WC-Ni Alloy Research Articles

Strengthening and toughening of WC-Ni alloys by adding novel (Ti, Hf, Ta, Nb, Zr)(C, N) high entropy powder

A strong and tough WC-11Ni cemented carbide was prepared by adding ultrafine (Ti, Hf, Ta, Nb, Zr)(C, N) high entropy powder with ellipsoidal-like particles of ∼300 nm and a single phase composition via low pressure sintering. WC-11Ni-0.6(Ti, Hf, Ta, Nb, Zr)(C, N) alloy has excellent mechanical properties: bending strength of 2752 MPa, HV30 hardness of 14.76 GPa and toughness of 15.35 MPa·m1/2, which increase by 22.58%, 20.29% and 20.78% respectively, compared with pure WC-11Ni alloy. (Ti, Hf, Ta, Nb, Zr)(C, N) addition with a small content not only inhibits the abnormal growth of WC grains, but also eliminates the aggregation of Ni binder phase and strengthens Ni binding phase. This work provides a simple route to strengthen and toughen WC-Ni alloys by introducing a novel high entropy inhibitor.

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.

Shrinkage and microstructure evolution during sintering of cemented carbides with alternative binders

Cemented carbides are used in the cutting tools industry thanks to their exceptional mechanical properties. Manufactured by the powder metallurgy route, they are made of a hard WC phase with a ductile metallic binder, most commonly Co. Due to the lower availability of Co and its classification as carcenogenic material by the REACH European Regulation, new metallic binders have to be considered: Fe and Ni binders are investigated in this work. Because Co is the most common binder used in the hard metal industry for decades, there is still a lack of knowledge regarding the specific effect of alternative binders on shrinkage and microstructure evolution of cemented carbides.The purpose of this work is to understand the effect of binder nature specifically, comparing classic Co binder used in the industry to pure Fe and Ni binder including the influence of carbon content. Shrinkage behaviour and microstructure evolution of WC-M alloys (M = Co, Ni, Fe) are studied from dilatometry experiments as well as qualitative and quantitative microstructural characterisations. Solid state sintering is delayed to higher temperature for WC-Fe in comparison to WC-Co and WC-Ni alloys. Densification mechanisms are discussed in relation with dilatometry results, microstructural analyses, DFT calculations and a theoretical kinetic model from the literature.

Interface characteristics in cemented carbides with alternative binders

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.

Carbide grain growth in cemented carbides sintered with alternative binders

Cemented carbides are composites made of a hard refractory ceramic phase and a ductile binder, most commonly WC and Co, respectively. Since the use of cobalt in the hard metal industry is questioned by the new European regulation on chemicals, extensive research has been done to develop new grades based on a Co-Ni-Fe binder. With similar mechanical, physical properties and affinity to C and W, nickel and iron are the best candidates for an efficient binder in cemented carbides. As mechanical properties are strongly dependent on the materials microstructure, and especially on the WC grain size, understanding the effect of the binder on the final microstructure is crucial.In this work, the carbide grain growth behaviour of WC-M alloys (M = Co, Ni, Fe) with different carbon contents is discussed from qualitative and quantitative microstructural analyses. Whereas grain growth is more or less inhibited in WC-Fe alloys, increasing carbon content promotes grain growth in WC-Co and WC-Ni alloys, with a slight abnormal grain growth in case of Ni binder. Different mechanisms for grain growth are discussed, in relation with the observed morphology of WC grains after sintering.

Development of the 90WC-8Ni-2Cr3C2 cemented carbide for engineering applications

In this paper, the microstructure and mechanical properties of 90WC-8Ni 2Cr3C2 cemented carbide, developed by powder metallurgy, were investigated using optical and scanning electron microscopy, XRD, and hardness tester. The results showed that the addition of 2 wt% Cr3C2 in the WC-Ni alloy system, using conventional adding method, was not favorable to densification. The porosity was characterized by the presence relatively large elongated pores distributed in the microstructure. As a result, there were not significant improvement of the hardness and flexural strength of the WC-8Ni-2 Cr3C2 cemented carbide in comparison with WC-10Ni cemented carbides without Cr3C2 addition, obtained from the literature. Fracture toughness results showed that the cemented carbide WC-8Ni-2Cr3C2 presented higher fracture toughness than that of WC-Co, WC-Co-2Cr3C2, and WC-Ni alloys from literature, which may be mainly attributed to the effectiveness of Cr3C2 to inhibit the excessive grain growth of the WC particles, producing a more refined and tough microstructure. Thus, despite the porosity, the mechanical properties values obtained of the developed 90WC-8Ni-2Cr3C2 cemented carbide are adequate for several engineering applications, where is required a good balance between hardness, wear resistance, and toughness.

