Effect of VC and (Ta,Nb)C on wear of WC–10Co based cemented carbides

Abstract

WC–Co cemented carbides, including small angular tungsten carbides particles, are used extensively to improve wear resistance. Some additives can affect mechanical and wear properties of these materials. In this study, the effect of VC and (Ta, Nb)C content on wear of WC–10Co were considered. The tests were performed at normal load of 230 N and sliding distance of 800 m up to 3200 m. Wear tests were carried out using dry sand/rubber wheel apparatus. Wear rate, standard and modified wear coefficients were calculated. The microstructures of prepared specimens were examined by optical microscopy. The morphological analysis of the worn surfaces was made by SEM. The results show that VC content has more effect than (Ta, Nb)C content on wear behaviour. Wear mechanism is different in the specimens, but removal of cobalt rich phase and fracture of carbide grains is clear in all of specimens. Abrasive wear is prevailing in all specimens.     

晶粒尺寸对WC硬质合金刀具材料摩擦磨损性能的影响

研究了三种不同晶粒尺寸的硬质合金材料的摩擦磨损性能,测量了摩擦系数,采用扫描电子显微镜观察分析了硬质合金磨损表面的形貌变化。结果表明,随着滑动速度和载荷的提高,硬质合金的摩擦系数呈下降的趋势;相同条件下,随着晶粒的减小,硬质合金的摩擦系数略有升高。粗晶粒的硬质合金主要磨损机制为WC晶粒脱落造成的磨粒磨损,细晶粒硬质合金磨损机制主要表现为塑性变形。     

Resistance of a binderless cemented carbide to abrasion and particle erosion

A binderless cemented carbide has been evaluated in abrasion and erosion tests. The binderless carbide was compared with: SiC, Al₂O₃ and two conventional cemented carbides with 6% Co and different WC grain sizes (1 and 7 μm). In the abrasion tests, the materials were ground with silica, silicon carbide and diamond particles in the size range of 5–15 μm. The erosion tests were performed with 80, 200 and 600 μm silicon carbide erodents. The angle of impingement was 45° and the erodent velocity 70 m/s. In all tests, the conventional cemented carbides showed the highest, the binderless cemented carbide an intermediate and the ceramics the lowest wear resistance. Scanning electron and atomic force microscopy of the abraded surfaces revealed that the binderless cemented carbide was worn by a preferential removal of TiC grains. In erosion, the wear mechanism was largely plastic for the cemented carbides, whereas the ceramics were worn by micro-fracture. The SEM analysis also showed an impact scaling effect for the cemented carbides in erosion. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sliding Wear of Electrically Conductive ZrO<Subscript>2</Subscript>−WC Composites Against WC–Co Cemented Carbide

ZrO₂-based composites with WC addition can be successfully machined by electrical discharge machining (EDM) in demineralised water. ZrO₂ composites with 40 vol.% WC were produced from nanocrystalline and micrometre sized WC starting powders in order to compare their tribological behaviour. Friction and wear data are obtained on wire-EDM’ed ZrO₂–WC composite flats sliding against a WC–Co cemented carbide pin using a small-scale pin-on-plate testing rig. Correlations between wear volume, wear rate and friction coefficient on the one hand and material properties and test conditions on the other hand were elucidated. The experimental results revealed that the grain size of the electro-conductive WC-phase exhibits a strong influence on the friction and wear behaviour of the ZrO₂-based composite.     

Wear properties of cemented carbides/Cu-based alloy composite strengthening materials for milling shoes

The microstructure and wear behavior of WC–8TiC–3TaC–8Co cemented carbide and CuZnNi alloy composite strengthening materials have been investigated by means of scanning electron microscopy (SEM), electron dispersion X-ray analysis (EDAX) and wear test. Effect of applied load and sliding distance on the wear behavior of the strengthening materials are also studied in this paper. The results show that the cemented carbide particles are surrounded by the α + β phases in the hardfacing layers. There exists an inter-diffusion zone at the interface of the cemented carbides and Cu-based matrix due to the mutual diffusion of elements. The wear volume of both the WC–8TiC–3TaC–8Co/CuZnNi and WC–8Co/CuZnNi composite strengthening layers increased with the increasing of applied load. The WC–8TiC–3TaC–8Co/CuZnNi hardfacing layers exhibited lower wear volume loss than that of WC–8Co/CuZnNi. According to the results of engineering application, the working efficiency and employing life of the milling shoes, which were strengthened by WC–8TiC–3TaC–8Co/CuZnNi composite materials, is by approximately two to three times the milling tools strengthened by WC–8Co/CuZnNi.     

