Diamond Like Carbon (DLC) with both sp3- and sp2-bonded carbon in DLC coatings is equipped with superior mechanical, tribological, electrical, and optical qualities. Depending on their composition and synthesis method, DLC films can be amorphous, hard, or strong. High residual stress in the film, however, limits its potential uses in many fields and results in poor adherence to the substrate materials. Increasing the deposition temperature, post-synthesis annealing, and vacuum furnace heat treatment are some popular techniques to lower residual stress. In this work, a DC magnetron sputtering method was used to create Cr-DLC thin films on silicon (100) substrates. Atomic force microscopy (AFM) and electrochemical testing, and nanoindentation test were used to assess the mechanical attributes of the thin film prior to production. According to the corrosion test, the annealing temperature increased corrosion resistance. The coating's young's modulus (E) and nanoindentation hardness (H) were computed. The internal stress of the produced coating was determined using Stoney's equation. The Cr-DLC coating was heat treated in a vacuum furnace at temperatures ranging from 270 to 360°C. Following heat treatment, nanoindentation was used to characterize the coating once more in order to evaluate its mechanical properties, such as H and E. The findings demonstrated that raising the heat treatment temperature to 360°C considerably reduced the coatings' residual stress. In contrast to the coatings' H and E decreasing, the residual stress of the coating heat treated at 300°C was somewhat reduced. From the electro chemical analysis, it was clearly understood that by increasing the temperature the corrosion resistance (CR) of Cr-DLC coatings' is increased up to 330°C. However, with the rise in temperature to 360°C the CR started decreasing.

Nickel aluminum bronzes (NAB) are copper alloys widely used in critical applications in the defense, aerospace and marine industries. These alloys exhibit excellent properties such as wear resistance, corrosion resistance, impact strength, hardness and ductility, which are highly dependent on their composition and production conditions. Despite the relatively low formation of oxide layers on the surface of nickel aluminum bronze components under heat treatment conditions due to the high nickel content, there are special applications where the formation of oxide layers on the surface is undesirable. For this reason, the heat treatment of CuAl10Ni5Fe3Mn alloy was carried out in a vacuum furnace and the heat treatment process conditions in a non-vacuum muffle furnace were compared. For comparison purposes, the microstructure of the materials was examined and hardness and tensile tests and potentiodynamic corrosion tests were performed. It was determined that heat treatment in the muffle furnace led to a decrease in the proportion of the α phase and a higher formation of the β and κ phases compared to the heat treatment in a vacuum atmosphere. The material heat treated in the muffle furnace exhibited higher hardness and strength values as well as improved corrosion resistance compared to the material treated in the vacuum furnace.

Abstract Niobium films are of interest in applications in various superconducting devices, such as superconducting radiofrequency cavities for particle accelerators and superconducting qubits for quantum computing. In this study, we address the persistent medium-field Q-slope issue in Nb film cavities, which, despite their high-quality factor at low RF fields, exhibit a significant Q-slope at medium RF fields compared to bulk Nb cavities. Traditional heat treatments, effective in reducing surface resistance and mitigating the Q-slope in bulk Nb cavities, are challenging for Nb-coated copper cavities. To overcome this challenge, we employed DC bias high-power impulse magnetron sputtering to deposit Nb film onto a 1.3 GHz single-cell elliptical bulk Nb cavity, followed by annealing treatments aimed at modifying the properties of the Nb film. In-situ annealing at 340 °C increased the quench field from 10.0 to 12.5 MV m−1. Vacuum furnace annealing at 600 °C and 800 °C for 3 h resulted in a quench field increase of 13.5 and 15.3 MV m−1, respectively. Further annealing at 800 °C for 6 h boosted the quench field to 17.5 MV m−1. Additionally, the annealing treatments significantly reduced the field dependence of the surface resistance. However, increasing the annealing temperature to 900 °C induced a Q-switch phenomenon in the cavity. The analysis of RF performance and material characterization before and after annealing has provided critical insights into how the microstructure and impurity levels in Nb films influence the evolution of the Q-slope in Nb film cavities. Our findings highlight the significant roles of hydrides, high local misorientation, and lattice and surface defects in driving field-dependent losses. By strategically optimizing film properties and controlling impurity levels, we demonstrate a promising pathway to mitigate the medium-field Q-slope, paving the way for more efficient superconducting RF technologies.