Microstructure and mechanical properties of 90WC-8Ni-2Mo2C cemented carbide developed by conventional powder metallurgy

In this paper, the microstructure and mechanical properties of a WC-Ni based cemented carbide with the addition of 2wt% Mo2C, processed by conventional powder metallurgy, was investigated. With the addition of only Mo2C in the WC-Ni alloy system, the wettability between the WC and Ni binder phase was improved, which was confirmed by the increased density, hardness, fracture toughness and flexure strength of the cemented carbide obtained, which is superior than those observed in WC-10Ni cemented carbides and similar to those observed in WC-Co and WC-Ni-TiC-Mo2C cemented carbides. Microstructural examinations of the developed cemented carbide 90WC-8Ni-2Mo2C indicated that there was no excessive grain growth of the WC particles during sintering, confirming that Mo2C is a grain growth inhibitor as effective as other carbides such as VC, TiC, Cr2O3, showing that the addition of only Mo2C is able to improve the overall mechanical properties of the WC-Ni alloy system without sacrificing the toughness.

Abrasion wear, thermal shock and impact resistance of WC-cemented carbides produced by PECS and LPS

The effects of rapid sintering by pulse electric current sintering (PECS), variation in starting WC size (0.1–0.8μm), Ni as a Co binder substitute and TiC, NbC and Mo2C additions on the microstructure, abrasion wear, thermal shock and impact resistance of WC–Co and WC–Ni alloys were studied. Abrasion wear tests were done using a ball-on-disk tribometer, with 100Cr6 steel and silicon nitride balls. Use of PECS gave finer microstructures with poorly distributed binder pools than similar liquid phase sintered (LPS) samples, although large angular WC grains of up to 1μm occurred in the nano (0.1μm) and ultrafine (0.4μm) grades. Addition of 5wt.% NbC to WC–10Co (wt.%) had negligible effect on the WC grain size, while 5wt.% Mo2C to WC–6.25TiC–9.3Ni significantly improved WC grain growth inhibition, leading to increased hardness (from ~13 to >21GPa) and reduced wear rate (from 2.73×10−4 to <8.0×10−5mm3·N−1·m−1), compared to the LPS WC–9.3Ni. Thermal shock and impact resistance were measured using a thermal imaging camera and force gauges while testing the samples as cutting tools on Ti–6Al–4V under aggressive interrupted milling conditions. The LPS samples had better thermal shock and impact resistance, due to their higher fracture toughness (>12.5MPa·m0.5) and B3B transverse rupture strength (>2100MPa), as a result of the larger and better binder pool distribution.

WC-Ni-SiCw Alloys Prepared by Hot-Pressed Sintering

WC-Ni-SiCw alloys were prepared through hot-pressed sintering by using WC, Ni, VC, TaC and SiC nano-whisker as raw materials. The influence of SiC whisker addition on the microstructure and mechanical properties of the as-prepared WC-Ni alloys was investigated. Except WC hard phase and Ni binder phase, no other phase was detected by X-ray diffraction. The observations by scanning electron microscope demonstrated that there were some micropores in the as-prepared materials, and their size and quantity increased with increasing amount of SiCw. Vickers hardness and flexural strength tests indicated that the bulk hardness of WC-Ni-SiCw alloys slightly decreased with increasing amount of SiCw; and the flexural strength increased at first and then decreased with increasing amount of SiCw. The alloys with 0.53 wt% SiCw presented the highest flexural strength of 1700 MPa.

スチールコード伸線用の超硬合金ダイスの摩耗

Cemented carbide dies with the five categories of composition, namely, WC-Co straight alloy, TaNbC-, Cr3C2- or VC-containing WC-Co alloys and WC-Ni alloy, were fabricated by sintering and HIP-treatment. The wear behavior of these cemented carbide dies for drawing steel cord wire is examined, and material properties such as hardness, transverse-rupture strength and corrosion resistance are evaluated. Through the above investigations, it is particularly noted that the TaNbC-containing alloy shows the longest life time of steel cord drawing die, which is followed by Cr3C2-containing alloy, WC-Co, VC-containing alloy and WC-Ni alloy. The results on strength and corrosion resistance have no relation with the drawing die life. The hardness has some degree of relation with the die life; for example, among the same category alloy, there is such a tendency that the longer die life is obtained for the higher hardness. However, it is not able to explain simply by the viewpoint of hardness the reason why TaNbC-containing alloy has the longest life although the VC-containing alloy has the finest grain size and the highest hardness. The wear mechanism of cemented carbide dies for steel cord wire drawing was discussed to consider WC/Co interface adhesion.

