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Materials Science and Engineering KTH Royal Institute of Technology
Stockholm, SWEDEN
Adding Rhenium to the Binder in Cemented Carbide A project by
Eyvind Engblom, Jenny Linden, Joakim Larsen, Kristoffer Pettersson and Patricia Lind
Stockholm, May 2013 Analysis and Design of Materials
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Abstract
The aim of the project was to investigate an alternative binder to cobalt (Co) in cemented carbides, for use in for example cutting tools. The problem of the currently used binders is that they soften at the working temperature (800°C). Alternative binder phases to cemented carbides, besides Co, include nickel (Ni) and iron (Fe). Common supplements to the binder phase are super-alloys and noble metals. This study is focused on the effects of using rhenium (Re) in addition to Co in the binder.
In order to evaluate the effects of adding Re, two samples were investigated; one containing WC-Co-Re and one reference tool containing WC-Co. The samples were evaluated using Vickers hardness test, SEM/EDS and light optical microscopy.
The Rhenium sample showed an increase in hardness of 150 MPa. The SEM/EDS analysis showed that Rhenium was dissolved together with cobalt in the binder.
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List of content
1. Introduction……………………………………………………………………………….…….3
2. Background……………………………………………………………………….…………….4
2.1 Manufacturing of Cemented Carbide………………………….……………….….….….…4
2.1.1 Milling…………………………………….………………………….………..……4 2.1.2 Drying/agglomeration………………………….………………….…………..……4 2.1.3 Pressing………………………………………………………………………..……4 2.1.4 Sintering…………………………………...…………………………………..……4
2.2 Binder Phases……………………………………………………………..………………...5 2.3 Rhenium……………………………………………….……………..….….…………....….6 2.4 Adding Rhenium to Cobalt in the Binder Phase……...…………….….....……..……......…6 2.5 Sustainability…………………………………………………………………………….….6
3. Characterization Techniques………………..……………………………………………….…8 3.1 X-ray Diffraction (XRD) …………………………………………………………………..8 3.2 Scanning Electron Microscopy (SEM)/ Electron-dispersive X-ray Spectroscopy (EDS)…8
4. Experimental Work………………..…………………………………………….………......…10
5. Results………………..…………………………………………………………….…………..11 5.1 Light Optical Microscopy (LOM) ………………..………………………………..…..….11 5.2 Hardness ………………..……………………………………………………..………..….12 5.3 Scanning Electron Microscopy (SEM) ………………………………………………....…12 5.4 Electron-dispersive X-ray Spectroscopy (EDS)..………………………………………..…13 5.5 X-ray Diffraction (XRD) ………………………………………………………….…….…14
6. Discussion………………..……………………………………………………………….....…15
7. Conclusion………………..……………………………………………………………..…..…15
8. Acknowledgement…………………………………………………………………………..…16
9. References………………..………………………………………………….……………....…17
10. Appendix 1: Calculations of Sample Composition…..……………………………..…….....…19
Appendix 2: Vickers Hardness……………….....…………………………………………...…21
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1. Introduction
Cemented carbide is a composite material consisting of W carbide (WC) and a binder phase, most commonly used is Co. The material is characterized by hardness, corrosion- and wear resistance and toughness. Cemented carbides are used in many types of applications, due to the fact that different material compositions change the properties of the product. Applications include, for instance, drilling equipment, mining equipment and cutting tools for machining.
The normal working temperature for machining operations is 800°C or above. However, during these operations above 800°C, the Co binder softens making the cutting tool blunt. In order to improve the material properties, the composition of the binder phase could be altered, either through changing the main component of the binder phase or adding a supplement. The main component of the binder phase is usually Co, Fe, Ni or a combination of those. Common supplements to the binder phase are carbides like TiC, TaC, NbC and Mo2C, or elements like Cr, Fe, Cu or Al.
