WC-Fe-Ni composite

Journal Pre-proof Influence of B4C coating on graphitization for diamond/WC-FeNi composite

Youhong Sun, Jinhao Wu, Linkai He, Baochang Liu, Chi Zhang, Qingnan Meng, Xuliang Zhang PII:

S0263-4368(19)30565-7

DOI:

https://doi.org/10.1016/j.ijrmhm.2020.105208

Reference:

RMHM 105208

To appear in:

International Journal of Refractory Metals and Hard Materials

Received date:

18 July 2019

Revised date:

8 January 2020

Accepted date:

18 January 2020

Please cite this article as: Y. Sun, J. Wu, L. He, et al., Influence of B4C coating on graphitization for diamond/WC-Fe-Ni composite, International Journal of Refractory Metals and Hard Materials(2019), https://doi.org/10.1016/j.ijrmhm.2020.105208

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© 2019 Published by Elsevier.

Journal Pre-proof Influence of B4C coating on graphitization for diamond/WC-Fe-Ni composite Youhong Suna,b,c, Jinhao Wua, Linkai Hea, Baochang Liua,c, Chi Zhanga, Qingnan menga,c,* [email protected], and Xuliang Zhanga a

College of Construction Engineering, Jilin University, Changchun, China;

b

c

China University of Geosciences, Beijing, China;

Key Laboratory of Drilling and Exploitation Technology in Complex Conditions

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of Ministry of Land and Resources, Jilin University, Changchun, China. *

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Corresponding author.

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Abstract

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Diamond/WC-Fe-Ni composite is a potential composition for impregnated diamond drill

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bits. It is necessary to avoid the graphitization of the diamond from Fe and Ni under the powder metallurgy process. Boron carbide (B4C) was coated on diamond, and

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diamond/WC-Fe-Ni composites were consolidated by hot pressing at different temperatures.

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The influences of sintering temperature and interfacial structure on bending strength and wear behavior were investigated. The bending strength for diamond/WC-Fe-Ni composite was dependent on matrix densification and interfacial graphitization. Un-coated diamond was eroded by Fe-Ni matrix and partially converted to graphite during the sintering process at all sintering temperatures. In opposite, B4C coating was beneficial to matrix densification at a lower sintering temperature, and delayed the appearance of graphitization to around 1300°C. Therefore, the diamond/WC-Fe-Ni composites with B4C coating exhibited larger bending strength and better wear behavior at a relative low sintering temperature.

Journal Pre-proof Keywords: B4C coating; diamond/WC-Fe-Ni; hot pressing sintering; interfacial graphitization

1. Introduction Impregnated diamond composite bits are widely used in drilling engineering, including geological survey, oil and gas exploitation, mining prospecting and civil

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constructions [1-4]. The working layer is the part of the bits which directly contact and

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cut the rock, and mainly contains diamond, skeleton materials and bonding materials.

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Tungsten carbide (WC) is one of the most typical skeleton materials; its volume

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fraction is largely dependent on the rock properties [5-9]. Cobalt has been regarded as

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the best bonding material because of its self-sharpening abrasiveness, good wetting ability, and good combination of toughness and hardness [10]. However, cobalt is an

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expensive and strategic metal with great pollution and toxicity, and its supply is not

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steady [11,12]. Thus, it is of great interest to replace Co by relatively low price and environmentally friendly metals [13]. In recent years, the combination of Fe and Ni has been considered to be a potential substitution material [14,15]. It is well known that diamond is the metastable allotrope of carbon, and thermodynamic studies have shown that the graphitization of diamond proceeds automatically [16]. The starting temperature of graphitization for diamond catalyzed by iron is 700°C [17], which often occurs during the sintering process [18]. Furthermore, the high dissolution potential of C in Fe and higher diffusion rate of C in Fe than Co result in the continuing conversion of diamond to graphite at a high

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temperature [19]. The occurrence of graphite has great impact on the interface between diamond and matrix, which highly influences the life of the working layer and the efficiency of impregnated diamond bit. To conquer the graphitization issue of iron-based diamond composite, two practical ways have been studied, in terms of advanced powder densification

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technology and interface modification. Using cutting edge sintering technology, such

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as pulse plasma sintering (PPS) [20] or spark plasma sintering (SPS) [21] could reduce

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the sintering time. But in the test of SPS consolidated method, thermally damaged

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un-coated diamond has still been observed at sintering temperature of 1280 °C. The

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more feasible and practical way is, therefore, interface modification. Strong carbide forming elements such as titanium [22], chromium [23], vanadium [24], molybdenum rare earth [25,26], boron [27], tungsten [21], and metal borides and, metal nitrides

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[19],

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such as CrB2, NbN, TiN, and VN, were applied to avoid the direct contact between diamond and Fe, Ni, Co by means of coating on the diamond or addition in the matrix [19,21-27].