The ceramic layers of 8 mol% yttria-stabilized zirconia (8YSZ), singly doped with Fe2O3 and doubly doped with Fe2O3 and Al2O3, have been deposited successfully on Inconel 625 substrates by the EPD (electrophoretic deposition) process. The oxide doping influenced the stability of the EPD suspension and affected the density of the resultant layer. In order to improve the adhesion between the layer and the substrate, a two-step sintering was performed up to 1200 ºC for a total duration of 4 hours in a horizontal vacuum furnace, with a heating rate of 2 ºC per minute in an Argon gas atmosphere. FE-SEM (field emission scanning electron microscopy) and vickers hardness tests were employed to investigate the effect of single and double doping on the morphology and hardness of the coating layers, respectively. EDS (energy dispersive spectroscopy) was employed to analyze the elemental composition of the layers, while XRD (x-ray diffractometry) was utilized to determine the crystalline phases. The results indicated that the double-doped coating sample possesses a better microstructure and the layer with double doping exhibits a denser microstructure and reduced porosity (3.84%) in contrast to the single doping layer (6.05%). The vickers hardness test indicates a rise in hardness from 65.3 HV with single doping to 283.78 HV with double-doping layers, due to the presence of Al2O3 as the interstitial agent, which reduces the layer's porosity and enhances adhesion between the layer and the substrate. Furthermore, the addition of Al­2O3 as the double dopant may impede the tà m phase transformation, leading to enhanced thermal stability in the double-doped coating sample compared to the single-doped coating sample. This study shows that double doping techniques can improve the efficiency of ceramic coatings for high-temperature applications, such gas turbine components, and also giving opportunities for more research in oxidation, corrosion, and erosion testing.

Brazing hot work steel is a popular method used in the production of casting tools. Usually, Ni-based alloy Ni 620 serves as the preferred filler metal. However, incorporating metalloids such as B and Si to lower the melting point can result in unwanted intermetallic phase formation within the joint. These phases can adversely affect the mechanical characteristics. Hence, it is vital to reduce intermetallic phase formation during brazing to maintain optimal mechanical properties. The research concentrates on W inoculation of Ni 620 to alter the microstructure of the joint. The alloys are produced via melt spinning, and their solidus and liquidus temperatures are investigated using DSC measurements. Next, X37CrMoV5-1 hot work steel samples are brazed in a vacuum furnace. The microstructure is then studied using SEM/EDS, and their hardness properties are evaluated using nanoindentation. Furthermore, their strength is analyzed in the shear test. Incorporating W into Ni 620 when brazing hot work steel alters the presence of brittle phases and hardness characteristics. Particularly, introducing W leads to a significant decrease in hardness, resulting in a more even distribution of hardness throughout the joining area. Using W to modify Ni 620 proves to be advantageous for improving hardness properties when brazing hot work steel.

Abstract Cu/Fe dissimilar metals are joined by welding-brazing in a vacuum furnace, and then typical defect formation mechanisms of the post-welded joints are observed and analyzed. As a result, it has been found that the major welding-brazing defects are elemental segregation, solidification cracks and poor fusion. It is worth noting that the causes of element segregation and slag inclusion are related to high welding-brazing temperature, impurity of raw materials, inadequate cleaning of materials before welding-brazing and volatilization of impurity metals in the chamber of the vacuum furnace. In addition, welding-brazing defects such as poor fusion and solidification crack are not only related to elemental segregation and slag inclusion, but also to other external factors such as excessive cooling rate and minor furnace leakage, etc., and the defects tend to occur at the interface near the Cu/Fe joint connection. By changing the welding-brazing process, it can effectively inhibit elemental segregation, reduce the slag inclusion and avoid poor fusion, solidification cracks and other interfacial welding-brazing defects, and ultimately obtain a good combination of copper and iron dissimilar metal joints, the shear strength has greatly increased compared to before improvement.