A study by Lisovskii [1] indicates that a Re-Co-binder phase could be preferable to Co alone. The study also shows that Re as a supplement to Co increases the hexagonal structure in the binder phase resulting in increased temperature stability and hardness. Norgan et al., investigated the effect of Re and super-alloy addition to the binder phase in machining tools. The study showed results such as improved tool life, machining speeds and tool wear [2]. The study also concludes that “no clear effect was evident from varying the super alloy-to-cobalt ratio in the alternative binders” which is an indication that Re caused the improvements mentioned above [2].
The aim of the project is to study an alternative binder phase that maintains its properties during machining operations above 800°C. The effects of Re addition to a Co binder phase, as a potential deformation hardening effect, was investigated.
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2. Background
2.1 Manufacturing of Cemented Carbide
2.1.1 Milling
Milling is the first step in the manufacturing process of cemented carbides through liquid-phase sintering. Milling reduces the grain size and mixes WC powder with binder powder. The grain size of WC usually varies between 1-5 µm [7]. In the milling process, a milling liquid and milling bodies are added. Milling liquid must be chosen in consideration to which pressing aid will be used. Milling bodies are added in order to reduce the grain size and receive a homogenous powder mixture.
2.1.2 Drying/agglomeration
After milling, the powder mixture is agglomerated and dried through spray drying. During the drying process of the powder, the milling liquid is evaporated and the powder agglomerate is formed from the particles and pressing aid. The agglomerates are spherical with a diameter of 100-200 µm [7]. This gives the powder the capability of floating, which is important for the pressing process.
2.1.3 Pressing
The agglomerate is then compromised through pressing into the dimensions of the product, but with a greater volume than the final product. There are two different pressing methods, uniaxial, which is the most common, and double sided pressing [7]. The pressing aid is used not only to create good pressing properties for the powder, but also to reduce the wear of the pressing tools.
2.1.4 Sintering
The next step in the manufacturing process of cemented carbides is liquid-phase sintering. During this process, the porosity decreases, resulting in an increase in density and strength of the product [7]. The driving force for the microstructure evolution during the sintering process is an increase in grain size. The sintering temperature varies between 1350-1520°C and is the process in which cavity shrinks and will be filled with the binder [7]. During the liquid-phase sintering the binder phase will melt and dissolve W and C. Pure Co, most commonly used as a binder phase, has a melting point of 1495°C, however, the solubility of both W and C decreases the melting point and the lowest existing melting point of Co is at the ternary eutectic between graphite, FCC-Co and WC at 1275°C [7]. See figure 1.
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2.2 Binder Phases
Co is commonly used as a binder phase for cemented carbide due to its properties of high melting point at 1495°C, the capability to form a liquid phase with WC at 1275°C, and its high temperature strength [3]. Usually the Co content in cemented carbide varies between 3-30%, which affects the material properties [4]. When Co wets WC, W and carbon stabilizes in its cubic form, resulting in Co being stronger as a binder than in its pure form [3]. Co exists in two different atom structures depending on temperature. At high temperature it has a cubic structure, FCC, Co Beta. At lower temperature Co takes a hexagonal form, HCP, called Co epsilon.
Ni and Fe can be used as potential binders [5], [6]. Fe is cheaper than Co, and has the possibility of martensitic hardening [5]. Having a slightly higher melting temperature than Co, Fe provides more difficulties during manufacturing through liquid-phase sintering. Another drawback is that Fe has a possibility to form Fe3C during processing [5], [7]. Ni, on the other hand, does not form a carbide phase. Ni has a lower melting temperature than Co, making it possible to sinter at lower temperatures. A combination of Ni and Fe increases the toughness as well as avoiding the unwanted Fe3C phase[5]. A binder consisting of 75% Fe and 25% Ni shows maximum strength values [5]. However, a binder containing Co remains as the harder and tougher alternative of binder phases in cemented carbides [5].
Figure 1: Phase diagram of WC-Co-C, with 10 wt% Co
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2.3 Rhenium
Re has a high melting point at 3186°C and maintains a high degree of hardness at high temperature. It has a HCP structure and a density of 21.02 g/cm3. It has a young’s modulus of 463 MPa and a Vickers hardness of 2450 MPa. It exists as 10-4 ppm in the earth crust [8].
