rss_2.0Powder Metallurgy Progress FeedSciendo RSS Feed for Powder Metallurgy Progress Metallurgy Progress 's Cover of the Corrosion Resistance of WC-Co Coating on AZ91 Applied by Electro Spark Deposition<abstract> <title style='display:none'>Abstract</title> <p>In order to enhance the surface properties of a magnesium-based substrate, WC-Co coating was applied on AZ91 alloy by electro spark deposition (ESD), successfully for the first time. The optimum parameters of the ESD process were achieved, based on the corrosion behavior and calculated corrosion rate of the coated samples when 5kHz and 25 A were chosen. For evaluation of the corrosion performance of the achieved WC-Co layers, polarization, and electrochemical impedance spectroscopy tests were carried out in the 3.5 wt % Na<sub>3</sub>PO<sub>4</sub> solution at room temperature. Polarization results show that the corrosion rate (mpy) is in the optimum condition almost half of a bulk sample of uncoated AZ91. Field emission scanning electron microscopy (FE-SEM) was used to examine the surface morphology of applied coatings. These results show that at a lower current, the amount of deposited WC-Co was reduced. The maximum surface microhardness obtained was 193 HV0.2.</p> </abstract>ARTICLE2021-07-31T00:00:00.000+00:00Powder Metallurgy Progress, an international open-access journal with 20 years of publishing history the Extension of the Journal`s Scope Phosphate Cement Modified with Silicon Nitride/Tricalcium Phosphate Microgranules<abstract> <title style='display:none'>Abstract</title> <p>Tetracalcium phosphate/monetite biocement was modified with 10 and 30 wt. % addition of highly porous silicon nitride/α-tricalcium phosphate (αTCP) microgranules with various content of αTCP. A composite cement powder mixture was prepared using mechanical homogenization of basic components. The accelerated release of dexamethasone from composite cement was revealed, which indicates their possible utilization for controlled drug release. The wet compressive strength of cements (&lt;17 MPa) was significantly reduced (more than 30%) in comparison with the unmodified cement and both compressive strength and setting time were influenced by the content of αTCP in microgranules. The addition of microgranules caused a 20% decrease in final cement density. Microgranules with a higher fraction of αTCP showed good in vitro SBF bioactivity with precipitation of hydroxyapatite particles. Microstructure analysis of fractured cements demonstrated excellent interconnection between microgranules and cement calcium phosphate matrix, but also showed lower mechanical strength of microgranule cores.</p> </abstract>ARTICLE2021-07-31T00:00:00.000+00:00Temperature-Dependent Electrical Characteristics of Disc-Shaped Compacts Fabricated using Calcined Eggshell Nano Powder and Dry Cassava Starch<abstract> <title style='display:none'>Abstract</title> <p>Disc-shaped compacts were fabricated from two mix proportions of calcined eggshell nanopowder and dry cassava starch and then used as test samples. The electrical resistance (R), thermal sensitivity index (β) and electronic activation energy (E<sub>a</sub>) of the samples measured over a temperature range from 35 to 75<sup>o</sup>C were found to decrease non-linearly in values with increasing temperature. It was also observed that the results obtained (R = 3.691E6 Ω – 6.210E7 Ω, β = 3812K – 5316K and Ea = 0.33 eV – 0.46 eV) fulfill market requirements by comparing very well with the established values for NTC thermistors. Hence, from manufacturing viewpoint, recycling of chicken eggshell wastes and cassava effluents can avail electronic industry with promising and alternative materials for fabrication of temperature sensing / monitoring / control devices suitable for engineering applications. This will also help to reduce environmental pollution.</p> </abstract>ARTICLE2021-07-31T00:00:00.000+00:00Powder Metallurgy Manufacturing of Iron Aluminides with Different Aluminium Contents and Magnesium Addition by Reactive Hot Pressing<abstract> <title style='display:none'>Abstract</title> <p>In this work, iron aluminide materials, which are promising candidates for high temperature applications, are manufactured through reactive hot pressing of elemental powder mixes, facilitating a straightforward preparation of well-densified materials with a high degree of microstructural homogeneity. The impact of varying Al additions on reaction behavior, microstructural and compositional features of the resulting materials is evaluated. Furthermore, the effect of adding 1 wt. % Mg on reactivity and phase formation is illustrated. The results show that reactive hot pressing of elemental powders in the Fe-Al and Fe-Al-Mg systems at 1000 °C results in residual porosities well below 5 %. Magnesium addition significantly increased reactivity between constituents, leading to slightly improved densification without exhibiting potentially detrimental segregation phenomena. The processing approach presented in this work leads to material characteristics which are promising in the context of developing materials with favorable mechanical and tribological performance at elevated temperatures.