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The study investigated the effect of retrogression and re-aging (RRA) on the structure and properties of the new Al–3.5Zn–3.5Mg–3.5Cu–1.6Er–0.2Zr–0.2Cr alloy through the use of scanning electron microscopy, thermodynamic calculations, hardness tests, current density, and corrosion potential. During the crystallization process, chromium is distributed between primary intermetallic compounds with an approximate composition of (Al,Zn)79.8Mg4.7Cu3Cr5.5(Er,Ti)7, with a size of approximately 10 μm and an aluminum solid solution. Following two-stage homogenization heat treatment, the Al8Cu4Er and Mg2Si phases exhibit minimal morphological changes, with the θ‑phase (Al2Cu) being completely dissolved and the T‑phase (Al,Zn,Mg,Cu) transformed into the S‑phase (Al2CuMg). Thermodynamic calculations indicate that the alloy should also contain the Al3Zr and Al45Cr7 phases, which precipitate from the supersaturated solid solution during homogenization. Age hardening in the temperature range of 150–210 °C occurs due to the release of metastable modifications of the T‑phase. The combination of hardness (140 HV) and corrosion resistance (minimum corrosion current density 1 μA/cm2) is optimized by retrogression and re-aging. [ABSTRACT FROM AUTHOR]

Aerosols deposited on the surfaces of alloys and coatings used in high-temperature applications react with the protective thermally grown oxide (TGO) and accelerate component degradation. Understanding how the TGO composition effects these reactions is essential to develop corrosion-resistant materials. This work studies the corrosion of Haynes-214 alloy, which forms a bilayer Ni(Cr,Al)2O4 (spinel) + Al2O3 TGO, exposed to complex oxide and sulfate deposits to understand how the Cr and Ni oxides affect the corrosion mechanisms. The deposit compositions were systematically varied to understand the effect of anion makeup (mixed oxides, oxide-sulfate, and sulfates). The results are compared to a FeCrAlY alloy that forms a simple Al2O3 TGO. On the Haynes-214 alloy, deposits containing mixed oxides (with or without sulfates) have limited corrosive effect. In contrast, a pure CaSO4 deposit reacts aggressively with the TGO to form calcium chromate and aluminate reaction products (RP) that substantially increase the TGO + RP thickness compared to that on the FeCrAlY alloy. Surprisingly, a deposit composed of a mixture of sulfates caused less severe corrosion than the CaSO4 alone since magnesium chromate formation appears to limit aggressive reactions involving Ca. The results are discussed in the context of opportunities for corrosion-resistant alloy design. [ABSTRACT FROM AUTHOR]

Refractory high-chromium alloy VZh159 (Haynes 282) obtained by the method of selective laser melting (SLM) is studied. C-curves of the precipitation of particles of a topologically closed-packed (tcp) phase are plotted for the temperature range of heat treatment and operation. It is shown that the content of the tcp-particles of unfavorable morphology increases and the ductility of the synthesized material during synthesis in a protective nitrogen environment decreases with increase in the chromium content in the alloy. The intensification of the precipitation of the particles of the tcp-phase is associated with decrease in the solubility of chromium in the solid solution at high temperatures due to elevation of the nitrogen content in the alloy. To stabilize the alloying system, the chromium content in alloy VZh159 is reduced by 1 wt.% with respect to the upper and lower alloying limits as compared to the deformable counterpart, which makes it possible to prevent marked lowering of the ductility of VZh159 fabricatedby SLM. [ABSTRACT FROM AUTHOR]

To improve their performance, this research characterized the effects of Si on various attributes of high-Cr white cast irons. Hypoeutectic alloys of 15 and 25% Cr white irons were produced with Si levels varying of 0.4, 1 and 1.6%Si and poured into 3-inch (75-mm) Y-block sand molds. Various tests were used to determine the optimum hardening temperature and the kinetics of pearlite transformation. In addition, image analysis was performed to determine eutectic carbide fraction. Furthermore, energy-dispersive spectroscopy analysis was conducted to determine the distributions of the alloying elements among the various solidification constituents. Raising Cr from 15 to 25% caused the optimum hardening temperature to rise from 1680 to 1920 °F (915 to 1050 °C). In the 15% Cr series, an increase of 1.2% Si raised the optimum hardening temperature by 80 °F (50 °C), whereas, for the 25% Cr series, the optimum hardening temperature was unchanged. Peak hardness was significantly higher (by 50 HB) in the leaner Cr alloys and the peak hardness in both the 15% and 25% Cr alloys decreased slightly (by 20 HB) when the Si content was increased from 0.4 to 1.6%. However, the hardenability (the time to the onset of pearlite transformation) increased with increasing Si content. The influence of Si on % eutectic saturation was not clear. When analyzing carbide fraction, Si had a negligible effect in the 15%Cr series, but seemed to cause the 25%Cr series to develop less eutectic carbide, that is, become more hypoeutectic. Cr was richest in the eutectic carbides and leanest in the eutectic austenite matrix. Si was largely rejected from the eutectic carbides and richest in the eutectic austenite. [ABSTRACT FROM AUTHOR]

P92 heat-resistant steel has been successfully submerged arc welded by employing designed CaF2–Cr2O3 fluxes. It has been demonstrated that δ-ferrite is retained in the weld metal, the area fraction of which is found an approximately 3.7-fold enhancement as the Cr2O3 content in the fluxes is raised from 5 to 25 wt pct. Such phenomenon has been elucidated through governing element transfer behaviors incurred by the decomposition of Cr2O3. Our findings possibly offer a viable solution towards developing welding fluxes geared towards durable heat-resistant steel grades. [ABSTRACT FROM AUTHOR]

The results of studies on the preparation of highly dispersed bimetallic materials based on platinum with chromium, molybdenum, and tungsten under autoclave conditions at 190°C are summarized in this report. The thermodynamic and chemical features of the interactions between [Pt(NH3)4]Cl2 and (NH4)2CrO4, (NH4)2MoO4 and (NH4)2WO4 are considered. Solid products (powders) are represented by two phases—Pt and disordered solid solutions based on platinum. The morphology of powders has been studied—spherical particles with a diameter of 300–700 nm form agglomerates up to 2 µm. A route for the reduction of platinum (II) and oxometalate anions to the corresponding metals with intrasphere ammonia is proposed. The results of this work can form the basis for the synthesis of catalysts that are widely used in a number of industrially important reactions. [ABSTRACT FROM AUTHOR]

A method for obtaining composite surface-alloyed castings from gray cast iron SCh25 by cavityless casting with the use of master alloys containing chromium and ferroboron deposited as a paste layer on the surfaces of the casting molds is considered. The microstructure and the phase composition of the surface layer and the microhardness of the structural components are determined. Mechanical tests of the cast samples for compression and wear are carried out. Self-propagating high-temperature synthesis is shown to occur between the components of the master alloys deposited on the surfaces the molds during the production of the castings. The types and compositions of the borides and carboborides formed in the alloyed layer are determined. The effect of the parameters of the alloyed layer on the properties of the composite castings is analyzed. [ABSTRACT FROM AUTHOR]

