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

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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