Showing papers on "Powder metallurgy published in 2020"

A review of additive manufacturing of cermets

Abstract: Cermets are a category of materials including ceramic and metallic phases, which possess the combined properties of both phases. Over the last few decades, numerous conventional processes such as powder metallurgy techinques and casting have been proposed for the fabrication of cermet components. In recent years, additive manufacturing (AM) has emerged as a promising method that can eliminate most of the limitations of conventional production methods. Among AM processes, selective laser sintering/melting (SLS/SLM), laser engineering net shaping (LENS), direct laser fabrication (DLF), binder jet 3D printing, and 3D gel/direct-ink-write/robocasting printing have been investigated for manufacturing bulk cermet parts. This study presents a summary of research that has been conducted to produce bulk cermets by additive manufacturing.

Effects of ZrO2 nanoparticle content on microstructure and wear behavior of titanium matrix composite

Abstract: The Ti-ZrO2 nanocomposites were fabricated by powder metallurgy route. The influence of ZrO2 additions on the microstructure and properties of the Ti-based composites were examined by X-ray diffraction, scanning electron microscopy, microhardness and wear properties tests. The result showed that spread of ZrO2 nanoparticles in the Ti matrix. XRD refers to no new phase are formed between Ti and ZrO2 during the sintering process. In addition, a good microstructure is achieved. The densification behavior of the sintered nanocomposites is increased with increasing ZrO2 percent. The highest microhardness was measured as 570 HV for titanium matrix nanocomposites fabricated by using 10%wt of ZrO2 nanoparticles content. 290 HV was obtained for the titanium matrix. Results showed that the sliding wear rate increase with increasing the normal load and decrease via increasing the addition of ZrO2 nanoparticles. In addition, the friction coefficient decreases with increasing the normal load and via increasing the addition of ZrO2 nanoparticles. The microstructure refines due to ZrO2 addendums illustrated a considerable function in the wear behavior of the Ti matrix.

Solving Recent Challenges for Wrought Ni-Base Superalloys

Abstract: This paper reviews the status of technology in design and manufacture of new wrought polycrystalline Ni-base superalloys for critical engineering applications. There is a strong motivation to develop new alloys that are capable of operating at higher temperatures to realize improvements in thermal efficiency, which are necessary to achieve environmental targets for reduced emissions of harmful green-house gases. From the aerospace sector, the development of new powder metallurgy and ingot metallurgy alloys is discussed for disk rotor and static applications. New compositions for powder metallurgy contain about 50 to 55 pct of gamma prime (γ′) strengthening precipitates to ensure components operate successfully at temperatures up to 788 °C (1450 °F). In contrast, new compositions for ingot metallurgy aim to occupy a design space in temperature capability between Alloy 718 and current powder alloys that are in-service, and show levels of γ′ of about 30 to 44 pct. The focus in developing these alloys was design for manufacturability. To complement the aerospace developments, a review of work to understand the suitability of candidate alloys for multiple applications in Advanced-Ultra Supercritical (AUSC) power plants has been undertaken by Detrois, Jablonski, and Hawk from the National Energy Technology Laboratory. In these power plants, steam temperatures are required to reach 700 °C to 760 °C. The common thread is to develop alloys that demonstrate a combination of high-temperature properties, which are reliant on both the alloy composition and microstructure and can be produced readily at the right price. For the AUSC applications, the emphasis is on high-temperature strength, long-term creep life, phase stability, oxidation resistance, and robust welding for fabrications. Whereas for powder disk rotors in aircraft engines, the priority is enhanced resistance to time-dependent crack growth, phase stability, and resistance to environmental damage, while extending the current strength levels, which are shown by existing alloys, to higher temperatures.