The effect of a minor amount of rare-earth element Nd addition (0.1 at%) on the microstructural properties, microhardness, and cyclic oxidation resistance of NiAl–Cr(Mo) alloy is investigated in detail. The microstructure of investigated alloys is composed of NiAl-based dendrites and a eutectic mixture whose components are NiAl and Cr(Mo) phases. The minor amount of Nd addition refines the microstructure and increases the microhardness considerably. The results of the cyclic oxidation tests reveal that the surface scales of both alloys are mainly consisted of α-Al2O3 and little amount of Cr2O3. A Cr(Mo)-rich layer is observed in the metal/oxide interface. With Nd addition, the oxidation resistance of Ni–33Al–31Cr–3Mo alloy is strongly improved. The Nd-added alloy exhibits lower oxidation mass gain and increased scale adherence. [ABSTRACT FROM AUTHOR]

Yttrium-stabilized zirconium (YSZ) thermal barrier coatings (TBCs) are applied in gas turbines due to their ability to shield metallic parts from exposure to high temperatures. The progress in this area is sought out, among others, by bond coat (BC) engineering providing a better stress relief at ceramic/metal boundary and excellent both oxidation and corrosion protection of the metallic substrate. The present BC based on NiAl intermetallic, being exposed to oxidizing atmosphere at high temperature, secure formation of Al2O3 layer fulfilling both these requirements. The NiCr alloys are not only capable to produce a dense Cr2O3 layer at the ceramic/BC boundary, but it may additionally offer closer coefficient of thermal expansion (CTE) to that of the metallic substrate. The aim of this work was a detail characterization of the microstructure, phase and local chemical composition of the TBC consisting of YSZ (ZrO2 with 8 wt.% of Y2O3) top coat (TC) and Ni 50 wt.% Cr bond coat. They were deposited over 321 s stainless steel substrates using a detonation gun (DG) technique. The investigations were performed with scanning and transmission electron microscopy backed with energy-dispersive x-ray spectroscopy (SEM/TEM/EDS). The high-temperature (HT) cycling of YSZ/Ni50Cr set was performed in air and comprised of 5 cycles, which consisted of heating the samples up to 900 °C at 10 °C/min., holding them at that temperature for 10 h, followed by their cooling down for ~ 30 min. The microstructure observations showed that DG allowed to produced dense YSZ coating of low porosity, while Ni50Cr bond coat differed in local chemical composition and contained numerous amorphous chromium oxide pockets. During the HT cycling, the oxygen from the air was still able to penetrate through the YSZ layer supporting formation of Cr2O3, while the amorphous chromium oxide transformed to R-CrO2 (rutile type). Only small amount of NiO was noted, being dispersed within Cr2O3. Simultaneously, a significant inter-diffusion of Ni into steel substrate and Fe and Cr into the bond coat were documented. The lack of oxide formation in the substrate proves that the DG YSZ/Ni50Cr set could serve as a good protection over parts subjected to HT cycling. [ABSTRACT FROM AUTHOR]

A series of chromium-doped calcium ferrite samples of composition Ca0.5Mg0.5Fe12−xCrxO19 (x = 0.0, 0.5, 1.0, 1.5, 2.0) was meticulously prepared using the standard sol-gel combustion route. Structural and morphological properties were comprehensively studied via X-ray diffraction and Scanning Electron Microscopy (SEM). The lattice parameters 'a' and 'c' unequivocally validated the space group of the samples as P63/mmc (194). Moreover, the lattice parameters derived from the XRD data demonstrated commendable agreement with the values extrapolated from theoretical cation distribution and Rietveld refinement calculations. It was further confirmed that the crystallite size, as determined by XRD, concurred excellently with the particle size measurements from the scanning electron micrographs. The samples' magnetic characterization was carried out using a vibrating sample magnetometer (VSM). Notably, the saturation magnetization (Ms) and remanence (Mr) were found to exhibit an increase, while coercivity (Hc) displayed a concurrent decrease with higher substitution ratios. The reason behind the enhancement of saturation magnetization and remanence, along with the reduction in coercivity, was elucidated based on involved factors such as crystallite size, anisotropy constant, and cation distribution. Results showed that including chromium significantly softened the ferrite materials, making them ideal for advanced high-end recording applications. The samples also exhibited low coercivity and impressive saturation magnetization, enhancing their value as storage devices tailored for information storage and recording purposes. [ABSTRACT FROM AUTHOR]

The paper studies the coating consisting of the Al–Cr sublayer and external Y–Al–O ceramic layer obtained by vacuum-arc deposition for the protection of the VTI-4 (Ti49–11Al–40Nb) intermetallic alloy from oxidation at 750°C. The coating degradation mechanism and phase transformations are studied during their heating in a furnace and thermal cyclic tests. Test results show the stability of the double-layer coating in both cases. [ABSTRACT FROM AUTHOR]

Introduction of 0.3% Cr into Al–Cu–Er–Zr alloy leads to significant modification of the grain structure and almost complete elimination of a dendritic structure. The average grain size of 40 μm corresponds to the size of a dendritic cell. The good modifying capacity is explained by formation of intermetallic compounds of the phase first identified of approximate composition Al75–80Cu10–12Er3–4Cr7, which is a substrate for nucleation of primary aluminum. After quenching and aging, slight hardening in the alloy is achieved due to L12 –Al3(Zr,Er) dispersoids with an average diameter of 40 nm and q'(Al2Cu) precipitates with a diameter up to 100 nm and a thickness up to 5 nm. No particles containing chromium are found within the matrix. According to thermodynamic calculations, hot rolling of AlCuErZrCr alloy at a temperature of 440°C should proceed in the ((Al)+Al3Zr+Al7Cr) phase region. However, analysis of the fine structure in an annealed condition after rolling showed presence of only L12 –Al3(Zr,Er) dispersoids. Differences in alloy hardness on annealing up to 300°C may be explained either by the influence of dissolved chromium atoms or by formation of chromium-containing particle clusters, which could not be detected. [ABSTRACT FROM AUTHOR]

AlMgSi alloys with two Cr compositions (0.17 wt% and 0.08 wt%) were subjected to different homogenization heat treatment soak conditions at: 560 °C, 580 °C, 600 °C with soak time duration of 6 h, 8 h, and 10 h; subsequently, alloys were cooled by air. Metallographic examination methods were used to determine microstructure after homogenization heat treatment. Hardness measurements were used to assess the mechanical properties. The results indicated that high Cr concentration in Al alloy contributed entirely transformation of β-AlFeSi into cubic α-AlFeSi phase with 580 °C–600 °C soak temperature condition. At the same time, high levels of Cr addition led to the formation of higher volume fractions in the alloy. The Mg2Si particles entirely dissolved in the Al matrix and homogeneously dispersed under this annealing condition. The specimens reached maximum hardness after homogenization heat treatment at 580 °C for 8 h. The hardness values of the sample with 0.17 wt% Cr are higher than the sample with 0.08 wt% Cr for relatively long-term soak time at 8 h–10 h and high soak temperature at 580 °C–600 °C. [ABSTRACT FROM AUTHOR]

