WC—8（Fe／Ni／Co）R硬质合金的研究

用Ｆｅ、Ｎｉ部分取代ＷＣ－８Ｃｏ合金（牌号ＹＧ８）中的粘结剂Ｃｏ,再添加微量稀土Ｒ制得ＷＣ－８（Ｆｅ／Ｎｉ／Ｃｏ）Ｒ硬质合金,测试了其物理机械性能,研究了粘结剂各种成份比例及烧结温度对硬质合金的影响。结果表明：ＷＣ－８（Ｆｅ／Ｎｉ／Ｃｏ）Ｒ硬质合金的性能可以达到ＹＧ８的性能标准。利用扫描电镜（ＳＥＭ）及Ｘ射线衍射（ＸＲＤ）对其作了显微结构分析,同时探讨了影响ＷＣ－８（Ｆｅ／Ｎｉ／Ｃｏ）Ｒ合金性能的     

Experimental investigation and thermodynamic assessment of the C–Co–Fe–Ni–W system

The liquid phase formation temperatures of WC–(Co,Fe,Ni) alloys with free carbon and M₆C phase, respectively, were determined by means of Differential Scanning Calorimetry (DSC) analysis. Based on the experimental results, a thermodynamic modelling is conducted on the C–Co–Fe–Ni–W quinary system using the CALPHAD (CALculation of PHAse Diagram) technique. Temperature-composition sections and projections concerning the sintering areas of the WC–(Co,Fe,Ni) hardmetals are calculated to verify the rationality of the present modelling. Comprehensive comparisons between the experimental and calculated results show that all the experiments can be well reproduced by the present modelling.     

Highly dense,inexpensive composites via melt infiltration of Ni into WC/Fe preforms

Traditionally, WC-based composites use Co as the metal binder phase to consolidate using liquid-phase sintering with a small percentage of Co, but a potentially lower cost binder phase can be made with a different approach when using large amount of metal binder phase. FeNi as a metal binder material is much cheaper than Co. WC can be liquid-phase sintered and melt infiltrated with FeNi, but by making FeNi in situ, costs lower even further. Composites of WC-(Fe-Ni) were made by first pressing a mixture of WC and Fe powders and subsequently melt infiltrating Ni in an amount corresponding to less volume than the porosity of the preform to ensure high WC content. The research objective was to make highly dense composites via melt infiltration with a low-cost metal binder phase in situ. This method has the potential to make fully dense composites, rather than hardmetals, with suitable properties at lower costs. The density and hardness are 97.4%TD and 6.72 GPa, respectively.     

Liquid phase sintering and oxidation resistance of WC–Ni–Co–Cr cemented carbides

Fully dense WC–Ni–Co–Cr alloys have been consolidated via sinter HIP processing. Dilatometric tests show that shrinkage undergoes several accelerations and decelerations during heating, a phenomenon likely associated to the heterogeneous distribution of Cr in the binder phase. WC grain growth follows trends similar to those described for WC–Co hardmetals, increasing with the C activity and the amount of liquid phase of the cermets. Finally, the oxidation resistance of WC–Ni–Co–Cr cemented carbides is observed to improve as the metal content increases and the C content decreases. In both cases, the oxide layers present a higher proportion of (Co, Ni)WO₄ tungstates. The oxide scales formed on compositions with low metal content contain a higher amount of WO₃ oxide.     

Effects of Ni addition and cyclic sintering on microstructure and mechanical properties of coarse grained WC–10Co cemented carbides

Coarse grained WC–10(Co, Ni) cemented carbides with different Ni contents were fabricated by sintering-HIP and cyclic sintering at 1450 °C. The effects of Ni addition and cyclic sintering on the microstructures, magnetic behavior and mechanical properties of coarse grained WC–10(Co, Ni) cemented carbides have been investigated using scanning electron microscope (SEM), magnetic performances tests and mechanical properties tests, respectively. The results showed that the mean grain size of hardmetals increases from 3.8 μm to 5.78 μm, and the shape factor Pwc decreases from 0.72 to 0.54, with the Ni content increases from 0 to 6 wt.%. Moreover, the W solubility reaches the highest value of 10.33 wt.% when the Ni content is 2 wt.%. The hardness and transverse rupture strength of WC–8Co–2Ni are 1105 HV₃₀ and 2778 MPa, respectively. The cyclic sintering is conducive to increase the WC grain size of WC–10(Co, Ni) and improves the transverse rupture strength of WC–10Co without compromising the hardness of alloys.     

