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1.
José Garcia 《International Journal of Refractory Metals and Hard Materials》2012,30(1):114-120
Nitridation of cemented carbides leads to the formation of wear resistant Ti(C,N)-enriched outer-surfaces (fcc-rich outer-surfaces). In this work the influence of the binder phase composition on the kinetics of formation of fcc-rich outer-surfaces was investigated. Sintered cemented carbides were nitrided at 1200 °C in a 5 bar N2 atm for 2 and 4 h. The thickness of the nitrided fcc-rich outer-surfaces increases with the addition of Fe to the Co and Ni binders. Correlations between nitrogen diffusion coefficients and nitrogen solubility levels in Fe-Ni-Co systems are investigated to understand the mechanisms governing the formation of graded layers on nitrided cemented carbides with Fe-Ni-Co binders. 相似文献
2.
Four cermets of composition TiC-10TiN-16Mo-6.5WC-0.8C-0.6Cr3C2-(32 − x)Ni-xCr (x = 0, 3.2, 6.4 and 9.6 wt%) were prepared, to investigate the effect of the partial substitution of Cr for Ni on densification behavior, microstructure evolution and mechanical properties of Ti(C,N)-Ni-based cermets. The partial substitution of Cr for Ni decreased full densification temperature, and the higher the content of Cr additive was, the lower full densification temperature was. The partial substitution of Cr for Ni had no significant effect of the formation of Mo2C and Ti(C,N) and the dissolution of WC, and however, it had a significant effect on the dissolution of Mo2C. Cr in Ni-based binder phase diffused into undissolved Mo2C to form (Mo,Cr)2C above 1000 °C at 6.4-9.6 wt% Cr additive, and a small amount of (Mo,Cr)2C did not dissolve after sintering at 1410 °C for 1 h at 9.6 wt% Cr additive. In the final microstructure, Cr content in Ni-based binder phase increased with increasing the content of Cr additive, and however, regardless of the content of Cr additive, coarse Ti(C,N) grains generally consisted of black core, white inner rim and grey outer rim, and fine Ti(C,N) grains generally consisted of white core and grey rim. The partial substitution of Cr for Ni increased hardness and decreased transverse rupture strength (TRS). Ni-based binder phase became hard with increasing the content of Cr additive, therefore resulting in the increase of hardness and the decrease of TRS. TRS was fairly low at 9.6 wt% Cr additive, which was mainly attributed hardening of Ni-based binder phase and undissolved (Mo,Cr)2C. 相似文献
3.
The early high-temperature oxidation behavior of Ti(C,N)-based cermets with equiatomic AlCoCrFeNi high-entropy alloy binder has been studied, as well as the cermet with Ni/Co binder as a reference. Experiments were performed at the temperature range of 800–1100 °C in static laboratory air. The micro-structural evolution of the multi-layered oxide scales on the cermets was investigated and the effect of binder phase constituent on the oxidation characteristics of Ti(C,N)-based cermets was evaluated. The results demonstrated that the cermet with AlCoCrFeNi multi-element alloy binder possesses superior oxidation resistance, which is greatly better than that of the cermet with Ni/Co metallic binder under the same condition. We suggest that the formation of a continuous and dense external oxide scale can effectively impede the outward diffusion of volatile tungsten oxides and inward oxygen transport, leading to a remarkable improvement of oxidation resistance. In addition, the enhanced oxidation resistance was related to the high Cr and Al concentration in AlCoCrFeNi binder phase that urges the formation of oxide layers with more efficient passivation effect against oxidation. 相似文献
4.
The phase equilibria in the Co-Fe-Zr ternary system were investigated by means of optical microscopy (OM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) on equilibrated ternary alloys. Four isothermal sections of the Co-Fe-Zr ternary system at 1300 °C, 1200 °C, 1100 °C and 1000 °C were experimentally established. The experimental results indicate that (1) no ternary compound was found in this system; (2) the solubility of Fe in the liquid phase of the Co-rich corner at 1300 °C is extremely large; (3) the liquid phase in the Zr-rich corner and the (Co,Fe)2Zr phase form the continuous solid solutions from the Co-Zr side to the Fe-Zr side; (4) the solubility of Zr in the fcc (Co, Fe) phase is extremely small. 相似文献
5.
