Laser Oscillating of Nickel Alloyed Welds on Press‑Hardened Steel

Laser oscillating welding was employed to fabricate Al-Si coated press-hardened steel(PHS)to improve the element homogeneity in the fusion zone.Laser oscillating welding was employed with various oscillation amplitudes(0 mm,0.5 mm and 1.3 mm)in this present.Ni foil of 0.06 mm thickness was used as an interlayer between two tailored PHS welded.The weld morphology,elemental profile,microstructure and tensile strength of welded joints were studied.The results showed that full penetration weld without any weld defects were achieved for any oscillation amplitudes,and weld width increased with increasing oscillation amplitudes.With the oscillation amplitudes increased,Ni and Al had an uneven elemental profile due to strong stirring force,but the Ni and Al content in the weld was decreased and Ni had a sharp descent compared to Al element.Only fewδ-ferrite was presented in fusion line with the oscillation amplitudes increased to 1.3 mm.The oscillation amplitudes did not have an effect on the tensile properties,which was similar to that of base metal.But if keeping increasing the oscillation amplitudes or reducing the thickness of Ni interlayer,it has a potential risk to form more and moreδferrite such that deteriorate the mechnical properties of welded joints.

Effect of Rare Earth Elements on Depositing Rate of Nickel Alloy Brush Plating Coatings

The effect of four kinds of rare earth elements on the depositing rate of Ni-based alloy brush plating coatings was investigated. The results indicate that all of the selected rare earth elements increase the depositing rate of Ni-based alloy coatings, and Sm increases the depositing rate most obviously. There is an optimum amount of rare earth addition in the plating solution. With the change of plating voltage to a certain extent, the results reveal no differences. The mechanism of the increase of the depositing rate was analyzed.

Control of Nickel Alloy Structural Change by the Atomic Emission Spectroscopy Method

The aim of the work was the assessment of capability for the change control in the structure of a compact material of pelletized heatproof nickel alloy grade EP741NP using the atomic emission method. The proposed method of evaluation is based on the statistical significance of the analytical response differences during atomic emission spectroscopy of solid specimens taken from one sample before and after heat treatment using the instruments AtomComp 81 and ARL 4460 with a high-voltage spark excitation. For calculations, the ratio of the line intensity of the analyzed element to the line intensity of the main sample component (in our case Ni2254) was used. The difference confidence estimation was made by the averages comparison method in a variance analysis. The study results are presented on the effect of material structure on analytical response during atomic emission spectroscopy of solid specimens. It was proved that the samples before and after heat treatment give statistically differing results while analyzed.

Heat-treated Nickel Alloys Produced Using Laser Powder Bed Fusion-based Additive Manufacturing Methods:A Review

Laser powder bed fusion(LPBF)is the most widely used metal additive manufacturing process.It is a novel layer-by-layer manufacturing technique based on a geometrical model that provides a suitable alternative for material processing.This mode is widely used in laser and electron beam welding.Nickel(Ni)alloy prepa-ration using the LPBF method has attracted considerable attention in several areas,owing to the high corro-sion resistance and good mechanical properties of the prepared alloys.The specific conditions of solidification through the metal fused during the selective laser fusion process and its layer deposition induces microstruc-tural peculiarities,including the formation of a supersaturated solid solution,extreme microstructural refine-ment,and the generation of residual stress.Consequently,heat treatment and hot isostatic pressing,which are generally applied to conventionally manufactured Ni alloys,may need to be altered to adapt to the met-allurgical properties of Ni alloys manufactured using direct metal laser deposition and address particular is-sues resulting from the process itself.Several studies have been conducted on this topic over the past few years,suggesting different approaches for addressing different alloying systems.This review summarizes the latest scientific findings in the area of thermal treatment for selective laser sintering of additively manufactured Ni alloys.

Wear Evaluation of Copper-Nickel-Aluminum Alloys under Extreme Conditions

Cu-Ni-Al alloys at different concentrations were obtained using a high frequency induction melting unit, keeping a balance in the nominal compositions. Light alloys are important to be used in industrial applications. Aluminum additions result in a positive hardness increment of the ternary alloys in comparison with the binary Cu-Ni alloys. Generalized wear mechanisms of the alloys with low aluminum content are basically type abrasive, while samples with 5 and 10 at.% Al present an oxidative-adhesive wear mechanism. Wear results have indicated that aluminum addition affects positively the wear resistance, mainly in samples with high aluminum content product of the creation during the test of different oxides corresponding to the elements present in the alloys.