In this study we report vaporization coefficients for silica, alumina, and molten anorthite and gehlenite obtained by continuous weight loss measurements in a thermogravimetric system with a tungsten mesh vacuum furnace. Free surface vaporization rates are measured using 2.5 mm droplets on Ir-wire loops. Vaporization rates were converted to partial pressures with the Hertz-Knudsen-Langmuir equation. Where possible, equilibrium pressure are determined using iridium Knudsen cells in addition to model calculations. Silica and alumina exhibit no change in vaporization coefficient on melting with αSiO2 = 0.024 ± 0.001 (all uncertainties are 1s) and αAl2O3 = 0.57 ± 0.07. The anorthite and gehlenite composition melts exhibit vaporization coefficients (αAN = 0.033 ± 0.003 and αGEH = 0.131 ± 0.014) close to those of pure silica suggesting only a weak, if any, dependence of vaporization coefficients of silicates studied on the melt structure. The Knudsen cell equilibrium pressures are preferred over model calculations. Implications of experimental data to volatilization and formation of Ca-Al-rich inclusions in meteorites are considered.

MAB phases have recently garnered significant interest due to their excellent properties, such as high thermal and electrical conductivity, oxidation resistance, and exceptional corrosion resistance. Although the Mn2AlB2 phase has been synthesized using multiple methods recently, it requires long experimental durations (up to 7 days), high costs, and extensive experimental efforts to achieve high purity. In our study, the Mn2AlB2 MAB phase was synthesized using Al, B, and Mn as precursor materials. Specifically, we investigated the effect of Al ratios (Al:1.3, Al:3, and Al:10) on the formation of the Mn2AlB2 MAB phase. The precursor powders were mixed homogeneously in stoichiometric ratios using ball milling and cold-pressed in a 1-inch die set to form green pellets, which were then sintered in a high-temperature vacuum furnace at 1200°C. The resulting Mn2AlB2 MAB phase were characterized in terms of crystal structure, impurity, and microstructure using XRD, FESEM, and EDS.

When heterogeneous joints are created, problems with the formation of intermetallic phases arise. There are various ways to reduce the formation of intermetallics. One of the ways that is discussed in this article is to use a suitable interlayer of appropriate thickness when forming the joint. A too-thin interlayer does not protect against the formation of brittle intermetallic phases. On the other hand, a too-thick interlayer increases the heterogeneity of the joint and, thus, decreases its useful properties. Within this paper, the formation of diffusion joints between the base material (AISI 304 steel, duplex steel, AISI 316L steel, or titanium grade 2) and the 0.2 mm thick intermediate layer (nickel or vanadium) was studied. Initial diffusion joints were prepared in a Gleeble 3500 machine, and samples for the study of diffusion kinetics were subsequently heat-treated in a vacuum furnace. The result of the research was the determination of specific diffusion parameters of nickel and vanadium into all four tested base materials. The initial diffusion depth (simple heating to the target temperature without holding at this temperature) of nickel was 4.46 µm into duplex steel and 5.48 µm into Ti Gr. 2 at 950 °C. At the same temperature, the initial diffusion depth of vanadium was 14.54 µm into duplex steel and 14.32 µm into Ti Gr. 2. In addition, general equations for the calculation of diffusion coefficients for the mentioned materials in the temperature range of 850 to 1150 °C were established.

