Fe-Ni Matrix Research Articles

Tribological properties of Fe–Ni-based composites with Ni-coated reduced graphene oxide–MoS2

Fe–Ni-based composites with Ni-coated reduced grapheme oxide (RGO)–MoS2 were fabricated by powder metallurgy technique, and their morphology, phase composition, and tribological properties at different temperatures were investigated systematically. Results showed that Fe–Ni-based composite with Ni-coated RGO–MoS2 possessed much more uniform and denser microstructure, and higher hardness than that with RGO–MoS2. Furthermore, Ni-coated RGO–MoS2 additive greatly allowed increasing the friction-reducing and wear-resistant properties, due to the reinforcing and lubricating effect new phase (Fe3W3C, CrxS1+ x, etc.) and the improvement on interfacial compatibility between Ni-coated RGO–MoS2 and Fe–Ni matrix. In particular, as the content of Ni-coated RGO–MoS2 was 5 wt%, the friction coefficient and wear rate of the corresponding composite was decreased nearly 50% and 75%, respectively. More importantly, Ni-coated RGO–MoS2 reinforced composite kept excellent tribological properties at elevated temperature. Its friction coefficient decreased firstly with the increased temperature from 25℃ to 400℃, then increased slightly when the temperature increased to 600℃. Besides, the wear rate was only 0.73–0.9 × 10−4 mm3/Nm during the whole temperature range. This suggested that Ni-coated RGO–MoS2 was a promising additive of metallic-based composites suitable for high-temperature sliding condition.

Effect of high energy ball milling on structure and properties of 95W-3.5Ni-1.5Fe heavy alloys

In this article, an attempt is made to prepare tungsten heavy alloy (WHA) powder by high energy ball milling of 95wt% W, 3.5wt% Ni and 1.5wt% Fe in a dual drive planetary ball mill (DDPBM). The present study mainly focusses on the effect of milling on density, microstructure and mechanical properties of sintered WHAs. The minimum crystallite size of 18nm was observed in 15h milled WHA powder. Sintering of WHAs was carried out at 1500°C for 1h in hydrogen atmosphere. The sintered samples prepared from un-milled and ball milled WHA powders were characterized for microstructure (SEM equipped with EDS) and mechanical properties (Rockwell hardness and nanoindentation). The internal attributes and uniformity in distribution of W spheroids in sintered WHA were investigated with X-ray microcomputed tomography (X-ray μ-CT). All sintered samples exhibited sintered density in the range of 97.1 to 98.6% theoretical. Uniform distribution of W spheroids in Ni-Fe matrix was observed in sintered samples. The mean grain size of sintered WHAs varies in the range of 22.7–31.1μm and W-W contiguity (CWW) ranges from 0.58–0.69. Despite relatively less density (97.1%), the sintered WHA prepared from 15h milled powder offered good combination of bulk hardness ~64.8 HRA and elastic modulus ~431GPa.

Friction welding of tungsten heavy alloy with aluminium alloy

This paper is a study of mechanical properties and microstructure of friction welded coupe of weight heavy alloy (WHA) with aluminium alloy (AA). Scanning electron microscopy (SEM) was used for investigation of the fracture morphology and phase transformations taking place during friction welding process. Chemical compositions of the interfaces of the welded joints were determined by using energy dispersive spectroscopy (EDS). Effects of friction time (FT) and friction pressure (FP) on the ultimate tensile strength (UTS) were studied by plotting graphs. The maximum average strength of 234MPa, which is 84.78% of the aluminium alloy base material, is achieved at a friction time of 3.5s and friction pressure of 40MPa, respectively. The UTS of joints increases with increasing of FP and FT and then decreases after reaching the maximum value, with increase of friction load and time. Microstructure of friction welds consisted of fine equiaxed grains (formed due to dynamic recrystallization) and coarse grains in the periphery region on AA side. A plastic deformation in the direction of burrs is visible mainly on AA side. EDS-SEM scan line analyses across the interface have not confirmed the diffusion of tungsten and nickel to AA side. The nature of the friction welding joints is rather adhesive than diffusive. The EDS point spectrometry showed some enrichment of Ni-Fe matrix with Al atoms close to the joint. Absence of intermetallic phases was found in the weld interface on SEM level observation. The fracture procedes mainly through the cleavage planes at the interface.