Re is a noble metal and does not form carbides in WC-Co alloys. This is very important since less noble metals form carbides, which changes the role of the binder.
2.4 Adding Rhenium to Cobalt in the Binder Phase
In the WC-Co-system, the presence of Re increases formation of HCP-structured Co [2]. This is believed to increase the hardness on the microscopic scale, which is presumed to give an overall increase in strength and brittleness for the binder phase.
Re also reduces the stacking-fault energy in Co by a factor of three [2]. Lower stacking-fault energy means wider stacking faults. Stacking faults is an interruption of the regular structure in a material. For example, in a FCC-metal the sequence of atoms is ABCABC- etc. In case of a stacking fault, the sequence may become ABABCA- etc, as can be seen in figure 2. Stacking faults decrease cross slip, which is mobility of dislocations outside the slip planes. In other words, large stacking faults which is large dislocations stops dislocation movement and the material will be deformation hardened [9].
2.5 Sustainability
W and WC have low solubility in water. W is considered to be a lithophilic (soil binding) element. Areas most exposed to emissions of particles are within the proximity of industries, mines, production plants, etc. Studies show that very high concentration of W can be harmful to living organisms [10]. Most health risks are however occupational. The toxic effects of W and WC are still being investigated [11].
Co is widely spread naturally in air, water and ground. It is not considered a risk to health except if consumed in high doses [12].
Figure 2: Illustration of stacking faults in a FCC structure. To the right regular FCC structure, and the left showing stacking faults in the FCC structure [24].
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Although Co is widely spread in nature it only occurs in approximately 10 ppm of the earth crust. W is a rare metal, estimated to occur in about 1.5 ppm. Re is even rarer with an average concentration of 0.001 ppm [13].
WC can be recycled by gathering of used material which is then processed in various ways. An estimation of the average global recycling of used material is about 30 % [14]. W is considered a conflict mineral because of unethical practices associated with mining in The Democratic Republic of Congo [15].
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3. Characterization Techniques
3.1 X-ray Diffraction (XRD)
X-ray diffraction (XRD) is an analysis technique used to investigate and quantify the crystal structures in materials [16]. The x-rays are reflected by planes of atoms, which make up the crystal structure, and scattered into specific directions. Specific angles of incidence will generate an equal angle of reflection from the plane [17]. This is linked to the concept of constructive interference, which means that the x-rays will have the same phase after the reflection, even though they travel over a different distance (see figure 2) [18]. These angles can be calculated using ‘Bragg’s law’, 𝑛𝜆 = 2𝑑 ∗ sin (𝜃), where d=distance between planes, θ=the incidence angle, λ = wavelength of the x-ray and n is an integer. Bragg’s law describes the relation between the wavelength of the x-ray and the distance between the planes in the crystal [17], [18].
In practice, a detector measures the intensity of the x-rays (with known wavelength) that are reflected and the angle. This information can be used to determine both the type of the crystal structures and quantity in the material [17].
In figure 3, two beams of equal wavelength and phase are scattered by two different atom planes. Constructive interference occurs when the distance 2𝑑 ∗ 𝑠𝑖𝑛(𝜃) is equal to an integer times the wavelength [18].
3.2 Scanning Electron Microscopy (SEM)/ Electron-dispersive X-ray Spectroscopy (EDS)
With microscopy techniques it is possible to get information on the microstructure and composition of the material.
Scanning Electron Microscopy (SEM) is a technique used to create an image of a specimen by scanning it with a beam of electrons. The best SEM-microscopes are able to enlarge objects up to 100 000 times [19]. Compare this to a light optical microscope, which can magnify up to 1000 times. SEM has a greater depth of field than light optical microscope.
There are different ways in which SEM-microscopes can be used to gather information from the specimen. Two different detectors can be used in a SEM (as seen in figure # 4): a secondary electron (SE) detector and a backscatter electron (BSE) detector. SE reveals the
Figure 3: Illustrates diffraction of two beams of equal wavelength when constructive interference occurs. [18].