In this work, the Fe-Cr-Mo-V-W-C-MoS2 composites were fabricated using the powder metallurgy process. The uniaxial cold compaction was used to produce green specimens with the density of 6.3 g/cm3. Subsequently, the specimens were sintered at temperatures of 1150 and 1200 °C for 45 min in a vacuum furnace. Sintered specimens were cooled down in the furnace with N2 at a cooling rate of 0.1 °C/s. The influence of MoS2 addition on the density, hardness and microstructure were investigated. Density and hardness of composites were improved due to MoS2 addition, especially, 5 wt.% MoS2 addition and sintering at 1200 °C. The dissociation of MoS2 contributed to the formation of sulfide phases and hard carbide particles within the composites. Sulfide phases such as FeS, CrS and other sulfides were detected by x-ray diffraction analysis. The reciprocating wear test was used to study the effect of MoS2 addition on friction and wear resistance of composites. The synergy of FeS and CrS contained in the compacted layer and hard carbide particle formation within the matrix were expected to enhance tribological properties of composites by decreasing friction coefficient and improving wear resistance.

The III-V compound semiconductors exhibit the advantage of wide bandgap and high electron mobility, making them appropriate for optoelectronics and microelectronics sector. Vertical directional solidification (VDS) is a technique developed to grow the high quality III-V semiconducting bulk crystals. One of the Sb based III-V materials, Gallium Antimonide (GaSb) was grown by VDS. This direct band gap semiconductor was realized as a ρ-type substrate and thermally diffused in vacuum by Tellurium(Te) ions as n-type dopant to fabricate ρ-n junction. Fabrication of successful ρ-n junction was confirmed by its electrical behaviour. It was later subjected to furnace annealing in vacuum at 200°C and 400°C for dopant to compensate deep in crystal geometry. Rectification characteristics of this junction were distinctly sharp for either biasing. It is revealed that rectification was approaching to optimum ideality factor (1-2) after vacuum furnace annealing at higher temperature. This device exhibits an applicability for NIR sensing close to 1.7µm.

Ni-based brazing fillers are primarily utilized in vacuum furnaces or continuous furnaces. However, the application of such furnace techniques imposes technical and economic limitations on the size of brazeable components. Induction brazing offers an alternative to overcome these limitations, enabling the brazing of large components by means of localized heating and gas shielding. This study aims to improve the understanding of process control and required gas quality for effective brazing by conducting experiments on tube-to-tube joints using Ni-based brazing alloys. To determine their impact on brazing outcomes, process gases with varying oxygen contents were systematically tested. The microstructure of the brazed joints was analyzed by light microscopy. The influence of process gas quality on corrosion behavior was examined using a capillary microcell. High residual oxygen contents in the process gas led to a shift in the corrosion potentials. Additionally, the mechanical properties of the joints are affected. Therefore, the monotonic mechanical properties were investigated at ambient temperature. The findings of this research offer practical recommendations and present a newly developed shielding gas nozzle for industrial applications. These insights support the optimization of induction brazing processes and highlight the potential for increasing the quality and efficiency of brazing large components.

Pt-Ni alloys possess unique catalytic and magnetic properties, and it is highly desirable to synthesize conformal thin films of these materials for integration into magnetic devices and energy conversion systems. Electrodeposition provides large scale and complex form plating without the need for additional equipment such as a vacuum system or furnace used in traditional Pt-Ni synthesis. While nickel and platinum electrodepositions can individually plate effectively, co-deposition provides its own challenges. Large differences in deposition potentials between the two metals and platinum’s reduced overpotential for undesirable hydrogen evolution are necessary challenges that need to be addressed. Investigation into various nickel and platinum bath chemistries over a range of pH’s will help develop a Pt-Ni co-deposition bath that will produce a uniform deposition with desired morphologies.A rotating disk electrode experiment was conducted on each electrodeposition bath along with a Koutecky-Levich analysis to determine the baths diffusion coefficient and rate constant. Nickel baths include boric acid, acetic acid, citric acid, hydrochloric acid, and phosphoric acid. Platinum baths include hydrochloric acid and acetic acid. Hydrogen suppression techniques were also studied for both nickel and platinum baths to determine the effect on hydrogen generation and metal deposition. Successful suppression of the hydrogen generation reaction would result in greater control of nickel deposition onto platinum as well as thicker platinum films.