Thermodynamic calculations have shown that adding Cr and Ti into the matrix component results in an interfacial reaction that and automatically separates diamond from Fe matrix by forming metallic carbides around diamonds. Because the Gibbs free energy of forming chromium carbide, or titanium carbide are lower than the diamond graphite transition, the graphitization is suppressed [16]. The theoretical calculation has been verified by experiments; coatings such as Ti, Cr, Mo have been

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reported to be an efficient way, not only to protect diamond from direct contact with matrix, but also to improve the interface between diamond and matrix via chemical bonding [19]. Raman spectroscopy analysis has verified that Ti coating successfully avoids graphitization of diamond for a diamond/Cu-Fe composite sintered at 900 °C [28].

In our previous work [27], the addition of element B improved the properties of

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iron-based diamond composites. Therefore, it is valuable to study the effect of B4C

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coating on interfacial graphitization in iron-based diamond composites.

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In this paper, WC-Fe-Ni composites with un-coated diamond and B4C-coated

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diamond are sintered by hot pressing under vacuum. The ability of B4C coating to

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prevent graphitization is investigated. Furthermore, the influence of interfacial

behavior is studied.

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structure between diamond and WC-Fe-Ni matrix on bending strength and wear

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2. Materials and Methods

B4C was coated on high pressure high temperature (HPHT) diamond particles (HSD90, particle size 35/40 mesh (380~425 μm), Henan Huanghe Whirlwind International Corp., Ltd., China) and chemical vapor deposition (CVD) diamond beams (1 mm×1 mm×10 mm) by heating with a mixture of boron (B, 95 % pure, Aladdin Industrial Corporation) and boric acid (H3BO3, 99.5 %, Sino Pharm Chemical Reagent Corp., Ltd., China) at 1200 °C for 6 h in Ar atmosphere in a tube furnace [29,30].

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The composite with HPHT diamond particles were used for testing mechanical properties as well as wear behavior. The designations for different combinations of composition and sintering temperature are shown in Table 1. The volume fraction of diamond particles were 20 %. In the matrix component, WC (99.8 % pure, 74μm) was 80 wt.%, while Fe (99.8 % pure, 100 μm), Ni (99.8 % pure, 100 μm) shared the

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remaining 20 wt.%, with a weight ratio of 3:1. WC, Fe, Ni, and diamond particles (if

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needed) were mechanically mixed with methane at room temperature. Each sample

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was filled into a graphite mold, the shape of sample and mold was showed in Figure

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1(a).

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The composite with a CVD diamond beam was used for the interface analysis. The demonstration of hot pressing procedure for a composite with a CVD diamond

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beam is shown in the Figure 1(b). A pair of alumina rings with holes ( 1 mm× 1 mm)

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ensured the CVD diamond beam to remain vertical during the hot pressing. The composites with CVD diamond beams were used for the EDS line scan and Raman mapping analyses.

The sample was desiccated in a vacuum drying oven before fabricated by hot pressing. The temperature raised at a steady heating rate of 10 °C/min to sintering temperature, which ranged from 1100 to 1300 °C in this paper. The holding time was 10 minutes, and then cooling with the furnace. A pressure of 25 MPa was applied from room temperature to the sintering temperature and maintained to 600 °C during the furnace cooling. The sintered samples for mechanical properties and wear

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behavior were polished by electroplated diamond grinding disc before the following tests. Laser cut was applied to get the cross section of the samples with CVD diamond beam for EDS line scans and Raman maps. The phase analysis was evaluated by X-ray diffractometry (XRD, Shimadzu XRD6000, Kyoto, Japan) with Cu Kα radiation. The microstructure and composition

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were investigated by scanning electron microscopy (SEM, Hitachi-SU8010, Tokyo,

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Japan) with an energy dispersive spectrometer (EDS, Horiba). The SEM picture of a

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B4C-coated diamond particle is shown in Figure 2. The Raman mapping analysis

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(Horiba Raman Spectrometer) was applied for phase distribution of carbon at

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interface between matrix and CVD diamond beam. The Raman mapping was carried out on 110 μm×50 μm area with 21 lines and 5 points per line.

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The density of each sample was tested by Archimedes’ principle, and the relative

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density was calculated using the theoretical density of diamond (3.52 g/cm3), WC (15.63 g/cm3), Fe (7.8 g/cm3), and Ni (8.9 g/cm3). The hardness of matrix was determined by the Rockwell hardness scale C (HRC), using a Rockwell hardness tester (Huayin HRS-150, Yantai, China) with a load of 150 kg and a dwelling time of 10 s. At least 10 random points were applied for each sample for improving test accuracy. Bending strength for each sample was tested by using a three-point bending test, and was calculated by following formula 1:

σ=3FL/ 2bh2

(1)

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where σ is the bending strength, MPa; F is the axial load, N; L is the length of support span, 24 mm; b is the width, 5 mm; and h is the thickness, 8 mm [27] . Wear behavior of samples was measured by an abrasive ratio tester [2]. The sample was held at a clamp and ground by an 80 mesh SiC grinding wheel with a linear velocity of 15 m/s, 500 g pressure load. The size of samples was 12 mm× 8 mm× 5 mm, and the abrasive

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R=ΔMw/ ΔMs

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ratio (R) was calculated as

(2)

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where ΔMw and ΔMs means the weight loss of SiC grinding wheel and sample.