Diffusion Control and Metallurgical Behavior of Successive Buttering on SA508 Steel Using Ni–Fe Alloy and Inconel 182

The metallurgical deterioration and carbon diffusion caused during welding in the vicinity of the fusion interfaces between dissimilar metals have been investigated in case of gas tungsten arc and shielded metal arc welded SA508Gr.3Cl.1 steel substrate with Ni–Fe alloy and Inconel 182. The study was conducted to investigate the effect of Ni–Fe matrix as buffer layer and SMAW process for buttering deposition on the carbon diffusion and metallurgical changes. Quantitative measurement and validation of carbon/alloying elements distribution in as-welded, thermally aged, and postweld heat-treated conditions were performed in buttering deposits by using optical emission spectrometry and electron probe microanalysis. The extent of carbon diffusion has been estimated using Groube’s diffusion couple and confirmed with microstructure microhardness and X-ray diffraction. Martensite formation has been estimated for its thickness and validated with metallurgical properties. The effect of buffer layer is significant for carbon diffusion and tempering of martensite with thermal aging, PWHT, and multipass deposition. The concentration and activity gradient of carbon has been established due to Ni–Fe matrix as buffer layer and higher dilution for buttering. The obtained results are confirming the control of carbon diffusion and lesser metallurgical deterioration in suggested buttering procedure.

Densification of W–Ni–Fe powders using laser sintering

In this paper, Laser Sintering (LS) of 90%W–7%Ni–3%Fe (wt.%) powders have been investigated, with the goal to understand the influence of final density by laser power, scanning speed, laser trace width, and the number of scanning passes. The results suggest that the laser power and scanning speed are the most important factors influencing density; the influence of trace width and number of scanning passes are not significant. With the increase of laser power and decrease of scanning speed, higher density can be achieved. The microstructure analysis indicated that the porosity changed from open porosity to closed porosity with higher laser energy input. Energy-Dispersive X-ray Spectroscopy (EDX) analysis shows that during the sintering process, W was not melted but dissolved into the Ni–Fe matrix. Contact flattening and grain accommodation of W grains have been observed. It suggests that both rearrangement and solution-reprecipitation mechanisms are responsible for the densification. The sintered density with respect to laser power and scanning speed was modeled by continuum modeling theory and compared with experimental results.

Microstructure and Properties of Si3N4 and TiN Nano-Particles Reinforced Electrodeposited Functional Ni-Fe Matrix Nanocomposite

Functional Ni-Fe/Si3N4-TiN nanocomposite coatings were electro-codeposited from sulphamate-N,N-dimethylformamide bath containing dispersed Si3N4 and TiN nano-particles 10 g/L each. The effect of current density on the incorporation of the ceramic particulate and on the properties of the deposits was investigated. The deposited coatings were characterized using various advanced techniques such as scanning electron microscopy, X-ray diffractometry, transmission electron microscopy and atomic force microscopy. Physical properties such as microhardness, corrosion resistance and magnetic property of the composite were evaluated. Results indicated that Si3N4 and TiN both the ceramics has prodigious effect on the microstructure and properties of the coating. Ni-Fe/Si3N4-TiN coatings showed higher hardness in comparison with the Ni-Fe, Ni-Fe/Si3N4 and Ni-Fe/TiN coatings. Hardness values of the coatings ranged from 650 HV to 773 HV and the coating with maximum hardness was obtained at current density 3.0 A dm−2. Further, significant influence had been observed on corrosion resistance by the ceramic particles. Magnetic investigations revealed characteristic superparamagnetic behavior of the coatings.

