamics and kinetics of dehydrogenation reaction that decomposition occurs when hydrogen partial pressure is ∼10−2 Pa at 300°C. The temperature range of dehydrogenation is within that of debinding so that the dehydrogenation and debinding can be carried out simultaneously. The hydrogen content of the sample debound in 10−2 Pa is merely 0·016 wt-% as the temperature raised up to 525°C, indicating that the hydrogen can be removed effectively. Finally, the sintered parts with average tensile strength of 770 MPa and specific elongation of 4·3% were prepared, of which the impurity contents were satisfactory. The sintered parts have the uniform fully lamellar microstructure, in which the interlamellar spacing between α phases is thin.
23 citations
TL;DR: Physical and mechanical properties for prealloyed 6061 Al powder processed with and without additions of solid and/or liquid lubricants and sintering aids (Pb, Sn, Ag) are presented in this paper.
Abstract: Physical and mechanical properties for prealloyed 6061 Al powder processed with and without additions of solid and/or liquid lubricants and sintering aids (Pb, Sn, Ag) are presented. For comparison, both vacuum and nitrogen sintering were carried out on as received (gas atomised) and degassed powder compacts pressed at 340 and 510 MPa. Vacuum degassing of the prealloyed powder provided better compressibility and thus higher green densities than those for the as received powder. Highest sintered densities of ∼98–99% of theoretical were obtained for the prealloyed (and degassed) Al compacts by sintering under pure nitrogen with an addition of 0·6 wt-% paraffin wax as solid lubricant or 1·33 vol.-% liquid paraffin, or with a 0·12 wt-%Pb addition as sintering aid and no lubricant. It was found that additions of solid lubricants such as lithium stearate and acrawax to both the premixed (elemental) and prealloyed powders provided reasonable green densities of ∼94·5–95·5% TD, but had deleterious effect o...
22 citations
TL;DR: The use of diamond impregnated cutting tools has undergone a fantastic development since the invention of synthetic diamond in the 1950s as discussed by the authors and the last five decades witnessed a spectacular, >50fold, increase in the total consumption of industrial diamond.
Abstract: The methods of making diamond impregnated cutting tools have undergone a fantastic development since the invention of synthetic diamond in the 1950s. The last five decades witnessed a spectacular, >50fold, increase in the total consumption of industrial diamond. Over this time, modern production techniques based on diamond tooling have been implemented into various areas of industrial activity enabling to do the job faster, more accurately and at less cost. They revolutionised machinery and processing techniques in the stone and construction industries, road repair, petroleum exploration, production of glass, dense ceramics, etc. In the production volume terms, by far the largest group of diamond tools comprises the so called 'metal bonded' diamond impregnated tools such as circular and frame saw blades, wire saws and core drills for cutting natural stone and construction materials, as well as core bits for drilling in medium to hard rock formations. The role of powder metallurgy (PM) in the produ...
22 citations
TL;DR: In this paper, the powder is conventionally compacted, pre-sintered to burn off the lubricant, recompacted using HVC and finally sintered traditionally.
Abstract: In the search for PM components with improved mechanical properties, high velocity compaction (HVC) offers a significant increase in density, and thus properties, coupled with low production cost. In HVC, density increase is achieved using a very high rammer speed in the pressing operation. To reach even higher densities, SKF has developed a route involving HVC recompaction. The powder is conventionally compacted, pre-sintered to burn off the lubricant, recompacted using HVC and finally sintered traditionally. Using this industrially applicable process, components of density 7·7 g cm−3 can routinely be produced, and potentially even higher density levels. Examples of applications are presented, with typical properties, and research to improve the process further is described.
22 citations
TL;DR: In this article, two powder metallurgy cold work tool steels were compacted to full density by utilisation of super solidus liquid phase sintering in vacuum and nitrogen atmospheres.
Abstract: Two different powder metallurgy cold work tool steels, D7 and a nickel alloyed D7 modification, were compacted to full density by utilisation of super solidus liquid phase sintering in vacuum and nitrogen atmospheres. The experiments were carried out with respect to the fabrication of wear resistant metal matrix composites. These materials exhibit a higher durability than cast materials and are increasingly used in the mineral and mining industry. In the present paper, sintering exhibits a more cost effective processing of these materials compared with hot isostatic pressing. The experiments were supported by thermodynamic calculations with Thermo-Calc. Significant differences of the sintering behaviour in vacuum and nitrogen atmospheres were detected. Full density could be obtained at a sintering temperature as low as 1210°C.