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3. Results

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3.1. Characteristics of the diamond/WC-Fe-Ni composites

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Demonstrated below in Figure 3 is a typical surface of WC-Fe-Ni composite with B4C-coated diamonds, wherein diamonds are homogeneously dispersed. The diamond particles are embedded in the matrix, and the edges of them are sharp.

Figure 4 illustrates the phase structure of B4C-coated diamond reinforced WC-Fe-Ni composites, in which the XRD peaks are attributed to WC and Fe-Ni patterns. Comparing with the standard JCPDF#51-0939 card, the diffraction peaks located at 31.5 °, 35.6 °, 48.3 °, 64.0 °, 65.8 °, 73.1 °, 75.5 °, and 77.1 ° are ascribed to the typical WC structure. And the diffraction peak located at around 44 ° is the product of Fe-Ni alloy according to the reference [31]. The diamond patterns are not

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revealed in the spectra since diamonds are impregnated in the matrix. Moreover, the volume fraction of diamond is low and therefore XRD peaks for diamond and the coating are difficult to be detected [20]. The grain size of WC for samples sintered at all temperature is 20 nm which is calculated by Scherrer’s equation since the sintering temperature is far below the melting temperature of WC (2870 °C).

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3.2. Relative density of the diamond/WC-Fe-Ni composites

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The relative density of the three series of composites shown in Figure 5. Among

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the three series of composites, the relative density generally increases as the sintering

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temperature increases. With increasing sintering temperature from 1100 to 1200 °C

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the relative density for matrix composite rises from 74 to 90 %, meanwhile the

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relative density for un-coated diamond particles and B4C-coated diamond particles

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reinforced composites rises from 76 to 93 %, and 90 to 97 %, respectively. Generally, adding diamond into matrix results in a decrease in relative density, no matter whether the diamond is Cr-coated, Ti-coated or un-coated [32]. However, the relative densities of composites with B4C-coated diamonds are higher than those of un-coated diamonds at the same sintering temperature (1100 to 1200 °C), because of the enhanced sintering from Fe-Ni-B-C solid solution (discussed in next section). As the sintering temperature reached 1300 °C, the relative density for matrix composite rises to 98 %, and the relative density for both un-coated or B4C-coated diamonds reinforced composites rises to 95 %.

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The hardness of matrix was determined by the Rockwell hardness scale C (HRC), which is listed in Table 1. As shown in Table 1, the hardness of matrix increases from 10 to 76 HRC with increasing sintering temperature from 1100 to 1300 °C because of the densification.

3.3. Bending strength of the diamond/WC-Fe-Ni composites

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Figure 6 shows the bending strength of three series of composites sintered at

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different temperatures. As the sintering temperature increases from 1100 to 1300 °C,

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the bending strength of matrix goes up from 229 to 1700 MPa. Meanwhile, the

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bending strength of composites with un-coated diamond particles increases from 136

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to 559 MPa. In contrast, the bending strength of composites with B4C-coated

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diamonds exhibits an increase followed by a slight decrease. The samples with

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B4C-coated diamonds sintered at 1100 °C (B1) show a bending strength of 454 MPa, which is about three times the bending strength of samples with un-coated diamonds sintered at 1100 °C (D1) and even larger than the bending strength of matrix samples without diamond sintered at 1100 °C (T1). When sintering temperature reached 1200 °C, the samples with B4C-coated diamonds (B2) exhibit a maximum bending strength of 644 MPa, which is still larger than the bending strength of composite with un-coated diamonds (D2, 473 MPa) but lower than that of matrix (T2, 798 MPa) sintered at the same temperature. When the sintering temperature increased to 1300 °C, the bending strength of composite with B4C-coated diamonds (B3) slightly decreases to 524 MPa, which is close to the bending strength of samples with

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un-coated diamonds (D3, 559 MPa) but quite lower than the bending strength of matrix samples (T3, 1646 MPa) sintered at 1300 °C.

3.4. Wear behavior of the diamond/WC-Fe-Ni composites Figure 7 demonstrates the wear behavior of composites sintered at different temperatures. The abrasive ratios of matrix (not shown on the figure)

fluctuate from

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1 to 10, which are obviously lower than that of samples with diamond suggesting that

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the addition of diamond particles gives rise to a transition of wear mechanism. The

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abrasive ratio of samples with B4C-coated diamonds decreases steadily from 2417 to

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1281, and ends up at 607 as sintering temperature increases from 1100 to 1300 ℃. In

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opposite, for un-coated diamonds, the abrasive ratios of samples first increases from

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384 at sintering temperature of 1100 ℃ to 888 at sintering temperature of 1200 ℃ and

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then decreases to 281 at sintering temperature of 1300 ℃.