Carbide tool wear mechanism in turning of Inconel 718 superalloy

Wear surfaces of the cutting tools are analyzed to study the wear mechanism of cemented carbide tools in turning in Inconel 718 superalloys. SEM and EPMA analyses indicated that the wear of carbide tools during high speed turning condition (V = 35 m min⁻¹) was caused by diffusion of elements (Ni or Fe) in workpiece into tool's binder (Co) by a grain boundary diffusion mechanism. This action weakened the bonding strength between carbide particles (WC, TiC, TaC) and the binder (Co). The carbide particles were then detached out of the cemented carbide tool by high flow stresses. The proposed grain boundary diffusion mechanism is also confirmed by theoretical analysis.     

Wear properties of cemented carbides/Cu-based alloy composite strengthening materials for milling shoes

The microstructure and wear behavior of WC–8TiC–3TaC–8Co cemented carbide and Cu–Zn–Ni alloy composite strengthening materials have been investigated by means of scanning electron microscopy (SEM), electron dispersion X-ray analysis (EDAX) and wear test. Effect of applied load and sliding distance on the wear behavior of the strengthening materials are also studied in this paper. The results show that the cemented carbide particles are surrounded by the α-Cu + β-Zn phases in the hardfacing layers. There exists an inter-diffusion zone at the interface of the cemented carbides and Cu-based matrix due to the mutual diffusion of elements. The wear volume of both the WC–8TiC–3TaC–8Co/CuZnNi and WC–8Co/CuZnNi composite strengthening layers increased with the increasing of applied load. The WC–8TiC–3TaC–8Co/CuZnNi hardfacing layers exhibited lower wear volume loss than that of WC–8Co/CuZnNi. According to the results of engineering application, the working efficiency and employing life of the milling shoes, which were strengthened by WC–8TiC–3TaC–8Co/CuZnNi composite materials, is by approximately two to three times the milling tools strengthened by WC–8Co/CuZnNi.     

Effect of 10 wt% VC on the Friction and Sliding Wear of Spark Plasma–Sintered WC–12 wt% Co Cemented Carbides

The effect of 10 wt% VC addition on the friction and sliding wear response of WC–12 wt% Co cemented carbides produced by spark plasma sintering (SPS) was studied. The SPS of WC–12 wt% Co alloys with and without 10 wt% VC, at 1100 and 1130°C, respectively, yielded dense materials with minimal porosity. No eta phase was found in any of the alloys. The WC–12 wt% Co–10 wt% VC alloy showed the formation of a hard WV₄C₅ phase, which improved the alloy's hardness. Friction and dry sliding wear tests were done using a ball-on-disk configuration under an applied load of 10 N and sliding speed of 0.26 m.s^?1, and a 100Cr-steel ball was used as the counterface. A significant improvement in the sliding wear response of the harder and more fracture tough WC–12 wt% Co–10 wt% VC alloy compared to the WC–12 wt% Co alloy was found. Analysis of the worn surfaces by scanning electron microscopy showed that the wear mechanisms included plastic deformation, preferential binder removal, adhesion, and carbide grain cracking and fragmentation.     

腐蚀介质条件下NiCrBSi/WC喷熔层的摩擦学性能研究

采用氧-乙炔火焰喷熔工艺,制备了碳化钨颗粒增强镍基合金喷熔层(NiCrBSi/WC),研究了它在腐蚀介质条件下的摩擦磨损行为与机理,并考察了载荷、滑动速度对其摩擦磨损性能的影响规律。研究结果表明:NiCrBSi/WC具有良好的耐腐蚀磨损性能,且当WC含量为20%时,腐蚀磨损率最低;WC含量超过20%后,由于喷熔层存在“腐蚀原电池”效应,其腐蚀磨损率增大。NiCrBSi/WC的腐蚀磨损率随载荷增加而变大,随速度增大而减小。载荷的增加使喷熔层的犁削磨损加剧,导致摩擦系数和磨损率增大;速度的增大造成摩擦界面温度上升,可生成摩擦转移膜,从而降低了喷熔层的磨损率。     

Particle erosion of cemented carbides with low Co content

Cemented carbides are well known for their high erosion resistance and are therefore used in many demanding applications involving erosion, such as grit blasting nozzles. A number of investigations on the erosive wear resistance of conventional cemented carbides have been published. The present paper is aimed at investigating the erosion resistance of a series of modern cemented carbides containing no or very small amounts of Co, so-called binderless carbides, and relating their performance to conventional sorts.