Cemented tungsten carbides with Co, Ni or Fe binders were studied by transmission electron microscopy. Particular attention was paid to phase and grain boundaries. A striking feature is the high frequency of coherent carbide/binder interfaces with Fe. The Fe rich binder adopts an epitaxy orientation relationship with prismatic facets of WC, with a parametric misfit of about 1.5%. A special orientation relationship with basal facets of WC grains is sometimes observed with Ni binder, as already noticed for Co. It is associated with a parametric misfit of about 15%. Binder segregation in WC grain boundaries was studied taking into account the effect of carbon content in the alloys. Whatever the binder, no influence of the carbon content could be pointed out. The analyses performed in random grain boundaries in WC-Co alloys agree with the literature value of 0.5 monolayer of segregated Co while slightly larger values are obtained for Ni and Fe binder. ∑ = 2 special grain boundaries were studied in WC-Co and WC-Ni alloys and no segregation was detected. The higher grain boundary segregation as well as the occurrence of coherent interfaces should influence the mechanical properties of WC-Fe alloys. 相似文献
6.
F.J.J. Kellner R. Lynch S. Virtanen 《International Journal of Refractory Metals and Hard Materials》2010
The effect of temperature and Ca ions on the corrosion behavior of hardmetals was investigated in 0.1 M NaOH and 0.05 M Ca(OH)2 alkaline electrolytes using impedance spectroscopy, potentiodynamic polarization and surface analytical techniques. It was found that calcium containing alkaline solutions efficiently decrease the anodic currents up to 5 times by forming a calcium containing deposit on the top of the WC–Co hardmetal surface, which remains stable even at higher temperatures (40 °C and 60 °C). This positive influence of Ca ions is predominant under polarization in the range from 0 to +0.85 V (Ag/AgCl) but is not apparent under OCP conditions. In NaOH, however, the corrosion resistance strongly decreases at higher temperatures as compared with the room temperature. At the slightly elevated temperature in 0.1 M NaOH the Co binder phase loses its passivity and is almost completely washed out of the compound material. A WC skeleton remains on the surface and hence the ductility in the hardmetal is lost. In the end, the material could completely fail under such operating conditions. Also the Ni alloyed binder loses its strong passivation ability at the elevated temperatures. 相似文献
7.
Multilayers of combinations of NiO, Ni3N and Ni have been grown by ALD and CVD techniques at 250 °C. Layers of low thermodynamical stability have been modified to reach the target structures. The Ni layers have been formed by decomposition of metastable Ni3N layers, i.e., the Ni3N layers act as precursor for Ni film growth. This new reaction route enables production of Ni/NiO layer structures by chemical means for the first time. By choosing suitable low temperature annealing conditions like 180 °C in a 1 Torr hydrogen atmosphere, good control of the interfaces is obtained.It has also been shown that it is possible to grow multilayers which are ordered both with respect to each other, the substrate and the Ni films. For instance the following structure Ni (111)/NiO (111)/α-Al2O3 (00l) has been grown. Moreover, another new reaction route is deposition of thin epitaxial seed layers of NiO (111) for subsequent growth of Ni3N at a high rate. Single phase Ni (111) films could then be obtained by decomposition at 350 °C of the Ni3N layers. The demonstrated reaction routes for film growth in the Ni-O-N system can also be applied in several similar systems. 相似文献
8.
The aluminized coating on type 310 stainless steel prepared by high-activity Al pack cementation method has been annealed at 900 °C for 12 h to transform the brittle δ-Fe2Al5 phase into the more ductile β-FeAl phase. The microstructure is studied in detail with transmission electron microscopy. The thick outer layer has β-(Fe, Ni)Al as matrix with cube-like Cr2Al precipitates. The interfacial layer has a thin layer of metastable FCC phase (layer I) and then mixed β-(Fe, Ni)Al grains and α-(Fe, Cr) grains (layers II and III). The Cr2Al precipitates are present in the β-(Fe, Ni)Al grains in layer II but not in those in layer III, while β-FeAl precipitates are present in the α-(Fe, Cr) grains in both layers. The orientation relationships between various phases, the formation of the layers, and the precipitation of Cr2Al in β-(Fe, Ni)Al are discussed. 相似文献
9.
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. 相似文献
10.