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morphology and topography of the sample through inelastic interactions between the beam electrons and the electrons in the atoms. An inelastic reaction means that there is energy loss. SE are produced when a beam electron hit the sample and excite an electron in the sample [20]. The excited electron can then escape from the sample if it has enough energy. If the detector picks up more SE, the image gets brighter. This method can collect information at a depth of up to 10 Å [20]. BSE are produced by elastic reactions between the beam electrons and the nucleus, which means that there is no energy loss. Scattered angles range up to 180°, but the average angle is around 5° [21]. This reveals knowledge of the composition of the sample.
Another detector that is used in SEM is the EDS (energy-dispersive X-ray spectroscopy) detector. With this technique the chemical composition of the material can be detected. When the electrons hit the surface of the specimen, the impact can excite an electron from one of the inner shells, allowing another electron in an outer shell to jump inwards. The energy difference from this reaction is specific for each element. This information can therefore be used to classify the existing elements in the specimen. [22].
Figure 4: illustration of a set up in a SEM microscope [19]
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4. Experimental work
In order to determine the properties due to Re additions to the binder in cemented carbides, two samples were investigated. One sample contains Re and Co in the binder phase (WC-Co-Re) and the other only Co (WC-Co), as a reference. Both samples had a binder phase content of 10 wt%. The sample with Re addition contains 22 wt% Re in the binder phase, which is 2.2 wt% of the entire WC-Co-Re sample.
From the binary phase diagram of Re and Co, a suitable sintering temperature was determined as 1520°C in order for the binding phase to melt.
Each sample should consist of 100 g and a maximum 7 cm3. For calculations of the samples, see appendix 1.
The metal powders were weighted with a scale and put into a container together with milling liquid, milling bodies and compression aid. The calculated amounts of each component are listed in table 1.
The two containers were then milled for 8h, pressed to receive desired shape and then sintered for 1 hour at 1520°C.
The microstructure of each sample was investigated with LOM, SEM and EDS mapping. Hardness was tested with Vickers.
Table 1: Sample composition
Material Type WC-Co-Re WC-Co
wt% wt%
W VM00637 1.097 0.260
WC WC4B003 88.901 89.747
Co CPUUR09 7.795 9.994
Re LOT: G18X001 2.200 0
Compression aid Polyethylene glycol
2.00 g 2.00 g
Milling bodies PS181 800.00 g 800.00 g
Milling liquid Ethanol 50 ml 50 ml
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5. Results
5.1 Light Optical Microscopy (LOM)
In figure 5 a light optical photograph can be seen for the WC-Co sample. The darker parts are WC and are held together by the light binder phase of Co
In figure 6 and 7, the grey parts are WC grains and the lighter parts are the binder consisting of Re and Co. Parts of concentrated binder, mainly near the edges, can be seen in figure 7.
Figure 6: LOM on WC-Co-Re sample Figure 5: LOM on WC-Co sample
Figure 7: LOM on edge of the WC-Co-Re Sample
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5.2 Hardness
The hardness was measured through Vickers hardness test. Ten indents with 2000 g were made in each sample and the average hardness from these indents was calculated. For calculations of Vickers hardness, see appendix 2.
The two samples show a difference in hardness. The WC-Co-Re sample has an average Vickers hardness of 1635 MPa. The WC-Co sample has a Vickers hardness of 1485 MPa.
5.3 Scanning Electron Microscopy (SEM)
A backscatter SEM picture, figure 8 a), shows the WC-Co-Re sample where the light grey parts are WC grains and the black parts are binder consisting of Re and Co. Figure 8 b) shows the WC-Co sample. Figure 9 shows another part of the WC-Co-Re sample and this is further investigated with EDS mapping in 5.4.