A series of binderless carbides with varying grain size (0.6, 2 and 5 μm) and binder content (0.25 and 1 wt.%) has been tested. The materials were eroded by SiC particles of three sizes (80, 200 and 600 μm) from four angles (90, 70, 50 and 30°) with a velocity of 70 m/s. Three conventional WC-Co grades of corresponding grain sizes were also tested, under identical test conditions.

The materials are ranked with respect to their erosion rate and scanning electron microscopy is used to analyse the worn surfaces. The influence of carbide grain size and binder amount on the wear behaviour is discussed.     

Influence of secondary phases on the tribological response of electro-discharge machined zirconia-based composites against WC-Co cemented carbide

Three ceramic composite grades, consisting of a ZrO₂ matrix and 40 vol.% WC, TiC_0.5N_0.5 or TiN phase, were completely self-developed by hot pressing powder mixtures of yttria-stabilised zirconia (Y-TZP) and distinctive WC, TiC_0.5N_0.5 or TiN powder sources. The friction and wear characteristics of the zirconia-based composites against WC-Co cemented carbide were investigated by performing dry reciprocating sliding experiments on a pin-on-plate tribometer under various normal contact forces. The generated wear was quantified using surface scanning topography. Post-mortem obtained wear volumes were correlated to real-time recorded wear depth. The ZrO₂-40 vol.% WC grade displayed more favorable tribological properties compared to the other grades with equal secondary phase content. The worn surfaces and the wear debris were analysed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), revealing several wear mechanisms such as polishing, abrasion and wear debris layer formation, mainly depending on the imposed contact load and the material composition.     

Wear characterization of electrodeposited Ni–WC composite coatings

The present contribution reports the tribological properties of Ni–WC composite coatings, electrodeposited on steel substrate. Commercial WC particles with an average size of 5 μm were codeposited with Ni on a mild steel substrate using a Watts bath at 50°C. The effect of plating variables on deposition behavior was studied. The amount of WC in the deposited layer decreased and plating efficiency increased with an increase in current density from 0.1 to 0.3 A/cm². The tribological properties of the coatings were studied using a small amplitude reciprocating friction wear tester. The addition of WC in Ni increases the microhardness of the electrodeposited coatings. An important result is that the presence of embedded WC particles in the electrodeposited coatings results in a much lower coefficient of friction (COF) of 0.34, when compared with pure Ni (COF 0.62) and mild steel (COF 0.54).     

Friction and dry sliding wear behaviour of cermets

The friction and wear behaviour of cermets/steel rubbing pairs were investigated. Friction and wear tests were carried out using three different crèmets on the base of tungsten, titanium and chromium carbides under dry sliding conditions against steel disk (0.45% C). Sliding wear tests were carried out using modified block-on-ring equipment at a sliding speed of 2.2 m/s and normal load 40 N.It is shown that wear resistance and coefficient of friction depend on the type and chemical composition of the cermets. The WC–Co cermets have the highest wear resistance. The wear rate of WC–Co and TiC–NiMo cermets increased with increasing binder content in the cermets. The wear of Cr₃C₂–Ni cermets is more complicated and depends on the composition of cermets. The wear of WC–Co cermets is caused mainly by preferential removal of the cobalt binder, followed by fracture of the intergranular boundaries and fragmentation of the carbide grains. The main wear mechanism in the TiC–NiMo cermets is polishing (micro-abrasion) and adhesion, resulting in a low wear rate. The main wear mechanism of Cr₃C₂–Ni cermets involves thermal cracking and fatigue-related crushing of large carbide grains and carbide framework and also adhesion.     

等离子喷涂WC/Co Fe基涂层摩擦与磨损性能

以普通铸铁为基体,碳化钨陶瓷粉末WC 12Co为热喷涂材料,采用大气等离子法制备WC/Co Fe复合涂层.通过SEM、EDS、XRD等手段对WC/Co Fe涂层微观组织与结构进行表征,并对WC/Co Fe复合涂层耐磨损性能进行测试.结果表明,等离子喷涂制备的WC/Co Fe涂层物相以WC相为主;WC涂层摩擦因数波动小于铸铁材料摩擦因数,表明WC复合涂层具有良好的抗摩擦性能.WC涂层耐磨损性能高于铸铁,主要归因于WC颗粒韧性好、硬度高、抗冲击及抗磨损性能强,与基体金属的结合性好.     