Effects of heat treatment on mechanical properties of ODS nickel-based superalloy sheets prepared by EB-PVD

A Y2O3 dispersion strengthened nickel-based superalloy sheet（0.15 mm thick） was prepared by electron beam physical vapor deposition（EB-PVD） technology.Different heat treatments were used to improve the mechanical properties of the alloy sheet.Differential thermal analysis（DTA） was used to examine the thermal stability of the as-deposited sheet.Element contents,phase composition and microstructure investigations on as-deposited and heat treated specimens were performed by X-ray fluorescence spectrometer（XRF）,X-ray diffraction（XRD） and scanning electron microscopy（SEM）.Tensile tests were conducted at room temperature on specimens as-deposited and heat treated.The results show that the as-deposited sheet is composed of equiaxed grains on the substrate side and columnar grains on the evaporation side.The as-deposited sheet shows poor ductility due to micropores between columnar grains.The strength and ductility can be improved effectively by annealing at 800°C for 3 h.For samples treated at 1100°C,the strength drops down due to the precipitates of Y3Al5O12（YAG）.

Effect of ultrasonic impact treatment on the surface integrity of nickel alloy 718

Ultrasonic impact treatment(UIT)is a type of surface strengthening technology that can improve the fatigue properties of materials by improving the surface quality,residual stress,and other aspects.In this study,the influence of ultrasonic impact parameters on the surface integrity of nickel alloy 718 was studied.The micro stress concentration caused by the surface morphology was also explored.The cosine and exponential decay functions were used to fit and characterize the distribution of residual stress and work hardening in the surface material.The results showed that the feed rate had the greatest influence on surface roughness,stress concentration,and surface residual stress.It was not appropriate to evaluate the surface hardening effect only by the number of impacts per unit area,the ultrasonic impact parameters such as feed speed and pre extrusion depth should also be considered.The grain refinement was obvious after UIT.The multiobjective optimization of machining parameters was performed with the objective of surface stress concentration and residual stress.A surface with a smaller surface stress concentration factor and larger compressive residual stress can be obtained simultaneously using medium linear velocity,medium pre extrusion depth,and smaller feed rate.

Localized Corrosion Characteristics of Nickel Alloys： A Review

There are a great variety of commercial nickel alloys mainly because nickel is able to dissolve a large amount of alloying elements while maintaining a single ductile austenitic phase. Nickel alloys are generally designed for and used in highly aggressive environments, for example, those where stainless steels may experience pitting corrosion or environmentally assisted cracking. While nickel alloys are generally resistant to pitting corrosion in chloride-containing environments, they may be prone to crevice corrosion attack. Addition of chromium, molybdenum and tungsten increases the localized corrosion resistance of nickel alloys. This review on the resistance to localized corrosion of nickel alloys includes specific environments such as those present in oil and gas upstream operations, in the chemical process industry and in seawater service.

DENDRITE REFINING AND EUTECTIC TRANSFORMATION BEHAVIOR OF NICKEL-BASE SINGLE CRYSTAL (NBSC) SUPERALLOY

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New approach for assessing the weldability of precipitation-strengthened nickel-base superalloys

A new procedure was proposed for evaluating the weldability of nickel-base superalloys. The theory is on the basis of two microstructural patterns. In pattern I, the weld microstructure exhibits severe alloying segregation, many low-melting eutectic structures, and low weldability. The weld requires a weaker etchant and a shorter time for etching. In pattern Ⅱ, the weld microstructure displays less alloying segregation, low quantity of eutectic structures, and high weldability. The weld needs a stronger etchant and a longer time for etching. Five superalloys containing different amounts of Nb and Ti were designed to verify the patterns. After welding operations, the welds were etched by four etchants with different corrosivities. The weldability was determined by TG-DSC measurements. The metallography and weldability results confirmed the theoretic patterns. Finally, the etchant corrosivity and etching time were proposed as new criteria to evaluate the weldability of nickel-base superalloys.

Analytic estimation and numerical modeling of actively cooled thermal protection systems with nickel alloys

Actively cooled thermal protection system has great influence on the engine of a hypersonic vehicle, and it is significant to obtain the thermal and stress distribution in the system. So an analytic estimation and numerical modeling are performed in this paper to investigate the behavior of an actively cooled thermal protection system. The analytic estimation is based on the electric analogy method and finite element analysis（FEA） is applied to the numerical simulation. Temperature and stress distributions are obtained for the actively cooled channel walls with three kinds of nickel alloys with or with no thermal barrier coating（TBC）. The temperature of the channel wall with coating has no obvious difference from the one with no coating, but the stress with coating on the channel wall is much smaller than that with no coating. Inconel X-750 has the best characteristics among the three Ni-based materials due to its higher thermal conductivity, lower elasticity module and greater allowable stress. Analytic estimation and numerical modeling results are compared with each other and a reasonable agreement is obtained.