Processing and microstructural characterization of liquid phase sintered tungsten–nickel–cobalt heavy alloys

In this study, the effects of composition and sintering temperature on the microstructural characteristics of liquid phase sintered 90W–Ni–Co alloys were investigated. 90W–Ni–Co alloys having Ni/Co ratios of 3/1, 4/1 and 6/1 were examined. It was found that the alloys studied have reached almost to full density when sintered at and above 1475 °C. The microstructures of the alloys were typical of liquid phase sintered alloys, which consisted of rounded, nearly pure W grains embedded in a ternary Ni–Co–W binder matrix phase. The binder matrix phase in these alloys was observed to dissolve up to 42 wt.% W. The relative amount of the binder matrix phase and the average size of the W grains were found to increase with increasing sintering temperature. The activation energies for grain coarsening are determined for the investigated alloys by assuming that the coarsening process is mainly governed by Ostwald ripening mechanisms in the liquid state. The calculated activation energies, which were within 113–162 kJ/mol range, were found to be in rather close agreement to the literature data given for W–Ni–Fe alloys. This indicates that grain coarsening in W–Ni–Co and W–Ni–Fe alloys most probably takes place through similar diffusional processes.     

Comparative investigation of the Ni and the Fe effect on the structure and mechanical response of a WC-W-Ni hardmetal obtained by infiltration

In the present work, and in order to enhance the efficiency of drilling tools for the oil and gas industry, the influence and performance of Ni and Fe during spontaneous infiltration on a WC-W-Ni composite material mechanical behaviour was addressed. Solid-state activity of Fe and Ni during infiltration exhibits partial dissolution in the metallic binder. The chemical affinity between Fe and Ni, provided by the Fe powder and the binder respectively, derived on the formation of the (Fe, Ni) solid solution and FeNi₃ intermetallic precipitates in the particle/matrix diffusion region, with a hardness (12 GPa) close to that of WC and high elastic modulus (230 GPa). Furthermore, the diffusion of Fe to the matrix leads to the formation of sub-micrometer precipitates of α-Fe with some (Ni, Mn) in solid solution and of Ni₃Sn with a small amount of Cu dissolved, driving to an increase of about 30% in its elastic modulus, and without appreciable effect in the hardness observed.     

The research on the binder phase for the (W0.5Al0.5)C0.5 system

Cemented carbide hard alloys (W_0.5Al_0.5)C_0.5-M (Fe, Co, and Ni) were successfully produced by mechanical alloying and hot-pressing. The density, microhardness and bending strength of the samples were also tested. The relative density of the bulk samples can reach over 98% under the hot-pressing sintering. Comparison of sintering behavior, microstructure and mechanical property of the hard alloys (W_0.5Al_0.5)C_0.5 with different binders (Fe, Co, and Ni) has been made. It found that no η-type phases formed in all the three kinds of hard alloys (W_0.5Al_0.5)C_0.5-Co, (W_0.5Al_0.5)C_0.5-Ni and (W_0.5Al_0.5)C_0.5-Fe during the sintering process. The results also showed that, in (W_0.5Al_0.5)C_0.5-M (Fe, Co, and Ni) hard alloys with constant grain size and binder phase content, the hardness of (W_0.5Al_0.5)C_0.5-Fe is similar to (W_0.5Al_0.5)C_0.5-Co hard alloys and the bending strength of (W_0.5Al_0.5)C_0.5-Ni is a little lower than (W_0.5Al_0.5)C_0.5-Co hard alloys.     

