Ni Alloy Powder Research Articles

AlCrCuFeNi3 Dual‐Phase High‐Entropy Alloy Manufactured by Selective Laser Melting in Situ Alloying: Alloying Degree, Microstructure, and Strength

Herein, the Co‐free, low‐cost dual‐phase AlCrCuFeNi3 high‐entropy alloy (HEA) is successfully developed by in situ alloying induced by selective laser melting (SLM) technique from an initial mixture of Ni and AlCrCuFeNi alloy powders. The effect of process parameters on the microstructure and strength of the SLMed AlCrCuFeNi3 HEA is investigated. It is found that the degree of in situ alloying strongly depends on the laser power. Low laser power leads to insufficient in situ alloying, and a large amount of incompletely diffused Ni and body‐centered cubic (BCC) AlCrCuFeNi alloy powder blocks remain, forming the eutectic structure with alternating face‐centered cubic and BCC phases. With the increase in laser power, the degree of in situ alloying increases, resulting in a decrease in the number of BCC phases as well as the yield strength of the SLMed AlCrCuFeNi3 HEA. The highest yield strength of the SLMed AlCrCuFeNi3 HEA is obtained at low laser power (200 W–600 mm s−1), reaching 689.02 ± 17.54 MPa.

Plasma Spheroidization of Al–Zn–Mg–Fe–Ni Alloy Powders for Selective Laser Melting

Plasma Spheroidization of Al–Zn–Mg–Fe–Ni Alloy Powders for Selective Laser Melting

Processing, Microstructure, and Properties of Bimetallic Steel-Ni Alloy Powder HIP

This work explores technical feasibility in hot isostatic pressing (HIP) manufacturing of an integral bimetallic component using steel and Ni alloy powder for supercritical carbon dioxide (sCO2) turbomachinery. Lab-scale bimetallic HIP specimens using HAYNES® 282® and SS316L or SS415 powder are investigated in powder configuration, heat treatment, microstructure, and tensile properties up to 400 °C. Interdiffusion profiles at dissimilar alloy interfaces caused by HIP cycle is predicted by DICTRA simulations and validated by electron probe microanalysis (EPMA). The interdiffusion distance of most elements is around 100 μm, while C and N have a higher interdiffusion distance. Dense distribution of Ti-rich carbonitrides and alumina particles are found to decorate prior particle boundaries near joining interface on the 282 side, affecting tensile strength across interface as well as tensile failure location. A higher amount of excessive carbonitride formation near interface is observed in SS316L/282 than in SS415/282, which is consistent with the predicted greater degree of interdiffusion effect in SS316L/282. Typical HAYNES® 282® heat treatment condition is applicable to 282/SS316L and 282/SS415 combinations, resulting in a higher strength than cast CF8M and CA6NM. A pilot-scale bimetallic SS415/282 pipe is then demonstrated to show the promise of scaleup.

Properties of 6061 aluminum alloy treated with laser alloying

In this study, a laser surface alloying method is used to alloy 1.8 mm thick 6061 aluminum alloy sheets with Ni alloy powder. The mechanical properties of the resulting alloy are investigated. The experimental results show that, following laser surface alloying, a crack-free zone can be generated but some fine porosity appears. The hardness and the wear properties of the laser alloying specimens are superior to those of the Al-matrix. A hardness of 539 HV is achieved, which is five times greater than that of the Al-matrix. As a result, the laser alloying specimens exhibit excellent wear properties and higher sliding wear distances and speeds compared to those of the Al-matrix, whereby the sliding distance is greater by up to eight times and the sliding speed is increased four-fold.