Figure 9: SEM BSE picture of WC-Co-Re sample
Figure 8 a): SEM EBS picture of WC-Co-Re sample b): SEM EBS picture of WC-Co sample
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5.4 Electron-dispersive X-ray Spectroscopy (EDS)
Figure 10 is a 4200x magnification in SEM of the WC-Co-Re sample and is in figure 11 investigated with EDS mapping in order to determine the distribution of W, Re and Co. Figure 11 further investigates the positions of each element in the sample, where the lighter parts in the top two and bottom left pictures show where each element is located in the sample. This shows that Co and Re are located on the same place, indicates that Re together with Co is the binder. The grey area in the center of figure 9 is a Re-Co alloy consisting mostly of Re due to the light color that indicates a high density material. It also shows that there are some WC grains dissolved in the Re-Co alloy.
Figure 10: EDS picture on Re sample
Figure 11: EDS mapping on WC-Co-Re sample
Figure 10: SEM backscatter picture of Re sample, 4200x magnification
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5.5 X-ray Diffraction (XRD)
Figure 12 shows XRD results on WC-Co (red) and WC-Co-Re (blue) sample. The intensity staples show the phases in the sample. Due to technical problems, no conclusions can be drawn from the results.
Figure 12: XRD on WC-Co sample (red) and WC-Co-Re sample (blue)
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6. Discussion
The Vickers hardness test showed that the sample with the Re-Co binder was 150 MPa harder than the sample containing pure Co in the binder. This might indicate that the wanted HCP structure in Co has increased by addition of Re in the binder or due to deformation hardening by stacking faults. There could be several reasons for the increased hardness - but further investigations (studies and techniques) are beyond the scope of this study. This makes it hard to draw any further conclusions regarding the hardening mechanism of Re in the binder phase.
Investigations of the pictures in EDS mapping showed that Re is dissolved in the Co. The WC grains are evenly distributed in the binder phase. This indicates that Re worked, as intended, as a supplement to the binder phase without forming carbides.
The aim of the project was to create a heat resistant cutting tool and determine the mechanical properties at 800°C. Due to limitations in the extent of this project, no such test was done. On the other hand, the Re sample was harder at room temperature which is a good indication of a better starting position for lathing. This does not mean that it has better perseverance during machining operations.
The WC-Co-Re sample was inhomogeneous. One of the main reason could be that the grain size of Re was much larger than the size of the WC- and Co-grains. Modifications to receive a more homogenous microstructure may include smaller Re grains and improved milling process.
The test results are based on a single specimen where there is one manufacturing process used. Further studies might alter the manufacturing process such as the sintering temperature, sintering time, milling and composition in order to receive even better results.
7. Conclusion
• Re addition to the binder increases the Vickers hardness with 150 MPa at room temperature.
• Re was dissolved in Co but resulted in an inhomogeneous microstructure.
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8. Acknowledgement
Thanks to Sandvik Coromant for making this project possible. Thanks to Susanne Norgren and Andreas Blomqvist at Sandvik Coromant for experimental guidance and expertise in the area of cemented carbides.
Special thanks to Ida Borgh for support, guidance and engagement in this project.
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9. References
[1] A. F. Lisovskii, “Sintered Metals and Alloys: Cemented Carbides Alloyed with Ruthenium, Osmium and Rhenium,” Powder Metallurgy and Metal Ceramics, vol. 39, no. 415, pp. 428–433, 2000.
[2] M. Stender, S. Liu, D. Waldorf, and D. Norgan, “Alternative Binder Carbide Tools for Machining Superalloys,” in Internation Conference on Manufacturing Science and Engineering October 7-10, 2008, pp. 1–9.
[3] J. D. Donaldson and D. Beyersmann, “Cobalt and Cobalt Compounds,” Ullman’s Encyclopedia of Industrial Chemistry. pp. 429–465.
[4] S. Liu, K.-H. Xu, and M. Wang, “Preparation of Co powders for cemented carbides in China,” International Journal of Refractory Metals and Hard Materials, vol. 24, no. 6, pp. 405–412, 2006.