Investigations on microstructure and mechanical properties of Mg-5wt.% Cu-TiB2 composites produced via powder metallurgy route

Abstract: Magnesium alloy matrix composite reinforced with constant weight fraction of 5% Cu and various weight fractions of (0%, 5%, 10%, 15%) titanium diboride (TiB2) fabricated by Powder Metallurgy route. In this work, the mechanical properties like hardness, impact strength, compression strength, and wear rate of the Mg-Cu alloy and fabricated composites were investigated. The results showed that the addition of weight percentage of 15% TiB2 increased the hardness value about 58.56 HV, due to better bonding between the Mg-Cu and TiB2. Further, impact and compressive strengths improved, as the weight percentage of TiB2 increased. Uniform distribution of reinforced particles enhanced the impact strength and the work hardening effect improved the compression strength. Moreover, the wear rate decreased about 0.0112 mg by the addition of weight percentage of 15% TiB2. X-ray diffraction (XRD) analysis was carried out for each composition. Optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests were conducted to study the characterization of the base alloy and the prepared new composite.

Synergistic strengthening mechanisms of copper matrix composites with TiO2 nanoparticles

Abstract: The trade-off between strength and ductility has been a dilemma in copper matrix composites. In this work, we introduce a way of strengthening copper matrix composites containing TiO2 nanoparticles with remarkable ductility. The Cu–8wt%TiO2 composites were fabricated using the powder metallurgy route with spark plasma sintering (SPS) for different holding times incorporating hot extrusion. The sintered composites for longer holding times showed an inhomogeneous distribution of large dispersed particles located mostly along the grain boundaries. However, tensile strength was improved compared with pure copper while ductility was reduced. In contrast, after hot extrusion, a homogeneous distribution of reinforcement particles and grain refinement concurrently triggered strong strengthening and enhanced ductility. The contribution of synergistic strengthening mechanisms, i.e. Hall–Petch strengthening, Orowan pinning, dislocation density and load transfer effect, was studied and the key strengthening mechanisms were elucidated. It was found that composite yielding was strongly affected by sintering time, particulate size and interparticle spacing so that HExt-SPS@30min composite presented the excellent yield strength of 290 MPa, about 72% above pure copper. © 2019 Elsevier B.V.

Processing Methods and Mechanical Properties of Aluminium Matrix Composites

Abstract: Processing methods of aluminium matrix composites (AMCs) have been changing continuously considering the ease of manufacturing and the final quality of the desired composite. The most well-known processing techniques of AMCs such as stir casting, powder metallurgy, spark plasma sintering, squeeze casting, friction stir processing, liquid metal infiltration, spray codeposition, and reactive in situ techniques have elaborated here with their respective distinguishing features and mechanical properties of the fabricated composites. Moreover, this review paper contains the factors affecting the mechanical properties of AMCs as well as their clear justifications. The mechanical properties of AMCs are highly affected by the type of processing method, process parameters, and type, size, and composition of the reinforcing material. Concerning this, the mechanical properties of aluminium and its alloys are highly improved by adding a variety of reinforcing materials in a broader spectrum.

Microwave sintering of ceramic reinforced metal matrix composites and their properties: a review

Abstract: By developing the applications of metal matrix composites (MMCs), employing more efficient fabrication methods seems necessary. Within the two last decades, microwave (MW) sintering was int...

Effect of graphene nanoparticles on the physical and mechanical properties of the Al2024-graphene nanocomposites fabricated by powder metallurgy

Abstract: Recently, a growing interest has been dedicated towards improving the properties of Al alloys for use in various industrial applications. In this sense, mechanical alloying technique followed by sintering process at 460 and 560 °C in argon atmosphere was used to prepare Al2024 alloy matrix nanocomposites-reinforced by different graphene contents up to 2 wt%. Both XRD technique and TEM were employed to characterize the prepared nanocomposites powders. Microstructure analysis was performed on the sintered composites using SEM. Moreover, the relative density, corrosion rate, thermal expansion and electrical properties of the sintered nanocomposites were measured. Furthermore, their mechanical properties were measured with ultrasonic non-destructive technique. SEM and TEM micrographs revealed a uniform distribution of graphene in the Al alloy matrix. The relative density, coefficient of thermal expansion (CTE) and electrical conductivity of the specimens sintered at 460 °C decreased until reached 90.9%, 13.6 × 10−6/°C and 8.41 × 105 S/m, respectively as the graphene content increased to 2 wt%, while they increased to 93.8%, 1.5 × 10−6/°C and 4.20 × 106 S/m as the sintering temperature increased to 560 °C. On the other hand, the mechanical properties of the nanocomposites such as microhardness, elastic modulus and yield strength were enhanced to 155, 134 and 97%, respectively after adding 2 wt% graphene and sintering at 560 °C. Additionally, the corrosion rate decreased from 5.74 to 2.73 and 5.34 to 2.59 for the sample having 2 wt% graphene and sintered at 460 and 560 °C with increased the exposure from 24 to 144 h, respectively.