Andreas Ruh 《Corrosion Science》2006,48(3):679-695
Thermogravimetric (TG) experiments have been carried out to study the kinetics of hot corrosion of Fe, Cr and Ni, covered by a molten KCl-ZnCl2 mixture of a composition close to the eutectic (50 mol% KCl-50 mol% ZnCl2). Furthermore binary and ternary phase diagrams were calculated in order to describe the corrosion process. The tests were conducted at a temperature of 320 °C in an atmosphere consisting of argon and oxygen. For iron different stages are observed in a TG curve. They can be attributed to the different reaction steps of iron chloride formation (incubation phase), oxide precipitation (linear stage) and scale formation (parabolic or logarithmic stage). Based on these observations a model, described by Spiegel [A. Spiegel, Molten Salt Forum 7 (2003) 253], is confirmed. For Cr and Ni these stages are not observed. At 8 vol% O2 only slight oxidation of Cr and Ni was observed accompanied by evaporation of the salt deposit. At 16 vol% O2 the rate of oxidation increases and the experiments yield a curve that is either parabolic or logarithmic for both Ni and Cr. As a result it is shown that the solubility of iron chloride in the KCl-ZnCl2 melt is higher than the solubility of nickel chloride and chromium (III) chloride in the KCl-ZnCl2 melt. This enables a higher diffusibility of iron chloride to the upper region of the melt where a higher oxygen partial pressure (p(O2)) is present leading to a higher oxidation rate of iron. 相似文献
11.
Yubi Zhang Changrong Li Zhenmin DuCuiping Guo Junqin LiMiao Liu 《Journal of Alloys and Compounds》2011,509(15):4944-4949
Some primary crystalline phases of the Co-Ni-Sb and the Co-Fe-Sb systems are studied on the basis of the crystalline structure analysis by X-ray diffraction (XRD), the microstructure observation by scanning electron microscopy (SEM), the composition determination by electron probe microanalysis (EPMA) and the phase equilibrium relations of the constituent binary systems. From the experimental measurements of the present work and the phase equilibrium relations of literature reports, the liquidus projections of the Co-Ni-Sb and the Co-Fe-Sb ternary systems are determined. There exist 6 primary crystalline phases in each of the ternary systems, which are γ(A1)-Fcc_A1, β(Co,Ni)3Sb-D03, γ(Co,Ni)Sb-NiAs, ζ(Co,Ni)Sb2-FeS2, η(Co,Ni)Sb3-CoAs3 and Sb-Rhombo_A7 in the Co-Ni-Sb system and γ(A1)-Fcc_A1, α(A2)-Bcc_A2, γ(Co,Fe)Sb-NiAs, ζ(Co,Fe)Sb2-FeS2, η(Co,Fe)Sb3-CoAs3 and Sb-Rhombo_A7 in the Co-Fe-Sb system. Two of invariant reactions are proposed, which are the eutectic reaction L → γ(A1) + β(Co,Ni)3Sb + γ(Co,Ni)Sb in the Co-Ni rich side of the Co-Ni-Sb system and the transition reaction L + γ(A1) → α(A2) + γ(Co,Fe)Sb in the Co-Fe rich side of the Co-Fe-Sb system. 相似文献
12.
The diffusion behaviour of the grain-growth inhibitors (GGI) Cr and V during early sintering stages from 950 to 1150 °C was investigated by means of diffusion couples of the type WC-GGI-binder/WC-binder. Besides Co, also alternative Fe/Ni and Fe/Co/Ni binder alloys were investigated. It was found that the diffusion in green bodies differs significantly from sintered hardmetals. Diffusivities in the binder phase were determined from diffusion couples prepared from model alloys and were found to be almost equal for Co and alternative binder alloys. The diffusion parameters determined from green bodies allowed to estimate the GGI distribution in a hardmetal during heat up. This was subsequently used to estimate an appropriate grain size of VC and Cr3C2 in hardmetals, which is required to ensure a sufficient GGI distribution during sintering before WC grain-growth initiates. 相似文献
13.
The influence of a nitridation treatment on the microstructure and the properties of (W,Ti)C-based cemented carbides with Co and Ni binders is investigated. Nitridation results in the formation of a very fine-grained (Ti,Ta,Nb)(C,N) phase (γN-phase) with inclusions of binder and WC clusters in the near-surface region of the cemented carbides. Rietveld refinements of X-ray diffractograms reveal differences in the domain size and the microstrains of the γN-phase for cemented carbides with Co-binder and Ni-binder. Nitridation reduces the domain size and increases microstrains in the γ-phase. The chemical composition, the morphology and defects of the binder were investigated by TEM/EDX before and after the nitridation treatment. The results reveal that a high nitrogen activity leads to the preferred dissolution of the core-rim structure of the mixed cubic carbide grains during the formation of the γN-phase. The nitridation heat treatment improves the wear and corrosion resistance of cemented carbides with both Co-binder and Ni-binder. 相似文献
14.