In situ synthesis of WC ceramic particle reinforced composite coating by GTAW

WC ceramic particles reinforced composite coatings were in situ synthesised on the surface of Q235 steel by GTAW processing using mixtures of W, C, Ni, B–Fe and a small amount of Si iron. Microstructures and phase of the coating were analysed by scanning electron microscope, energy dispersive spectrometer and X-ray diffractometer. Furthermore, microhardness and abrasion resistance also were studied using microhardness tester and abrasive tester, respectively. The results showed that the coating was no pore and crack free. The coating consisted of FeNi matrix, M7C3, Ni2Si, Ni3B, Fe2B and WC blocky particles. Owing to the uniform distribution of in situ synthesised carbide particles, high hardness and excellent wear resistance were achieved. The maximum hardness of the coating was 1578.8 HV0.2. The relative wearability of the composite was 23.5 times higher than Q235 steel substrate which showed good wear resistance.

Novel Fe–Ni-Graphene composite electrode for hydrogen production

We have developed a novel, efficient and economical composite electrode for hydrogen production. The electrode has been formed by embedding graphene in the Fe–Ni matrix via room temperature electrodeposition. The obtained active coatings have been tested for their efficiency and performance as electrode surfaces for hydrogen evolution reaction (HER) in 6 M KOH by cyclic voltammetry and chronopotentiometry techniques. The coating obtained at 60 mA cm−2 exhibited approximately 3 times higher activity for hydrogen production than that of binary Fe–Ni alloy. Addition of graphene to electrolyte bath resulted in porous 3D projections of nano-sized spheres of Fe–Ni on the surface of graphene, which effectively increased the electrochemically active surface area. XPS analysis results showed the equal distribution of both Ni metal and NiO active sites on the composite. The addition of graphene favoured the deposition of metallic nickel, which accelerated the rate determining proton discharge reaction. All these factors remarkably enhanced the HER activity of Fe–Ni-Graphene (Fe–Ni-G) composite electrode. The Tafel slope analysis showed that the HER follows Volmer-Tafel mechanism. The structure–property relationship of Fe–Ni-G coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results.

Solution combustion synthesis of Fe-Ni-Y2O3 nanocomposites for magnetic application

Fe-Ni-Y2O3 nanocomposites with uniform distribution of fine oxide particles in the gamma FeNi matrix were successfully fabricated via solution combustion followed by hydrogen reduction. The morphological characteristics and phase transformation of the combusted powder and the Fe-Ni-Y2O3 nanocomposites were characterized by XRD, FESEM and TEM. Porous Fe-Ni-Y2O3 nanocomposites with crystallite size below 100 nm were obtained after reduction. The morphology, phases and magnetic property of Fe-Ni-Y2O3 nanocomposites reduced at different temperatures were investigated. The Fe-Ni-Y2O3 nanocomposite reduced at 900 °C has the maximum saturation magnetization and the minimum coercivity values of 167.41 A/(m2·kg) and 3.11 kA/m, respectively.

Producing a gradient-composition nanocrystalline structure on nitrided surfaces of invar-type Fe-Ni alloys using megaplastic deformation

A nanocrystalline Fe-Ni matrix strengthened by dispersed CrN and TiN nitrides has been produced on the ion-plasma-nitrided surfaces of the austenitic Fe-Ni38-Cr15 and Fe-Ni36-Ti4 alloys using cyclic “nitride dissolution-nitride precipitation” phase transformations induced by megaplastic deformation. The high-pressure torsion of the nitrided alloys has led to the dissolution of the CrN nitrides and Ni3Ti intermetallic compounds, which appeared in the matrix, in the surface layer and to the mechanical alloying of the nitrided subsurface layer and the unnitriderd bulk of the specimens. Subsequent annealing has resulted in the formation of secondary nitrides, which propagated to a depth substantially exceeding the thickness of the original nitrided layer.