</p> </abstract>ARTICLE2021-07-31T00:00:00.000+00:00Finishing of Tubes using Bonded Magnetic Abrasive Powder in an Abrasive Medium<abstract> <title style='display:none'>Abstract</title> <p>Magnetic abrasive flow finishing (MAFF) is an unconventional process capable of producing fine finishing with machining forces controlled by a magnetic field. This process can be utilized for hard to achieve inner surfaces through the activity of extrusion pressure, combined with abrasion activity of a magnetic abrasive powder (MAP) in a polymeric medium. MAP is the key component in securing systematic removal of material and a decent surface finish in MAFF. The research background disclosed various methods such as sintering, adhesive based, mechanical alloying, plasma based, chemical, etc. for the production of bonded MAP. This investigation proposes bonded MAP produced by mechanical alloying followed by heat treatment. The experiments have been conducted on aluminum tubes to investigate the influence of different parameters like magnetic field density, extrusion pressure and number of working cycles. The bonded magnetic abrasive powder used in MAFF is very effective to finish tubes’ inner surfaces and finishing is significantly improved after processing.</p> </abstract>ARTICLE2021-07-31T00:00:00.000+00:00The Effect of Plasma Pretreatment on the Morphology and Properties of Hitus Coatings<abstract> <title style='display:none'>Abstract</title> <p>WC coatings prepared by High Target Utilization Sputtering (HITUS), a relatively new technology, were deposited on three types of substrates. These were silicon (111), steel (100Cr6), and ceramic (WC-Co). The influence of RF plasma power pretreatment on final properties of WC coatings was investigated with two interlayer materials for bonding. The morphology, roughness, and mechanical properties of coatings were studied. The relation between plasma RF power and roughness was found. No significant change in mechanical properties was detected with change in plasma RF power. The dependence of nanohardness and scratch behavior on HITUS WC coatings was investigated.</p> </abstract>ARTICLE2021-07-31T00:00:00.000+00:00T Dependence of the Mechanical Properties on the Microstructural Parameters of WC-Co<abstract> <title style='display:none'>Abstract</title> <p>The effect of binder content and WC grain size on the mechanical properties is widely investigated in literature. An increase in binder amount and WC grain size leads to a decrease in hardness and an increase in fracture toughness. Actually, these correlations are related to the influence of binder content and WC grain size through the contiguity and mean binder free path, which are the microstructural parameters that affect the mechanical properties. The aim of this study is to verify the dependence of the two microstructural parameters that govern the WCCo mechanical behaviour, namely the contiguity and mean binder free path, on the mechanical properties of an extended range of WC-Co samples, which differ in terms of Co content and tungsten carbide grain size.</p> </abstract>ARTICLE2020-06-15T00:00:00.000+00:00Die Wall - Vs. Bulk Lubrication in Warm Die Compaction: Density, Microstructure and Mechanical Properties of Three Low Alloyed Steels<abstract> <title style='display:none'>Abstract</title> <p>The influence of die wall lubrication during warm die compaction on densification, microstructure and mechanical properties of three low alloy ferrous powders was investigated. Specimens were sintered at 1250°C. Die wall lubrication leads to higher green and sintered density and enhances the dimensional stability. It does not affect the microstructure of the matrix, while pores are smaller and more rounded than in bulk lubricated specimens. In TRS tests, both strength and deformation are higher in die wall lubricated specimens than bulk lubricated ones.</p> </abstract>ARTICLE2020-06-15T00:00:00.000+00:00Study on Sintering of Artificially Oxidized Steel Compacts<abstract> <title style='display:none'>Abstract</title> <p>Sintering of Cr-prealloyed PM steels requires atmospheres with good quality – low oxygen potential – to achieve satisfactory sintering results. But during heating even the best atmospheres may be oxidizing, the system turns to reducing conditions only at high temperatures, which can be monitored by thermal analysis. During the dewaxing process, oxidizing conditions are favourable for effective dewaxing without sooting and blistering. However, this may result in some oxygen pickup during heating, and then the final properties of the produced parts may be strongly influenced by this intermediate oxidation. This study demonstrates the behaviour of artificially oxidized steels (Fe-C and Fe3Cr-0.5Mo-C) during the sintering process