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Preparation of polycrystalline cubic boron nitride compact by high-pressure infiltration using cemented carbide
Int. Journal of Refractory Metals and Hard Materials 41 (2013) 138–142
Contents lists available at ScienceDirect
Int. Journal of Refractory Metals and Hard Materials journal homepage: www.elsevier.com/locate/IJRMHM
Preparation of polycrystalline cubic boron nitride compact by high-pressure infiltration using cemented carbide H.S. Jia a, Y.L. E a, J. Li a, X.P. Jia b, H.A. Ma b, F.Z. Liu a, L.H. Liu a, H.B. Li a,⁎ a b
Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, China State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
a r t i c l e
i n f o
Article history: Received 13 November 2012 Accepted 23 February 2013 Keywords: HPHT PcBN compact Infiltrating method Cemented carbide
a b s t r a c t Polycrystalline cubic boron nitride (PcBN) compacts, using the infiltrating method in situ by cemented carbide (WC–Co) substrate, were sintered under high temperature and high pressure (HPHT, 5.2 GPa, 1450 °C for 6 min). The microstructure morphology, phase composition and hardness of PcBN compacts were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The experimental results show that the WC and Co from WC–Co substrate spread into cubic boron nitride (cBN) layer through melting permeability under HPHT. The binder phases of WC, MoCoB and Co3W3C realized the interface compound of PcBN compact, and the PcBN layer formed a dense concrete microstructure. Additionally the Vickers hardness of 29.3 GPa and cutting test were performed when sintered by using cBN grain size of 10–14 μm. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Polycrystalline cubic boron nitride (PcBN) compacts, consisting of a cubic boron nitride (cBN) layer on a cemented carbide (WC–Co) substrate, are sintered relying on binding phases at high temperature and high pressure (4.8–5.2 GPa, 1400–1500 °C) conditions. As kind of important tool materials of cBN, PcBN compacts fully reflect the material requirements of modern manufacturing industry, and widely used for cutting hardness materials because of their superior performance, such as good thermal conductivity and chemical inertness to iron or iron alloys [1–5]. However, the performance of PcBN compact will show clear differences because of the manufacturing method and sintering mechanism. At present, the method of preparation PcBN is usual sintered by the cBN and adhesive powders on a WC–Co substrate [6], while the content ratio of cBN and binders is often difficult to achieve the optimal as result of narrow interval of synthetic conditions, and bring a bad sintering microstructure such as “bridging”, “reunion” or “delaminating”, which serious effect the performance of PcBN tools [7]. Therefore, further developing of polycrystalline cubic boron nitride and PcBN compact interface of microscopic sintering mechanism, can not only to improve the defects of PcBN compact for guiding effect of the material, and still infer the composite process and sintered mechanism through the microstructure and physical phase, while little attempt has been made to study this aspect [8,9]. In this paper, the sintering method of PcBN compact by high pressure infiltration was used, and combined with the SEM, XRD, EDS and hardness tester analytical, the high pressure physics ⁎ Corresponding author. Tel./fax: +86 434 3292210. E-mail address: [email protected] (H.B. Li). 0263-4368/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijrmhm.2013.02.017
chemical reaction of PcBN compact, melt diffusion characteristics of WC–Co, sintering mechanism and hardness were discussed. 2. Experimental procedures 2.1. Sample preparation All specimens were synthesized in a SPD-6 × 800 MN cubic-anvil high pressure apparatus (CHPA). Cubic boron nitride powders (grain size: 10–14 μm and 3–5 μm, Henan Funik Ultrahard Material, China) and cemented carbide substrate (YG8, Jinan Metallurgical Science Institute, China) were used as the starting materials. Firstly, the cBN powders of 0.65 g and cemented carbide substrate of Φ15 mm × 3 mm were put into the shielding appliances of molybdenum capsule and preloaded at 40 MPa, and then heated at 700 °C for 1 h for vacuum treatment. Secondly, the raw material assembly of molybdenum capsule was put into the salt tube within graphite tube, and the assembly figure is shown in Fig. 1. Finally, all the parts were put together into pyrophyllite composite block of 37.5 mm × 37.5 mm × 37.5 mm for HPHT sintering run. The PcBN samples were kept at 5.2 GPa and 1450 °C for 6 min, then quenched to room temperature slowly and finally decompressed to ambient pressure. PcBN compacts of Φ15 mm × 5 mm were sintered with two kinds of grain size of cBN, respectively signed for specimen No. 1 and No. 2. 2.2. Sample characterization and cutting test In order to discuss the sintering mechanism, all specimens were polished, fractured and purified for measurements. XRD (Rigaku D/Max-2500/PC) and EDS were used to investigate the