ERRATUM: PROPERTIES OF BULK Fe-Ni/CNT NANOCOMPOSITES PREPARED BY MECHANICAL MILLING AND SINTERING

The effects of carbon nanotubes (CNTs) on mechanical and tribiological properties of the NiFe/CNT composites prepared by high energy mechanical alloying and hot pressing, were investigated. Bulk samples were prepared by sintering of cold pressed (300 MPa) samples at 1040°C for 1 h. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and optical microscopy were employed for evaluation of the phase composition, surface morphology and porosities of the samples. The microhardness of as-milled Ni3Fe and NiFe powders reached to 720 and 650 VHN, respectively. The hardness of NiFe and Ni3Fe bulk samples reduced to 190 and 270 Vickers because of the grain growth during sintering and remaining porosity. The hardness of NiFe-CNT and Ni3Fe-CNT bulk samples reached to 360 and 400 Vickers, respectively. The friction and wear properties of the bulk samples were investigated under dry conditions using a pin-on-disk test rig under an applied load of 8 N. The wear rate, mass loss and friction coefficient of the composite samples remarkably reduced in comparison with NiFe and Ni3Fe matrix alloys which demonstrate effects of the CNTs on mechanical and tribiological behavior of the composites resulting from the excellent mechanical properties and unique topological structure of the CNTs.

Formation of monophase Fe23B6-type alloy via crystallization of amorphous Fe–Ni–Nb–B system

This study is focused on rapidly quenched Fe–Ni–Nb–B system in a wide compositional range of substitution of Fe by Ni with varying boron content. This system is known to have a good glass forming ability and to crystallize in either two distinct transformation stages or in one single step, depending on the boron content and on the ratio of Fe to Ni. On the basis of our results we have identified and quantified the formation of a complex phase (Fe–Ni–Nb)23B6 alongside with fcc-FeNi. In a specific case it was possible to obtain only a single-phase Fe23B6 type alloy and thus to explore and characterize this phase, especially as there is no prior evidence of preparing such a monophase system. Detailed characterization of composition, structure and selected magnetic properties of both phases is presented. We have proposed a model of possible local structural and chemical arrangement in (Fe–Ni–Nb)23B6 phase as well as possible building units responsible for specific features of transformation from amorphous state and for preferential formation of this phase. This was confirmed by refinement of selected X-ray patterns together with high resolution (S)TEM analysis combined with energy filtered TEM. EFTEM analysis has shown a unique interface between the Fe23B6-type phase and the remaining FeNi matrix in systems where both phases were present. On the other hand, high resolution z-contrast STEM analysis applied to a single phase system revealed atomic positions of constituent atoms. Niobium was confirmed on positions as predicted by the proposed structural model and as refined from the diffraction experiments. Conventional high resolution TEM analysis was used to characterize the Fe23B6-type grains with respect to defects and faults.

Synthesis and characterization of permalloy-reinforced Al2O3 nanocomposite powders by mechanical alloying

Intermetallics of Fe and Ni, which are known as permalloy, are under attention due to their excellent magnetic performance. Besides, mechanical properties of the materials can be improved by decreasing crystallite size of FeNi intermetallics or by reinforcing them with hard secondary phases such as Al2O3. In this study, FeNi–Al2O3 nanocomposite powders with three different compositions were successfully synthesized through mechanical alloying of Fe2O3, Ni, and Al powders mixture. Characterization of the samples was accomplished by scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and X-ray diffraction. Effects of various parameters such as chemical composition of received materials, milling time, and annealing on the phase evolution, morphology, and microhardness of samples were investigated. It was found that by the addition of Fe as diluent, the required milling time for formation of FeNi intermetallic increased. By increasing milling time, mean crystallite size of FeNi decreased and reach to about 28 nm for FeNi-30 wt% Al2O3 nanocomposite powder sample. TEM observations also showed that in situ-formed Al2O3 particles, with particle size of about 65 nm, were uniformly dispersed within FeNi matrix.

Structural and magnetic characterization of the “GASPAR” meteorite from Betéitiva, Boyacá, Colombia

A structural and magnetic characterization has been performed of a plate obtained from the “Gaspar” meteorite from the Otenga region of the Beteitiva municipality, Boyaca, Colombia. The sample was provided by Ingeominas (Colombian Geological Agency). After the studies the sample was classified as an octahedral iron meteorite, due the Fe and Ni concentrations and the Widmanstatten pattern which was observed on the surface of the sample. The plate shows a crack which divides the sample in two regions (side A and B, respectively). Both sides were studied using techniques like X-rays diffraction (XRD), Mossbauer spectrometry, optical microscopy, and scanning electronic microscopy (with EDAX). On both sides an iron Fe-Ni matrix (kamacite) was found; a large quantity of carbon in the form of graphite and in two types: nodular and laminar; and different preferential orientation in both sides of the sample. The studies permit to prove that Gaspar is a fragment of the registered Santa Rosa de Viterbo meteorite.