High-temperature oxidation behavior of conventionally cast and additively manufactured (AM) Co-base alloy MAR-M-509 was compared in the present study. The specimens were exposed in air at 1000 °C and characterized by means of scanning electron microscopy equipped with energy/wavelength dispersive x-ray spectroscopy (EDX/WDX) and electron backscatter diffraction as well as transmission electron microscopy. Substantial differences in the oxidation processes of two alloy versions were observed. Faster oxidation of the cast alloy was mainly induced by (1) oxidation of coarse primary carbides, (2) internal oxidation and nitridation processes and (3) incorporation of other alloy constituents (e.g., Co, Ni, W) into the Cr-oxide scale. AM specimens, in contrast, formed a more homogeneous, thinner and better adherent external oxide scale. The results are discussed in terms of differences in the chemical composition and alloy microstructure, including the grain size distribution in the material and the morphology of the strengthening precipitate phases. [ABSTRACT FROM AUTHOR]

Interdiffusion coefficients in low-Al Fe–Cr–Al alloys at 1000 °C were experimentally determined by using a diffusion-couple method, and the effects of Cr on the interdiffusion flux of Al were evaluated. The main-term interdiffusion coefficients, D ~ AlAl Fe and D ~ CrCr Fe , decreased with increasing Cr content, and the D ~ AlAl Fe values were two to three times greater than the D ~ CrCr Fe values. The cross-term interdiffusion coefficient, D ~ AlCr Fe , was positive, indicating a positive chemical interaction between Cr and Al in the Fe–Cr–Al alloys. D ~ AlCr Fe was one order of magnitude smaller than D ~ AlAl Fe and decreased with increasing Cr content. Because of the positive D ~ AlCr Fe value, when the concentration gradients of Al and Cr had the same sign, the Al interdiffusion flux was increased by Cr and increased with increasing Cr content due to the steeper Cr concentration gradient. [ABSTRACT FROM AUTHOR]

The microstructure and early-stage oxidation behavior of the equiatomic CoCrCuFeMnNi high-entropy alloy (HEA) and its six sub-alloys, obtained by omitting one element each, were investigated. Alloys were prepared using induction levitation melting, cold rolled, and oxidized for 1 h at 800°C in air. The Ni-free and Co-free HEAs showed an inhomogeneous microstructure associated with liquid phase separation. The other alloys were either single-phase (Cu-free HEA) or contained two face-centered cubic phases, one Cu-rich and one Cu-poor. The Cu and Mn-containing two-phase alloys showed preferential oxidation of the Cu/Mn-rich phase, leading to Mn-rich oxides that are prone to spallation. The Mn-free alloy exhibited a thicker oxide (~ 5 µm) on the Cu-rich phase, whereas the Cu-poor phase was covered by a thin base oxide (< 1 µm). The single-phase Cu-free ('Cantor') alloy formed an approximately 1-µm-thick oxide of the crystal structure types of Mn3O4, Mn2O3, MnCr2O4, and Cr2O3. For prospective high-temperature applications, reducing the Cu and Mn content and thus avoiding formation of a second Cu-rich phase is a promising route to facilitate formation of a protective oxide. [ABSTRACT FROM AUTHOR]

In this work, stainless steel pickling sludge (SSPS) and Ni-bearing electroplating sludge (ES) were co-treated to prepare Ni matte and Fe–Cr–Si alloy. A two-stage sulfurization-smelting method was used for preparing the Ni matte. At the sulfurization stage, carbon, SSPS, and ES were mixed and reacted at 1000 °C. It was found that NiO in the SSPS and ES can be sulfurized to (Fe,Ni)0.955S by CaSO4. After that, the sulfurized sludge was smelted at 1450 °C, and the liquid Fe–Ni–S matte was separated from slag by gravity at this stage. The Ni grade (37.5 wt pct) of the matte prepared at a C/CaSO4 molar ratio of 4 was higher than most of the industrial mattes (13 to 35 wt pct). Meanwhile, the recovery efficiency of Ni was 98.1 pct. For recovering Cr, Fe–Cr–Si alloy was prepared by the silicothermic reduction of the smelting slag. The sulfur (0.008 wt pct) and carbon (0.01 wt pct) contents of the Fe–Cr–Si alloy produced were lower than the threshold values for commercial Fe–Cr–Si alloy (0.01 wt pct S, 0.02 wt pct C). Therefore, this alloy can be used for stainless steel making. [ABSTRACT FROM AUTHOR]

Blast furnace ironmaking produces a reducing and carburizing atmosphere in the blast furnace which may lead to metal dusting. However, there is limited research on metal dusting under this particular atmosphere. This paper investigated metal dusting behaviors of ferritic Fe-(10, 20, 25)Cr and austenitic Fe-20Cr-(20, 33)Ni, Fe-25Cr-20Ni (wt.%) alloys at 550 and 650 °C in an Ar-33CO-7H2-7CO2-2H2O (vol.%) gas simulating a blast furnace operating condition. A relatively short reaction time, up to 100 h, was used to evaluate the initial stage of metal dusting of these alloys in the blast furnace gas condition. Severe metal dusting and coke deposition were observed at 550 °C, while no significant dusting but internal oxidation and carburization were observed at 650 °C. Higher Cr and Ni contents in the alloy lowered kinetics of metal dusting at 550 °C and of carburization at both temperatures. Austenitic alloys were more susceptible to metal dusting and coke deposition than ferritic alloys with the same Cr content at 550 °C. At 650 °C, however, ferritic alloys experienced higher extents of carburization and oxidation than austenitic alloys with the same Cr concentration. The effects of alloy composition and reaction temperature on metal dusting in this simulated blast furnace operating condition were discussed. [ABSTRACT FROM AUTHOR]

Mechanical characteristics of composite materials based on Fe – 18% Cr – 10% Ni alloy and composed of plastic macroscopic austenite regions distributed in a high-strength martensite matrix are studied. Stress-strain curves are obtained for the specimens with austenite regions differing in size and in shape. The plotted curves are used to determine the shapes of the austenite regions optimal in terms of combining the strength and ductility parameters of the material. [ABSTRACT FROM AUTHOR]

