Browse Topic: Refractory materials
A new high-temperature resistant material exhibits great potential for applications such as energy-efficient aircraft turbines. Karlsruhe Institute of Technology, Karlsruhe, Germany A new material might contribute to a reduction of the fossil fuels consumed by aircraft engines and gas turbines in the future. A research team from Karlsruhe Institute of Technology (KIT) has developed a refractory metal-based alloy with properties unparalleled to date. The novel combination of chromium, molybdenum, and silicon is ductile at ambient temperature. With its melting temperature of about 2,000 degrees Celsius, it remains stable even at high temperatures and is at the same time oxidation resistant. The results are published in the journal Nature. High-temperature-resistant metallic materials are required for aircraft engines, gas turbines, X-ray units, and many other technical applications. Refractory metals such as tungsten, molybdenum, and chromium, whose melting points are around or higher than 2,000 degrees Celsius, can be most resistant to high temperatures. Their practical application, however, has limitations: They are brittle at room temperature and, in contact with oxygen, they start to oxidize causing failure within short time already at temperatures of 600 to 700 degrees Celsius. Therefore, they can only be used under technically complex vacuum conditions - for example as X-ray rotating anodes.
Recent advances in both alloy development and additive manufacturing have enabled the production of ultrahigh-strength steels in nearnet shape parts. Army Research Laboratory, Aberdeen Proving Ground, Maryland Ultrahigh-strength steels are traditionally defined as those steels with a minimum yield strength of approximately 1380 MPa. Notable examples of steels in this category include AISI 4130, AISI 4140, and AISI 4340. In many cases, maximizing the performance of these alloys requires a rather complex approach that involves a series of tempering, annealing, or stress-relieving treatments. As a result, they are produced using a variety of traditional processing methods such as casting, rolling, extrusion, or forging. These traditional methods - combined with the ultrahigh strength of the steels - often meant that the production of complex, near-net shape parts of high quality was quite difficult. In addition, these production methods often entailed repetitive treatments or long production cycles, both of which resulted in elevated production costs. Additive manufacturing (AM, also known as 3D printing) has recently been recognized as a manufacturing method that enables the production of near-net shape parts. In these methods, a complex part is iteratively built in a layer-by-layer process that involves powder deposition followed by selective melting/sintering of the powder to form the part. With the continued development of processing lasers, it is now possible to form fully dense components from a wide range of metals powders, including refractory alloys, steels, and other high-temperature alloys.
When it comes to quantum technology, niobium is making a comeback. For the past 15 years, niobium has been sitting on the bench after experiencing a few mediocre at-bats as a core qubit material. Qubits are the fundamental components of quantum devices. One qubit type relies on superconductivity to process information.
High-strength steel has several industrial applications such as automobile, tool and die, construction industries etc. However, it is challenging to achieve it. Various strengthening mechanisms, such as dispersion strengthening, alloying, grain boundary strengthening etc., plays a vital role in deciding the properties of the steel. At the industrial level, high-strength steel is produced by adding alloying elements such as Tungsten, Chromium, and Molybdenum in the steel matrix, increasing the high-strength steel cost. On the other hand, Wire Arc Additive manufacturing (WAAM) can produce dispersion strengthening in steel to mimic the properties of a high-strength steel matrix. The WAAM is a relatively low-cost additive manufacturing technology which uses a welding process to build up layers of material to fabricate the finished product. We have dispersed hard silicon carbide (SiC) particles in the mild steel matrix using the WAAM process in this work. SiC-dispersed steel's hardness is 28% higher than mild steel samples prepared by the WAAM process. The SEM micrograph shows the presence of dispersion of SiC in the steel matrix, which increases hardness compared to mild steel samples.
New research suggests that laser-based devices are poised to become a lot smaller. Researchers at Columbia University and Politecnico di Milano studied a 2D material called molybdenum disulfide (MoS2) and characterized how efficiently devices built from stacks of MoS2 less than one micron thick — 100 times thinner than a human hair — convert light frequencies at telecom wavelengths to produce different colors.
This specification covers a corrosion and heat-resistant steel in the form of bars, wire, forgings, mechanical tubing, flash welded rings, and stock for forging or flash welded rings.