Enhanced tensile properties and electrical conductivity of Cu-CNT nanocomposites processed via the combination of flake powder metallurgy and high pressure torsion methods

Abstract: Using flake powder metallurgy (FPM) technique, combined with high pressure torsion, super high strength-ductile Cu-CNT nanocomposite with high electrical conductivity is developed. The nanocomposite with 4 vol% CNT showed high tensile strength of ~474 MPa, high electrical conductivity of ~82.5% IACS as well as appreciable ductility of ~11%. According to microstructural studies, the excellent properties of the nanocomposite are attributed to the formation of trimodal grains, high density of twin and low angle grain boundaries, improvement in CNT and Cu interfacial bonding, and appropriate distribution and maintaining the microstructure of the nanotubes in the production process. The results of this work provide a new pathway to produce strong, conductive, and ductile metal matrix nanocomposites.

Effect of fine powder particles on quality of binder jetting parts

Abstract: Despite their desired effects on quality metrics of powder metallurgy parts, fine powder materials are rarely used in powder-based additive manufacturing as powder feedstock materials due to their poor flowability and inefficient layer recoating. As such, process-structure-property relationships of powder-based AM processes have been explored primarily for coarse powder particle sizes (i.e., 25 μm–150 μm in diameter). With the new developments in powder recoating systems in modern binder jetting additive manufacturing (BJ-AM) printers, it seems now feasible to process fine powder materials that have average particle size of ∼10 μm (or smaller). In the current research, the use of fine copper powders (average particle size of 5 μm) in BJ process and its effects on green and final part properties are experimentally investigated. Specially, the authors studied the effects of different powder recoating settings on the density of printed green parts. The density of the sintered parts was also explored for various sintering parameters (i.e., heating rate and peak sintering temperature). Linear/volumetric shrinkage, microstructure and mechanical characteristics of sintered specimens were explored, and the results were compared to those of copper specimens made via coarse powder materials. The results indicated that fine copper powder resulted in parts with properties (UTS of 179.4 MPa and elongation of 42.2 %) greater than bimodal powder parts, which in turn eliminates extra time and work needed for powder mixing ratio optimization and blending process.

Additive Manufacturing of Tungsten Carbide Hardmetal Parts by Selective Laser Melting (SLM), Selective Laser Sintering (SLS) and Binder Jet 3D Printing (BJ3DP) Techniques

Abstract: Additive manufacturing is a process of transforming 3D CAD models into a finished part by adding layers of material. The technology is being used for more than three decades to make prototypes using polymer powders. Over the years, the technique has evolved, which currently allows the industries to manufacture functional parts out of different metals that have high complexity and limited lot size. Tungsten carbide (WC-Co) is a refractory metal with a very high melting point of around 2900 °C and is difficult to manufacture by conventional methods. Hence, tungsten carbide hardmetal parts are made by powder metallurgy technique, wherein tungsten carbide and binder metal powders (cobalt, nickel, iron or alloys of these metals) are pressed into the desired shape and sintered. However, due to the recent advancements, researchers have proven that complex tungsten carbide parts can be made by additive techniques. Hence, the article aims to summarize the three major techniques, Selective Laser Melting (SLM), Selective Laser Sintering (SLS), and Binder Jet 3D printing (BJ3DP) used in the manufacturing of tungsten carbide hardmetal parts. The process variables, metallurgical and mechanical characteristics, and challenges in manufacturing are presented which would serve as a knowledge pool for prospective researchers.