超细碳化钨的无黏结相固结技术研究

利用放电等离子烧结技术尝试烧结出了超细纯碳化钨粉。研究表明该技术所烧结的无黏结相超细碳化钨材料工艺简单，组织精细，致密度高，硬度高，可以用作优异的硬质材料。     

Two-body dry abrasive wear of cermets

The present paper concerns the two-body dry abrasive wear phenomenon of a series of cermets on the base of titanium and chromium carbides with different composition, using a “block on abrasive grinding wheel” test machine. WC–Co hardmetals were used as reference material. Abrasive wear resistance of WC-base hardmetals is superior to that of TiC- and Cr₃C₂-base cermets. The wear coefficient of the cermets reduces with the increase of carbide content in the composites. The volume wear decreases with the increase in bulk hardness. At the first period volume wear of cermets increases linearly with the sliding distance up to the first 100 m; after that the alumina grits become blunt. Scanning electron microscopy examination of the wear tracks in the worn blocks suggests that abrasive wear mechanisms of different cermets are similar and occur through surface elastic-plastic and plastic deformation (grooving). The fracturing of bigger carbide grains and carbide framework the formation of sub-surface cracks by a fatigue process under repeated abrasion is followed by loss of small volumes of the material.     

改性方法对WC基硬质合金刀具材料组织及性能的影响

采用真空烧结法制备了WC基硬质合金刀具材料,研究了不同改性方法对其组织及性能的影响。结果表明:粘结剂镍和钛代替镍提高了硬质合金刀具材料的硬度和抗弯强度,大大降低了后刀面的磨损;添加纳米SiCp使硬质合金刀具材料的组织更加均匀,相对密度、硬度、抗压强度及耐磨性进一步提高;粘结剂钴比镍对WC表面具有更好的润湿性,可进一步提高硬质合金刀具材料的硬度;WC表面化学镀包覆粘结金属钴进一步提高了硬质合金刀具材料的整体性能。     

Impact wear resistance of WC/Hadfield steel composite and its interfacial characteristics

A composite coating of WC/Hadfield steel was fabricated through centrifugal casting process to improve the impact wear resistance of Hadfield steel under the conditions of low or medium impact energy. The interfacial structure between WC ceramic particle and the steel matrix was analyzed with scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The impact wear tests at different impact energy were carried out on a MLD-10 type impact wear rig to investigate the wear-resistant properties of three kinds of composites with different WC particle sizes. For comparison, the wear tests of Hadfield steel were also carried out under the same conditions. The results show that WC particles are partially dissolved in the steel during centrifugal casting. The elements W, C and Fe in steel react to form new carbides such as Fe₃W₃C or M₂₃C₆, which precipitate around former WC particles forming fine particles during subsequent solidification. So the interface between WC particles and Hadfield steel matrix is a strong metallurgical bonding. The composite reinforced with smaller WC particles has better impact wear resistance than that of Hadfield steel regardless of impact energy level. Whereas, the composite reinforced with larger WC particles has better impact wear resistance property than that of Hadfield steel when the impact energy is small but an opposite result is gained when the impact energy is higher. So, it is very essential to choose suitable size of WC particles as reinforcement in Hadfield steel to make the composite material more durable in the service conditions.     

Friction and wear behaviour of WC-Co-Cr3C2-VC cemented carbides obtained from nanocrystalline mixtures

The effect of adding Cr₃C_2, VC or a mixture of both as a grain growth inhibitors to cemented carbides obtained from WC-12 wt.%Co nanocrystalline mixtures on the behaviour of friction and dry sliding wear have been studied. All the wear tests were performed on a tribometer with ball on disc configuration, using a WC-6 wt.%Co ball as a counterpart with normal contact loads of 40 and 60 N, sliding distance of 2000 m and a sliding speed of 0.1 m/s. A significant reduction in the wear rates was observed by the effect of the aforementioned additives, in particular for the VC, which showed an increase in the wear resistance of the order of 90%. The analysis of wear and surface damage were correlated to the observed behaviour.     

Metallurgical and mechanical characteristics of cryogenically treated tungsten carbide (WC–Co)

This paper aims to present the metallurgical and mechanical characterization of cryogenically treated tungsten carbide (WC–Co) in terms of α-, β-, γ-, and η-phase particles and wear behavior, respectively. The specimens of commercially available uncoated WC–Co in the form of round turning inserts were procured and subjected to cryogenic treatment at two levels ?110°C (shallow treatment) and ?196°C (deep treatment) of temperature. The microstructures obtained after cryogenic treatments have been characterized with a prominence to comprehend the influence of cryogenic treatment on the nature, size, and distribution of α-, β-, γ-, and η-phase particles as compared to untreated specimen. The mechanical properties such as hardness and wear rate of the specimens have also been compared by performing Rockwell A hardness test and pin-on-disk wear test, respectively. Microstructures, hardness, wear rate, and analysis of worn surface divulge the underlying metallurgical mechanism responsible in improving mechanical properties of the WC–Co.