[5] H. E. Exner, “Physical and Chemical Nature of Cemented Carbides,” International Metals Reviews, vol. 24, no. 1, pp. 149–173, 1979.
[6] A. Zerr, H. Eschnauer, and E. Kny, “Hard Materials,” Ullman’s Encyclopedia of Industrial Chemistry. pp. 1–21, 2012.
[7] B. Uhrenius, Pulvermetallurgi. Stockholm: Institutionen för Materialvetenskap, 2000, p. 243.
[8] “Rhenium (Revised),” Chemical Elements: From Carbon to Krypton. [Online]. Available: http://www.encyclopedia.com/topic/rhenium.aspx.
[9] S. Jonsson, Mechanical Properties of Metals and Dislocation Theory from an Engineer’s Perspective. Stockholm, Sweden: Department of Material Science and Engineering, 2006.
[10] “Public Health Statement for Tungsten.” [Online]. Available: http://www.atsdr.cdc.gov/phs/phs.asp?id=804&tid=157.
[11] “Tungsten and Its Environmental Impacts,” 2012. [Online]. Available: http://news.chinatungsten.com/en/tungsten-information/406-ti-7.
[12] Lenntech, “Cobalt.” [Online]. Available: http://www.lenntech.com/periodic/elements/co.htm.
[13] “Rhenium (Re),” Encyclopaedia Britannica, 2013. [Online]. Available: http://www.britannica.com/EBchecked/topic/501132/rhenium-Re/.
[14] P. C. Angelo and R. Subramanian, Powder metallurgy: science, technology and applications. New Delhi: Asoke K. Ghosh, PHI Learning Private Limited, 2008, p. 300.
[15] M. A. McCrae, “Four Leading Conflict Materials,” 2013. [Online]. Available: http://www.mining.com/infographic-four-leading-conflict-minerals-26308/.
[16] “XRD - X-Ray Diffraction.” [Online]. Available: http://www.uq.edu.au/nanoworld/index.html?page=160084.
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[17] “The X-ray Diffraction Small Research Facility: What is XRD?” [Online]. Available: http://www.sheffield.ac.uk/materials/research/centres/2.4449/whatxrd.
[18] “Bragg’s Law.” [Online]. Available: http://en.wikipedia.org/wiki/Braggs_law.
[19] “Scanning Electron Microscopy (SEM).” [Online]. Available: http://serc.carleton.edu/research_education/geochemsheets/techniques/SEM.html.
[20] J. H. Wittke, “Secondary Electrons.” [Online]. Available: http://www4.nau.edu/microanalysis/microprobe/Interact-SE.html.
[21] “Back scattered electrons.” [Online]. Available: http://www.emal.engin.umich.edu/courses/sem_lecturecw/sem_bse1.html.
[22] “Energy-dispersive X-ray spectroscopy.” [Online]. Available: http://en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy.
[23] W. D. Callister, Materials Science and Engineering: An Introduction, 7th ed. .
[24] H. Föll, “Partial Dislocations and Stacking Faults.” [Online]. Available: http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_5/backbone/r5_4_1.html.
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10. Appendix 1: Calculations of Sample Composition
Table 1: Data of WC-Co-Re sample
wt% atom% Molar mass[23] C 5.45 42.91 12.01 Co 7.80 12.51 58.90 W 84.55 43.47 183.84 WC 90.00 42.91 195.85 Re 2.20 1.12 186.20
Calculating the wt% of the WC-Co-Re sample
𝑊𝐶: 42.906 ∗ 195.85
42.91 ∗ 195.85+ 1.12 ∗ 186.20+ 12.51 ∗ 58.90+ 0.56 ∗ 183.84 ∗ 100 = 88.901wt%
𝑊:0.564 ∗ 183.84
42.91 ∗ 195.85+ 1.12 ∗ 186.20+ 12.51 ∗ 58.90+ 0.56 ∗ 183.84 ∗ 100 = 1.097𝑤𝑡%
𝐶𝑜:12.51 ∗ 58.9
42.91 ∗ 195.85+ 1.12 ∗ 186.20+ 12.51 ∗ 58.90+ 0.56 ∗ 183.84 ∗ 100 = 7.795 𝑤𝑡%
𝑅𝑒:1.12 ∗ 186.2
42.91 ∗ 195.85+ 1.12 ∗ 186.20+ 12.51 ∗ 58.90+ 0.56 ∗ 183.84 ∗ 100 = 2.206𝑤𝑡%
100 g gives a recipe of: 88.9 g WC, 1.097 g W, 7.795 g Co, 2.206 g Re
Controlling the volume does not exceed 7 cm3: !!.!"#!".!"