EVALUATION OF A TUBULAR MESH AND A SPIRAL STENT WOVEN FROM TITANIUM NICKEL ALLOY FOR PROSTATIC OBSTRUCTION IN PATIENTS AT HIGH RISK FOR SURGERY REPORT OF 62 CASES

The use of two urethral stents woven from titanium nickel alloy (TiNi) in the form of a tubular mesh or a spiral stent (both made in China) is described. They were implanted in 62 patients,vith prostatic outflow obstruction. till patients were considered contraindicated for surgery. They were divided into a spiral stent group (group I) treated between March 1992 and May 1993, comprising 35 cases, and a tubular mesh group (group 2) treated between October 1993 and December 1994, comprising 31 cases, including four failures in group 1. Thirty-three out of the 35 patients in group 1 were treated successfully. Good results were achieved in eight cases (22.8%) and significant improvements occurred in 24 (68.5%), giving a total effective rate of 91.3%, with a follow-up of 11 to 27 months. Fourteen stents were removed within 6 months after the insertion and six more were removed within 12 months. The mean effective time of the stent in situ was 10.8 months. All 31 cases in the mesh group were treated successfully. Dramatically good effects were obtained in 28 cases (over 90%) and distinct improvements were achieved in two, giving a total effective rate of over 96.5%, with a follow-up of 6 to 14 months (mean 10.5 months). Cystoscopy was carried out in 12 patients after 6 months following the insertion. The major part of the meshes became covered by urothelium. Compared with the spiral, the mesh makes it possible to insert a prosthesis with a larger diameter and anti-pressure. The spiral, however, can be used as a temporary alternative for the relief of prostatic obstruction. A tubular mesh can work well for the relief of prostatic obstruction and remain in situ without causing major problems for at least I year.

Effect of electropulsing treatment on corrosion behavior of nickel base corrosion-resistant alloy

Electropulsing treatment（EPT） was performed on a nickel base corrosion resistant alloy during aging.The effect of EPT on the microstructure and corrosion resistance of the alloy and the mechanisms were investigated.The results show that the intergranular corrosion resistance can be improved substantially without the degradation of mechanical properties of the alloy by EPT.The EPT has an effect of enhancing the interface diffusion rate of the alloying element,which is higher than the body diffusion rate.And thus discontinuous precipitation of M23C6 type carbides appears at the grain boundary in the alloy by EPT,which decreases the depletion extent of the alloying elements at the grain boundary substantially.As a result,the intergranular corrosion resistance of the alloy can be improved by the EPT without any degradation of mechanical properties.

Combined “Gateway” and “Spillover” effects originated from a CeNi_(5) alloy catalyst for hydrogen storage of MgH_(2)

Efficient catalysts enable MgH2 with superior hydrogen storage performance.Herein,we successfully synthesized a catalyst composed of Ce and Ni (i.e.CeNi_(5) alloy) with splendid catalytic action for boosting the hydrogen storage property of magnesium hydride (MgH_(2))The MgH2–5wt%CeNi_(5) composite’s initial hydrogen release temperature was reduced to 174℃ and approximately 6.4wt%H_(2) was released at 275℃ within 10 min.Besides,the dehydrogenation enthalpy of MgH_(2) was slightly decreased by adding CeNi_(5).For hydrogenation,the fully dehydrogenated sample absorbed 4.8wt%H_(2) at a low temperature of 175℃.The hydrogenation apparent activation energy was decreased from(73.60±1.79) to (46.12±7.33) kJ/mol.Microstructure analysis revealed that Mg_(2)Ni/Mg_(2)NiH_(4) and CeH_(2.73) were formed during the process of hydrogen absorption and desorption,exerted combined“Gateway”and“Spillover”effects to reduce the operating temperature and improve the hydrogen storage kinetics of MgH_(2).Our work provides an example of merging“Gateway”and“Spillover”effects in one catalyst and may shed light on designing novel highly-effective catalysts for MgH_(2) in near future.