Welding processes of titanium alloys with steels are analyzed. The following research directions are distinguished: the use of prefabricated bimetallic transition elements (welded by traditional methods); minimization of energy and heat expenditure in the weld area of metals; the use of methods of welding metallurgical engineering. The advances in welding technology have led to innovative solutions such as friction welding with stirring, as well as the use of liquid-phase layers and 3D printing of nanostructured layers at the edges to accelerate diffusion processes in diffusion welding. The new methods in welding metallurgical engineering increase the efficiency of Ti–Fe compounds due to the use of multilayer compositions of tantalum or niobium from the side of titanium and bronze – from the side of steel, and also vanadium inserts and its alloys, for example, alloyed with tungsten or chromium. The urgency of further development of standards for support and dissemination of industrial technologies for welding of Ti–Fe joints, training and preparation of technical personnel for the implementation of these technologies is noted. [ABSTRACT FROM AUTHOR]

The evolution of phase composition and thermal oxidation behavior of high-entropy AlCrFeCoNiMnx alloys (x = 0.5 and 1) during long-term oxidation at 900°C were studied. A single- phase ordered (B2) bcc alloy formed in the starting as-cast state regardless of manganese content. The scale phase composition varied with exposure time and manganese content. After 10 h of oxidation, high-entropy spinel-type MeMn2O4, as well as Mn3O4 and Al2O3, formed on the AlCrFeCoNiMn alloy, while only Mn3O4 and Al2O3 oxides emerged on the AlCrFeCoNiMn0.5 alloy. Increase in the oxidation time for the equiatomic alloy up to 25 h led to spinel NiMn2O4 and bixbyite FeMnO3 in the oxide scale; Mn3O4 and Al2O3 were also present. The phase composition of the oxidized layer on the AlCrFeCoNiMn0.5 alloy did not change. After 50 h, the structure of the oxide scale was similar for both alloys and consisted of NiMn2O4, FeMnO3, Mn3O4, and Al2O3 in different ratios. The oxidation kinetics of the alloys naturally depended on the manganese content: the higher the manganese content, the higher the oxidation rate. A continuous layer of the fcc solid solution rich in chromium, iron, and cobalt was observed under the scale in both alloys. An internal oxidation area was also found in the subscale layer of the AlCrFeCoNiMn alloy. Long-term (more than 50 h) oxidation at 900°C substantially changed the phase composition of the alloy matrices: the bcc (B2) solid solution underwent spinodal decomposition to form bcc and fcc phases and tetragonal σ phase. Analyses of the alloy matrices showed a sharp increase in their microhardness after annealing. This can be attributed to the formation of a significant amount of the σ phase. [ABSTRACT FROM AUTHOR]

Structural and phase compositions of castings of chromium cast irons ChKh32 (2–4% C; 30% Cr; 2.4% Mn; 0.6% Si) alloyed with nitrogen using nitrided chromium as a master alloy are studied by X-ray diffraction, metallographic analyses, and scanning electron microscopy methods. It is shown that nitrogen in cast iron obtained is present mainly in iron-based solid solution, along with chromium, manganese and carbon, and is partly included within the composition of carbide phase (Fe, Cr)7C3. Nitrogen alloying of ChKh32 (2% C) stabilizes austenite. Nitrogen alloying of ChKh32 (3–4% C) followed by heat treatment leads to formation of an austenitic-martensitic structure with an increase in material hard-ness. It is shown that addition of nitrogen in an amount of 0.2% to ChKh32 (2% C) improves corrosion resistance, and an increase in carbon content in these materials increases abrasive wear resistance. [ABSTRACT FROM AUTHOR]

The microstructure of cast billets and grinding balls fabricated from rail steels of different chemical compositions is studied. The samples are heat treated by annealing, quenching, and quenching with tempering. The microhardness and the structures of the samples after the treatments are compared. It is shown that chromium alloying above the standardized values causes development of dendritic segregation in the cast structures, which is reduced but not removed completely after the heating for rolling. Assessment of the microstructures and of the hardness of the grinding balls shows that the optimum composition for their production corresponds to rail steel 76KhF. [ABSTRACT FROM AUTHOR]

Six alloys (25 wt% Cr, 0.4 C, 1.6 Ti, Co and Ni (bal.)) were prepared by casting for evaluating their oxidation and creep properties at 1200°C. Their microstructures consist of a dendritic matrix with eutectic carbides in the interdendritic spaces. Carbides are TiC for the alloys richer in Co than in Ni, and chromium carbides in the alloys richer in Ni than in Co. Differential thermal analysis shows that all alloys start melting above 1250°C. The oxidation tests in air at 1200°C allow observing a chromia–forming behavior of the alloys rich in nickel better than the cobalt alloys. In contrast, the creep resistance tests at 1200°C demonstrate an undeniable superiority of the alloys rich in cobalt. Good compromise for both types of high temperature behavior appears to be obtained by a Co-base alloy containing nickel as minor element but with significant proportion in nickel (15–30 wt% Ni). [ABSTRACT FROM AUTHOR]

Titanium alloy (Ti-6Al-4 V) is widely used in a number of fields such as medical, aeronautical, and nuclear fields. Since the surface finish should be enhanced as much possible in efficient way, the micro EDM process can be used for machining such materials. The process mechanism can be enhanced by utilizing the coated electrode in the process. In the present study, an effort was made to investigate the effects of process parameters on drilling titanium alloy with aluminum chromium nitride (AlCrNi)-coated aluminum electrode in micro EDM process. An optimization approach was also implemented using Taguchi-DEAR approach. From the experimental interpretation, the conclusions were made as follows. The AlCrNi-coated aluminum electrode can enhance the machinability of micro EDM process. The optimal combination of voltage (140 V), capacitance (10000pF), and spindle rotation (200 rpm) could provide better quality measures among the chosen variables. The moderate voltage and capacitance can remove the material effectively with lower overcut, since the electrical conductivity can effectively enhance the conductivity of the plasma energy column. The coated electrode can create the tiny craters with uniform energy distribution. [ABSTRACT FROM AUTHOR]

The influence of the oxygen-induced surface segregation process of Cr and Si solutes on the anti-corrosion properties of Fe–Cr and Fe–Cr–Si alloys was studied using X-ray photoelectron spectroscopy (XPS) and 57Fe transmission Mössbauer spectroscopy (TMS). To select the optimal procedure for preparation of the studied alloys with the highest possible surface concentrations of both solutes, the samples were prepared by various thermal treatments. The XPS results clearly show that despite the initial surface segregation during the samples preparation, the additional thermal treatment at 900 K greatly enhances this process. Moreover, it was proved that to get the most efficient segregation, the surfaces of the alloys must be covered by oxygen during the additional annealing. The samples with the highest surface concentration of Cr and Si solutes were oxidized in air at 870 K, and their anti-corrosion properties were characterized by TMS. It was found that the additional thermal treatment at 900 K significantly improved the corrosion resistance of all studied alloys. Furthermore, it can be concluded that it is possible to reduce the Cr and Si content in properly prepared alloys without deteriorating their anti-corrosion properties. [ABSTRACT FROM AUTHOR]