+ !.!"#!".!"
+ !.!"#!.!"
+ !.!"#!".!"
= 6.73 𝑐𝑚!
Table 2: Data of WC-Co sample
wt% atom% Molar mass [22] C 42.13 12.01 Co 10.00 15.60 58.90 W 42.26 183.84 WC 90.00 42.13 195.85
Calculating the wt% of the WC-Co sample
20
𝑊:0.13 ∗ 183.84
42.13 ∗ 198.85+ 15.60 ∗ 58.90+ 0.13 ∗ 183.84 ∗ 100 = 0.260𝑤𝑡%
𝑊𝐶:42.13 ∗ 195.85
42.13 ∗ 198.85+ 15.6 ∗ 58.9+ 0.13 ∗ 183.84 ∗ 100 = 89.747𝑤𝑡%
𝐶𝑜:58.9 ∗ 15.6
42.13 ∗ 198.85+ 15.6 ∗ 58.9+ 0.13 ∗ 183.84 ∗ 100 = 9.944𝑤𝑡%
100 g gives a recipe of: 0.260 g W, 89.747 g WC, 9.944 g Co
Controlling the volume does not exceed 7 cm3: !.!"#!".!"
+ !".!"!!".!"
+ !.!""!.!"
= 6.878 𝑐𝑚!
Table 3: contents of samples, in grams
Material Type WC-Co-Re WC-Co Calculated Measured Calculated Measured W VM00637 1.097 1.091 0.260 0.259 WC WC4B003 88.901 88.946 89.747 89.714 Co CPUUR09 7.795 7.788 9.994 9.994 Re LOT:
G18X001 2.200 2.225
Compression aid
Polyethylene glycol
2.00 2.00 2.00 2.06
Milling bodies
PS181 800.00 800.30 800.00 800.02
Milling liquid Ethanol 50 ml 50 ml 50 ml 50 ml
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Appendix 2: Vickers Hardness
𝐻𝑉 =1854 ∗ 2000
𝑑!
Table 1: calculating Vickers hardness
Average Vickers hardness: WC-Co 1514,395 HV=1635 MPa
WC-Co-Re 1666,652 HV= 1485 MPa
WC-‐Co d1 [µm] d2 [µm] d [µm] HV 49,6451 49,0211 49,33310 1523,572 49,2234 49,4193 49,32135 1524,298 49,4628 50,2426 49,85270 1491,978 48,2126 49,4186 48,81560 1556,046 49,6546 50,4302 50,04240 1480,688 49,8381 49,8387 49,83840 1492,834 48,8274 48,6245 48,72595 1561,777 49,2502 48,8117 49,03095 1542,407 50,6563 50,6325 50,64440 1445,696 49,2053 49,4257 49,31550 1524,659
WC-‐Co-‐Re d1 [µm] d2 [µm] d [µm] HV 47,8457 47,0066 47,42615 1648,557 46,8049 47,4408 47,12285 1669,847 47,8007 47,8155 47,80810 1622,321 47,4110 46,2408 46,82590 1691,093 46,8141 46,8135 46,81380 1691,967 46,6027 46,6113 46,60700 1707,015 45,5915 47,5913 46,59140 1708,159 47,6139 47,2387 47,42630 1648,547 47,4207 48,0178 47,71925 1628,368 46,7826 48,0097 47,39615 1650,645
Figure 1: Vicker’s hardness test on WC-Co cutting tool