rss_2.0Powder Metallurgy Progress FeedSciendo RSS Feed for Powder Metallurgy Progress Metallurgy Progress Feed 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>ARTICLEtrue 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>ARTICLEtrue Metallurgy Progress, an international open-access journal with 20 years of publishing history the Extension of the Journal`s Scope 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue of the Processing Routes on the Properties of CoCrFeMnNi Alloy<abstract> <title style='display:none'>Abstract</title> <p>High entropy alloys are one of the most developing classes of materials of the 21<sup>st</sup> century. Their properties can significantly vary depending on their chemical composition and processing method. Thus, the microstructure and mechanical properties of CoCrFeMnNi high entropy alloy prepared by conventional casting, melt-spinning and mechanical alloying were investigated in this study. The observed structure and grain size were typical for this type of alloy and production methods. It was found that the hardness of the sample prepared by mechanical alloying with subsequent spark plasma sintering is higher compared to cast and melt-spun samples due to the finer microstructure and higher deformation energy stored.</p> </abstract>ARTICLEtrue of Residual Stress and Tensile Properties of Railway Axle Using Instrumented Indentation Method<abstract> <title style='display:none'>Abstract</title> <p>This paper deals with the characterization of residual stresses of the railway axle made of EA4T steel using the instrumented indentation technique (IIT). Additionally, tensile properties were also evaluated by using IIT. Moreover, the hole drilling method was carried out to measure the residual stress. Multiple comparison tests between conventional methods and IIT were carried out. The obtained results were also discussed against the literature data. Results of the residual stress assessed by IIT and the hole drilling follow the same trend and are in acceptable agreement. The tensile data obtained by IIT were as follows: YS ≥ 420 MPa and UTS ∈ ❬650-800❭MPa which is in satisfactory agreement with the results of standardized tensile tests.</p> </abstract>ARTICLEtrue of Hybrid Lap Welds of TI6AL4V and Stainless Steel with Bronze Interlayer<abstract> <title style='display:none'>Abstract</title> <p>Welding of the austenitic stainless steel AISI 304 and Ti6Al4V is complicated by hard and brittle intermetallic compound formation. In this contribution, we study a laser welding method that partially overcomes this problem using interlayer. Bronze foil (CuSn6) of thickness 100 µm and 200 µm was inserted between steel and titanium sheets and lap welds were realized on pulsed Nd:YAG laser. Representative samples were investigated by nanohardness measurement, SEM/EDS, and XRD analysis to detect the localization of the intermetallic phases. The macrostructure of the weld cross sections was displayed by optical and digital microscopy. The nano-hardness test revealed the presence of very hard intermetallic mainly around the interface between the fusion zone and bottom metal sheet. EDS mapping displayed the main elements Fe, Cr, Cu and Ti distribution in the fusion zone, EDS line scanning detected elements‘ signals in the diagonal and horizontal directions. XRD analysis revealed expected intermetallic compounds FeTi and CuTi<sub>2</sub> and solid solution Cu<sub>0.8</sub>Fe<sub>0.2</sub>.</p> </abstract>ARTICLEtrue Influence of Tilt on Berkovich Indentation of a Steel Sample Using FEM Analysis and Nanoindentation<abstract> <title style='display:none'>Abstract</title> <p>The main shape deviations of a Berkovich indenter are the indenter bluntness and indenter tilt. The influence of the Berkovich indenter tilt on the results of the FEM modelling of steel nanoindentation is evaluated in this paper. The indenter tilt has an impact on the indentation curves and contact area. The X5CrNiCuNb 16-4 steel nanoindentation was modelled by FEM and the indentation curves were obtained. The Berkovich indenter was blunted and the tilt of the indenter was changed to determine its influence on the indentation curves. The results showed that growing tilt shifts the indentation curves to higher values of indentation forces and makes unloading curves steeper which is in agreement with a larger contact area. The calculated indentation curves were compared with the experimental indentation curves and the impact of the indenter tilt to the indentation curves was determined.</p> </abstract>ARTICLEtrue of Machining on Mechanical Properties of Borosilicate Glasses<abstract> <title style='display:none'>Abstract</title> <p>Although optical properties are essential for materials for optical purposes, their mechanical properties must also be considered as they directly govern their practical applicability as well as their machining. The machining of optical glasses is mainly carried out by mechanical removal of the material using free or bonded abrasives. The relationship between the local mechanical properties of three types of borosilicate glasses used to produce optical elements (mirrors) and the type of surface machining was investigated. The samples were machined using two approaches, namely 7-axis CNC surface machining and conventional manual machining. Advanced analysis of nano/micro-mechanical properties was performed on glass samples using quasi-static nanoindentation and microindentation and dynamic impact test complemented by the analysis of the acoustic emission signals generated during the mechanical tests.</p> <p>The results show a difference in mechanical properties between industrial and optical borosilicate glasses. The type of machining has a strong influence on studied mechanical properties and surface quality. Glasses manufactured by CNC have more pronounced acoustic emission signal and crack more than glasses manufactured by hand. The different behavior of hand- and CNC-machined surfaces can be linked to different subsurface damage caused by different contact conditions between the workpiece and the instrument/abrasive. As a result, a different density of surface and especially (near)-subsurface flaws are present in the glass. Simax is slightly softer than BG33 glass, which together with the less pronounced AE may indicate a lower amount of subsurface cracks/damage.