Diffusion modeling in cemented carbides: Solubility assessment for Co,Fe and Ni binder systems

The increasing interest in alternative binder solutions for WC based cemented carbide systems leads to more integration of ICME (Integrated Computational Materials Engineering) based concepts in the materials development. This work investigates the non-equilibrium W and C solubilities upon furnace-cooling in a wide range of Co and Fe-Ni based binder systems by computational means. It is shown that the solubilities strongly depend on the C-activity and binder matrix elements, revealing that Ni dissolves most W and Fe most C out of the investigated systems. Furthermore, the effect of the binder mean free path and the cooling rates on the solubilities was investigated. The presented method and results provide insights to control the binder chemistry and will help to design the properties for future binder systems in a fast and efficient way.     

Electrodeposited Ni,Fe,Co and Cu single and multilayer nanowire arrays on anodic aluminum oxide template

The Ni, Fe, Co and Cu single and multilayer nanowire arrays to make perpendicular magnetic recording media were fabricated with nanoporous anodic aluminum oxide (AAO) templates from Watt solution and additives by the DC electrodeposition. The results show that the diameters of Ni, Fe, Co and Cu single and multilayer nanowires in AAO templates are 40–80 nm and the lengths are about 30 μm with the aspect ratio of 350–750. The magnetic properties of the prepared nanowires are different under different electrodepositing conditions. The remanences (B_r) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires, and coercivity (H_c) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires. These are compatible with the required conditions of high density magnetic media devices that should have the low coercivity to easily success magnetization and high remanence to keep magnetization after removal of magnetic field.     

Effects of Ni addition on mechanical properties and corrosion behaviors of coarse-grained WC-10(Co,Ni) cemented carbides

The effects of the Ni content on the mechanical properties and corrosion behavior of coarse-grained WC-10Co cemented carbide, with a grain size of 3.5 μm, were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical measurements, and mechanical property tests. The results indicate that the strength and toughness are improved with the addition of 2 wt% Ni without sacrificing hardness. Furthermore, the existence of Ni can decrease the corrosion current density (i_corr) of WC-10Co cemented carbide in both 0.1 M HCl and 0.1 M NaOH solutions. The SEM and XPS results reveal that only a minor amount of WO₃ formed in the corroded surface in HCl solution. The corrosion behavior was determined by the dissolution of the binder phase, and Ni can develop the charge-change resistance (R_ct). Contrarily, the Co binder phase were oxidized to a dense passive film (Co(OH)₂ and Co₃O₄) in NaOH solution, and the addition of Ni was conducive to the enhancement of the diffusion resistance (R_f). This may give insights into adding an appropriate Ni content in coarse-grained WC-Co cemented carbide, in which the wear and corrosion of the components coexist.     

The corrosion behavior of Fe-Cr alloys containing Co,Mn, and/or Ni and of a Co-base alloy in the presence of molten (Li,K)-carbonate

The corrosion behavior or commercial Fe ana Co base alloys and Fe-Cr model alloys with different contents of Co and/or Mn was investigated by continuous exposure tests in the presence of a thin carbonate film. All alloys studied form multi-layered corrosion scales consisting of outer Li containing oxides and inner Cr rich oxides, i.e. spinels or LiCrO₂. The LiCrO₂ is formed on alloys with high Cr contents (≤ 20 wt.%), whereas mixed (Fe,M)_3-x Cr_xO₄ spinels (M = Co, Mn, Ni) were found on alloys with lower Cr content (15–20 wt.%). Insoluble Cr containing oxides occur only in the inner layers of the corrosion scale, whereas on the surface of corroded specimens soluble chromates were detected. Alloys with Mn contents greater than 15 wt.% form Mn₂O₃ in the initial stages of the experiments, this oxide reacts with the melt and formation of Li₂MnO₃ takes place. In exposure tests up to 500 h Fe-Cr alloys with low contents of Mn and Co (10 wt.% Co or Mn) form iron rich oxides (LiFeO₂ and LiFe₅O₈) with varying amounts of dissolved Mn or Co. In the later corrosion stages outward diffusion of Mn and/or Co takes place and LiCoO, and Li₂MnO₃ are formed on top of LiFeO₂, whereby the concentration of Mn and/or Co in the inner layers (LiFeO₂ and spinel) decreases. The outer Li containing oxides LiFeO₂, LiCoO₂ and Li₂MnO₃ are nearly insoluble in the melt and when present at the surface protect the metallic material from further corrosive attack. Fe-Cr model alloys containing Co and Mn form multi-layered corrosion layers after 2000 h of exposure. These layers consist of four oxides in the following sequence from the metal-scale to the scale-melt interface: (Fe,Cr,Co,Mn)₃O₄ spinel, LiFeO₂, Li₂MnO₃ and LiCoO₂.     