Hydrothermal modification of the Sikhote-Alin iron meteorite under low pH geothermal environments. A plausibly prebiotic route to activated phosphorus on the early Earth

The Sikhote-Alin (SA) meteorite is an example of a type IIAB octahedrite iron meteorite with ca. 0.5wt% phosphorus (P) content principally in the form of the siderophilic mineral schreibersite (Fe,Ni)3P. Meteoritic in-fall to the early Earth would have added significantly to the inventory of such siderophilic P. Subsequent anaerobic corrosion in the presence of a suitable electrolyte would produce P in a form different to that normally found within endogenous geochemistry which could then be released into the environment. One environment of specific interest includes the low pH conditions found in fumaroles or volcanically heated geothermal waters in which anodic oxidation of Fe metal to ferrous (Fe2+) and ferric (Fe3+) would be coupled with cathodic reduction of a suitable electron acceptor. In the absence of aerobic dioxygen (Eo=+1.229V), the proton would provide an effective final electron acceptor, being converted to dihydrogen gas (Eo=0V). Here we explore the hydrothermal modification of sectioned samples of the Sikhote-Alin meteorite in which siderophilic P-phases are exposed. We report on both, (i) simulated volcanic conditions using low pH distilled water and (ii) geothermally heated sub-glacial fluids from the northern Kverkfjöll volcanic region of the Icelandic Vatnajoküll glacier. A combination of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements using the scanning Kelvin probe (SKP) method reveals that schreibersite inclusions are significantly less susceptible to anodic oxidation than their surrounding Fe–Ni matrix, being some 550mV nobler than matrix material. This results in preferential corrosion of the matrix at the matrix-inclusion boundary as confirmed using topological mapping via infinite focus microscopy and chemical mapping through Raman spectroscopy. The significance of these observations from a chemical perspective is that electrochemically noble inclusions such as schreibersite are likely to have been released into the geological environment through an undermining corrosion of the surrounding matrix, thus affording localised sources of available water-soluble, chemically reactive P in the form of H-phosphite [H2PO3-, Pi(III) as determined by 31P NMR spectroscopy]. This compound has been shown to have considerable prebiotic chemical potential as a source of condensed P-oxyacids. Here we demonstrate that Pi(III) resulting from the hydrothermal modification of Sikhote-Alin by sub-glacial geothermal fluids can be readily dehydrated into the condensed P-oxyacid pyrophosphite [H2P2O52-, PPi(III)] by dry-heating under mild (85°C) conditions. The potential significance of this latter condensed P-compound for prebiotic chemistry is discussed in the light of its modified chemical properties compared to pyrophosphate [H2P2O72-, PPi(V)].

Fabrication of FeNi–Al2O3 nanocomposites and optimization of mechanical properties using Taguchi method

Abstract FeNi–Al2O3 composites are under attention for many applications because of their good magnetic properties, high strength and fracture toughness and excellent corrosion and wear resistance. In the current study, FeNi–Al2O3 nanocomposite powders were synthesized through mechanical alloying of Fe2O3, Al and Ni powder mixture. Bulk samples were prepared under subsequent cold pressing and sintering processes. Study of the phase evolution using SEM, EDS and XRD showed that FeNi matrix nanocomposites reinforced with 10, 15 and 30 wt.% of Al2O3 were fabricated in 300, 240 and 180 min of milling, respectively. Mean crystallite size of FeNi phase at these samples after 720 min milling was calculated about 28, 35 and 22 nm, respectively. Effect of various parameters such as Al2O3 weight percentage, uniaxially cold pressure, sintering temperature and sintering time on the fabrication (densification and consolidation) and mechanical properties (hardness, compression strength and specific wear rate) of these nanocomposites was investigated. Because of numerous experiments needed, design of experiment based on Taguchi method was applied. Considering optimized condition offered by analysis of variance (ANOVA), maximum density (5.314 g/cm3), maximum hardness (786 HV), maximum compression strength (97.76 MPa) and minimum specific wear rate (0.0251 mm3/Nm) of FeNi–Al2O3 nanocomposites were obtained.