José Garcia Greta LindwallOrlando Prat Karin Frisk 《International Journal of Refractory Metals and Hard Materials》2011,29(2):256-259
Kinetics of formation of fcc-free layers on Co-W-Ti-Ta-Nb-C-N cemented carbides was investigated by experimental methods and DICTRA simulations. The layer formation obeys a parabolic law, indicating a diffusion-controlled process. For DICTRA simulations, the influence of the mobilities for all diffusing elements in the liquid binder phase at the sintering temperature was investigated. The best agreement between experimental and simulations was obtained considering that the mobility of all metallic elements is two times slower compared with the mobility of the non-metallic elements. 相似文献
15.
In this study structural and magnetic character of the expanded austenite phase (γN) layer formed on a medical grade CoCrMo alloy by a low-pressure Radio-Frequency plasma nitriding process was investigated. The formation of the expanded austenite phase is facilitated at a substrate temperature near 400 °C for 1, 2, 4, 6 and 20 h under a gas mixture of 60% N2–40% H2. The magnetic state of the γN layers was determined by a surface sensitive technique, magneto-optic Kerr effect (MOKE), and with a scanning probe microscope in magnetic force mode (MFM). Strong evidence for the ferromagnetic nature of the γN-(Co,Cr,Mo) phase is provided by the observation of stripe domain structures and the hysteresis loops. The ferromagnetic state for the γN phase observed here is mainly linked to large lattice expansions (~ 10%) due to high N contents (~ 30 at.%). As an interstitial impurity, nitrogen dilates the host lattice i.e. the Co–Co (or Fe–Fe) distance is increased, which strongly influences the magnetic interactions. An analogy between the magnetic properties of the expanded phases, γN-(Fe,Cr,Ni) and γN-(Co,Cr,Mo), formed in austenitic stainless steel alloys and the CoCrMo alloy of this study is made, and it is suggested that the ferromagnetic states for the γN-(Co,Cr,Mo) and γN-(Fe,Cr,Ni) phases may be correlated with the volume dependence of the magnetic properties of fcc-Co/Co4N and fcc-Fe/Fe4N, respectively. 相似文献
16.
The coating Cr3C2 with 50 wt.% Ni20Cr deposited by high velocity oxy-fuel (HVOF) spray process was characterized in detail to investigate the effect of annealing on the solid particle erosion behaviour and understand the influence of the binder properties. Systematic characterization of the coating was carried out using electron microscopy (scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA)), X-ray diffraction (XRD), microindentation and nanoindentation techniques. The solid particle erosion tests were done on the as-sprayed coating and coatings annealed at 400 °C, 600 °C and 800 °C using silica erodent particles. The coefficient of restitution of the coated samples was also measured by WC ball impact tests to simulate dynamic impacts. The as-sprayed coating consisted of primary carbides and binder that was a mixture of amorphous and nanocrystalline phases. Annealing leads to recrystallisation of binder phase and precipitation of secondary carbides. The coating hardness and binder ductility change with annealing temperature. The erosion resistance improves with annealing up to 600 °C. In the as-sprayed coating, the amorphous phase, inter-splat boundaries and the elastic rebound characteristics affect the erosion response. While in the case of the coating annealed at 600 °C, the presence of ductile crystalline binder, fine carbide precipitates and embedment of erodent particles together improve solid particle erosion resistance. 相似文献
17.
The superhard Ti–Al–Si–N films were synthesized by multi-arc ion plating technology and the influence of vacuum annealing on the structures and properties of the films was investigated. Transmission electron microscopy observation confirmed that the as-deposited Ti–Al–Si–N films were consisted of fcc-TiN/hcp-AlSiN multilayers with a period of 8 nm. The result also showed that a minute layer of cubic structure was observed in hcp-AlSiN layer at the interface between TiN layers and AlSiN layers, which resulted in an epitaxial growth between TiN layers and AlSiN layers. The annealing experiment of the Ti–Al–Si–N films was performed in vacuum furnace for 2 h at temperatures ranging from 700 to 1100 °C. With increasing annealing temperatures, no novel phases were observed indicating that the film retained the sharp interfaces. The grains of the film coarsened and showed mixed orientations at 1100 °C. The transformation of h-AlSiN into h-AlN and Al-depleted AlSiNx and partial crystalline SiNx was speculated during the annealing process by the XPS and DSC results. The film retained super hardness of above 47 GPa even at 1100 °C due to the formation of crystalline SiNx and the minute c-(Al, Si)N layer between c-TiN layers and h-AlSiN layers which delayed the transformation of (Al, Si)N from cubic phase to hexagonal phase. The adhesion strength of the film was also discussed and that vacuum annealing could improve the adhesion strength. 相似文献
18.