This specification covers a special aircraft-quality, low-alloy steel in the form of bars.
This specification covers a premium aircraft-quality alloy steel in the form of bars and forgings 199 square inches (1284 cm2) and under in cross section, and forging stock of any size.
This specification covers two types of carbon steel in the form of sheet, strip, and plate.
The element niobium (Nb), a transition metal, stands ready to improve the performance of one of the lithium-ion (Li-ion) battery’s confusing array of possible electrode chemistries — the LTO (lithium titanium oxide) anode, which after graphite is the second most-produced. During battery charging, lithium ions leave the positive cathode and move through the battery’s electrolyte to take up positions of higher energy in the anode. During discharge, this process reverses and drives electrons through an external circuit to power the load.
This specification covers an aircraft-quality, low-alloy steel in the form of heat treated bars and forgings 1.00 inches (25.4 mm) and under in nominal cross section or diameter and for hexagonal shapes, least distance between parallel sides.
Performance evaluation of martensitic press-hardened steels by VDA 238-100 three-point bend testing has become commonplace. Significant influences on bending performance exist from both surface considerations related to both decarburization and substrate-coating interaction and base martensitic steel considerations such as structural heterogeneity, i.e., banding, prior austenite grain size, titanium nitride (TiN) dispersion, mobile hydrogen, and the extent of martensite tempering as result auto-tempering upon quenching or paint baking during vehicle manufacturing. Deconvolution of such effects is challenging in practice, but it is increasingly accepted that surface considerations play an outsized role in bending performance. For specified surface conditions, however, the base steel microstructure can greatly influence bending performance and associated crash ductility to meet safety and mass-efficiency targets. This study reports and elucidates the positive effect of niobium microalloying on bendability of the base PHS alloy through combined structural refinement, microalloy carbide precipitation, and modifications to tempered martensite morphology. Prior austenite grain size refinement due to microalloying results in both incremental strengthening and a reduced solute carbon (C) content in the austenite matrix prior to in-die quenching due to both enhanced segregation of C to austenite grain boundaries. Martensite-start temperature is thusly increased, and a greater degree of auto-tempering results in as-quenched steels. Additionally, the reduction of C content in the as-quenched martensite reduces driving force for oriented transition carbide precipitation during tempering. Measured bend angles are accordingly improved, and reduced strength of martensite, as a result of reduced matrix C, is compensated by the fine dispersion of microalloy carbonitrides. Alloy design and process recommendations are offered based on observed mechanisms.
Alumina (Al2O3) thin film coatings are applied on Al alloys using Plasma Electrolytic Oxidation (PEO) method to reduce the wear and corrosion problems. Plasma Electrolytic Aluminating (PEA) is a technique which could generate Alumina coatings on cast iron, mild steel and copper alloys. In this study, the aim is to explore the anti-wear and anti-corrosion behaviours of PEA Alumina coatings on gray cast iron. The dry sliding tribology test data was obtained from Pin-on-Disk (POD) tests against SAE 52100 steel and Tungsten Carbide (WC) counterfaces. Comparing with the PEO Alumina coatings, the PEA Alumina coating has much lower Coefficient of Friction (COF) and less wear. The microstructure, chemical composition and phase composition of this coating were investigated with Scanning Electron Microscope (SEM), Energy-Dispersive X-Ray Spectroscopy (EDX) and X-Ray Diffraction (XRD), respectively. There was FeO (or FeAl2O4) found on the PEA Alumina coating. To figure out the relationship between FeO and the COF, 500 °C heat treatment was conducted on PEA Alumina coated samples, in which FeO could be fully oxidized into Fe2O3 by heat treatments. Differences between unheated and heated samples in chemical composition and wear behaviours were observed. The co-existence of FeO (or FeAl2O4) compounds in PEA Alumina coating is an important factor which introduce relative low COF. The corrosion resistance was evaluated by electrochemical tests. It could be observed and be calculated that the PEA Alumina coated gray cast iron has much better corrosion resistance than uncoated samples. Since the PEA coating can also be applied onto steel materials, the coating technology can be used to protect the hinges of doors and other joint parts from frequent wear and corrosion issues.
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