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Fig. 2(a) shows the whole cross-section of PcBN compact near interface, and Fig. 2(b) for the local amplification can be seen that the original cBN powders had a scanning trace by melting permeability and packaged by binding phase under high temperature, and finally formed a “concrete” microstructure. SEM microscopic appearances can speculate that the cBN grains have to pass through the process of high pressure crushing, refining rearrangement and liquid phase sintering. The whole crosssectional PcBN have a homogeneous microstructure, and found no “bridging effect”. As shown in Fig. 3, Fig. 3(a) is for the whole area of the interface morphology of sintered sample, and Fig. 3(b) is for amplification figure. The dotted line position (Fig. 1, HPLT zone) shown in white area can be found that the cBN and WC–Co substrate formed firmly bonded, and had an obvious borderline. The grain sizes near the interface is far less than that of the original, and the microcrystallines (~1–2 μm) clearly existed in WC–Co substrate side and packaged by the binding phase, which is due to the result of the broken grains under high pressure. During sintering, the interface of PcBN compact existed in high temperature low pressure zone, a lot of combination reaction would occur under the high temperature condition, which formed a metal-rich zone. The direction of sintering PcBN was from the interface to surface by WC–Co infiltration (Fig. 1, from HPLT to LPHT zone), and the pressure gradient is a driving force of sintering. Fig. 1. Sample assembly sketch for experiment (1, WC–Co substrate; 2, cBN powders; 3, molybdenum capsule; 4, NaCl + graphite tube).
phase composition of PcBN samples, and the microstructural features were investigated by SEM (Rigaku, S-570). Vickers hardness and cutting test were practiced to detect the mechanical properties. X-ray diffraction was measured and operated at 40 kV and 100 mA, using CuKα radiation with the angular between 20° and 90°. Hardness was tested using a microhardness tester (HVS-50, China) with 49 N of applied load and 10 s indented time. The PcBN tool prepared by specimen No. 1 (cBN grain size of 10–14 μm) was tested to cut hardness steels (GCr15) with hardness at 60–62 HRC. 100–150 m/min of cutting speed, 0.3 mm/rev of feed, and 0.2 mm of cutting depth were applied for the cutting test. No lubricant or coolant was used during turning. 3. Results and discussion 3.1. Microstructural feature analysis In this paper, the HPHT infiltrating method in situ by WC–Co was used to achieve a firmly bonded composite of PcBN compact. In order to more clearly observe their microstructure morphology, the specimen No. 1 near interface layer section was observed by means of SEM.
3.2. Energy spectrum analysis In order to analyze the infiltration characteristics and element composition from WC–Co substrate to cBN layer direction, the PcBN cross-section was investigated by EDS scanning. As shown in Fig. 4, the EDS photograph for specimen No. 1 in which shows the B element is not detected. The existence of O element shows that the raw powders surface has an oxidation layer. A few Ti, Al, Fe and K and a shielding material of Mo elements from the original cBN powders are discovered, while the Fe and Mo elements existed among cBN grains have a good wettability, which can increase the strength of PcBN. Additionally the medium action of fluid pressure is more favorable to obtain well-sintered PcBN compact [10]. From Fig. 5, EDS scanning photograph for specimen No. 2 can be seen that the infiltration and diffusion capability of WC–Co is very strong, using a fine grain size of 3–5 μm, could also infiltrate into the cBN layer to forming effective sintering. In the PcBN, The Mo, Fe and K elements also have existed in the sintered sample. During the sintering process, because the cBN was insoluble into binder metal, there would be no dissolution, precipitation and growth process of cBN grains. The Co liquid metal had filled into the cBN boundaries and occurred combination reaction, therefore hypothesized that the Co from WC–Co is the main binding component of sintering PcBN,
Fig. 2. SEM micrographs for specimen No. 1: (a) whole area; (b) local amplification.