Fabrication and Damping Property of Porous Cu–Al–Ni Shape Memory Alloys Fabricated using Different Raw Materials

Porous Cu–Al–Ni shape memory alloys (SMAs) are fabricated via powder metallurgy method using Cu, Al, Ni powders and Cu–Al–Ni alloy powder as raw materials, respectively. It is found that the two kinds of specimens have similar macroscopic morphologies: connected pores are uniformly distributed in the Cu–Al–Ni matrix, forming a 3D network structure. By comparison, the specimen fabricated using alloy powder has much finer microstructures than the specimens fabricated using Cu, Al, Ni powders. After adding Ce element to the latter, the microstructure of the Cu–Al–Ni matrix is significantly refined because of the formation of Ce‐rich particles. Damping tests show that the latter has superior damping capacity than the former. With the increase of Ce content, the damping of the latter increases first and then decreases. When the Ce content reaches 0.05 wt%, the highest damping can be achieved. Correlated mechanisms are discussed based on the microstructural observations.

Hydrogen storage property improvement of ball-milled Mg2.3Y0.1Ni alloy with graphene

In this paper, Mg2.3Y0.1Ni + x wt.% graphene (x = 1, 3, 5, 7) composite hydrogen storage alloys were fabricated by mechanical ball milling of Mg2.3Y0.1Ni alloy powder and graphene. The experimental results show that the phases of the composite alloy consist mainly of Mg2Ni, Mg, MgNi2 and Ni3Y phases, and graphene tends to be distributed at the edges of the alloy, increasing the phase boundary resulting from the contact between the C-boundary and the Mg2.3Y0.1Ni alloy, providing more channels for the diffusion of H2. In which 7 wt.% of graphene is added, the gestation period of the composite alloy completely disappears. And the ball-milled alloy with 3 wt.% graphene at different temperatures has the highest hydrogen uptake in 2 min and the highest hydrogen release in 10 min. At 573 K, the composite alloy has a hydrogen absorption capacity of 3.251 wt.% H2 in 2 min and reaches 90.21% of the maximum hydrogen absorption, while it is able to release 3.389 wt.% H2 in 10 min and reaches 99.04% of the maximum hydrogen release. And the composite alloy with 3 wt.% graphene has the smallest dehydrogenation activation energy. The absolute value of the enthalpy change is reduced from 60.1 kJ/mol to 54.8 kJ/mol, and the desorption enthalpy change is reduced from 73.4 kJ/mol to 67.5 kJ/mol.

Modeling residual stresses of functionally graded deposits using the PTAAM

High maintenance costs due to significant abrasive wear of components is experienced in the energy and mining sectors despite the current use of tough and hard coatings. During the coating process significant tensile residual stresses may build up and result in premature failure of a component. These tensile stresses can be reduced by adopting functionally graded structures of the composite. The main goal of the present study is to design an ideal material gradient in the additively manufactured composite using the plasma transferred arc (PTA) with a WC-Ni alloy graded in WC. To develop a comprehensive analysis of the functionally graded deposit, the thermal history of the WC and Ni alloy powders are first simulated as they travel through the plasma and deposit on the substrate. The initial temperature of each deposited bead depending on the WC content is deduced. These results are used as an input to predict the temperature and stress history of the solidifying deposit. Thermal stresses are computed and trends of residual stresses are obtained as a function of the WC gradient selected. The trends obtained are compared quantitatively before concluding on the most favorable gradient for this wear resistance application.

Mechanism of Enhanced Flowability/Spreadability in 3D Printed Ni Alloy Powder

Mechanism of Enhanced Flowability/Spreadability in 3D Printed Ni Alloy Powder

Correlation between surface texture and internal defects in laser powder-bed fusion additive manufacturing

The availability of an in-situ monitoring and feedback control system during the implementation of metal additive manufacturing technology ensures that high-quality finished parts are manufactured. This study aims to investigate the correlation between the surface texture and internal defects or density of laser-beam powder-bed fusion (LB-PBF) parts. In this study, 120 cubic specimens were fabricated via application of the LB-PBF process to the IN 718 Ni alloy powder. The density and 35 areal surface-texture parameters of manufactured specimens were determined based on the ISO 25,178–2 standard. Using a statistical method, a strong correlation was observed between the areal surface-texture parameters and density or internal defects within specimens. In particular, the areal surface-texture parameters of reduced dale height, core height, root-mean-square height, and root-mean-square gradient demonstrate a strong correlation with specimen density. Therefore, in-situ monitoring of these areal surface-texture parameters can facilitate their use as control variables in the feedback system.