TL;DR: In this paper, a method to estimate the pore free density and the open and closed porosities of a PM specimen by helium pycnometry is introduced, and the results of the method as applied to pressed and sintered specimens of a commercially pure iron powder in the density range from 6·7 to 7·5 g cm−3 are presented and compared with the values obtained on the same specimens using the standard oil impregnation and water immersion method.
Abstract: A method to estimate the pore free density and the open and closed porosities of a PM specimen by helium pycnometry is introduced. The findings of the method as applied to pressed and sintered specimens of a commercially pure iron powder in the density range from 6·7 to 7·5 g cm−3 are presented and compared with the values obtained on the same specimens using the standard oil impregnation and water immersion method. It was found that the observed density values by the two methods were similar, but that the open and closed porosity values were not. In general, the pycnometric method indicated substantially higher open porosity values and correspondingly lower closed porosity values than the standard method at all densities.
TL;DR: In this article, a comparison between compaction, sintering, microstructural and mechanical properties of the 6061 aluminium alloy prepared via premixed elemental (EL) and prealloyed (PA) powders is made.
Abstract: A comparison has been made between compaction, sintering, microstructural and mechanical properties of the 6061 aluminium alloy prepared via premixed elemental (EL) and prealloyed (PA) powders (as ...
TL;DR: In this article, tin powders were produced using a supersonic nozzle in a close coupled gas atomisation system, and the effects of those variables on powder mean size, powder morphology and gas/melt mass flow ratio were investigated.
Abstract: Gas atomisation is one of the most commercially used methods for producing metal powders. It is known as the break-up of a liquid metal into fine droplets by gas jets. In the present study, tin powders were produced using a supersonic nozzle in a close coupled gas atomisation system. Atomisation pressure and the protrusion length of the melt delivery tube were varied, and the effects of those variables on powder mean size, powder morphology and gas/melt mass flow ratio were investigated. The powder size decreased with increasing atomisation pressure. The reason of the increase in the gas/melt mass ratio with shorter protrusion length is a decrease in the melt mass flow rate, although the gas mass flow rate is constant at the same pressure. A decrease in the melt mass flow rate is caused by the effect of recirculation zone acting on the tip of the melt delivery tube. The produced tin powders had spherical shapes and clean surfaces.
TL;DR: In this paper, a new process for synthesizing homogeneous ultrafine and nanoscaled tungsten carbide with good stability in air from well dispersed colloidal carbon-coated nano-tungsten precursor with highly agglomerated nan-scaled tengsten powder as starting material in a cost effective way is introduced.
Abstract: A new process for synthesising homogeneous ultrafine and nanoscaled tungsten carbide with good stability in air from well dispersed colloidal carbon coated nano tungsten precursor with highly agglomerated nanoscaled tungsten powder as starting material in a cost effective way is introduced. It is shown that hydrogen atmosphere facilitates the carbon and tungsten reaction process. Inheritance character in grain size distribution of tungsten carbide from tungsten starting material with BET calculated grain size of 46·1 nm has been observed. When the carburisation temperature increases from 1000 to 1300°C, the Brunauer–Emmett–Teller calculated grain size of tungsten carbide powder increases from 68·6 nm to 339·4 nm and the oxygen content decreases from 0·44 to 0·10%.
TL;DR: Charpy V notch (CVN) impact testing was conducted on full size and subsize specimens of sintered and wrought 17-4-PH stainless steel (17-4 PH SS).
Abstract: Charpy V notch (CVN) impact testing was conducted on full size and subsize specimens of sintered and wrought 17–4 PH stainless steel (17–4 PH SS) in the as sintered and H900 heat treated conditions. Test geometries correspond to the American Society for Testing and Materials (ASTM) and Metal Powder Industries Federation (MPIF) impact testing standards. Merits of a notched specimen compared with an unnotched specimen were analysed for both the wrought and sintered materials. The notched ASTM standard bars had a lower coefficient of variance for impact energy than the unnotched MPIF standard bars and displayed greater toughness. Porosity and grain size have a detrimental synergistic effect on impact toughness for the sintered material. Following a discussion about the differences in the wrought and sintered microstructures, it is recommended that impact testing of the injection moulded and sintered specimens should be evaluated according to the ASTM test specifications.
TL;DR: In this paper, the development of powder metallurgy alloys based on the Al-Ni-Mg system was initiated, and binary and ternary alloys were prepared, compacted and sintered using elemental and master alloy feedstock powders.