镍含量对超细WC-Ni-VC-TaC硬质合金结构和力学性能的影响

采用放电等离子烧结(SPS)方法,结合使用VC和TaC晶粒抑制剂,制备Ni质量分数为6%~10%的超细WC-Ni硬质合金。研究表明,所制备WC-Ni-VC-TaC硬质合金WC晶粒在0.2~0.4μm;合金中含有大量微孔,但微孔大小随合金中粘结相Ni含量增加而减小。且随合金中Ni含量增加,合金中WC晶粒略有增长,合金相对密度先减小后增大,硬度由24500MPa逐渐减小到18600MPa(HV1),但抗弯强度却由1600MPa增大到2140MPa。     

Electrospinning of carbon nanofiber supported Fe/Co/Ni ternary alloy nanoparticles

Polyacrylonitrile (PAN)-based carbon nanofiber supported Fe/Co/Ni ternary alloy nanoparticles were prepared by using the electrospinning technique for potential fuel cell applications. The solution was prepared by adding pre-solved catalytic precursor into PAN/DMF solution. The effect of PAN and catalyst precursor concentration on solution properties (viscosity and conductivity) and heat stabilization temperature has been investigated. Electrospun nanofibers were characterized by field emission scanning electron microscope, transmission electron microscope, energy dispersive spectrometer and X-ray diffractometer. It has been found that ternary nanoparticle size is in the range of 5–115 nm (average: 20 nm) and is a crystal alloy of Fe, Co and Ni. Also, TEM results demonstrate that in some regions metal nanoparticles tend to agglomerate into larger particles mainly due to the non-uniform distribution of nanoparticles in as-spun condition. PAN-derived carbon nanofiber mean diameter was measured as 200 nm by varying from 40 nm to 420 nm.     

Corrosion behaviour of WC‐Co based hardmetal in neutral chloride and acid sulphate media

A comparative study of the corrosion behaviour of WC‐Co based hardmetals with Ni and Cr₃C₂ additions is carried out. The aggressive environments are neutral and acidic aerated aqueous solutions of NaCl and H₂SO₄. This study is based on electrochemical (linear sweep voltammery), compositional (surface EDX analyses, AAS analyses of attack solutions), structural (XRD) and morphological (SEM) investigations. Electrochemical figures of merit were computed from linear sweep voltammograms in order to rank the corrosion behaviour close to free‐immersion conditions in the studied environments and with presence of oxidising agents. EDX and XRD analyses allow to accurately characterise the penetration depth of the attack as well as the preferential dissolution of the constituents. Binders containing Ni show a significantly improved corrosion resistance in the studied systems. The amount of Ni in the binder is the single most important factor affecting corrosion performance. Cr₃C₂ additions to hardmetals with lower‐Ni binders cannot balance the effect of Ni, but give an improved resistance in neutral chloride‐containing solutions.     