Impact of wire-EDM on dry sliding friction and wear of WC-based and ZrO2-based composites

Abstract Linearly reciprocating sliding wear experiments on WC-Co and WC-Ni cemented carbides and ZrO2-WC, ZrO2–TiCN and ZrO2–TiN composites with different surface finishes corresponding to sequential wire-EDM or grinding/polishing have been performed using an ASTM G133 system with WC-6 wt%Co cemented carbide as counter body. The WC-based alloys contained 6 up to 12 wt% of binder, whereas the amount of secondary phase for the ZrO2-based composites was 40 vol.% pin-on-plate testing was carried out in unlubricated circumstances at constant oscillating frequency with fixed displacement amplitude and normal contact loads ranging between 15 and 35 N. 3D topography mapping and volumetric quantification of the wear tracks was obtained by surface profilometry. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were employed to observe morphological and chemical features of worn surfaces and wear debris. The identified wear mechanisms are discussed. The highest wear resistance was encountered with the WC-Ni alloy, whereas the ZrO2–TiN composite displayed the lowest wear resistance. Wire-EDM surfaces displayed higher friction and wear compared to their ground/polished equivalents, especially during running-in. The inferior wear resistance of wire-EDM’ed samples could be correlated to 3-point bending tests, revealing a considerable decrease in flexural strength compared to ground samples.

Tribological Characteristics of WC-Ni and WC-Co Cemented Carbide in Dry Reciprocating Sliding Contact

Four WC-based cemented carbides produced by liquid phase sintering with different binder composition and similar carbide grain size were tested in order to evaluate their dry reciprocating sliding friction and wear behavior against WC-6 wt.%Co cemented carbide. The pin-on-flat wear experiments were executed on a Plint TE77 tribometer using normal contact loads of 15 N up to 35 N and a sliding velocity of 0.3 m/s. Analysis of the wear tracks revealed several wear mechanisms; i.e., polishing of WC grains, abrasion, adhesion, formation of wear debris layer, and removal of the surface binder from between the WC grains. Higher contact load increased the wear volume and slightly decreased the friction coefficient. The hardness as well as the type and the amount of binder phase were found to affect the wear resistance significantly. One WC-Ni alloy exhibited superior tribological characteristics compared to the other grades.

K-1014 パルス通電焼結法によるWC-Ni系超硬合金の開発(S12-2 粉末成形とその評価(2))(S12 粉末成形とその評価)

K-1014 パルス通電焼結法によるWC-Ni系超硬合金の開発(S12-2 粉末成形とその評価(2))(S12 粉末成形とその評価)

Fracture resistance and strength of two-phase WC–Ni alloy

Microcracking near a crack tip in a material with microinhomogeneity is regarded as a stochastic process. Both the critical deformation energy density and minimum ligament size of a structural element at global failure are related to a fracture resistance parameter which depends also on the strength. This parameter is also known as the critical energy density factor. For composites it is shown that transition of material behaviour from one structural state to another could alter the fracture resistance depending on character of the critical defect size and strength. The theoretical result is shown to be in agreement with the experimental data.

傾斜機能材料 ＷＣ‐Ｎｉ‐Ｃｒ系合金の腐食特性に及ぼすＣｒ，Ｃの影響

Cemented carbides with nickel binder have been widely used in place of cemented carbide with cobalt binder for improved corrosion resistance. For the cemented carbides of WC-Ni and WC-Ni-Cr alloys, the corrosion properties and the effects of carbon and Cr3C2 contents on their corrosion resistance were investigated by both immersion test and electrochemical measurement. In immersion test, dissolved elements and the amounts of them in 3%NaCl and 3%NaC1+0.1NH2SO4 solutions were analyzed by ICP spectroscopy. In electrochemical measurement, polarization curves in these solutions were measured. The anodic reaction was dissolution of the binder metals in both solutions, and the cathodic reactions were reduction of dissolved oxygen in 3%NaC1 solution, and reductions of both proton and dissolved oxygen in 3%NaC1+0.1NH2SO4 solution respectively. Anodic current densities in the polarization curves showed that corrosion resistance of WC-Ni-Cr was superior to that of WC-Ni. WC-Ni alloys with low carbon content showed the superior corrosion resistance to that of high carbon alloy, which was revealed by both conspicuous appearance of passivated region and low anodic current density in polarization curve.