Abstract: The objective of this research was to initiate the development of powder metallurgy alloys based on the Al–Ni–Mg system. In doing so, binary (Al–Mg) and ternary (Al–Ni–Mg) blends were prepared, compacted and sintered using elemental and master alloy feedstock powders. Research began with fundamental studies on the sintering response of the base aluminium powder with additions of magnesium. This element proved essential to the development of a well sintered microstructure while promoting the formation of a small nodular phase that appeared to be AlN. In Al–Ni–Mg systems a well sintered structure comprised of α aluminium plus NiAl3 was produced at the higher sintering temperatures investigated. Of these ternary alloys studied, Al–15Ni–1Mg exhibited mechanical properties that were comparable with existing commercial 'press and sinter' alloys. The processing, reaction sintering and tensile properties of this alloy were also found to be reproducible in an industrial production environment.
TL;DR: In this article, the microstructure in the materials and the combination interface between HA and 316L stainless steel fibres was observed in detail, showing that the bending strength and compressive strength of the composite increased with the increase in volume of the stainless steel fibers, but decreased with increasing diameter and mean length of the fibres.
Abstract: Hydroxyapatite (HA)–316L stainless steel composite biomaterials with different 316L stainless steel fibre volume fraction in the composite were fabricated by hot pressing and sintering at elevated temperature. 316L stainless steel fibres were enwrapped in the HA matrix with integration being very tight. Metallographic microscope, SEM and EDAX analysis were carried out in order to investigate the microstructure in the materials and the combination interface between HA and 316L stainless steel fibre was observed in detail. While the composite contained 20 vol.-%316L stainless steel fibre, the bending strength and the compressive strength are equal to ∼200 MPa and 400 MPa, respectively. The research displayed that mechanical properties increase with the increase in volume of the 316L stainless steel fibres, but decrease with increasing diameter and mean length of the fibres. Toughness of the composite increases with the rise of 316L stainless steel contents. It has been shown that some Fe atom diffus...
TL;DR: In this paper, the authors used X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscope (AES) to assess how surface oxides limit the gas nitriding depth of gas atomised M4 high speed steel powder and compacts.
Abstract: In the present study the authors have used X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to assess how surface oxides limit the gas nitriding depth of gas atomised M4 high speed steel powder and compacts. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been used for phase identification. In model experiments XPS and AES analyses of vacuum annealed powder were performed in an interconnected furnace, limiting reoxidation. Sintering cycles with and without vacuum annealing treatment were also evaluated. Generally, the authors found that an increased vacuum annealing treatment time decreased the amount of residual oxygen, which improved densification. AES and XPS analyses of the model experiments showed that the vacuum annealing time increased the absorption of nitrogen. In the sintered compacts, SEM, AES and XRD analysis as well as Thermo–Calc simulations showed that similar amounts of nitrogen were tied to vanadium carbonitrides. An AES comparison b...
TL;DR: The approach suggests the feasibility of using porous HA–TCP bioceramics for the transplantation of autogenous osteoblasts to regenerate bone tissue.
Abstract: Porous bioceramics hydroxyapatite–tricalcium phosphate (HA–TCP), aimed to be applied in clinic, was fabricated by powder metallurgy and evaluated using both in vitro and in vivo models. Porous HA–TCP was supposed as a partially biodegradable material and designed as a scaffold for bone reconstruction or regeneration. The material processing was proposed and the physical properties as well as the microstructure feature were characterised here. Biological postulation of the relationship between seeding density, proliferation and viability of human osteoblasts cultured on the porous HA–TCP was quantitatively measured. Bone reconstruction was investigated both in vitro and in vivo by use of these biodegradable scaffolds with pore sizes ranged from 200 to 400 μm in diameter. The degradable bioceramic supported cellular proliferation seeded on the scaffold and showed normal differentiated function in vitro. Suitable pore size of the porous bioceramic was required if promotion of bone reconstruction was ...
TL;DR: In this paper, a continuous isostatic pressure sintering process combined with sizing, produces aluminium alloys with finely dispersed Si particles having excellent ductility, combining parts obtained by these two process routes can give interesting tribological systems.
Abstract: The automotive industry's focus on weight saving has increased interest in optimised process routes and alloy compositions for light alloy PM components Conventional pressing, sintering and sizing of aluminium alloys containing about 16%Si has been applied to produce components with high wear resistance and mechanical strength CISIZE®, a novel continuous isostatic pressure sintering process, combined with sizing, produces aluminium alloys with finely dispersed Si particles having excellent ductility Combining parts obtained by these two process routes can give interesting tribological systems Complete sintered aluminium cam phaser systems, including the sprocket wheel, are being produced in series using this approach, which also shows promise for automotive parts such as oil pumps and rotors
TL;DR: In this article, the authors investigated the effect of aspiration and the melt-gas configuration of interaction on median particle diameter, standard deviation, and flake formation in two designs of atomisation nozzles.