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Fig. 3. SEM micrographs of PcBN–WC interface for specimen No. 1: (a) whole area; (b) local amplification.
which not only help to reduce the sintering conditions, but also improve the toughness of PcBN. Additionally the sintering condition of HPHT has a certain role in promoting a close bond between cBN and WC–Co. 3.3. Composition and reaction mechanism analysis In order to investigate the form of components and reaction mechanism, the samples of PcBN surface were characterized by XRD. During HPHT conditions, the strong chemical combination would occur within PcBN, and the reaction happened as follows: Mo þ Co þ B–MoCoB
ð1Þ
WC þ Co–Co3 W3 C:
ð2Þ
of WC and Co formed a solid diffusion melt through melting permeability, as shown in formula (2). Because the eutectic temperature of WC and Co is 1320 °C and the wetting angle of cobalt atoms on the tungsten carbide is 0° under sintering condition in 1340 °C [11], a little Co3W3C formed in the course of sintering. The presence of high temperature boundary phase of WC is conducive to reducing the stress of crystallization and further enhancing the adhesion of grain boundaries of cBN, and maintaining a high wear resistance of PcBN. Additionally the phase of hBN is not reflected in XRD patterns. As shown in Fig. 6, XRD analysis results show that the phases of PcBN sample prepared by using two particle sizes have the same ingredients, such as the content of cBN, WC, MoCoB and Co3W3C. It also shows that the PcBN composite material depends on the bonding strength combination between cBN layer and WC–Co substrate. 3.4. Vickers hardness and cutting test
The Co from the WC–Co had spread into cBN layer and happened interface reaction, generating a stable phase of MoCoB, as shown in formula (1). The existence of the Co3W3C shows that the substrate
Sintered PcBN compacts have a good processability, PcBN samples were polished to a smooth mirror surface and then prepared as a
Fig. 4. EDS photograph of element distribution for specimen No. 1.
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Fig. 5. EDS photograph of element distribution for specimen No. 2.
cutting tool to cut hardness steels (GCr15). The resistance of 2 Ω and Vickers hardness of 29.3 GPa were tested on specimen No. 1. The workpiece for cutting is shown in Fig. 7, the workpiece surface is very smooth, and maintains a good finish after cutting. 4. Conclusions PcBN compacts (cBN size: 10–14 μm and 3–5 μm) were sintered through the permeability and diffusion of WC–Co under the conditions of high temperature and high pressure (5.2 GPa, 1450 °C). SEM and EDS results show that the cBN grains packaged by the binding phase, and formed a dense “concrete” microstructure. Parts of alloy compounds of WC–Co spread to cBN layer through melt permeability, which could maintain the high wear resistance of PcBN. A small amount of metal components such as Mo and Fe more effectively improve the wettability between cBN and binders. XRD results show that the PcBN layer formed cBN, metal strong carbide of WC,
Fig. 6. X-ray diffraction patterns for PcBN: (a) specimen No. 1 (b) specimen No. 2.
interstitial of Co3W3C and MoCoB, which are the main mechanism of bonded compound of cBN–WC because of their super hardness, high heat resistance and stability. The hardness and cutting test also show that PcBN compacts have the higher Vickers hardness of 29.3 GPa, and the workpiece surface has a good finish after cutting by PcBN tool.
Acknowledgments This research was financially supported by the Open Project of State Key Laboratory of Superhard Materials, Jilin University (201201).