The oxidation of four Co-20Ni-xCr-yAl (x = 8,15 wt.%; y = 3,5 wt.%) alloys under 1 atm O2 for 24 h was studied at 800 and 900 °C. All the alloys formed complex scales, irregular both in thickness and composition. The formation of external alumina scales was more favored at 800 °C than at 900 °C and for larger chromium and aluminum contents, but was never complete. The simultaneous presence of chromium and aluminum is beneficial for increasing the oxidation resistance of these alloys with respect to ternary Co-20Ni-xCr and Co-20Ni-yAl alloys of similar composition. However, an Al content of 5 wt.% is not yet sufficient to form continuous alumina scales even when coupled with 15 wt.% Cr. The partial substitution of cobalt by nickel has a beneficial effect on the ability of the quaternary Co-20Ni-xCr-yAl alloys to form protective external alumina scales in comparison with the ternary Co-Cr-Al alloys with similar chromium and aluminum contents. [ABSTRACT FROM AUTHOR]

The effect of hydrogen on oxygen permeability has been studied in a diluted Pd–Cr alloy in dual- and single- atmosphere conditions between 600 and 950 °C. The 0.3 mm thick Pd–1.5Cr foil was exposed in dry and humid air as well as in dual-atmosphere conditions, with one sample surface being exposed to air and one to hydrogen, as encountered in solid oxide fuel cells. At all temperatures, Cr oxidized internally forming internal oxidation zones which were measured in metallographic cross sections. Below 800 °C, an external layer of PdO formed on the surface decreasing the internal oxidation kinetics. No measurable effect of hydrogen on the internal oxidation of Cr in Pd has been detected. [ABSTRACT FROM AUTHOR]

The microstructure of alloy Al – 2.5% Fe – 1.5% Cr obtained by crystallization from melt at cooling rates of 0.5 – 940 K/sec and the effect of the type of the initial microstructure on the behavior of the alloy under laser treatment are studied. An x-ray phase analysis of cast alloys is conducted, the solidus temperature and the microstructure are determined. The Thermo-Calc software is used to plot polythermal sections of the Al – Fe – Cr system, and the changes in the mass fraction of the hard phases in the structure are computed. It is shown that elevation of the cooling rate in crystallization of the alloy causes decrease in the concentration of the primary crystals of the Al45Cr7 phase until their total disappearance and formation of a homogeneous microstructure. The surface of the specimens is treated with a laser beam, and then the microstructure of cross sections of the tracks obtained is investigated. This type of surface treatment imitates the impact on the material in additive technologies. Laser treatment of the surface of the alloy raises the hardness substantially (from 43 to 77 HV), which is explainable by formation of a supersaturated aluminum solid solution and a small size of the dendrite cells. [ABSTRACT FROM AUTHOR]

Contact interaction of the nickel-matrix self-fluxing NiCrBSiC eutectic alloy with hot-pressed chromium diboride ceramics was studied by the sessile drop method in vacuum at 1100°C. The structure and phase composition of the starting alloy were examined. Chemical interaction between components in the NiCrBSiC system was found to occur in the melting process to promote a heterophase structure consisting of chromium carbide and boride grains distributed in the metallic matrix. The composite rather than the alloy took part in the wetting of chromium diboride. The wetting kinetics in the NiCrBSiC–CrB2 system was studied. The self-fluxing NiCrBSiC alloy was shown to wet CrB2 to form contact angle θ = 17°. Intensive chemical interaction between the alloy and substrate chemical elements was observed in the NiCrBSiC–CrB2 system. The distribution of chemical elements in the interaction area of the NiCrBSiC–CrB2 system was analyzed. Chromium was an interfacially active element in this system, and contact interaction proceeded through dissolution of the CrB2 ceramics along the grain boundaries simultaneously with penetration of the nickel-matrix alloy. The contact interaction resulted in CrB and Cr2B with lower microhardness than that of CrB2. Interaction in the NiCrBSiC–CrB2 system is unpredictable and changes the ceramic composition, resulting in decrease in the composite microhardness. Therefore, the use of CrB2 particles as reinforcing additives for the self-fluxing NiCrBSiC alloy to produce composite powders for thermal spray coatings with high wear resistance is not reasonable. [ABSTRACT FROM AUTHOR]

The results of a study of the anodic behavior of the chromium-doped Zn55Al alloy in HCl, NaCl, and NaOH electrolyte media at various pH values of the medium are presented. It is shown that for all samples of chromium-doped alloys, compared to the original Zn55Al alloy, there is a shift in the electrochemical potentials of corrosion, pitting, and repassivation to the region of positive values. Alloys containing 0.01–1.0 wt % chromium are the most resistant to pitting corrosion in the pH range of 3–10. It was established that the corrosion rate of alloys doped with (0.01–0.1%) chromium is 1.5–2 times lower than that of the Zn55Al alloy. Alloy corrosion products consist of a mixture of Al2O3, ZnO, ZnAl2O4, Al2O3·Cr2O3 oxides. [ABSTRACT FROM AUTHOR]

A thick silicon-enriched layer was formed on the surface of Fe and Fe-15 mass% Cr alloys by Si electrodeposition using a molten salt as the medium. This surface-treated sample was embedded in the molten salt and the high-temperature corrosion behavior was investigated. For comparison, the high-temperature corrosion behavior of untreated samples was also investigated. The effect of the surface Si conversion by the molten salt electrodeposition treatment on the high-temperature corrosion resistance of the Fe and Fe-15 mass% Cr alloys was then evaluated. As a result, the surface Si electrodeposition-treated Fe did not improve the corrosion resistance as compared to the untreated sample. However, for the Fe-15 mass% Cr alloy, the untreated corrosion weight loss sharply increased and the corrosion rate increased. On the other hand, the corrosion rate was lower on the surface of the Si-treated sample. After the high-temperature corrosion test, a cross section of the sample to which the molten salt was attached was observed and analyzed by SEM and EPMA. As a result, in the untreated sample of Fe, the elemental metal dissolved in the molten salt. In the Si electrodeposition-treated Fe, cracks were generated at the Fe interface between the electrodeposition layer and the substrate, and corrosion proceeded from there. On the other hand, for the Fe-15 mass% Cr alloy, it was confirmed that the surface Si-treated sample formed a continuous SiO2 layer on the surface. It is considered that this SiO2 improved the corrosion resistance. [ABSTRACT FROM AUTHOR]