S. Bhattacharya G.P. DindaA.K. Dasgupta H. NatuB. Dutta J. Mazumder 《Journal of Alloys and Compounds》2011,509(22):6364-6373
In the current investigation Cu-30Ni alloy was successfully laser deposited on a rolled C71500 plate substrate by Direct Metal Deposition technology. The microstructural investigation of the clad was performed using optical and scanning electron microscopy. The phase and crystal structure analysis was performed using X-ray diffraction technique and transmission electron microscopy. The microstructure consisted of columnar and equiaxed dendrites with face centered cubic crystal structure. The dendrites grew epitaxially from the substrate and layer and bead boundaries. Dendrites’ growth direction 〈0 0 1〉 and growth angle 60° was maintained in each layer. The average primary dendritic arm spacing at the bottom part of the layers was about 7.5 μm and average secondary dendritic arm spacing in the upper part of the layer varied between 2 μm and 4.5 μm. The lattice parameter of the identified phase was found to be longer than that reported in literature. The reported lattice parameters in literature are however from samples processed under equilibrium conditions. The microhardness of the clad was found to be less than the substrate but very consistent along the clad. Cu-30Ni clad specimen showed higher ultimate tensile strength but lower yield strength and percentage elongation as compared to the C71500 substrate. DMD Cu-30Ni clad/C71500 substrate specimen showed the worst mechanical properties. The corrosion resistance of the specimens was found to decrease in the order DMD Cu-30Ni clad, half-and-half DMD Cu-30Ni clad-C71500 substrate, and C71500 substrate. 相似文献
19.
Effects of sintering additives on microstructure and mechanical properties of TiB2-WC ceramic-metal composite tool materials 总被引:1,自引:0,他引:1
Jinpeng SongChuanzhen Huang Bin ZouHanlian Liu Lin LiuJun Wang 《International Journal of Refractory Metals and Hard Materials》2012,30(1):91-95
TiB2-WC ceramic-metal composite tool materials were fabricated using Co, Ni and (Ni, Mo) as sintering additives by vacuum hot-pressing technique. The microstructure and mechanical properties of the composite were investigated. The composite was analyzed by the observations of scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The microstructure of TiB2-WC ceramic-metal composites consisted of the fine WC grains and uniform TiB2 grains. The brittle phase of Ni3B4 and a few pores were found in TiB2-WC-Ni ceramic-metal composite. A lot of pores and brittle phases such as W2CoB2 and Co2B were formed in TiB2-WC-Co ceramic-metal composite. The liquid phase of Co was consumed by the reaction which led to the formation of the pores and the coarse grains of TiB2. The pores, brittle phases and coarse grains of TiB2 were harmful to the improvement of the mechanical properties of the composite. The sintering additive of (Ni, Mo) had a significant effect on the density and the mechanical properties of TiB2-WC ceramic-metal composite. The formation of intermetallic compound of MoNi4 inhibited the consumption of liquid phase of (Ni, Mo). The liquid phase of (Ni, Mo) not only inhibited the formation of the pores and the coarse grains of TiB2 but also strengthened the interface energy between WC and TiB2 grains. The grain size was fine and the average relative density of TiB2-WC-(Ni, Mo) ceramic-metal composite reached 99.1%. The flexural strength, fracture toughness and Vickers hardness of TiB2-WC-(Ni, Mo) ceramic-metal composite were 1307.0 ± 121.4 MPa, 8.19 ± 0.29 MPa m1/2 and 22.71 ± 0.82 GPa, respectively. 相似文献
20.
Jonathan Weidow Hans-Olof Andrén 《International Journal of Refractory Metals and Hard Materials》2011,29(1):38-43
The microstructure of interfaces in WC-Co based cemented carbides with TiC, ZrC, NbC or TaC additions was analysed using energy dispersive X-ray analysis in a transmission electron microscope and using atom probe tomography. Segregation to WC/WC grain boundaries and WC/(M,W)C phase boundaries corresponding to between 0.4 and 1.2 atomic layers of close packed monolayers of Co was observed in all the materials. In addition to Co, Ti, Zr and Nb, but not Ta, segregate to the WC/WC grain boundaries. Segregation was also observed for B, P, Fe and Cr, but not Ni, to the boundaries. These are impurities that originate from the material production. Segregation of Ti, Zr, Nb and Ta to WC/binder phase boundaries was observed. If formation of a MC phase at the interface is assumed, the segregation corresponded to a thickness less than a monolayer. 相似文献