Fig. 7. Optical photo for workpiece surface after cutting test.
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References [1] Cook MW, Bossom PK. Trends and recent developments in the material manufacture and cutting tool application of polycrystalline diamond and polycrystalline cubic boron nitride. Int J Refract Met Hard Mater 2000;18:147–52. [2] Badzian A, Badzian T. Recent developments in hard materials. Int J Refract Met Hard Mater 1997;15(1–3):3–12. [3] Kurt A, Seker U. The effect of chamfer angle of polycrystalline cubic boron nitride cutting tool on the cutting forces and the tool stresses in finishing hard turning of AISI 52100 steel. Mater Des 2005;26:351–6. [4] Arsecularatne JA, Zhang LC, Montross C. MathewP. On machining of hardened AISI D2 steel with PCBN tools. J Mater Process Technol 2006;171(2):244–52. [5] Aslan E. Experimental investigation of cutting tool performance in high speed cutting of hardened X210 Cr12 cold-work tool steel (62 HRC). Mater Des 2005;26(1):21–7.
[6] Rong XZ, Yano T. TEM investigation of high-pressure reaction-sintered cBN–Al composites. J Mater Sci 2004;39:4705–10. [7] Liu Y, Lv Z, Guo H, Lin F. Strategic consideration on developing polycrystalline cubic boron nitride in China.Tool Eng 2008;42(8):3–5 (In Chinese). [8] Zhao YC, Wang MZ. Preparation of polycrystalline cBN containing nanodiamond. J Mater Process Technol 2008;198:134–8. [9] Lv R, Liu J, Li YJ, Li SC, Kou ZL, He DW. High pressure sintering of cubic boron nitride compacts with Al and AlN. Diam Relat Mater 2008;17:2062–6. [10] Li HB, Zhang HT, Dong H, Li M. Research manufacture and development of PCBN insert.Tool Eng 2007;41(10):10–3 (In Chinese). [11] Song YC, Liu YB, Wang QS. Diamond tools and metal science basics. China Build Mater Industry Press; 1999. p. 85 (In Chinese).
Contents lists available at ScienceDirect
Int. Journal of Refractory Metals and Hard Materials journal homepage: www.elsevier.com/locate/IJRMHM
Preparation of polycrystalline cubic boron nitride compact by high-pressure infiltration using cemented carbide H.S. Jia a, Y.L. E a, J. Li a, X.P. Jia b, H.A. Ma b, F.Z. Liu a, L.H. Liu a, H.B. Li a,⁎ a b
Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, China State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
a r t i c l e
i n f o
Article history: Received 13 November 2012 Accepted 23 February 2013 Keywords: HPHT PcBN compact Infiltrating method Cemented carbide
a b s t r a c t Polycrystalline cubic boron nitride (PcBN) compacts, using the infiltrating method in situ by cemented carbide (WC–Co) substrate, were sintered under high temperature and high pressure (HPHT, 5.2 GPa, 1450 °C for 6 min). The microstructure morphology, phase composition and hardness of PcBN compacts were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The experimental results show that the WC and Co from WC–Co substrate spread into cubic boron nitride (cBN) layer through melting permeability under HPHT. The binder phases of WC, MoCoB and Co3W3C realized the interface compound of PcBN compact, and the PcBN layer formed a dense concrete microstructure. Additionally the Vickers hardness of 29.3 GPa and cutting test were performed when sintered by using cBN grain size of 10–14 μm. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Polycrystalline cubic boron nitride (PcBN) compacts, consisting of a cubic boron nitride (cBN) layer on a cemented carbide (WC–Co) substrate, are sintered relying on binding phases at high temperature and high pressure (4.8–5.2 GPa, 1400–1500 °C) conditions. As kind of important tool materials of cBN, PcBN compacts fully reflect the material requirements of modern manufacturing industry, and widely used for cutting hardness materials because of their superior performance, such as good thermal conductivity and chemical inertness to iron or iron alloys [1–5]. However, the performance of PcBN compact will show clear differences because of the manufacturing method and sintering mechanism. At present, the method of preparation PcBN is usual sintered by the cBN and adhesive powders on a WC–Co substrate [6], while the content ratio of cBN and binders is often difficult to achieve