Microstructure and stress rupture properties of polycrystal and directionally solidified castings of nickel-based superalloys

A new directionally solidified Ni-based superalloy DZ24, which is a modification of K24 alloy without rare and expensive elemental additions, such as Ta and Hf, was studied in this paper. The microstructure and stress rupture properties of conventionally cast and directionally solidified superalloys were comparatively analyzed. It is indicated that the microstructure of K24 alloy is composed of γ, γ＇, γ/γ＇ eutectics and MC carbides. Compared with the microstructure of K24 polycrystalline alloy, γ/γ＇ eutectic completely dissolves into the γ matrix, the fine and regular γ＇ phase reprecipitates, and MC carbides decompose to M6C/M23C6 carbides after heat treatment in DZ24 alloy. The rupture life of DZ24 alloy is two times longer than that of K24 alloy. The more homogeneous the size of γ＇ precipitate, the longer the rupture life. The coarsening and rafting behaviors of γ＇ precipitates are observed in DZ24 alloy after the stress-rupture test.

GRAIN STRUCTURE CONTROL OF NICKEL－BASE SUPERALLOYS IN CASTING PROCESS： EFFECT OF MELT ADDITIONS

Grain structure, dendrite morphologies and shape of MC type carbides ina nickel-base superalloy IN 738 LC are investigated with the addition of carbides,boride, nitride and intermetallic compounds. The results show that the grain size of theingots can be refined extensively to the order of ASTM M11～12 by combination of anintermetallic compound NixAly, addition together with lowering melt homogeneoustreatment temperature during the melting and casting process. In addition, the processcould restrain the formation of script-type carbides. The new process does not changethe phase constitution, freezing characteristics and sub-structure stability. Therefore, itis considered as an effective and practical method of grain refinement for superalloys.

Mechanism of Nickel-Aluminium Alloy Electroplating

The effect of operating conditions on the aluminium content of Ni-Al alloy deposit and the catalytic function of NaF on electrodeposition in the nonaqueous solution containing aluminium are investigated.The results indicate that the plated aluminuim content will be increased with the rise of current density in a given range.When the current density is 2.5A/dm 2,nickle aluminium alloy containing 13.1 wt% aluminium will be deposited.The plated aluminium content will be increased by 2wt% as 0.1mol/L NaF is added to the bath.

Effect of additives on anode passivation in direct electrolysis process of copper–nickel based alloy scraps

Effects of nickel component,thiourea,glue and chloride ions and their interactions on the passivation of copper–nickel based alloy scrap anodes were investigated by combining conventional electrochemical techniques.Results obtained from chronopotentiometry and linear voltammetry curves showed that the Ni component made electrochemical stability of the anode strong and difficult to be corroded,caused by the adsorption of generated Cu2O,NiO or copper powder to the anode surface.The Ni2+reducing Cu2+to Cu+or copper powder aggravated the anode passivation.In a certain range of the glue concentration≤8×10–6 or thiourea concentration≤4×10–6,the increase of glue or thiourea concentration increases the anode passivation time.Over this range,glue and thiourea played an adverse effect.The increase of chloride ions concentration led to the increase in passivation time.

Liquid phase synthesis of dendritic nickel carbide alloy with high conductivity for advanced energy storage

Alloy materials have attracted increasing attentions because they possess superior electrical conductivity which can contribute to excellent electrochemical performance. Herein a dendritic Ni;C alloy material has been prepared by the pyrolysis of nickel acetylacetonate employing oleylamine as a reductant and 1-octadecene or octadecane as the solvent. The current–voltage curves indicating that the electrical conductivity of Ni;C is higher than that of nickel oxide. Electrochemical testing indicates that a high specific capacity of 390 C/g is found in alkaline electrolyte at 0.5 A/g, and deliver excellent rate characteristic as well as cycle life. The excellent electrochemical performance may be attributed to its high electrical conductivity and dendritic nanostructure that can promote diffusion of electrolyte ions. In addition, the AC//Ni;C asymmetric supercapacitor has been assembled at a cell voltages between 0 and 1.6 V, achieving a maximum energy density of 37 Wh/kg（at a power density of 0.3995 k W/kg）, and this manifests that the Ni;C alloy is a promising electrode material for electrochemical energy storage.

Investigation of Nickel Oxide Used for Alloying in BOF Steelmaking

Direct alloying of nickel oxide in a hot simulator of LD converter was investigated in laboratory.Reduction rate of nickel oxide in steelmaking process was analyzed with the test results. Under the condition oflower slag viscosity, the reduction rate of NiO increases and the [Ni] yield rises. When the slag viscosity is higher, a lot of metal particles with higher Ni content are contained in the slag so as to decrease the [Ni] yield.