3.5. Interfacial structure of the diamond/WC-Fe-Ni composites Figure 8 depicts the fracture information for samples with un-coated and B4C-coated diamond particles sintered at 1100 and 1300 °C. As shown in Figure 8a, the composite with un-coated diamonds (D1) exhibits a porous structure. In addition, large number of pores and cracks can be observed at the interface between diamond and matrix. In opposite, the composite with B4C-coated diamonds exhibits a denser structure (B1, see Figure 8b); only a few pores can be found in the high magnification image. Moreover, the interface between B4C-coated diamond and matrix is

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continuous and intact. For both composites with un-coated and B4C-coated diamonds sintered at 1300°C ( D3, B3, see Figure 8c and 8d), the matrix is fully densified. About 10 μm thick plate-like structure, however, is observed at the interface between diamond and matrix.

The element distribution was analyzed under EDS line scanning by using four

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laser-cut cross section of CVD diamond beam/WC-Fe-Ni composites as shown in

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Figure 9. The line scan is divided into three regions: diamond, matrix and interface.

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As shown in Figure 9a-c, a sharp decrease in intensity of the C signal is observed in

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the interface between diamond and matrix. In opposite, the composite with un-coated

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diamond sintered at 1200°C (D2) exhibits a significant difference. The intensity of C signal shown in Figure 9d exhibits a steadily decreasing trend from diamond region to

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matrix region, and the length of interface region is about 5μm. It implies the

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occurrence of the interface reaction.

Raman mapping is carried out in the interface region of samples with CVD diamond beams sintered at 1200 ℃ for further identifying the interfacial structure. As shown in Figure 10, graphite index is used to illustrate the graphite phase and diamond phase percentage of carbon. The index of graphite is calculated as in the following expression.

Index(graphite)=Intensity (graphite)/(Intensity (graphite) +Intensity (diamond))

(3)

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In Figure 10, obviously, large amount of graphite exist at the interface for the composite with un-coated diamonds sintered at 1200 ℃. Moreover, the graphite phase infiltrates into the diamond phase around 30 μm deep (at y=-30 to y=0, x=0 to x=20 in the Figure 10). On the contrary, the sample with B4C-coated diamonds sintered at 1200 ℃ (B2, Figure 11) shows a different morphology; the graphite is rarely

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distributed at the interface between diamond and matrix.

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4. Discussion

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For the sample with un-coated diamond particles sintered at 1100°C (D1), lots of

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pores can be found in the magnified SEM picture in Figure 8a, which leads to the high

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porosity and low density. When the sintering temperature rises to 1200 °C, the pores

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disappear and the relative density approaches 93%. Compared with the composites with un-coated diamonds, furthermore, the addition of B4C coating on diamonds gives

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rise to nearly fully dense composites at 1100 to 1200 °C. As shown in Figure 8b the matrix is fully dense; few obvious pores can be found even in the magnified picture. During sintering, the following reactions occurred at the interface between metal matrix and B4C coating on diamond [33].

4Fe+xB4C 4FeBx+xC

(4)

4Ni+xB4C4NiBx+xC

(5)

In addition, as well known, B and C atoms are easily dissolved and dispersed in Fe-Ni matrix. It means the B4C coating on diamond is decomposed by Fe-Ni matrix

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and forms a Fe-Ni-B-C solid solution. As the phase diagram suggests [34,35], B and/or C solute atoms lower the melting point for Fe-Ni alloy, resulting in a higher density and better mechanical properties for the composite sintered at the same temperatures. The samples with B4C-coated diamonds sintered at 1100 °C (B1), therefore, exhibit a relatively high density (90 %) compared with matrix samples (T1, 74 %) and samples

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with un-coated diamonds (D1, 76 %) sintered at the same temperature (as shown in

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Figure 5). Moreover, it should be noted that the interface between B4C-coated

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diamond and matrix is continuous and clear, and no graphite is obtained. It implies

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that the interfacial reaction is limited at 1100 °C, and the released carbon elements are

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completely dissolved into Fe-Ni alloy. With increasing sintering temperature, the interfacial reactions between B4C coating and matrix are intensified. As shown in

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SEM images (Figure 8d), enormous plate-like structures are produced at the interface

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between diamond and matrix for the composite with B4C-coated diamonds sintered at 1300 °C (B3). When B4C coating is completely absorbed by matrix, Fe-Ni matrix directly reacts with diamonds resulting in the graphitization of diamond. Because of the limitation of diffusion rate between C and Fe-Ni, large amounts of graphite are difficult to dissolve into Fe-Ni alloy in the limited sintering time and form the plate-like graphite interfacial structure. Raman maps and EDS line scan suggest that significant graphitization for composite with B4C-coated diamonds (B3) would not appear until sintering temperature reaches 1300 °C. Compared with un-coated diamond/WC-Fe-Ni composites, for which the graphitization is obtained at 1200 °C,

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the addition of B4C coating is beneficial to delay the graphitization by Fe-Ni alloy during sintering. The bending strength for matrix composites without diamond is dependent on density, which is widely observed in materials sintered by hot pressing process [36,37]. A composite consist of matrix, reinforcement and interface. In this work, diamond is

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considered as a rigid body because of its high hardness and modulus, therefore, it has

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no contribution to bending strength of composite. The bending strength of composite,

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thereby, depends on the strength of matrix and interface. With increasing sintering

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temperature, the densification of matrix contributes to an increase in bending strength,

a weaker interface.

