Cubic boron nitride sintered body and coated cubic boron nitride sintered body

Abstract

A CBN sintered body contains CBN, a binder phase and inevitable impurities. An amount of CBN by volume is between 50%-80%. A total amount of binder phase and inevitable impurities by volume is between 20%-50%. The binder phase contains an Al compound and a Ti compound. The Al compound contains Al and one or more of N, O and B. The Ti compound contains Ti and one or more of C, N and B. When an X-ray diffraction intensity at a (100) plane of the AlN is I.sub.1 and an X-ray diffraction intensity at a (104) plane of the Al.sub.2O.sub.3 is I.sub.2, I.sub.1/I.sub.2 is between 6 and 40. When a total area of the cubic boron nitride and the Al compound is S1, and an area of a region at which the CBN and the Al compound are continuously contacted is S2, S2/S1 is between 0.98 and 1.00.

Claims

1. A cubic boron nitride sintered body comprising: cubic boron nitride, a binder phase and inevitable impurities, an amount of the cubic boron nitride is 50% by volume or more and 80% by volume or less, a total amount of the binder phase and the inevitable impurities is 20% by volume or more and 50% by volume or less, the binder phase contains an Al compound and a Ti compound, the Al compound contains an Al element and at least one element selected from the group consisting of N, O and B, the Ti compound contains a Ti element and at least one element selected from the group consisting of C, N and B, the Al compound contains AlN and Al.sub.2O.sub.3, when an X-ray diffraction intensity at a (100) plane of the AlN is given by I.sub.1, and an X-ray diffraction intensity at a (104) plane of the Al.sub.2O.sub.3 is given by I.sub.2, then I.sub.1/I.sub.2 is 6 or more and 40 or less, and when a total area of the cubic boron nitride and the Al compound is given by S1, and an area of a region at which the cubic boron nitride and the Al compound are continuously contacted is given by S2, then S2/S1 is 0.98 or more and 1.00 or less.

2. The cubic boron nitride sintered body according to claim 1, wherein: the Ti compound contains TiB.sub.2, and when an X-ray diffraction intensity at a (101) plane of the TiB.sub.2 is given by I.sub.3, then I.sub.3/I.sub.1 is 0.5 or more and 2.0 or less.

3. The cubic boron nitride sintered body according to claim 1, wherein an area of the Al compound is given by S.sub.A, and an area of the Ti compound is given by S.sub.T, then S.sub.T/S.sub.A is 1 or more and 3 or less.

4. The cubic boron nitride sintered body according to claim 1, wherein an average grain diameter of the cubic boron nitride is 0.3 m or more and 1.5 m or less.

5. The cubic boron nitride sintered body according to claim 1, wherein: the Ti compound contains TiB.sub.2; when an X-ray diffraction intensity at a (101) plane of the TiB.sub.2 is given by I.sub.3, then I.sub.3/I.sub.1 is 0.5 or more and 2.0 or less; an area of the Al compound is given by S.sub.A, and an area of the Ti compound is given by S.sub.T, then S.sub.T/S.sub.A is 1 or more and 3 or less; and an average grain diameter of the cubic boron nitride is 0.3 m or more and 1.5 m or less.

6. A coated cubic boron nitride sintered body comprising: the cubic boron nitride sintered body according to claim 1; and a film formed on a surface of the cubic boron nitride sintered body.

7. The coated cubic boron nitride sintered body according to claim 6, wherein the film comprises: at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al and S1, and at least one element selected from the group consisting of C, N, O and B.

8. The coated cubic boron nitride sintered body according to claim 6, wherein the film is a single layer film or a laminated film containing two or more layers.

9. The coated cubic boron nitride sintered body according to claim 6, wherein an average film thickness of the film is 0.5 m or more and 20 m or less.

10. The coated cubic boron nitride sintered body according to claim 6, wherein: an average film thickness of the whole film is 0.5 m or more and 20 m or less; and the film comprises: at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al and S1, and at least one element selected from the group consisting of C, N, O and B.

11. The coated cubic boron nitride sintered body according to claim 10, wherein: the film is a laminated film containing two or more layers.