In Situ Bulk Observations and Ab Initio Calculations Revealing the Temperature Dependence of Stacking Fault Energy in Fe\u2013Cr\u2013Ni Alloys

The dependence of stacking fault energy ({gamma }_{text{SFE}}) on temperature in austenitic Fe–Cr–Ni alloy powders was investigated by in situ high energy synchrotron X-ray diffraction and ab initio calculations in the temperature range from − 45 °C to 450 °C. The X-ray diffraction peak positions were used to determine the stacking fault probability and subsequently the temperature dependence of γSFE. The effect of temperature on the diffraction peak positions was found to be mainly reversible; however, recovery of dislocations occurred above about 200 °C, which also gave an irreversible contribution. Two different ab initio-based models were evaluated with respect to the experimental data. The different predictions of the models can be explained by their respective treatment of the magnetic moments for Cr and Ni, which is critical for the alloy compositions investigated. Ab initio calculations, taking longitudinal spin fluctuations (LSF) into consideration within the quasi-classical phenomenological model, predict a temperature dependence of {gamma }_{rm SFE} in good agreement with the experimentally evaluated trend of increasing γSFE with increasing temperature: left|Updelta {gamma }_{rm SFE}/Updelta Tright|=0.05 {text{mJ}} {text{m}}^{-2}/{text{K}}. The temperature effect on γSFE is similar for all three investigated alloys: Fe–18Cr–15Ni, Fe–18Cr–17Ni, Fe–21Cr–16Ni (wt pct), while their room temperature {gamma }_{rm SFE} are evaluated to be 22, 25, 20 mJ m−2, respectively.

Inductively Coupled Plasma Process for Reconditioning Ti and Ni Alloy Powders for Additive Manufacturing

Inductively Coupled Plasma Process for Reconditioning Ti and Ni Alloy Powders for Additive Manufacturing

Structure and еlectrocatalytic ability of Sn–Ni alloy powders prepared by direct and pulse electrodeposition

Sn–Ni alloy powders with a wide range of compositions and structures by constant current, constant potential and pulse potential modes were deposited. Increasing the Ni2+/Sn2+ ratio in the electrolyte from 1 to 8 in both stationary modes leads to changes in the shape and composition of the powder particles from typically dendritic (5 ÷ 7 wt%Ni), to cauliflower-like (90 ÷ 98 wt%Ni). With only an increasе of the pulse frequency from 100 to 1000 Hz, almost 20% increase in the nickel content is achieved. The Sn–Ni powders deposited in both potentiostatic modes have much more homogeneous structure than those, deposited by galvanostatic mode. The powders are composed mainly from a cubic phase (f.c.c.) of β-Ni and of small amounts of β-Sn as a result of recrystallization from metastable amorphous tin phase. The Sn–Ni powders show electrocatalytic alility to the oxygen reduction reaction (ORR) in a model Metal-Air system seriously excel features of the reference (Ag) catalyst. The ORR is very sensitive to the morphology of the tested electrocatalysts.

Microstructure evolution and reaction behavior of Cu–Ni alloy and B4C powder system

Microstructure evolution and reaction behavior of Cu–Ni alloy and B4C power system was studied by in-situ and static experimental investigations along with theoretical calculations. The reaction process was as follows. Firstly, B4C decomposed into B and C atoms, and then B atoms diffused into Cu–Ni matrix, leading to the formation of Ni2B particles. Subsequently, Ni atoms diffused into B4C, forming a loose mixture of Ni2B and amorphous C at the initial powder boundary. Finally, with the completion of reaction, Ni2B particles at the powder boundary grew into a monolithic block, and then C substance was excluded out and accumulated at the edge of this monolithic Ni2B block. It is believed that the formation of Ni2B phase is caused by the most negative change of Gibbs free energy among all the potential reactions between Ni–B and Ni–B4C systems.