微粒ＷＣ‐Ｎｉ合金中に生じるポア

It has been known by the present authors that mechanical properties of WC-Ni alloy were improved towards the values of WC-Co alloy with decreasing grain size of WC, and also the micro-grained WC-Ni alloy could be obtained by the addition of VC, etc., with the result that small pores were apt to appear in the micro-grained WC-Ni alloy in the sintered state, differing from the case of micro-grained WC-Co alloy. Then, the study on this subject, that is, on the reason why small pores often appear in the micro-grained WC-Ni alloy was carried out. The WC-10mass%Ni alloy containing VC up to 5 mass% in binder was used as specimens.It was suggested that the fact that the Ni rich agglomerates peculiar to WC-Ni alloy (consisting of Ni and fine WC particles) formed during ball-milling of mixture could not perfectly be removed from the ball-milled mixture, and the fact that the temperature at which liquid phase appeared was higher in WC-Ni alloy by about 701C, comparing with in WC-Co alloy, were the most responsible for the above subject.

微粒ＷＣ‐Ｎｉ超硬合金の機械的性質

The micro-grained WC-10mass%Ni medium carbon alloys having additional VC up to 10mass% in binder were sintered in vacuum at 1450-1500°C, using starting WC powder with particle size of 0.7 and 1.4μm. The mechanical properties of the alloys such as hardness(HV) and transverse-rupture strength(σm) were mainly studied as a function of carbide grain size (dWC) in the range from 1.5 to 0.4μm. The results obtained were compared with those of micro-grained WC-10mass%Co alloys previously reported by the present authors.It was found that the RV and σm of WC-Ni alloy increased with decreasing dWC towards the values of micro-grained WC-Co alloy. It was also found that the above values became almost the same as those of WC-Co alloy, when dWC decreased to the values less than 0.5-0.6μm. The phenomena were in detail discussed from a viewpoint of characteristics different between Ni and Co binder metals.

Corrosion Behaviour of Ion Implanted Wc–Co and Wc–Ni Alloys in Acid and Chloride Containing Media

Alloys of WC–Co (6-30 wt-%Co) and WC–Ni (6-15 wt-%Ni) were implanted with chromium, molybdenum, and titanium ions at fluences from 1 × 1021 to 4 × 1021 ions m-2. Their corrosion resistance was evaluated before and after implantation using accelerated electrochemical techniques in a 0.005M H2S04 and a 0.001M NaCl + 0.05M Na2S04 solution. In general, ion implantation tended to decrease the corrosion rate and improve the pitting resistance. The most promising results were obtained with molybdenum implantation, which increased the passive range and substantially raised the pitting potential.

ＷＣ‐１５％Ｎｉの二相域に及ぼすＣｒ３Ｃ２添加の影響

The WC-Ni alloy containing Cr3C2 has been widely used for non-magnetic or corrosion resisting parts. However, the (WC+γ) two-phase region of WC-Ni alloy affected by the Cr3C2 addition seems not to have been studied. The present work was concerned with this subject for WC-Cr3C2-15%Ni alloy. It was found that the two-phase and the adjacent (WC+γ+Cr3C2) three-phase regions shifted markedly to the high carbon side. It was also found that the solid solubility of Cr in the binder phase varied according to the carbon content of alloy and it showed a maximum value of about 16% for the alloy containing about 5.8%C.

ＷＣ‐Ｎｉ系超硬合金の破壊じん性

Fracture toughness of WC-(4-20)%Ni alloys and WC-10%Ni alloys with different WC grain size (1.31-2.21μm) was compared with that of WC-Co alloy. Effect of various additions on the fracture toughness of WC-10%Ni alloy was also investigated.The results obtained are as follows:(1) Fracture toughness of WC-Ni alloy increases with the increase of the Ni content and the WC grain size.(2) WC-Ni alloy shows a fracture toughness equal to WC-Co alloy in relation to hardness. However, for the same WC grain size, the WC-Ni alloy shows a lower hardness and a higher fracture toughness than those of WC-Co alloy. The reason is considered to be in that the binder phase of WC-Ni alloy has lower hardness and higher fracture toughness.(3) By addition of Si, Ti, Cr and Mo which are soluble in Ni, the hardness of the WC-Ni alloy is increased. It is found that WC-Ni alloys containing 6%Si, 1-2%Ti, 5-10%Cr and Mo in the Ni binder show the same hardness and fracture toughness as the WC-Co alloy has.