A set of novel Co-free high-entropy alloys CrxFeNi(3-x)Al (x = 0.25, 0.5, 0.75, 1, 1.25, 1.5) were fabricated by non-self-consumable vacuum melting method, and their solidification microstructures as well as compression properties were investigated. The research results firstly demonstrate that the solidification microstructures of Cr-0.25, Cr-0.5 and Cr-0.75 are composed of primary B2 phase and (FCC + B2) eutectic structure; Secondly, there are primary B2 phase and (FCC + B2) eutectic structure in the solidification microstructure of Cr-1, with a tiny amount of BCC phase distributing on the matrix of primary phase B2; In addition, as a "sunflower-like" structure of BCC phase and B2 phase, the solidification microstructure of Cr-1.25 is identified. Also, the core of the sunflower is B2 phase, and the petals are alternately arranged by BCC phase and B2 phase; Last but not least, it is a fine BCC phase and B2 dual-phase structure that form the solidification microstructure of Cr-1.5. Among the phases mentioned above, the FCC phase is abundant in Ni and Fe elements, the B2 phase is abundant in Ni and Al elements, and the BCC phase is abundant in Cr element. With the ascending trend of Cr content, the strength of CrxFeNi(3-x)Al high-entropy alloy descends initially and then climbs, during which the primary reasons for the rise of strength are solid solution strengthening, fine crystal strengthening and precipitation of BCC phase. The compressive strengths of Cr-1.25 and Cr-1.5 alloys are 2111.5 and 1985.3 MPa, respectively, and the compressibility can attain to 41.36 and 49.87%, respectively, manifesting comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

The ZrB2–MoSi2–AlN, ZrB2–SiC–AlN, and (Ti, Cr)B2–AlN ceramic composites were wetted with a nickel-based alloy in the Ni–Cr–W–Mo system. The alloy was found to wet the ceramic composites well to form contact angles θ = 0–12° for 3–7 min on their surface. The wetting process was less influenced by the composition of the main phase (ZrB2 and (Ti, Cr)B2) and greater by the content of SiC and AlN dielectric additions, impairing the wetting of the composites. The interaction areas were studied on cross-sections of the wetted samples. Three characteristic areas were found: refractory substrate area, transition area, and metal droplet area. The composition and microstructure of the starting ceramic material were retained by the refractory substrate area. The pores and cracks were filled with the molten alloy in the transition area at a depth up to 150 μm. There was no active chemical interaction between the metal alloy and ceramic composites, though there was insignificant diffusion (up to 3%) of some elements between the refractory substrate and the metal alloy in a thin contact area to form limited solid solutions. This was mostly observed in the wetting of materials containing SiC and MoSi2 and was manifested through the diffusion of silicon into the metal alloy. In the wetting of (Ti, Cr)B2-based materials, 1–2% of the ceramic substrate was insignificantly depleted of chromium in a narrow (3–7 μm) contact area. Despite this, the composition of the refractory substrate and the metal alloy in the interaction area was close to the starting one. In the droplet area, besides the main phase based on the NiCr solid solution, whose composition was close to that of the starting material, single inclusions of the chromium-based phase with high tungsten and molybdenum contents were found. Good wetting of the ceramic composites with the metal alloy and zero active chemical interaction between the components allow them to be jointly used for spraying coatings and making metal–ceramic composites. [ABSTRACT FROM AUTHOR]

We have designed and fabricated four previously unexplored body-centered cubic (BCC) single phase VCrMo, VCrMoNb, VCrMoTa, and VCrMoNbTa refractory medium- to high-entropy alloys using a simple thermodynamic approach. The effectiveness of this approach was further theoretically and experimentally demonstrated by using calculation of phase diagrams (CALPHAD) simulations and arc-melting synthesis, respectively. The elemental segregation could be successfully predicted by the Scheil–Gulliver model. All the samples exhibited as-cast dendritic microstructures with high microhardness values. Finally, a general route is proposed to design equiatomic and non-equiatomic medium- to high-entropy alloys based on the rational selection of a binary system and by adding a premeditated amount of principal elements using a simple thermodynamic parameter. [ABSTRACT FROM AUTHOR]

The electronic inhomogeneities in Co, Ni, and Cr doped BaFe2As2 single crystals are compared within three bulk property regions: a pure superconducting (SC) dome region, a coexisting SC and antiferromagnetic (AFM) region, and a non-SC region. Machine learning is utilized to categorize the inhomogeneous electronic states: in-gap, L-shape, and S-shape states. Although the relative percentages of the states vary in the three samples, the total volume fraction of the three electronic states is quite similar. This is coincident with the number of electrons (Ni0.04 and Co0.08) and holes (Cr0.04) doped into the compounds. The in-gap state is confirmed as a magnetic impurity state from the Co or Ni dopants, the L-shape state is identified as a spin density wave which competes with the SC phase, and the S-shape state is found to be another form of magnetic order which constructively cooperates with the SC phase, rather than competing with it. [ABSTRACT FROM AUTHOR]

The phase constituent, phase stability, microstructure, and hardness of seven arc melted AlxCr2-xCoFeNi (x = 0.25~1.75) high-entropy alloys, in as-cast and 800 or 1000°C annealed states, were investigated using XRD, SEM, EDS and DSC. With the increase of Al content, the FCC phase disappeared in the as-cast AlxCr2-xCoFeNi alloys. As for the as-cast alloys with 25~30 at.%Al, the composition difference between the former and the later solidified B2 phase can be clearly identified. As for the AlxCr2-xCoFeNi (x = 0.25~1.0) alloys, the σ phase formed at above 576°C and decomposed at 912~1033°C. Fine FCC, BCC, B2 and σ phases existed in the 800°C annealed AlxCr2-xCoFeNi (x = 0.25~1.25) alloys. And the hardness became higher than that of the as-cast alloys. When the Al content was 25 at.%, the hardness of the alloy decreased significantly with the disappearance of the σ phase. After annealing at 1000°C, the σ phase only existed in the Al0.25Cr1.75CoFeNi and Al0.5Cr1.5CoFeNi alloys. With the increase of Al content, the alloy hardness also increased. Prolonging the annealing time, from 120 h to 480 h, can decrease the Al content in precipitated FCC or BCC phases and coarsen the phase grains, which will decrease of the alloy hardness. In all, the change of hardness after annealing depends on the contributions of formation of the harder σ phase or the softer FCC/BCC phases and the grain size of the precipitates. The results will help design the composition and treatment process of Al-Co-Cr-Fe-Ni high-entropy alloys. [ABSTRACT FROM AUTHOR]

A single-phase Fe35Mn10Cr20Ni35 (presented in at.%, unless otherwise stated) high-entropy alloy (HEA) was synthesized by an electric arc melting plus copper mold casting method. The microstructure was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The thermostability of the prepared alloy was examined by differential scanning calorimetry. The mechanical behavior was examined by a tensile test. The prepared Fe35Mn10Cr20Ni35 alloy possesses a simple FCC phase structure with excellent structural stability. This alloy has a good combination of strength and ductility. It is observed that the prepared HEAs, either in the as-cast state or in the as-homogenized state, have a considerably higher strain hardening exponent than common alloys during tensile deformation, and the deformation mechanism was determined to be that first dislocation slipping and then twinning support continuous plastic deformation. [ABSTRACT FROM AUTHOR]