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meanwhile, the high sintering temperature gives rises to a graphite interface leading to

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The SEM images of diamond samples after bending test (Figure 8) show that

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the diamond surface is clean, and no dimple is observed on diamond. It means the strength of interface between diamond and matrix for all diamond composites is weaker than the strength of corresponding matrix. Anomalously high bending strength for samples with B4C-coated diamonds sintered at 1100 °C (B1) compared with the corresponding matrix sample without diamond sintered at 1100 °C (T1) is attributed to the B4C coating as a sintering aid. For samples with un-coated diamonds sintered at 1100 °C (D1), a large amount of holes is observed in matrix and interface between diamond and matrix. Hereby, both matrix strength and interfacial strength for D1 samples are low, resulting in the lowest bending strength. With increasing sintering

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temperature to 1200 °C, the obvious increase in matrix strength gives rise to the increase in strength of both composites with un-coated (D2) and B4C-coated diamond (B2). The existence of graphite interface between diamond and matrix in sample with un-coated diamond sintered at 1200 °C (D2) limits the increase in bending strength, therefore, the bending strength of D2 sample is lower than that of samples with

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B4C-coated diamond (B2). With further increasing sintering temperature to 1300 °C,

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the bending strength of matrix (T3) exhibits a significant increase. However, that of

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samples with un-coated diamonds (D3) shows a slight increase, meanwhile, that of

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B4C-coated diamonds (B3) endures a slight decrease. Since the wide graphite

strengths are almost the same.

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interface between diamond and matrix exists in both composites, their bending

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The wear behavior of impregnated diamond samples consists of a cyclic

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process. Firstly, the emerged diamonds provide the major contributions for grinding. Secondly, during grinding process, the diamonds detach and lead to the emergence of subsurface diamond. Lastly, the latter diamonds provide the major contributions for grinding. The whole regeneration process means the abrasive ratio of composite is dependent on the appropriate detachment of diamonds. Three potential failures contribute to the premature detachment of diamonds, including diamond breakage, matrix wear and interface fracture [38,39]. As mentioned in the early researches under the same testing configuration, no diamond breakage is obtained after the wear test [2,27,40]. The abrasive swarf is

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automatically siphoned off during the tests, so the matrix would not be abraded intensively. Furthermore, the bending strength and abrasive ratio do not have a positive relationship as the previous study [2,27], which confirm that the properties of the matrix might not directly influence the abrasive ratio of composites with diamond. So the only potential failure is the interface fracture.

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From the SEM result (see Figure 8), three interface structures can be seen, a

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discontinuous interface (D1), and continue interface without graphite (B1), and a

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continuous interface with graphite (D2, B2, D3, B3). In the samples with a

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discontinuous interface, the fracture initiates from the pores and cracks near the

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diamond, which also means the actual bonding area is smaller than the samples with continuous interface, thus bringing about the undesirable abrasive ratio (D1,384). The

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sample sintered at 1100°C with B4C-coated diamond (B1) has a clean boundary as

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seen in Figure 8b and has the highest abrasive ratio (2417). The graphite on the interface is believed to be the brittle phase and reduces the interface strength. It can be seen from the Figure 8c (D3, with un-coated diamond) and Figure 8d (B3, with B4C-coated diamond), enormous plate-like structure is produced at the interface between diamond and matrix, which is confirmed to be graphite in the Raman spectrum testing. So, the abrasive ratios of these group of samples mainly depend on the amount of graphite, ranked in the following order, B2 (1281), D2 (888), B3 (607), D3 (282). So, the wear behavior of impregnated diamond samples in this study is highly dependent on the interface between the diamond and the matrix.

Journal Pre-proof 5. Conclusions Boron carbide is coated on diamond and diamond/WC-Fe-Ni composites, which are consolidated by the hot-pressing method at different temperatures. B4C coating dissolves and disperses in Fe and Ni matrix, forming a Fe-Ni-B-C solid solution, resulting in a higher density and better mechanical properties than the samples with

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un-coated diamond sintered at the same temperatures. Un-coated diamond is eroded

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by Fe-Ni matrix and converted to graphite during the sintering process before 1200

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°C, as identified by Raman spectrometry. In opposite, B4C coating delays the

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significant appearance of graphitization to around 1300 °C. The bending strength of composite with B4C-coated diamond is up to 644 MPa, compared to 559 MPa for the

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composite with un-coated diamond because of its brittle graphite interface between

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diamond and matrix. The wear behavior does not show a positive relationship with