Description

EXAMPLE 1

(1) Cubic boron nitride (cBN) powder, TiN powder, Al.sub.3Ti powder, AlN powder, Al powder and Ti.sub.2AlN powder were mixed with the ratio shown in Table 1. An average particle diameter of the cubic boron nitride (cBN) powder is 0.4, 1.2 and 2.0 m. An average particle diameter of the TiN powder is 1.0 m. An average particle diameter of the Al.sub.3Ti powder is 2.0 m. An average particle diameter of the AlN powder is 1.0 m. An average particle diameter of the Al powder is 2.0 m. An average particle diameter of the Ti.sub.2AlN powder is 2.0 m.

(2) The raw powder obtained by mixing was charged in a cylinder for a ball mill with balls made of a cemented carbide, a hexane solvent and paraffin, and further mixed. The powder obtained by mixing and pulverizing with a ball mill was molded under pressure. Deparaffinization treatment of the obtained molded article was carried out under the conditions of 1.3310.sup.3 Pa and at 450 C. The molded article subjected to the deparaffinization treatment was heated in a vacuum of the same pressure at 850 C. to carry out preliminary sintering. The obtained preliminary sintered body was charged in an ultrahigh-pressure and high temperature generating device and sintered under the conditions of a pressure of 5.5 GPa, a temperature of 1500 C. and a retention time of 30 minutes. According to this procedure, cubic boron nitride sintered bodies of Present products and Comparative products were obtained.

(3) TABLE-US-00001 TABLE 1 Sample number Composition (vol %) Present product 1 67cBN29Al.sub.3Ti4TiN Present product 2 59cBN36Al.sub.3Ti5TiN Present product 3 83cBN15Al.sub.3Ti2TiN Present product 4 67cBN18Al.sub.3Ti9AlN6TiN Present product 5 67cBN29Al.sub.3Ti4TiN Present product 6 61cBN30Al.sub.3Ti9TiN Present product 7 60cBN28Al.sub.3Ti12Al Comparative product 1 67cBN26Al.sub.3Ti7Ti.sub.2AlN Comparative product 2 52cBN38Al.sub.3Ti10Ti.sub.2AlN Comparative product 3 88cBN10Al.sub.3Ti2Ti.sub.2AlN Comparative product 4 67cBN10Al23TiN Comparative product 5 67cBN10AlN23TiN Comparative product 6 66cBN16Al18Ti.sub.2AlN Comparative product 7 70cBN9Al21Ti.sub.2AlN Comparative product 8 58cBN32Al10Ti.sub.2AlN

(4) The composition of the cubic boron nitride sintered body was examined by subjecting to X-ray diffraction measurement of the obtained cubic boron nitride sintered body. In addition, the sectional structure of the cubic boron nitride sintered body was photographed by the SEM to measure % by volume of the cubic boron nitride (cBN) and % by volume of the binder phase. These results were shown in Table 2.

(5) A height of the peak of the diffraction line of the cubic boron nitride sintered body was measured by using an X-ray diffractometer RINT TTRIII manufactured by RIGAKU CORPORATION. Measurement of the X-ray diffraction is carried out by 2/ concentrated optical system using a Cu-K line. The measurement conditions are as follows.

(6) Output: 50 kV, 250 mA

(7) Solar slit at incident side: 5

(8) Divergence vertical slit:

(9) Divergence vertical limit slit: 10 mm

(10) Scattering slit:

(11) Solar slit at photoreception side: 5

(12) Photoreception slit: 0.15 mm

(13) BENT monochromator

(14) Photoreception monochrome slit: 0.8 mm

(15) Sampling width: 0.02

(16) Scanning speed: 2/min

(17) From the obtained X-ray diffraction diagram, the X-ray diffraction intensity I.sub.1 of the (100) plane of AlN, the X-ray diffraction intensity I.sub.2 of the (104) plane of Al.sub.2O.sub.3 and the X-ray diffraction intensity I.sub.3 of the (101) plane of TiB.sub.2 were obtained. Further, the ratio of I.sub.1 to I.sub.2 (I.sub.1/I.sub.2) and the ratio of I.sub.3 to I.sub.1 (I.sub.3/I.sub.1) were obtained. The ratios of the X-ray diffraction intensities can be obtained by the ratio of the heights of the peaks. These values were shown in Table 3.