The effect of niobium addition up to 3.4 wt% on the microstructure and mechanical properties of heat-treated high-Cr cast iron containing 13.5 wt% Cr was investigated. Niobium addition caused small hard NbC particles to precipitate within the proeutectic austenite which impede the development of austenite dendrite growth resulting in structure refinement. This austenitic matrix upon heat treatment changed to mainly martensitic one with some retained austenite and reinforced with small amounts of secondary carbides of M7C3 type. It was found that the hardness increased with increasing Nb content due to structure refinement and precipitation of hard NbC particles. These particles caused a depletion of carbon in the austenite matrix and thus most of the austenite was transformed to martensite upon heat treatment. The highest impact value was obtained for the base alloy without Nb addition which could be attributed to the high amount of retained austenite. The high-Cr cast iron alloyed with Nb in the range of 1.55–3.4 wt% showed an increase in hardness without any deterioration in toughness. The wear resistance was significantly enhanced by the presence of hard NbC particles up to 2.52 wt% Nb. Exceeding this optimum amount of addition leads to agglomeration of NbC particles and hence deterioration of the wear resistance through three body abrasion wear mechanism. [ABSTRACT FROM AUTHOR]

In the manufacture of sintered steels by metal injection molding (MIM), typical microstructural defects, such as pores and pore agglomerates, phase structure heterogeneities, and boundaries between different phases, are hard to avoid. Such heterogeneities cause crack origination, growth, and propagation when sintered materials are subjected to mechanical loads. The crack propagation path and fracture resistance are associated with the complex heterogeneous structure including ferrites, cementites, martensites, pores, and weak interfaces. With increasing sintering times, metal grains grow rapidly, leading to brittle fracture of the samples. Subsequent heat treatment substantially decreases the grain size and changes brittle fracture to ductile one. Multicycle sintering of the Catamold 8740 low-alloy steel greatly increases the impact strength of V-notched samples (from 7.55 to 13.95 J/cm2). Greater density of the samples and fewer stress concentrators favorably influence the material's capability to withstand impact loads. Thus when density of the billets following six sintering cycles increases by 2.5%, their impact strength becomes 1.8 times higher. With a greater number of sintering cycles, the ductile dimples become significantly larger, while the increase in shock impact and density of the sintered material gradually slows down. The grain size substantially increases (in turn, suppressing pore healing) and density of the samples becomes greater over the total sintering time. X-ray diffraction and spectral analysis revealed additional phases after sintering and heat treatment. Additional fine-crystalline carbide and oxide phases become more distinguished with further increase in the sintering temperature and heat treatment. Brittle inclusions, along with residual porosity, present in sintered steel decrease the dynamic properties of the material. [ABSTRACT FROM AUTHOR]

Immense epidemiological studies have been indicated about adverse effects of the welding fumes on the health of the welders, especially respiratory problems and other physiological disorders. The different types of welding mechanisms produce aerosols/fumes that contain different metals including chromium (Cr) and manganese (Mn). In the present study, the welders of two age groups (adolescents and adults) were selected; simultaneously the age-matched adolescents and adults belong to nonindustrial area as referents/control subjects. Biological samples (scalp hair) were collected from welders and referents, along with analyzed for Cr and Mn by electrothermal atomic absorption spectrometer, prior to acid digestion. To evaluate the occupational exposure on the health of the workers, the clinical features and biochemical parameters of selected population (exposed and non-exposed age-matched groups) were also carried out. The resulted data indicated that the concentrations of Mn and Cr were significantly higher in scalp hair samples of welders as compared to referent subjects (p < 0.01), verifying the absorption/exposure of both metals produced in welding fumes. The high prevalence of anemia and stomach disorder was observed in adolescent than adult welding workers. The incidence of asthma and related symptoms was elevated in adult welders than in younger boys. The neurological problems were particularly observed in aged welders > 50 years, might be due to long time exposure of welding fumes contains different toxicant especially Mn in ill ventilation system of workshops. [ABSTRACT FROM AUTHOR]

This study investigates the effects of Multistage Heat Treatment (MSHT) on the development of an oxide-scale layer on the surface of FeCrAl sintered-metal-fibers. The oxide-scale layer was developed using an MSHT cycle at 930 °C for 1 h, followed by 960 °C for 1 h, and finally at 990 °C for 2 h. In this study, three samples were considered: Sample 1 was kept without thermal oxidation, while Samples 2 and 3 were exposed to one and eighteen MSHT cycles. Thermo-gravimetric analyses show that the weight gain of the heat-treated sample slows with time, confirming the growth of the protective oxide-scale layer. Scanning electron microscope images, after one MSHT cycle, reveal nonuniform oxide-scale growth with platelet-like on the surface. After eighteen MSHT cycles, however, clumped particles formed on the surface of the fibers. Atomic force microscopy was utilized to study the surface topography of the fibers. The results show that MSHT increases the surface roughness, where the surface roughness of one and eighteen MSHT cycles are the same. The x-ray diffraction analyses of the baseline sample and the sample with one MSHT cycle show pattern peaks of crystalline Fe2CrAl. In contrast, the results of eighteen MSHT cycles displayed diffraction pattern peaks of crystalline Cr and stable α-Al2O3. In summary, the results of this study reveal the changing nature of the oxide-scale layer. The findings of this study form the foundation for new techniques to protect and prepare the FeCrAl fibers as a support for catalysts. [ABSTRACT FROM AUTHOR]

We study the influence of decrease in the magnesium content and alloying with scandium, zirconium, manganese, and chromium on the structure, phase composition, strength, plasticity, corrosion potential, and corrosion current in alloys of Al−Mg and Al−Mg−Sc systems obtained with the help of a magnetohydrodynamic foundry. The positive influence of lowering of the content of magnesium and replacement of manganese with chromium in alloys of the Al−Mg−Sc system is demonstrated. [ABSTRACT FROM AUTHOR]

Aiming to understand fundamentally the alloying effects on the oxidation behaviors of Nb alloys, we combined the first-principles density functional theory and Kinetic Monte Carlo simulations to calculate systematically the binding energies, energy barriers, and diffusion coefficients of oxygen in Nb-X alloys where X = thirty 3d, 4d, and 5d transition metal (TM) elements plus Al and Si in this work. According to the calculated binding energies and energy barriers, we classify the alloying effects into three categories: (a) local short-range trapping effects (X = V, Ti, Cr, Y, Zr, and Hf); (b) local long-range trapping effects (X = Si and Ru); (c) non-local non-trapping effects (X = Mo, W, and Al). Our results show that the solute elements with the short-range trapping effects at near regions had the most effective reduction effects on the O diffusion coefficients while the long-range trapping effects and the non-local effects are less significant but non-negligible. Specifically, the reduction effects of the partial studied alloying elements decrease in the order of Y> V> Ti> Si> Cr> Zr> Hf> Al> Mo> Ru> W. For all the studied 30 TM elements, the diffusion coefficients were calculated for O at the near regions of the solute atoms and their trends were discussed. These intrinsic alloying effects on the oxygen diffusion in Nb alloys provide the theoretical evidence for the rational composition design of oxidation-resistant Nb alloys. [ABSTRACT FROM AUTHOR]