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bending strength; it mainly reflects the aspect of interface. The continuity and intactness of the boundary of composite with B4C-coated diamond sintered in 1100 °C contributes to desirable abrasive ratio (2417). Increasing the sintering temperature can result in equal or worse graphitization and poorer wear behavior. Therefore, the B4C coating on diamond decreases the sintering temperature requirement and contributes to enhancement of bending strength and wear behavior for diamond/WC-Fe-Ni composite. Acknowledgements: We would greatly thank Lijian Chen from 46th Research Institute of China Electronic Science and Technology Group Corporation for the aiding of sampling

Journal Pre-proof species for Raman mapping and EDS lining. And we would like to give thanks to Bing Yin, for her donation in technical support of polishing species through the experiment. Funding: This research was funded by National Natural Science Foundation of China - Youth Science and Technology Fund Project under grant 41502344, Jilin Province Science and Technology Development Plan Project - Youth Research Fund Project under grant 20160520043JH, Special grant for the 9th batch of China Postdoctoral Science Foundation, and Graduate Innovation Fund of Jilin University under grant 101832018C047.

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5. 6. 7. 8. 9. 10.

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Weidenmann, K.A.; Tavangar, R.; Weber, L. Mechanical behaviour of diamond reinforced metals. Materials Science and Engineering: A 2009, 523, 226-234, doi:https://doi.org/10.1016/j.msea.2009.05.069. Sun, Y.; Wu, H.; Li, M.; Meng, Q.; Gao, K.; Lü, X.; Liu, B. The Effect of ZrO2 Nanoparticles on the Microstructure and Properties of Sintered WC– Bronze-Based Diamond Composites. Materials 2016, 9, 343. Mizuuchi, K.; Inoue, K.; Agari, Y.; Kawahara, M.; Makino, Y.; Ito, M. Trend in development of diamond particle dispersed metal matrix composites. Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 2012, 59, 714-720, doi:10.2497/jjspm.59.714. Zhao, X.; Li, J.; Duan, L.; Tan, S.; Fang, X. Effect of Fe-based pre-alloyed powder on the microstructure and holding strength of impregnated diamond bit matrix. International Journal of Refractory Metals & Hard Materials 2019, 79, 115-122, doi:10.1016/j.ijrmhm.2018.11.015. Keshavan, M.K. Diamond-containing cemented metal carbide. 1991. Moriguchi, H.; Arisawa, Y.; Otsuka, M. Superhard composite member and method of manufacturing the same. 1999. Houston, R.S.; Fisk, R.C. Method for making a metal bonded diamond abrasive tool. 1971. Koljaka, F. Sintered metal carbide containing diamond particles and induction heating method of making same. 1971. Keshavan, M.K. Cemented carbide composite for a downhole tool. 2016. Dai, H.; Wang, L.; Zhang, J.; Liu, Y.; Wang, Y.; Wang, L.; Wan, X. Iron based partially pre-alloyed powders as matrix materials for diamond tools. Powder Metallurgy 2015, 58, 83-86, doi:10.1179/0032589915Z.000000000220. Lison, D. Human toxicity of cobalt-containing dust and experimental studies on the mechanism of interstitial lung disease (hard metal disease). Critical reviews in toxicology 1996, 26, 585-616.

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1.

of

References:

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17.

18.

19.

20.

21.

22.

23.

of

ro

-p

16.

re

15.

lP

14.

na

13.

Gál, J.; Hursthouse, A.; Tatner, P.; Stewart, F.; Welton, R. Cobalt and secondary poisoning in the terrestrial food chain: data review and research gaps to support risk assessment. Environment international 2008, 34, 821-838. Waratta, A.; Hamdi, M.; Ariga, T. Effect of Decreasing of Cobalt Content in Properties for Diamond/Cemented Carbide Tools. In International Conference on Advancement of Materials and Nanotechnology 2007, Rusop, M., Wul, W.T., Kamarulzaman, N., Subban, R.Y., Noorsal, K., Saleh, M.H., Ibrahim, R., Idris, R., Zainol, I., Zakaria, F.A., Eds. 2010; Vol. 1217, pp. 1-5. Schubert, W.D.; Fugger, M.; Wittmann, B.; Useldinger, R. Aspects of sintering of cemented carbides with Fe-based binders. International Journal of Refractory Metals and Hard Materials 2015, 49, 110-123, doi:10.1016/j.ijrmhm.2014.07.028. Yu-Zan Hsieh, S.-T.L. Diamond tool bits with iron alloys as the binding matrices. Materials Chemistry and Physics 2001, 72, 121-125. Li, W.-S.; Zhang, J.; Dong, H.-F.; Chu, K.; Wang, S.-C.; Liu, Y.; Li, Y.-M. Thermodynamic and kinetic study on interfacial reaction and diamond graphitization of Cu—Fe-based diamond composite. Chinese Physics B 2013, 22, 018102, doi:10.1088/1674-1056/22/1/018102. Artini, C.; Muolo, M.L.; Passerone, A. Diamond–metal interfaces in cutting tools: a review. Journal of Materials Science 2011, 47, 3252-3264, doi:10.1007/s10853-011-6164-6. Cabral, S. Influence of the use of coatings on diamonds on the properties of diamond composites obtained by powder metallurgy. MSc dissertation 2009, 1-90. Chang, R.; Zang, J.; Wang, Y.; Yu, Y.; Lu, J.; Xu, X. Preparation of the gradient Mo layers on diamond grits by spark plasma sintering and their effect on Fe-based matrix diamond composites. Journal of Alloys and Compounds 2017, 695, 70-75, doi:https://doi.org/10.1016/j.jallcom.2016.10.172. Michalski, A.; Rosinski, M. Sintering Diamond/Cemented Carbides by the Pulse Plasma Sintering Method. Journal of the American Ceramic Society 2008, 91, 3560-3565, doi:10.1111/j.1551-2916.2008.02738.x. Shi, X.L.; Shao, G.Q.; Duan, X.L.; Xiong, Z.; Yang, H. The effect of tungsten buffer layer on the stability of diamond with tungsten carbide–cobalt nanocomposite powder during spark plasma sintering. Diamond and Related Materials 2006, 15, 1643-1649, doi:10.1016/j.diamond.2006.01.021. Klotz, U.E.; Liu, C.; Khalid, F.A.; Elsener, H.-R. Influence of brazing parameters and alloy composition on interface morphology of brazed diamond. Materials Science and Engineering: A 2008, 495, 265-270. Lu, J.; Cao, Z.; Qi, F.; Qian, M.; Zhang, W. Evolution of interface carbide diamond brazed with filler alloy containing Cr. Diamond and Related Materials 2018, 90, 116-125, doi:10.1016/j.diamond.2018.10.009.