by stepwise sintering. Iron and steel powder were slightly oxidized and then pressed and sintered at different temperatures. In parallel, as a second approach, pressed samples were oxidized and then sintered. Density, hardness and impact energy were measured and dilatometry/MS was used for online monitoring of the sintering process. The starting oxygen content of 0.20 to 0.30 wt% is high enough to change the sintering behaviour of the materials, but still leads to rather good properties. Thermal analysis showed that most of the oxygen picked up was present as iron oxides on the surface which were reduced by hydrogen at rather low temperatures, confirming that these were iron oxides, which also holds for the Cr-prealloyed variant. The biggest influence on the final performance was exerted by the final carbon content and the microstructural development of the material.</p> </abstract>ARTICLE2020-06-15T00:00:00.000+00:00Polymorphs of Neodymium Niobate and Tantalate Thin Films Prepared by Sol-Gel Method<abstract> <title style='display:none'>Abstract</title> <p>Neodymium niobate NdNbO4 (NNO) and tantalate NdTaO4 (NTO) thin films (~100 nm) were prepared by sol-gel/spin-coating process on Pb(Zr0.52Ti0.48)O3/Al2O3 substrates with annealing at 1000°C. The precursors of films were synthesized using Nb or Ta tartrate complexes. The XRD results of NNO and NTO films confirmed tetragonal T-NdNbO4 and T-NdTaO4 phases, respectively, with traces of monoclinic MNdNbO4 and M´-NdTaO4. The surface morphology and topography were investigated by SEM and AFM analysis. NTO was smoother with roughness 5.24 nm in comparison with NNO (6.95 nm). In the microstructure of NNO, small spherical (~ 20-50 nm) T-NdNbO4 and larger needle-like particles (~100 nm) of M-NdNbO4 phase were observed. The compact clusters composed of fine spherical T-NdTaO4 particles (~ 50 nm) and cuboidal M´-NdTaO4 particles (~ 100 nm) were found in NTO. The results of this work can contribute to formation of different polymorphs of films for the application in environmental electrolytic thin film devices.</p> </abstract>ARTICLE2020-06-15T00:00:00.000+00:00Influence of Sodium Alginate on Properties of Tetracalcium Phosphate/Nanomonetite Biocement<abstract> <title style='display:none'>Abstract</title> <p>The tetracalcium phosphate/nanomonetite (TTCPMH) biocements with the addition of sodium alginate were prepared by mechanical homogenization of powder mixture with hardening liquid containing sodium alginate. The effect of various viscosity of different alginates on properties of TTCPMH cement mixture was investigated. The medium viscous (MED) alginate had a more negative effect on setting process and compressive strength than low viscous (LOW) alginate. An approx. 50% decrease in mechanical properties (compressive strengths, Young´s modulus, work of fracture (WOF)) was revealed after an addition of 0.25 wt % with rapid fall above 1 wt % of LOW alginate in biocement. A statistically significant difference in the WOF was found between of 0.25 and 0.5 LOW alginate biocements (p&lt;0.035) whereas no statistical differences were revealed between WOF of 0.5 and 1 LOW alginate biocements (p˃0.357). In the microstructure of composite cements, the increased amounts of granular or finer needle-like nanohydroxyapatite particles arranged into the form of more separated spherical agglomerates were observed. A low cytotoxicity of cement extracts based on measurement of cell proliferation was revealed.</p> </abstract>ARTICLE2020-06-15T00:00:00.000+00:00Experimental Investigations on Impact Toughness and Shear Strength of Novel Lead Free Solder Alloy Sn-1Cu-1Ni-XAg<abstract><title style='display:none'>Abstract</title><p>Lead is known to be banned in alloy making, highlighting toxicity concerns and environmental legislations. Researchers and scholars around the globe were in immediate search of new lead free solder alloys which could potentially replace the old Sn-Pb alloy. In this comprehensive study, shear strength and impact toughness tests were conducted on Sn-1Cu-1Ni when different amounts of Ag (0.25, 0.5, 0.75 1 % by wt.) is added. Shear strength test is tested using micro force test system. Impact toughness test is analyzed using Charpy impact test set up by calculating the energy difference before and after impact. The study reveals that, Ultimate shear stress increased from 19 MPa to 21.3 MPa. Yield strength increased from 27.4 MPa to 29.7 Mpa. Impact toughness of the alloys increased from 9.4 J to 10.1 J. Thus, Sn-1Cu-1Ni-1Ag is found to have improved shear strength and impact toughness than Sn-1Cu-1Ni.</p></abstract>ARTICLE2020-06-15T00:00:00.000+00:00Additive Manufacturing of Steel and Copper Using Fused Layer Modelling: Material and Process Development<abstract><title style='display:none'>Abstract</title><p>Fused Layer Modelling (FLM) is one out of several material extrusion (ME) additive manufacturing (AM) methods. FLM usually deals with processing of polymeric materials but can also be used to process metal-filled polymeric systems to produce metallic parts. Using FLM for this purpose helps to save costs since the FLM hardware is cheap compared to e.g. direct metal laser processing hardware, and FLM offers an alternative route to the production of metallic components.