The continuous improvement of thermal protection efficiency for rocket and space technology (RST) components is a key aspect of progress in this field. Today, carbon-carbon composite materials (CCCM) are increasingly becoming the standard in thermal protection systems. Simultaneously, CCCMs are being used more frequently in devices for testing RST materials and evaluating component durability. For instance, CCCMs serve as structural and heating elements in vacuum furnaces under high mechanical and thermal loads. The expanding application of such materials requires enhancements to existing methods and the development of new approaches for studying and determining their thermophysical properties. This paper addresses this need by investigating heat propagation in flat CCCM samples with different fiber orientations in the matrix using a combined experimental-computational method to determine their heat capacity and thermal conductivity in the temperature range of 300–1200 K. The study involved furnace heating of CCCM samples, with the selected temperature range justified by the onset of thermoerosion at 1200 K for CCCMs. Temperatures up to 1200 K with heating durations of up to 60 seconds typically do not cause significant surface degradation. Heat capacity was determined at temperatures up to 700 K using the IT-с-400 device and calculated up to 2000 K using the «ASTRA 4.0» software. Thermal conductivity was obtained through a computational-experimental approach, employing a heat conduction model and an inverse problem methodology. Experimental temperatures from two surfaces of a flat sample during one-sided heating were used to solve the inverse problem. The COMSOL Multiphysics® software package, an integrated platform for modeling physical processes (including heat transfer) in environments and objects of various geometries, was employed for the calculations.

Wetting behaviour of nickel-based brazing alloy BNi-5a on conventionally cast and laser-melted austenitic stainless steel 316L

The oxygen content of M2 high-speed steel has not been intentionally controlled in industrial production through secondary refinement in vacuum furnaces. However, a lower oxygen content has a significant effect on the cleanliness, toughness, and addition of rare-earth elements to M2 high-speed steel. The changes in total oxygen content controlled by vacuum carbon deoxidation (VCD) treatment and inclusion evolution were investigated in M2 high-speed steel to understand the effects of carbon on dissolved oxygen and oxides in the carbon–oxygen (C-O) reaction process. Furthermore, the microstructure and properties of M2 high-speed steel caused by vacuum insulation and the role of reducing oxygen content in rare-earth alloying were briefly demonstrated. The results showed that the [O%] decreased from 30 ppm to 3 ppm in a vacuum at holding times above 25 min through the C-O reaction, leading to an inclusion reduction of approximately 70%. In the case of [O%] = 3 ppm in M2 high-speed steel, the addition of rare-earth elements has a greater effect on the inclusion characteristics. Lowering the oxygen content of M2 high-speed steel improves cleanliness and plays a significant role in rare-earth alloying.

To impregnate graphite of the GMZ brand with liquid aluminum alloy D16, a high-pressure method and apparatus previously used for impregnating carbon frames with liquid coal pitch in the isostatic technology for the production of carbon-carbon composite materials were used. The graphite blank and the amount of aluminum alloy calculated from the initial porosity of graphite were placed in a thin-walled container, degassed in a vacuum furnace, after which the container with the contents was sealed. Thermobaric treatment was carried out at a temperature of 750°C and pressure of 100 and 200 MPa. After finishing the treatment, the density and porosity of the obtained metallographic composites, as well as their compressive strength, were determined. As a result of these thermobaric treatments, the density and compressive strength of the obtained composites increased significantly, and the porosity decreased markedly.

Preparation and properties of Ta fiber reinforced high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-SiC composite ceramics

Enhanced properties of hard metal WC-Ni processed from nanostructured powders

Oxygen vacancies, hydroxyl groups and fluorine ions in the local environment of Yb3+ ions doped in CeO2 nanoparticles