the optimal as result of narrow interval of synthetic conditions, and bring a bad sintering microstructure such as “bridging”, “reunion” or “delaminating”, which serious effect the performance of PcBN tools [7]. Therefore, further developing of polycrystalline cubic boron nitride and PcBN compact interface of microscopic sintering mechanism, can not only to improve the defects of PcBN compact for guiding effect of the material, and still infer the composite process and sintered mechanism through the microstructure and physical phase, while little attempt has been made to study this aspect [8,9]. In this paper, the sintering method of PcBN compact by high pressure infiltration was used, and combined with the SEM, XRD, EDS and hardness tester analytical, the high pressure physics ⁎ Corresponding author. Tel./fax: +86 434 3292210. E-mail address: [email protected] (H.B. Li). 0263-4368/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijrmhm.2013.02.017
chemical reaction of PcBN compact, melt diffusion characteristics of WC–Co, sintering mechanism and hardness were discussed. 2. Experimental procedures 2.1. Sample preparation All specimens were synthesized in a SPD-6 × 800 MN cubic-anvil high pressure apparatus (CHPA). Cubic boron nitride powders (grain size: 10–14 μm and 3–5 μm, Henan Funik Ultrahard Material, China) and cemented carbide substrate (YG8, Jinan Metallurgical Science Institute, China) were used as the starting materials. Firstly, the cBN powders of 0.65 g and cemented carbide substrate of Φ15 mm × 3 mm were put into the shielding appliances of molybdenum capsule and preloaded at 40 MPa, and then heated at 700 °C for 1 h for vacuum treatment. Secondly, the raw material assembly of molybdenum capsule was put into the salt tube within graphite tube, and the assembly figure is shown in Fig. 1. Finally, all the parts were put together into pyrophyllite composite block of 37.5 mm × 37.5 mm × 37.5 mm for HPHT sintering run. The PcBN samples were kept at 5.2 GPa and 1450 °C for 6 min, then quenched to room temperature slowly and finally decompressed to ambient pressure. PcBN compacts of Φ15 mm × 5 mm were sintered with two kinds of grain size of cBN, respectively signed for specimen No. 1 and No. 2. 2.2. Sample characterization and cutting test In order to discuss the sintering mechanism, all specimens were polished, fractured and purified for measurements. XRD (Rigaku D/Max-2500/PC) and EDS were used to investigate the
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Fig. 2(a) shows the whole cross-section of PcBN compact near interface, and Fig. 2(b) for the local amplification can be seen that the original cBN powders had a scanning trace by melting permeability and packaged by binding phase under high temperature, and finally formed a “concrete” microstructure. SEM microscopic appearances can speculate that the cBN grains have to pass through the process of high pressure crushing, refining rearrangement and liquid phase sintering. The whole crosssectional PcBN have a homogeneous microstructure, and found no “bridging effect”. As shown in Fig. 3, Fig. 3(a) is for the whole area of the interface morphology of sintered sample, and Fig. 3(b) is for amplification figure. The dotted line position (Fig. 1, HPLT zone) shown in white area can be found that the cBN and WC–Co substrate formed firmly bonded, and had an obvious borderline. The grain sizes near the interface is far less than that of the original, and the microcrystallines (~1–2 μm) clearly existed in WC–Co substrate side and packaged by the binding phase, which is due to the result of the broken grains under high pressure. During sintering, the interface of PcBN compact existed in high temperature low pressure zone, a lot of combination reaction would occur under the high temperature condition, which formed a metal-rich zone. The direction of sintering PcBN was from the interface to surface by WC–Co infiltration (Fig. 1, from HPLT to LPHT zone), and the pressure gradient is a driving force of sintering. Fig. 1. Sample assembly sketch for experiment (1, WC–Co substrate; 2, cBN powders; 3, molybdenum capsule; 4, NaCl + graphite tube).