Abstract: Convergent–divergent close coupled nozzles are used for the production of spherical and clean powders. A close coupled nozzle consists of a convergent–divergent gas flow channel concentric to which a melt flow tube is inserted. These nozzles have been proved to be efficient for melt atomisation. However, the aspiration created at the tip of the delivery tube and the gas–melt configuration of interaction play a key role in determining the atomisation efficiency, mean particle size and standard deviation. In this investigation, aspiration has been measured for different protrusion lengths of metal and ceramic tubes from the nozzle exit. Two designs of atomisation nozzles are investigated. In one of the nozzles, flow channel is directed away from the centreline, whereas, in the other, it is directed on the centreline of the flow tube. Atomisation experiments are carried out to study the effect of aspiration and the melt–gas configuration of interaction on median particle diameter, standard deviation and flake formation. Aspiration, at the tip of the delivery tube, shows strong dependence on the combination of protrusion lengths. A change in the melt–gas configuration of interaction results in variation in median particle diameter and standard deviation. The nozzle with flow channel directed on the centreline showed better atomisation efficiency. This is manifested in smaller amount of flakes and narrow powder size distribution. The results have been presented and discussed.
TL;DR: In this article, an analytical densification model describing the final stages of hot pressing and sintering has been developed and found to be consistent with empirical findings, and the behavior of composite powders for the matrices of diamond tools has been studied under hot pressing conditions.
Abstract: An analytical densification model describing the final stages of hot pressing and sintering has been developed and found to be consistent with empirical findings. The behaviour of composite powders for the matrices of diamond tools has been studied under hot pressing conditions. Differential scanning calorimetry was used to determine the heat capacity at constant pressure C p of pure Co, 663Cu, and composite iron- and cobalt based powders (also containing WC, Ni and 663Cu). The relationship between C p and composite densification has been analysed, and it has been found that optimised rare earth additions to the iron based composite powders can produce C p characteristics close or equivalent to that of pure Co powders. This modified composite powder has been used to hot press diamond drill and saw bits that show good properties. Employing a densification regime guided by the dynamic model has been found radically to improve stability in service (bend strength, hardness, impact, ductility and poro...
TL;DR: In this article, a metal matrix composite with a matrix composition of Al-3·8Cu, 1Mg, 0.75Si, and 0.5Sn was fabricated by sintering a particulate ceramic reinforcement with elemental metal powders.
Abstract: A metal matrix composite with a matrix composition of Al–3·8Cu–1Mg–0·75Si–0·5Sn was fabricated by sintering a particulate ceramic reinforcement with elemental metal powders. The sintering characteristics were examined as a function of reinforcement volume fraction, particle size and particle size ratio. At high volume fractions of reinforcement, densification ceased completely and the compacts expanded during sintering. Coarse reinforcement particles, not large particle size ratios, maximised the sintering response. Clustering of the ceramic was studied using Dirichelet tessellations of sintered microstructures. While clustering is evident in the sintered microstructures, it does not correlate to sintered density through the particle size ratio because the ceramic particles appear to rearrange in the presence of a large volume of sintering liquid. The effect of particle size is not due to clustering but maybe due to ceramic particle surface area.
TL;DR: In this article, high density powder metallurgy duplex stainless steels were obtained by mixing water and gas atomised powders, and aISI 434L water atomised ferritic powders were mixed with different percentages.
Abstract: High density powder metallurgy duplex stainless steels have been obtained by mixing water andgas atomised powders. AISI 434L water atomised ferritic powders were mixed with differentpercentages (up...
TL;DR: In this paper, the compressive properties of porous Ni materials were investigated by innovated powder metallurgical (PM) method and they showed that the Ni materials first show a short elastic region, then a long and oblique stress yield region within the strain range of about 10-50%, and finally, a densification region where the stress increases rapidly.
Abstract: Compressive properties are investigated for the porous Ni materials processing by innovated powder metallurgical (PM) method. The porous Ni materials first show a short elastic region, then a long and oblique stress yield region within the strain range of about 10–50%, and finally, a densification region where the stress increases rapidly.