Jo ur

12.

Journal Pre-proof

30.

31.

32.

33.

34. 35. 36.

37.

of

ro

29.

-p

28.

re

27.

lP

26.

na

25.

Mechnik, V.; Bondarenko, N.; Kuzin, N.O.; Gevorkian, E. Influence of the Addition of Vanadium Nitride on the Structure and Specifications of a Diamond–(Fe–Cu–Ni–Sn) Composite System. Journal of Friction and Wear 2018, 39, 108-113. Dai, Q.; Luo, C.; Xu, X.; Wang, Y. Effects of rare earth and sintering temperature on the transverse rupture strength of Fe-based diamond composites. Journal of materials processing technology 2002, 129, 427-430. Zou, Q.H. Diamond Tools Matrix Composites of Co Replaced by Fe with Doping Rare Earth. Advanced Materials Research 2012, 424-425, 848-851, doi:10.4028/www.scientific.net/AMR.424-425.848. Li, M.; Sun, Y.; Meng, Q.; Wu, H.; Gao, K.; Liu, B. Fabrication of Fe-Based Diamond Composites by Pressureless Infiltration. Materials (Basel) 2016, 9, doi:10.3390/ma9121006. de Oliveira, L.J.; Cabral, S.C.; Filgueira, M. Study hot pressed Fe-diamond composites graphitization. International Journal of Refractory Metals and Hard Materials 2012, 35, 228-234, doi:10.1016/j.ijrmhm.2012.03.015. Ras, A.; Auret, F.; Nel, J. Boron carbide coatings on diamond particles. Diamond and Related Materials 2010, 19, 1411-1414. Sun, Y.; Meng, Q.; Qian, M.; Liu, B.; Gao, K.; Ma, Y.; Wen, M.; Zheng, W. Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles. Scientific reports 2016, 6, 20198, doi:10.1038/srep20198. Polini, R.; Delogu, M.; Marcheselli, G. Adherent diamond coatings on cemented tungsten carbide substrates with new Fe/Ni/Co binder phase. Thin solid films 2006, 494, 133-140. Webb, S.W. Diamond retention in sintered cobalt bonds for stone cutting and drilling. Diamond and Related Materials 1999, 8, 2043-2052, doi:10.1016/s0925-9635(99)00167-3. Aizenshtein, M.; Mizrahi, I.; Froumin, N.; Hayun, S.; Dariel, M.; Frage, N. Interface interaction in the B4C/(Fe–B–C) system. Materials Science and Engineering: A 2008, 495, 70-74. Raghavan, V. B-Fe-Ni (boron-iron-nickel). Journal of Phase Equilibria and Diffusion 2007, 28, 377-379, doi:10.1007/s11669-007-9098-6. Romig, A.; Goldstein, J. Determination of the Fe-rich portion of the Fe-Ni-C phase diagram. Metallurgical transactions A 1978, 9, 1599-1609. Sun, Y.; He, L.; Zhang, C.; Meng, Q.; Liu, B.; Gao, K.; Wen, M.; Zheng, W. Enhanced tensile strength and thermal conductivity in copper diamond composites with B4C coating. Scientific Reports 2017, 7, doi:10.1038/s41598-017-11142-y. Sun, Y.; Zhang, C.; He, L.; Meng, Q.; Liu, B.-C.; Gao, K.; Wu, J. Enhanced bending strength and thermal conductivity in diamond/Al composites with B 4

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Journal Pre-proof

of

ro -p re lP

40.

na

39.