Formation of Fe-19 wt%Cr-9 wt%Ni Nanocrystalline Alloy with Excellent Corrosion Resistance: Phase Transition and Microstructure

In this paper, microstructure characteristics and phase transitions of Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy are comprehensively studied during the mechanical alloying and hot pressing sintering processes. Corrosion resistance of the sintered Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy samples is further analyzed. During the mechanical alloying process, Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy powders mainly composed of metastable ferrite phase are obtained after mechanical alloying for 8, 16 and 24 h, respectively. In the subsequent hot pressing sintering process, the phase transitions (from ferrite to austenite) occur from 650 to 750 °C for Fe-19 wt%Cr-9 wt%Ni alloy powders milled for 24 h. When the sintering temperature is raised to 1050 °C for 1 h, the ferrite phase has transformed into austenite phase completely, and the obtained grain size of sintered Fe-19 wt%Cr-9 wt%Ni alloy is around 40 nm. Electrochemistry test of the sintered Fe-19 wt%Cr-9 wt%Ni alloy has been operated in 0.5 mol L−1 H2SO4 solution to show the corrosion resistance properties. Results show that the sintered Fe-19 wt%Cr-9 wt%Ni alloy exhibits excellent corrosion resistance, which is proved by higher self-corrosion potential, lower self-corrosion current density and larger capacitive reactance, compared with that of commercial 304 stainless steel.

Characterization of high-strength Ti–Ni shape memory alloys prepared by hot pressed sintering

High strength Ti–Ni shape memory alloy had been manufactured by hot-pressed sintering of Ti–Ni alloy powders. Due to the higher temperature sintering and assisted with the external pressure of 80 MPa, the higher density of Ti–Ni alloys can be obtained. The Ti–Ni alloy sintered at the appropriate sintering temperature was characterized by the network structure formed by the Ti2Ni phase distributing along the surface of original alloy powders. Merely one-stage B2⇌B19′ martensitic transformation was observed in the consolidated Ti–Ni alloy due to the homogeneous chemical composition, irrespective of the sintering temperature. The martensitic transformation temperature slightly changed, which was largely related to the number and distribution of Ti2Ni phase, as the sintering temperature increased. The mechanical properties of present Ti–Ni alloy were enhanced with the increased sintering temperature. Moreover, the outstanding strain recovery characteristics with the recoverable strain of 8.13% at the pre-strain of 10% condition can be achieved in Ti–Ni alloy prepared at the temperature of 1000 °C, which was attributed to the higher yield stress and weaker hamper effect of Ti2Ni phase on the movement of martensitic interface.

Oxidation resistance of Fe–Cr–Ni laser cladding layer under supercritical water

In this work, the laser cladding technology was applied to deposit Fe–Cr–Ni alloy powder on the surface of mild steel (AISI 1015) to improve the oxidation resistance of the materials under supercritical condition. During the oxidation of supercritical water, crystals in different regions were bonded, resulting in transformation from equiaxial crystal to columnar crystal. Meantime, the Cr and Mn elements diffused from coating to substrate. Cr2O3 and Fe2O3 were formed after the reaction between the Cr and Fe elements in the coating and supercritical water and oxygen. After supercritical water oxidation for 1000 h, the surface of the Fe–Cr–Ni laser cladding coating still had good compactness and could effectively inhibit the oxidation of supercritical water.

A scalable Al–Ni alloy powder catalyst prepared by metallurgical microstructure control

Metallurgical microstructure control of Al–Ni alloys enabled scalable and facile synthesis of large-area electrodes for alkaline hydrogen evolution catalysts comparable to conventional Pt catalysts.