TL;DR: In this article, the authors analyzed the nucleation of microcracks, their growth and coalescence in powder metallurgy (PM) material and found that the maximum tensile stress in three-point bend specimens was raised to 99·6% of the transverse rupture strength TRS of 1397 MPa.
Abstract: Nucleation of microcracks, their growth and coalescence are analysed in powder metallurgy (PM). Fe–1·5Cr–0·2Mo–0·7C steel by fractography allied to surface replica microscopy – at several stress levels as the maximum tensile stress in three-point bend specimens was raised to 99·6% of the transverse rupture strength TRS of 1397 MPa. The fatigue limit in this material is ∼240 MPa, at which stress level no microcracks were detected in static loading. Numerous microcracks, ranging in size from <5 to ∼20 μm, however, were nucleated above ∼800 MPa, i.e. beyond the yield strength of ∼620 MPa. With increasing stress, some microcracks became dormant, whilst others grew subcritically, stress step-wise, to some 400 μm. Of particular importance are observations of the coalescence of two and three of such microcrack systems to produce a critical, propagating crack. The then estimated stress intensity factor K a, could reach K 1C, independently estimated to be ∼36 MPa m1/2. Microcrack coalescence was associated...
TL;DR: In this article, a novel Cu-Cr-Zr alloy matrix composite reinforced with Al2O3particles was designed and fabricated by a powder metallurgy plus hot extrusion method, in order to obtain the combined effects of aging strengthening and composite reinforcing.
Abstract: A novel Cu–Cr–Zr alloy matrix composite reinforced with Al2O3particles was designed and fabricated by a powder metallurgy plus hot extrusion method, in order to obtain the combined effects of aging strengthening and composite reinforcing. The CuCrZr powder was produced through water atomisation technology and used as the starting materials of the matrix. The solid solubilities of Cr and Zr elements in copper, which increased during the rapid solidification process, helped to improve the strength of the matrix after aging treatment. This was in favour of exerting the load bearing effect of the Al2O3reinforcements. Fabrication experiments showed that by choosing the 38 μm CuCrZr powder, cold pressed at 380 MPa and hot extruded at 400°C, the relative densities of 7 vol.-%Al2O3composite reached 99·4%. The Al2O3particles significantly accelerated the aging process of the composites. With increasing Al2O3content, the Vickers hardness and ultimate tensile strength at elevated temperatures were effectivel...
TL;DR: In this paper, the development of a 30Fe-70NbC (wt-%) cermet by powder metallurgy techniques was studied, where the base powder was obtained by the process self-propagating high temperature synthesis, and this powder was modified by mechanical milling using two different approaches: comminution milling to reduce particle size (without modifying powder microstructure) and high energy milling in order to reduce both particle and reinforcement size.
Abstract: The present work studies the development of a 30Fe–70NbC (wt-%) cermet by powder metallurgy techniques. The base powder was obtained by the process self-propagating high temperature synthesis, and this powder was modified by mechanical milling using two different approaches: comminution milling to reduce particle size (without modifying powder microstructure) and high energy milling to reduce both particle and reinforcement size in order to improve powder microstructure. Both modified powders were compacted by uniaxial and cold isostatic pressing. The compacts were sintered in vacuum at different temperatures and times, and characterised by several techniques, including the determination of density and hardness, study by XRD to determine the constituents after sintering, and a complete microstructural analysis by SEM. The present study reveals that high energy milling permits to obtain enhanced materials when compared with materials sintered from comminuted powder.
TL;DR: In this article, the addition of Cu3P for developing the high strength 465 maraging stainless steel from elemental powders was studied and the sintering parameters investigated were sinting temperature, sinter time and wt-%Cu3P.
Abstract: The addition of Cu3P for developing the high strength 465 maraging stainless steel from elemental powders was studied The sintering parameters investigated were sintering temperature, sintering time and wt-%Cu3P In vacuum sintering, effective sintering took place between 1300 and 1350°C The maximum sintered density of 7·44 g cm−3 was achieved at 1350°C for 60 min with 4–6 wt-%Cu3P More than 6 wt-%Cu3P content and temperature >1350°C caused slumping of the specimens The sintered specimens were heat treated and a maximum ultimate tensile strength (UTS) of 767 MPa was achieved with 4 wt-%Cu3P content The maximum hardness of 45·5 HRC was achieved in heat treated condition with 4 wt-%Cu3P content Above 4 wt-%Cu3P content increase in density was observed whereas the response to heat treatment decreased Fracture morphologies of the sintered specimens were also reported A comparison of sintering behaviour and mechanical properties of elemental powders with prealloyed powders was also given in the