</p> </abstract>ARTICLEtrue Professor RNDr. Ján Dusza, DrSc – 70 years jubeeleum Properties of Reactive HiTUS TiNbVTaZrHf–N Coatings on Different Substrates<abstract> <title style='display:none'>Abstract</title> <p>High entropy ceramic coatings, including multicomponent transition metal nitrides called also high entropy nitrides (HEN), are usually deposited using reactive arc and/or DC magnetron (co)sputtering. High Target Utilization Sputtering (HiTUS) was not applied in HEN systems up to now. Subsequently, the mechanical properties of HEN coatings prepared by HiTUS are also not known. The transition metals from the 4<sup>th</sup> and 5<sup>th</sup> group of the periodic table (Ti, Zr, Hf, Nb, V, and Ta) are strong nitride formers which would be the most suitable for HEN coating systems and therefore, investigation of their properties would be of significant interest. However, the nanoindentation measurements on thin coatings always produce „composite“ values involving the contribution from the substrate. The separation of the coating properties from composite values requires upgraded analytical approaches different from standard Oliver &amp; Pharr analysis. Thus, the aim work is to investigate the structure, hardness, and elastic modulus of TiZrHfNbVTa–xN coatings with different nitrogen stoichiometry deposited by reactive HiTUS using both CSM for bulk and CSM for thin films methods and to compare the results obtained on 4 different substrates (Si wafer, sapphire, 100Cr6 steel, and Ti6Al4V alloy). The subsequent results showed systematic differences in the calculated mechanical properties depending on the substrate properties both in CSM and CSMTF modes. Stiffer substrates always resulted in the overestimations of the calculated hardness and indentation modulus compared to softer substrates with lower Young’s modulus and the differences were in the range of around 10 %. Obviously, better theoretical models for the calculations of true coating properties are required.</p> </abstract>ARTICLEtrue Toughness of Cement Paste Assessed with Micro-Scratch and Acoustic Emission<abstract> <title style='display:none'>Abstract</title> <p>Micro-scratch test was used to evaluate the fracture toughness of the main hydration products of ordinary Portland cement paste at the micro-scale. The evaluation was done with the aid of scanning electron microscopy and acoustic emission (AE) signals. Portlandite was found to be the only phase where AE detected elastic waves due to cracking during microindentation and micro-scratch test. Such behavior simplifies phase separation during the evaluation process of the micro-scratch test. The micro-scale fracture toughness results obtained from the tests were found in close agreement with other available experiments and models in the literature.</p> </abstract>ARTICLEtrue Eva Dudrová – 80 years of Sintering Time on Mechanical Properties of (Hf-Ta-Zr-Nb-Ti)C<abstract> <title style='display:none'>Abstract</title> <p>Advanced high-entropy (Hf-Ta-Zr-Nb-Ti)C ceramics were successfully fabricated by the combination of ball milling and a two-step sintering process at 2100 °C for 5, 10, and 20 minutes from commercially available powders. The microstructure characteristics and mechanical properties of the developed systems were investigated. The high-entropy ceramics exhibit: medium grain size from 8 μm to 11 μm, high compositional uniformity, and high relative density above 99.5 %. Vickers hardness for all systems decreased with increasing applied load, with the highest value HV1 = 22.0 GPa for the system sintered for 5 minutes, while the fracture toughness changed from 2.70 MPa.m<sup>1/2</sup> to 3.50 MPa.m<sup>1/2</sup>. The highest four-point flexural strength of 284 MPa was measured for the system with the smallest grain size.</p> </abstract>ARTICLEtrue Effect of Phosphate and Polymer Coating on Cytotoxicity and Hemocompatibility of Iron Foams<abstract> <title style='display:none'>Abstract</title> <p>The use of resorbable metallic biomaterials for temporary implants has increased dramatically in the last decade. Degradable biomaterials are desirable in some specific pediatric, orthopedic, and cardiovascular applications, in which they may overcome the disadvantages of permanent devices. The three main biodegradable metals: Mg, Fe, and Zn, are intensively studied as temporary orthopedic implant materials. Among them, iron, and iron-based alloys, have received attention as promising materials for the temporary replacement of bones, especially for applications where strong mechanical support during the bone healing process is required. The addition of a low amount of phosphorus can improve the mechanical properties of such materials without the risk of retarding the corrosion rate or affecting cell proliferation. The main goal of this work was to study the combined effect of phosphating and polymer coating of open-cell iron foams on their cytotoxicity and hemocompatibility. Obtained results indicated the positive influence of the PEG coating layer and phosphorus addition on material cytocompatibility. Moreover, the combination of these procedures led to the inhibition of hemolysis, platelet adhesion, and thrombus formation.</p> </abstract>ARTICLEtrue of Fe-Based Alloy Reinforced with Chromium Carbide Via Sintering of Iron-Ferrochrome Powder Mixture<abstract> <title style='display:none'>Abstract</title> <p>The results of the investigation of the structure, phase composition, and properties of the alloy sintered from a mixture of iron (65 %) and high-carbon ferrochrome (35 %) powders are presented in the article. It was shown that sintering of the consolidated specimens results in a substantially heterogeneous structure consisting of two predominant phases: austenitic phase and double ferrochrome carbide. A mechanism is proposed for the dissolution of ferrochrome particles in the iron matrix as follows: M7C3 → M3C (1000÷1150 ºС) → M7C3 (1200÷1250 ºС).</p> </abstract>ARTICLEtrue