</p><p>To produce metallic parts by FLM, the methodology is different from direct metal processing technologies, and several processing steps are required: First, filaments consisting of a special polymer-metal composition are produced. The filament is then transformed into shaped parts by using FLM process technology. Subsequently the polymeric binder is removed (”debinding”) and finally the metallic powder body is sintered. Depending on the metal powder used, the binder composition, the FLM production parameters and also the debinding and sintering processes must be carefully adapted and optimized.</p><p>The focal points of this study are as following:</p><p>1. To confirm that metallic parts can be produced by using FLM plus debinding and sintering as an alternative route to direct metal additive manufacturing.</p><p>2. Determination of process parameters, depending on the used metal powders (steel and copper) and optimization of each process step.</p><p>3. Comparison of the production paths for the different metal powders and their debinding and sintering behavior as well as the final properties of the produced parts.</p><p>The results showed that both materials were printable after adjusting the FLM parameters, metallic parts being produced for both metal powder systems. The production method and the sintering process worked out well for both powders. However there are specific challenges in the sintering process that have to be overcome to produce high quality metal parts. This study serves as a fundamental basis for understanding when it comes to the processing of steel and copper powder into metallic parts using FLM processing technology.</p></abstract>ARTICLE2020-06-15T00:00:00.000+00:00Preparation, Microstructure Evaluation and Performance Analysis of Diamond-Iron Bonded Magnetic Abrasive Powder<abstract><title style='display:none'>Abstract</title><p>The customary edged tool for machining is uneconomical for harder and hard to machine materials and furthermore the level of surface finish accomplished is not that great. As of late, a lot of consideration in mechanical engineering has been centered on finishing tasks. Not many investigations have been accounted for till date on the advancement of substitute magnetic abrasive powder (MAP). In this paper, to improve the finishing performance, the abrasive powder were prepared by mechanical alloying of diamond powder and iron (Fe) powder, compacting these with universal testing machine (UTM) and then sintered at different temperature in a sintering machine in an inert gas (H2) atmosphere. These compacts were crushed and sieved to obtain various sizes of MAP. This abrasive powder were micro-structurally examined. The results indicate that the densification increases and porosity decreases with increasing temperature. Moreover, the prepared bonded MAP has potential performance as a new MAP for fine finishing in Magnetic Abrasive Flow Machining (MAFM) process.</p></abstract>ARTICLE2020-06-15T00:00:00.000+00:00Supersolidus Sintering of Cr Prealloyed Steels by Inductive Heating<abstract><title style='display:none'>Abstract</title><p>For powder metallurgy products, high density is an essential requirements to obtain maximum mechanical properties. Here, supersolidus liquid phase sintering (SSPLS) is an effective means to attain high sintered density, as known from PM high speed steels. In the present work it is shown that this technique can also be applied to Cr prealloyed low alloy steel grades. Supersolidus sintering through indirect heating requires precise control of temperature and also the atmosphere, to avoid uncontrolled changes of the carbon level. Higher C contents are beneficial here since they enable lower temperatures and result in wider temperature windows for sintering. The temperatures necessary for SSLPS at moderate C levels are fairly high for standard sintering furnaces, therefore induction sintering was studied in this work. It showed that, as was to be expected, also here precise temperature control is required, but for any carbon level tested a sintering temperature could be identified that yielded high sintered density and good shape retention. The high density attained, in combination with the very high temperatures, results in pronounced grain growth, this process no more being inhibited by the presence of pores, which is undesirable but can however be remedied by suitable heat treatment.