Synthesis and Characterization of Nanocrystalline Fe(100−x)Ni(x) Alloy Powders by Auto-combustion and Hydrogen Reduction

Nanocrystalline Fe90Ni10, Fe70Ni30 andFe50Ni50 alloy powders were successfully synthesized using a simple auto-combustion route followed by hydrogen reduction. The experimental work consisted of two steps, where the first step was auto-combustion and, the second step was reduction of the combusted powders. Citric acid was used as fuel during combustion, and citrate to nitrate ratio (C/N) was maintained at 0.3. NiFe2O4 and Fe2O3 phase formation occurred in obtained powders. Obtained powders were reduced in a hydrogen atmosphere at 700 °C/1 h for alloy formation. X-ray diffraction results revealed the presence of BCC α-(Fe,Ni) and FCC γ-(Fe,Ni) phases in reduced powders. Rietveld refinement technique was used to confirm α-(Fe,Ni) and γ-(Fe,Ni) phases with Im-3 m and Fm-3 m space groups, respectively. The Fe50Ni50 powder has been found to have a single γ-(Fe,Ni) phase. Crystallite size of synthesized powders was calculated using the Scherrer equation and transmission electron microscopic analysis, which has been found < 50 nm. The nanocrystalline powders of all three compositions have shown soft magnetic nature with high saturation magnetization (Ms) and low coercivity (Hc). Effect of composition on the phase formation, microstructure and magnetic behavior was investigated. This rapid and simple process for attaining nanoparticles of Fe-Ni alloys with high Ms is expected to be useful in potent applications such as sensors, biomedical applications and electromagnetic wave absorbers.

Microstructure and Properties of Ni-Co Composite Cladding Coating on Mould Copper Plate.

In this study, a Ni–Co composite coating was fabricated successively on a copper substrate by laser, and the microstructure and properties of the composite coating were studied. Our results show that the elements from Ni and Co alloy powder were uniformly distributed in the binding region, which obtained a good metallurgical bonding with the substrate. The microhardness of Co-based coatings was 646 HV0.1, which was approximately 7.6 times greater than the hardness of Cu substrate. The Ni-based coating hardness was a little lower than that of the Co-based coating, which was approximately 7.0 times higher than the hardness of Cu substrate. The Co-based coating was comprised of reinforced phases, such as Co, Ni–Cr–Co–Mo, M7C3 and {Fe, Ni}. The wear volume of Co-based coatings was approximately 0.164 mm3 after the sliding wear test at 60 min, which was only 4% of the substrate’s wear volume. Meanwhile, the heat shock resistance experiment was carried out at 800 °C for 75 times before the Ni–Co composite coating was peeled off. It was shown that this Ni–Co composite coating had good wear resistance and high temperature properties, which is helpful to improve the service life of a mould copper plate. It not only saves the economic cost of steel plants, but also improves the quality of slabs and products.

Effect of milling duration on hydrogen storage thermodynamics and kinetics of ball-milled Ce–Mg–Ni-based alloy powders

To improve the hydrogen storage performance of CeMg12-type alloys, partially substituting Mg with Ni in the alloy was conducted. The way to synthesize the target alloy powders was the mechanical milling method, by which the CeMg11Ni + x wt% Ni (x = 100, 200) alloy powders with nanocrystalline and amorphous structure were obtained. The influence of the milling time and Ni content on the hydrogen storage properties of the alloys was discussed. The X-ray diffractometer and high-resolution transmission electron microscope were used to investigate the microstructures of the ball-milled alloys. The hydrogenation/dehydrogenation dynamics were studied using a Sievert instrument and a differential scanning calorimeter which was linked with a H2 detector. The hydrogen desorption activation energies of the alloy hydrides were evaluated by Arrhenius and Kissinger equations. From the results point of views, there is a little decline in the thermodynamic parameters (enthalpy and entropy changes) with the increase in Ni content. However, the alloys desorption and absorption dynamics are improved distinctly. What is more, the variation of milling time results in a dramatic influence on the hydrogen storage performances of alloys. Various maximum values of the hydrogen capacities correspond to different milling time, which are 5.805 and 6.016 wt% for the CeMg11Ni + x wt% Ni (x = 100, 200) alloys, respectively. The kinetics tests suggest that the hydrogen absorption rates increase firstly and then decrease with prolonging the milling time. The improvement of the gaseous hydrogen storage kinetics results from the decrease in the activation energy caused by the increase in Ni content and milling time.