Microstructure and mechanical behaviour of an advanced powder metallurgy nickel base superalloy processed through hot isostatic pressing route for aerospace applications

Abstract: An advanced powder metallurgy (P/M) nickel-base superalloy envisaged for aerospace applications is realized through hot isostatic pressing (HIPing) of inert gas atomized powder. Extensive characterization of the microstructural features at different scales by employing optical microscopy, SEM-EBSD and transmission electron microscopy (TEM) divulged multi-modal distribution of γʹ precipitates within austenitic γ-FCC matrix phase in the as-HIPed condition. Investigation of prior particle boundary precipitates (PPBs) through TEM and Electron Probe Micro Analysis (EPMA) techniques revealed the dominance of metallic oxides and MC type carbides. The suitability of the advanced P/M superalloy for realizing near-net shape components by Direct-HIPing for short duration aeroengine rotating components is assessed by evaluating the room temperature and elevated temperature tensile behaviour as well as stress-rupture life in the service temperature regimes. The yield strength and the ultimate tensile strength of the present alloy at 650 °C are found to be 850 MPa and 1275 MPa respectively combined with 28% of ductility which is comparable to those of the similar class of superalloys in service. On the other hand, the as-HIPed superalloy exhibited minimum 1000 h of stress rupture life around service temperatures and bettered the stress rupture life of wrought superalloy IN718 alloy showing its potential for fabrication of near-net shape components for aerospace applications.

Material characterization and unconventional machining on synthesized Niobium metal matrix

Abstract: The Purpose of this work is to develop a niobium based metal matrix alloy through sintering based powder metallurgy technique. The 2, 4 and 6 weight percentage of Titanium Carbide (TiC) is added to the alloy. Various material properties such as hardness, tensile strength, impact strength and density are measured after the addition of TiC particle. The characterization, microstructure and particle size of the developed metal matrix are learnt through Scanning Electron Microscope (SEM) and Energy Dispersive Analysis of X-rays (EDAX).Finally, the synthesized niobium metal matrix is machined by unconventional machining processes namely Ultrasonic Machining (USM) and Laser Beam Machining (LBM) processes. The various input and output parameters have been considered for this experimental work. The most influential parameters on Material Removal Rate (MRR) and Surface Roughness (SR) are found by Analysis of variance. The systematic evaluation of optimal parameters of MRR and SR are carried out by using taguchi approach.

Microstructural evolution and mechanical properties of non-Cantor AlCuSiZnFe lightweight high entropy alloy processed by advanced powder metallurgy

Abstract: In this study, multicomponent AlCuSiZnFe high entropy alloy (HEA) was fabricated through high energy ball milling (HEBM) of constituent powders, and further densification via spark plasma sintering (SPS). The results show the presence of a predominant face-centered cubic (FCC) phase with a minor body-centered cubic (BCC) phase in (45 h) HEBMed powders which further develop according to the SPS treatment. At a low SPS temperature of 600 °C, the alloying of individual elements was poor. Further, at 650 °C, alloying improves and the liquid Cu–Zn FCC phase separates from the high-temperature Fe–Si-rich BCC phase during SPS. At 700 °C, Al was noticed to stabilize the BCC phase leaving behind soft FCC (Cu–Zn). Further increase in SPS temperature to 800 °C causes a complete melting of HEA compacts and the formation of Cu–Al intermetallic compounds (IMCs). The microhardness of the HEA compacts increases with SPS temperature in the range of 690–974 HV. The compressive properties were found to be optimum at 650 °C, compressive strength ≈1987 MPa and elastic modulus ≈27,945 MPa respectively. The measured densities of HEAs varied from 4.98 to 5.24 g/cm3, comparable to the heaviest of lightweight Ti alloys reported so far.