phase composition of PcBN samples, and the microstructural features were investigated by SEM (Rigaku, S-570). Vickers hardness and cutting test were practiced to detect the mechanical properties. X-ray diffraction was measured and operated at 40 kV and 100 mA, using CuKα radiation with the angular between 20° and 90°. Hardness was tested using a microhardness tester (HVS-50, China) with 49 N of applied load and 10 s indented time. The PcBN tool prepared by specimen No. 1 (cBN grain size of 10–14 μm) was tested to cut hardness steels (GCr15) with hardness at 60–62 HRC. 100–150 m/min of cutting speed, 0.3 mm/rev of feed, and 0.2 mm of cutting depth were applied for the cutting test. No lubricant or coolant was used during turning. 3. Results and discussion 3.1. Microstructural feature analysis In this paper, the HPHT infiltrating method in situ by WC–Co was used to achieve a firmly bonded composite of PcBN compact. In order to more clearly observe their microstructure morphology, the specimen No. 1 near interface layer section was observed by means of SEM.
3.2. Energy spectrum analysis In order to analyze the infiltration characteristics and element composition from WC–Co substrate to cBN layer direction, the PcBN cross-section was investigated by EDS scanning. As shown in Fig. 4, the EDS photograph for specimen No. 1 in which shows the B element is not detected. The existence of O element shows that the raw powders surface has an oxidation layer. A few Ti, Al, Fe and K and a shielding material of Mo elements from the original cBN powders are discovered, while the Fe and Mo elements existed among cBN grains have a good wettability, which can increase the strength of PcBN. Additionally the medium action of fluid pressure is more favorable to obtain well-sintered PcBN compact [10]. From Fig. 5, EDS scanning photograph for specimen No. 2 can be seen that the infiltration and diffusion capability of WC–Co is very strong, using a fine grain size of 3–5 μm, could also infiltrate into the cBN layer to forming effective sintering. In the PcBN, The Mo, Fe and K elements also have existed in the sintered sample. During the sintering process, because the cBN was insoluble into binder metal, there would be no dissolution, precipitation and growth process of cBN grains. The Co liquid metal had filled into the cBN boundaries and occurred combination reaction, therefore hypothesized that the Co from WC–Co is the main binding component of sintering PcBN,
Fig. 2. SEM micrographs for specimen No. 1: (a) whole area; (b) local amplification.
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Fig. 3. SEM micrographs of PcBN–WC interface for specimen No. 1: (a) whole area; (b) local amplification.
which not only help to reduce the sintering conditions, but also improve the toughness of PcBN. Additionally the sintering condition of HPHT has a certain role in promoting a close bond between cBN and WC–Co. 3.3. Composition and reaction mechanism analysis In order to investigate the form of components and reaction mechanism, the samples of PcBN surface were characterized by XRD. During HPHT conditions, the strong chemical combination would occur within PcBN, and the reaction happened as follows: Mo þ Co þ B–MoCoB
ð1Þ
WC þ Co–Co3 W3 C:
ð2Þ
of WC and Co formed a solid diffusion melt through melting permeability, as shown in formula (2). Because the eutectic temperature of WC and Co is 1320 °C and the wetting angle of cobalt atoms on the tungsten carbide is 0° under sintering condition in 1340 °C [11], a little Co3W3C formed in the course of sintering. The presence of high temperature boundary phase of WC is conducive to reducing the stress of crystallization and further enhancing the adhesion of grain boundaries of cBN, and maintaining a high wear resistance of PcBN. Additionally the phase of hBN is not reflected in XRD patterns. As shown in Fig. 6, XRD analysis results show that the phases of PcBN sample prepared by using two particle sizes have the same ingredients, such as the content of cBN, WC, MoCoB and Co3W3C. It also shows that the PcBN composite material depends on the bonding strength combination between cBN layer and WC–Co substrate. 3.4. Vickers hardness and cutting test
The Co from the WC–Co had spread into cBN layer and happened interface reaction, generating a stable phase of MoCoB, as shown in formula (1). The existence of the Co3W3C shows that the substrate
Sintered PcBN compacts have a good processability, PcBN samples were polished to a smooth mirror surface and then prepared as a
Fig. 4. EDS photograph of element distribution for specimen No. 1.