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38.

C coating. Scientific reports 2018, 8, 11104, doi:10.1038/s41598-018-29510-7. Dhokey, N.B.; Utpat, K.; Gosavi, A.; Dhoka, P. Hot-press sintering temperature response of diamond cutting tools and its correlation with wear mechanism. International Journal of Refractory Metals and Hard Materials 2013, 36, 289-293, doi:https://doi.org/10.1016/j.ijrmhm.2012.10.008. Tönshoff, H.K.; Hillmann-Apmann, H.; Asche, J. Diamond tools in stone and civil engineering industry: cutting principles, wear and applications. Diamond and Related Materials 2002, 11, 736-741, doi:https://doi.org/10.1016/S0925-9635(01)00561-1. Li, M.; Sun, Y.H.; Dong, B.; Wu, H.D.; Gao, K. Study on effects of CNTs on the properties of WC-based impregnated diamond matrix composites. Materials Research Innovations 2015, 19, S5-59-S55-63, doi:10.1179/1432891715Z.0000000001337.

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Table 1. The designation, composition, and physical properties of composites. Rockwell Sintering

Hardness

Designation Composition

Density(g/cm3) Temperature(°C)

Scale

T1

Matrix

1100

9.77±0.12

10.3±2.2

T2

Matrix

1200

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C(HRC)

62.9±1.4

T3

Matrix

1300

12.95±0.14

75.8±0.5

1100

D2

1300

10.68±0.08

1100

10.15±0.03

1200

10.88±0.08

1300

10.68±0.04

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Un-coated D3

10.40±0.05

1200

diamond/Matrix

8.56±0.06

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D1

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Un-coated

11.90±0.03

diamond/Matrix B4C-coated

B1

diamond/Matrix B4C-coated B2 diamond/Matrix B4C-coated B3 diamond/Matrix

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Figure 1. The demonstration of hot pressing procedure. (a) Composite with HPHT diamond particles. (b) Composite with a CVD diamond beam.

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Figure 2. Micro-morphology of B4C-coated diamond.

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Figure 3. Optical picture of polished samples with B4C-coated diamond.

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Figure 4. XRD Spectra of B4C-coated diamond particles/WC-Fe-Ni with different

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sintering temperatures.

Journal Pre-proof Figure 5. Relative density of B4C-coated diamond particles/WC-Fe-Ni, un-coated

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diamond particles/WC-Fe-Ni, and WC-Fe-Ni with different sintering temperatures.

Journal Pre-proof Figure 6. Bending strength of B4C-coated diamond particles/WC-Fe-Ni, un-coated

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diamond particles/WC-Fe-Ni, and WC-Fe-Ni with different sintering temperatures.

Journal Pre-proof Figure 7. Abrasive ratio of B4C-coated diamond particles/WC-Fe-Ni, un-coated

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diamond particles/WC-Fe-Ni, and WC-Fe-Ni with different sintering temperatures.

Journal Pre-proof Figure 8. Micro-morphology of samples. (A) un-coated diamond particles/WC-Fe-Ni sintered at 1100℃; (B) B4C-coated diamond particles/WC-Fe-Ni sintered at 1100℃; (C) un-coated diamond particles/WC-Fe-Ni sintered at 1300℃; (D) B4C-coated

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diamond particles/WC-Fe-Ni sintered at 1300℃.

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Figure 10. The interface of B4C-coated CVD diamond beam/WC-Fe-Ni, and un-coated CVD diamond beam/WC-Fe-Ni. (a) B4C-coated CVD diamond beam/WC-Fe-Ni sintered at 1100℃; (b) un-coated CVD diamond beam/WC-Fe-Ni sintered at 1100℃; (c) B4C-coated CVD diamond beam/WC-Fe-Ni sintered at 1200℃;

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(d) un-coated CVD diamond beam/WC-Fe-Ni sintered at 1200℃.

Journal Pre-proof Figure 9. Index of graphite of un-coated CVD diamond beam/WC-Fe-Ni sintered at

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1200℃

Journal Pre-proof Figure 10. Index of graphite of B4C-coated CVD diamond beam/WC-Fe-Ni sintered

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Author Statement

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at 1200℃.

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Sun Youhong: Conceptualization, Resources, Supervision, Funding acquisition. Wu Jinhao: Formal analysis, Investigation, Data curation, Writing - original draft preparation. He Linkai: Investigation. Liu Baochang: Methodology, Writing review and editing. Zhang Chi: Visualization. Meng Qingnan: Validation, Writing original draft preparation, Writing - review and editing, Project administration, Funding acquisition. Zhang Xuliang: Visualization.

Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Highlights  B4C coating is benefit to matrix densification, and delay the diamond graphitization.  B4C coating contributes to enhancement bending strength for diamond/WC-Fe-Ni composite (up to 644 MPa).  B4C coating contributes to improvement in abrasive ratio (up to 2417), increased by 6 times.

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