Mechanochemical Synthesis and Characterization of FeNi-Al2O3 Nanocomposites

In this Study, FeNi-Al2O3 nanocomposites with three different compositions were successfully synthesized through mechanical alloying of Fe2O3, Ni and Al powders mixture. Characterization of the products was accomplished by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The effect of various parameters such as chemical composition of starting materials, milling time and annealing on the phase evolution, morphology and microhardness of samples was investigated. It was found that FeNi matrix nanocomposites reinforced with 10, 15 and 30wt.% of Al2O3 were fabricated in 300, 240 and 180 min of milling, respectively. The crystallite size of the intermetallic FeNi phase and particle size of Al2O3 in the 720 min milled FeNi-30wt.%Al2O3 nanocomposite sample were calculated 28nm and 5.15 µm, respectively. Microhardness results also showed the same sample had the maximum hardness value of 790 HV.

Influence of SiC nanoparticles and saccharin on the structure and properties of electrodeposited Ni–Fe/SiC nanocomposite coatings

In this study, Ni–Fe/SiC nanocomposite coatings with smooth and crack-free surface were successfully prepared by means of the conventional electrodeposition in the presence of saccharin in electrolyte. The goal of this work was to investigate the effect of SiC nanoparticles and saccharin on the structure and properties of permalloy nanocomposite coatings. The nanocomposite coatings were characterized using optical and scanning electron microscopy, energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) technique. The significant variation in the crystallographic texture of the coatings was observed due to the addition of SiC nanoparticles and saccharin in the electrodeposition bath. Increasing the amount of saccharin in the electrolyte led to a change in the texture from a (2 0 0) fiber texture to mixed (3 1 1) and (2 0 0) textures. Our results indicated that inclusion of SiC nanoparticles suppressed the preferred growth direction of the Ni–Fe matrix, resulting in a decrease in the sharpness of the (2 0 0) fiber texture and formation of a more random texture. The presence of SiC nanoparticles in the metallic matrix also led to the production of composite films with better corrosion resistance and higher microhardness than the Ni–Fe coating.

Development of the inner oxide zone upon steam oxidation of an austenitic stainless steel

The oxidation behaviour of TP 347H FG in mixtures of water, oxygen, and hydrogen was investigated in the temperature range 500–700°C for a fixed oxidation time of 336 h. The samples were characterised using reflective light and electron microscopy methods. Thin discontinuous double-layered oxide scales developed during oxidation at 500°C, whereas continuous double-layered oxide scales covered the entire sample surface after oxidation at 600 and 700°C. The major part of the scale grew into the former alloy grains, whereas Fe—Cr spinel grew along the former alloy grain boundaries. TEM and EELS investigations revealed that the part of the scale that grows into the alloy grains consists of particles of Fe—Cr spinel embedded in a metallic Fe—Ni matrix, which indicates that this part of the scale grows by an internal oxidation mechanism. Growth of the internal oxidation zone at high humidity (46%) is not significantly affected by the type of carrier gas used.

Room temperature magnetic stabilization of buried cobalt nanoclusters within a ferromagnetic matrix studied by soft x-ray magnetic circular dichroism

Single dusting layers of size-selected Co nanoclusters (NCs) of sizes ranging from 1.5–5.5 nm have been deposited by a gas-phase aggregation method in ultrahigh vacuum, and embedded within a NiFe matrix. Magnetic hysteresis loops have been obtained using soft x-ray magnetic circular dichroism, which shows that these Co NCs embedded in NiFe exhibit room temperature ferromagnetism with identical coercivity to the surrounding NiFe film. The strong local exchange field at the interface between NiFe and Co NCs, combined with the magnetic anisotropy of the NiFe film, allows stabilization of NC ferromagnetism which persists to room temperature.