</p></abstract>ARTICLE2020-06-15T00:00:00.000+00:00Phosphorus in Sintered Steels: Effect of Phosphorus Content and P Carrier in Sintered Steel Fe-C-P<abstract><title style='display:none'>Abstract</title><p>Phosphorus as an alloy element is quite common in powder metallurgy, the contents industrially used being markedly higher than those present in wrought steels. In this study, the influence of phosphorus addition through different P carriers was investigated. PM steels of the type Fe-0.7%C-x%P (x = 0.0 … 0.8%) were manufactured by pressing and sintering in H2. It showed that Fe3P is the best phosphorus carrier, resulting in fine and regular microstructure and in high impact energy data at 0.3 … 0.45%P while red P and also Fe2P showed a tendency to agglomeration, with resulting secondary porosity. At high P levels the mechanical properties tend to drop, for the tensile strength at P &gt; 0.60%P while for the impact energy the threshold is 0.45%P. The dimensional behaviour of Fe-C-P can be related to PM aluminium alloys, expansion by transient liquid phase being followed by shrinkage by persistent liquid phase, at least at higher temperatures. In contrast to the dimensional behaviour, degassing and reduction is hardly affected by the phosphorus content.</p></abstract>ARTICLE2016-11-08T00:00:00.000+00:00The Effect of Transient Liquid Phase on the Joining Process of Aluminum Foam Core Sandwiches<abstract><title style='display:none'>Abstract</title><p>Despite recent developments in sandwich panels production technology, there are some difficulties in joining core sandwiches. Liquid Phase Sintering is a conventional method to increase the density of powder metallurgy parts. In this paper, we applied LPS as a joining process between Al-foam and Al-metal by using Al-mixture powders with different compositions as the interlayer. At first stage, Al-Zn powder mixture was used and the possibility of this process was investigated. At later stages, we tried to increase the joint bonding strength with different Al-mixture powder compositions. 3-point bending test was applied and by using mathematical relations, bonding strengths were calculated. The highest bonding strength was obtained, about 9 kPa, when Al-Zn-Mg was used as the interlayer. Also energy dispersive spectrometry (EDS) was used to investigate the diffusion of additive elemental powders to Al-mixture powders.</p></abstract>ARTICLE2016-11-08T00:00:00.000+00:00Analytical Model of the Anisotropic Dimensional Change on Sintering of Ferrous PM Parts<abstract><title style='display:none'>Abstract</title><p>This work proposes an analytical model developed from experimental data to describe the anisotropic dimensional change on sintering. Axial-symmetric iron parts differing for geometry and sintering conditions have been investigated, aiming at highlighting the influence of geometry. The specimens were measured in the green and sintered state by a coordinate measuring machine (CMM). The dimensional changes of height, external diameter and internal diameter were derived from measurement results. The anisotropy of the dimensional variations has been studied with reference to the isotropic dimensional change derived from the change in volume of the parts. The influence of geometry and sintering temperature was highlighted. To properly describe the dimensional variations in the compaction plane, the dimensional change of the external diameter versus the dimensional change of the internal one has been analysed. By means of the experimental data, a reliable analytical relationship has been found, dependent on the parts geometry. An anisotropy parameter has been identified, which allows relating the dimensional change in the compaction plane and in the axial direction to the isotropic dimensional change. This parameter depends both on geometry and on sintering conditions. By means of the anisotropy parameter an analytical model for the anisotropic behaviour has been developed.</p></abstract>ARTICLE2016-11-08T00:00:00.000+00:00Copper Bronze Powder Surface Studied by XPS and HR SEM<abstract><title style='display:none'>Abstract</title><p>The state of the powder surface represents one of the main interests in the whole cycle of components’ production using powder metallurgy (PM) route. Large specific surface area of the powder in combination with often alloying with oxygen sensitive elements results in oxidation of the powder surface in most of the cases. The information about surface chemistry of the powder is of vital importance for further consolidation and sintering steps. Surface sensitive analytical techniques – X-ray photoelectron spectroscopy (XPS) and high-resolution scanning electron microscopy combined with energy dispersive X-ray analysis (HR SEM+EDX) were used for surface chemical analysis of the 60Cu-40Sn bronze powder. Determination of the compositional profiles and estimation of the surface oxide layer thickness was done by altering of ion etching and XPS analysis. The results showed tin oxide enrichment and presence of copper hydroxide on the surface of the powder particles. The impurities of P, Zn and Ca were also detected on the top surface of the powder in trace amounts.</p></abstract>ARTICLE2016-11-08T00:00:00.000+00:00en-us-1