High silicon molybdenum-alloyed cast irons (SiMo) with spherical graphite are widely used for cast thin-wall exhaust manifolds, worked in high-temperature oxidation environment; therefore, prevention of surface degradation during service is important for such common application. The base SiMo and two alloyed by 1 pct Cr and 3 pct Al cast irons were tested at high temperatures in air and a combustion atmosphere to study the microstructural processes of surface degradation. It was shown that surface degradation of SiMo cast irons involves several microstructural processes, including the formation of multilayered oxide scale and development of internal porosity, resulting in decarburization of graphite nodules. Monitoring weight change of the specimens and Leco C analysis were used for decoupling the rates of surface oxidation and metal matrix decarburization. SEM/EDX analysis was used to study the phase composition of scale and high-resolution TEM analysis was performed to determine the detailed information about the atomic structure of protection layers formed on scale/metal matrix interface. The results were used to qualify and link different surface degradation mechanisms. In the base SiMo cast iron, the protection efficiency of formed amorphous silica layers is limited by intensive decarburization at temperatures above 700 °C. It was shown that Cr and Al alloying prevents surface degradation and suppresses decarburization by developing thermally stable oxide films on metal-scale interface, thus allowed to increase a safe working temperature up to 800 °C in air and the combustion atmosphere. [ABSTRACT FROM AUTHOR]

The application of cryogenic treatments is gradually increasing in tool steels. In this sense, these heat treatments can modify the mechanical properties of high chromium alloy steels. However, the influence of the cooling parameter (during quenching) is often neglected. This investigation aims at evaluating the effects of cooling parameter and cryogenic treatment on microstructure and fracture toughness of AISI D2 tool steel. The cooling parameter (λ) was defined as the cooling time from 800 to 500 °C divided by 100. During quenching, different cooling parameters (λ1 = 2.8 and λ2 = 1.8) were employed, and the samples were tempered three times or, besides, cryogenically treated by a single tempering. Later, the samples were evaluated through phase analyses and their proportions, sizes, and distribution of carbides by optical and scanning electronic microscopy, hardness measurements, x-ray diffraction, and fracture toughness tests. For the λ2 cooling parameter followed by cryogenic treatment, the results presented an increase of 51% over the initial condition of secondary carbides. However, the higher hardness values were found in the λ1 cooling parameter followed by cryogenic treatment. In the fracture toughness evaluation, a reduction of 8% in KIC was observed for samples with cryogenic cycles compared to the samples without it. [ABSTRACT FROM AUTHOR]

The possibility of fabrication of granulate based on an alloy of the Fe – Cr – Co system with reduced (7 – 10%) cobalt content for synthesizing permanent magnets by the MIM process is considered. A multicomponent granulate composition (polyformaldehyde, high-pressure polyethylene, stearic acid, beeswax) of spherical powders of the Fe – Cr – Co alloy with reduced cobalt content is produced by gas sputtering (average particle diameter 4.2 μm, degree of polydispersity 0.75). The microstructure of the granulate and its granulometric composition are studied. The characteristics of the granulate (the mean diameter of the particles, their morphology and degree of polydispersity) exceed qualitatively the characteristics of the Catamold 42CrMo4 high-quality granulate produced by the BAFS Company. [ABSTRACT FROM AUTHOR]

A six-component system of CoNiCuCrx high-entropy alloys with different contents of chromium (where x = 0, 0.5, 1.0, 2.0, and 3.0 mole) is obtained by the method of argon-arc melting in a МІFІ-9 study. By the methods of X-ray diffraction analysis, scanning-electron microscopy, and indentation, we investigate the influence of chromium on the crystalline structure, microstructure, and hardness of these alloys in the as-cast state. In their structure, depending on the chromium content, we detect a mixture of the following phase components: two face-centered cubes + a body-centered cube + an intermetallic σ-phase (FCC1 + FCC2 + BCC + σ). It is also established that, as the chromium content increases, we observe the formation of the bcc structure and the σ-phase, which is the predominant factor of hardening of the alloy. [ABSTRACT FROM AUTHOR]

To investigate the effects of Cr doping on the microstructure and tribological properties of multi-layered diamond-like carbon (DLC) films, Cr-DLC films with Cr contents ranging from 0 to 22 at.% were deposited on 0Cr19Ni10 stainless steel and Si wafer surfaces by unbalanced magnetron sputtering. The thickness of the transition layer is 180 nm and the Cr-DLC film ranging from 1.3 to 1.5 µm. The microstructure, mechanical and tribological properties of the films were systematically investigated at room temperature in atmospheric environment. Results show that increasing the Cr target current can effectively improve the incident particle density and reduce surface roughness. As a strong carbon metal, Cr has significant influence on the structure and properties of the film for bonding with carbon atoms during deposition. High-energy Cr particles are favorable for films to increase the sp3 hybrid bond ratio and reduce internal stress. The high-hardness sp3 hybrid phase, Cr carbide, oxide dispersion can effectively improve the mechanical properties of the film, but overdoping is detrimental for mechanical properties of the film. The internal stress shows a continuous trend of decreasing with the increasing Cr content and it reduced up to 80% compared with pure DLC films. The films prepared with Cr sputtering current of 0.4 A demonstrate the best tribological properties, and the friction coefficient and wear rate are 0.15 and 2.9 × 10−7 mm3/Nm, respectively. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEA) based on CoNi systems contain of Mn, Cr, and Al elements were prepared through mechanical alloying and subsequent annealing method. The structural and magnetic properties of CoNi alloy system were discussed based on the results of X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and vibrating sample magnetometer (VSM) analysis methods. There were different chemical compounds formed in CoNi-Mn-Cr samples, while a simple solid solution phase with FCC or BCC structural evolved in CoNiMnCrAl high entropy alloy after mechanical milling and subsequent annealing process at 750 and 900 °C. This sample exhibited excellent soft magnetic properties with the saturation magnetization and coercivity of about 31 emu/g and 39 Oe, respectively, after annealing at 750 °C. Annealing at 900 °C could improve soft magnetic properties of CoNiMnCrAl high entropy alloy in the range of 58 emu/g for saturation of magnetization and 18 Oe for coercivity due to the formation of a single solid solution phase with BCC structure. [ABSTRACT FROM AUTHOR]