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Fig. 5. EDS photograph of element distribution for specimen No. 2.
cutting tool to cut hardness steels (GCr15). The resistance of 2 Ω and Vickers hardness of 29.3 GPa were tested on specimen No. 1. The workpiece for cutting is shown in Fig. 7, the workpiece surface is very smooth, and maintains a good finish after cutting. 4. Conclusions PcBN compacts (cBN size: 10–14 μm and 3–5 μm) were sintered through the permeability and diffusion of WC–Co under the conditions of high temperature and high pressure (5.2 GPa, 1450 °C). SEM and EDS results show that the cBN grains packaged by the binding phase, and formed a dense “concrete” microstructure. Parts of alloy compounds of WC–Co spread to cBN layer through melt permeability, which could maintain the high wear resistance of PcBN. A small amount of metal components such as Mo and Fe more effectively improve the wettability between cBN and binders. XRD results show that the PcBN layer formed cBN, metal strong carbide of WC,
Fig. 6. X-ray diffraction patterns for PcBN: (a) specimen No. 1 (b) specimen No. 2.
interstitial of Co3W3C and MoCoB, which are the main mechanism of bonded compound of cBN–WC because of their super hardness, high heat resistance and stability. The hardness and cutting test also show that PcBN compacts have the higher Vickers hardness of 29.3 GPa, and the workpiece surface has a good finish after cutting by PcBN tool.
Acknowledgments This research was financially supported by the Open Project of State Key Laboratory of Superhard Materials, Jilin University (201201).
Fig. 7. Optical photo for workpiece surface after cutting test.
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References [1] Cook MW, Bossom PK. Trends and recent developments in the material manufacture and cutting tool application of polycrystalline diamond and polycrystalline cubic boron nitride. Int J Refract Met Hard Mater 2000;18:147–52. [2] Badzian A, Badzian T. Recent developments in hard materials. Int J Refract Met Hard Mater 1997;15(1–3):3–12. [3] Kurt A, Seker U. The effect of chamfer angle of polycrystalline cubic boron nitride cutting tool on the cutting forces and the tool stresses in finishing hard turning of AISI 52100 steel. Mater Des 2005;26:351–6. [4] Arsecularatne JA, Zhang LC, Montross C. MathewP. On machining of hardened AISI D2 steel with PCBN tools. J Mater Process Technol 2006;171(2):244–52. [5] Aslan E. Experimental investigation of cutting tool performance in high speed cutting of hardened X210 Cr12 cold-work tool steel (62 HRC). Mater Des 2005;26(1):21–7.
[6] Rong XZ, Yano T. TEM investigation of high-pressure reaction-sintered cBN–Al composites. J Mater Sci 2004;39:4705–10. [7] Liu Y, Lv Z, Guo H, Lin F. Strategic consideration on developing polycrystalline cubic boron nitride in China.Tool Eng 2008;42(8):3–5 (In Chinese). [8] Zhao YC, Wang MZ. Preparation of polycrystalline cBN containing nanodiamond. J Mater Process Technol 2008;198:134–8. [9] Lv R, Liu J, Li YJ, Li SC, Kou ZL, He DW. High pressure sintering of cubic boron nitride compacts with Al and AlN. Diam Relat Mater 2008;17:2062–6. [10] Li HB, Zhang HT, Dong H, Li M. Research manufacture and development of PCBN insert.Tool Eng 2007;41(10):10–3 (In Chinese). [11] Song YC, Liu YB, Wang QS. Diamond tools and metal science basics. China Build Mater Industry Press; 1999. p. 85 (In Chinese).