On the effect of strain on peritectic reactions and transformations in Fe–Ni and Fe–Cu binary alloys

Abstract

Differential thermal analysis (DTA) experiments conducted on Fe–Ni and Fe–Cu alloys showed undercooling below the equilibrium peritectic temperatures, T_P . The intervals between the observed liquidus and peritectic temperatures were on average 11°C and 8°C larger than the intervals obtained from equilibrium phase diagrams of Fe–Ni and Fe–Cu respectively. The transformation from δ-Fe to γ-Fe during the peritectic reaction is associated with density change and strain build up at the δ-Fe/γ-Fe interface. Thermodynamic calculations showed that by introducing the strain energy at the δ-Fe/γ-Fe interface, T_P dropped 9 K below its equilibrium value and the increase in the liquidus-to-peritectic temperature interval was in reasonable agreement with the experimental observations. The growth rate of γ-Fe during a peritectic transformation was calculated based on the strain-induced undercooling in T_P and the results showed partial agreement with observations obtained from CSLM directional solidification experiments conducted earlier on Fe–Ni alloys.     

添加微量B元素对Al19Co20Fe20Ni41共晶高熵合金显微组织及性能的影响

同时强化合金的力学性能和磁性能是软磁材料的理想化制备策略.通过制备非等原子比的Al19Co20Fe20Ni41共晶高熵合金,研究硼元素合金化对显微组织演变、相形成、力学性能和软磁性能的影响.随着B含量的增加,(Al19Co20Fe20Ni41)100-xBx合金的显微组织从最初的层片状共晶组织(x=0)转变为离异共晶组...     

层叠Ni/Ti热扩散形成金属间化合物的规律

选择Ni和Ti粉末及其机械合金化粉末制备Ni/Ti扩散偶,利用扫描电镜和X射线衍射等手段研究了Ni/Ti扩散偶在固相热处理作用下金属间化合物的形成及生长规律.随着热处理温度的提高,Ni3Ti,Ti2Ni和NiTi金属间化合物的数量增加明显;随热处理保温时间的增加,NiTi金属间化合物呈抛物线规律生长,而对Ni3Ti和Ti2Ni的生长影响不大.结果表明,金属间化合物在形成过程中,Ni3Ti和Ti2Ni优先形成,达到一定厚度后,NiTi金属间化合物开始形成并快速增长.     

Alloyed W–(Co,Ni,Fe)–C phases for reaction sintering of hardmetals

It has been shown that W–Co–C phases could dissolve a substantial amount of metals such as V, Cr and Ta, which are known to positively influence the microstructure of hardmetals with respect to uniform grain size distribution and fine grain size. This offers a tool to circumvent the conventional doping of hardmetals with individual carbides. In the present study we used double- and triple-alloyed κ-W₉Co₃C₄ (i.e. κ-(W,V,Cr)₉Co₃C₄ and κ-(W,V,Cr,Ta)₉Co₃C₄) and applied a variety of sintering experiments to obtain WC–Co, WC–(Ti,Ta,Nb)C–Co and WC–(Ti,Ta,Nb)(C,N)–Co hardmetals. We also prepared κ-W₉Fe₃C₄, alloyed κ-W₉Ni₃C₄, and κ-W₉(Fe/Ni)₃C₄, and used the latter for sintering.     

Phase stability of the X2AlTi (X: Fe,Co, Ni and Cu) Heusler and B2-type intermetallic compounds

Ordering and phase separation between the B2 and L21 phases in the X2AlTi (X: Fe, Co, Ni, Cu) intermetallic compounds were investigated. The B2/L21 continuous ordering was determined using the diffusion couple technique in the temperature range of 1273–1573 K. It was found that the substitution of Co for Fe results in raising the B2/L21 ordering temperature and that of Cu for Ni brings about widening of the B2+L21 two-phase region on both the NiAl and NiTi sides. It is shown that the maximum temperatures of B2/L21 order–disorder transition (TcB2/L21max), the tricritical temperatures (TtB2/L21) and the phase boundaries of the miscibility gap between the B2 and L21 phases in the XAl–XTi pseudobinary systems can be well described by the 3d+4s electron concentration of the elements occupying the X site. On the basis of this finding, the phase stability and the interchange energies between Al and Ti in the next nearest neighbors of X–Al–Ti (X: Ti, V, Cr, Mn, Fe, Co, Ni and Cu) system are discussed.