(18) An average grain diameter of the cubic boron nitride contained in the cubic boron nitride sintered body was obtained by image analysis. Specifically, the sectional surface of the cubic boron nitride sintered body was photographed by the SEM. The photographed image was analyzed by using a commercially available image analysis software.

(19) More specifically, by using the SEM, a reflected electron image with 5,000-fold of the sectional surface of the cubic boron nitride sintered body was photographed. By using the energy dispersive X-ray spectroscopy (EDS) attached to the SEM, it was confirmed that the cubic boron nitride is black, the Al compound is dark gray and the Ti compound is light gray. Next, by using the commercially available image analysis software, a diameter of a circle the area of which is equal to that of the black cubic boron nitride was obtained. This diameter of a circle was used as a grain diameter of the cubic boron nitride. An average value of the grain diameters of the cubic boron nitride existing in the sectional surface of the cubic boron nitride sintered body was obtained. The average values were shown in Table 3.

(20) The cubic boron nitride sintered body contains the cubic boron nitride and the Al compound. An area of the region at which the cubic boron nitride and the Al compound are continuously contacted can be obtained from the photograph of the sectional structure of the cubic boron nitride sintered body photographed by the SEM. Specifically, by analyzing the photograph of the sectional structure of the cubic boron nitride sintered body with the commercially available image analysis software, the area of the region at which the cubic boron nitride and the Al compound are continuously contacted can be obtained.

(21) Specifically, by using the SEM, a reflected electron image with 5,000-fold of the sectional surface of the cubic boron nitride sintered body is photographed. In the sectional structure, black cubic boron nitride, dark gray Al compound and light gray Ti compound can be observed. A total area S1 of the black cubic boron nitride and the dark gray Al compound is obtained.

(22) An area of the Al compound which is not contacted with the cubic boron nitride and an area of the cubic boron nitride which is not contacted with the Al compound are deducted from the above-mentioned total area S1 to find the remainder. This remainder corresponds to the area of the region at which the cubic boron nitride and the Al compound are contacted. Next, among the area of the region at which the cubic boron nitride and the Al compound are contacted, the maximum area is obtained. This maximum area corresponds to the area S2 of the region at which the cubic boron nitride and the Al compound are continuously contacted.

(23) A ratio of the area S2 of the region at which the cubic boron nitride and the Al compound are continuously contacted to the total area S1 of the cubic boron nitride and the Al compound (=S2/S1) are shown in Table 3.

(24) TABLE-US-00002 TABLE 2 Cubic boron nitride sintered body Binder phase Ti compound Al compound CBN XRD XRD Content diffraction Content diffraction Content Sample number (vol %) measurement (vol %) measurement (vol %) S.sub.T/S.sub.A Present product 1 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Present product 2 52 TiN, TiB.sub.2 34 AlN, Al.sub.2O.sub.3 14 2.4 Present product 3 78 TiN, TiB.sub.2 15 AlN, Al.sub.2O.sub.3 7 2.1 Present product 4 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Present product 5 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Present product 6 52 TiN, TiB.sub.2 36 AlN, Al.sub.2O.sub.3 12 3.0 Present product 7 60 TiN, TiB.sub.2 20 AlN, Al.sub.2O.sub.3 20 1.0 Comparative product 1 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Comparative product 2 45 TiN, TiB.sub.2 38 AlN, Al.sub.2O.sub.3 17 2.2 Comparative product 3 85 TiN, TiB.sub.2 10 AlN, Al.sub.2O.sub.3 5 2.0 Comparative product 4 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Comparative product 5 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Comparative product 6 60 TiN, TiB.sub.2 28 AlN, Al.sub.2O.sub.3 12 2.3 Comparative product 7 60 TiN, TiB.sub.2 32 AlN, Al.sub.2O.sub.3 8 4.0 Comparative product 8 60 TiN, TiB.sub.2 18 AlN, Al.sub.2O.sub.3 22 0.8

(25) TABLE-US-00003 TABLE 3 Cubic boron nitride sintered body Thermal Average grain conduc- diameter of tivity Sample number cBN (m) I.sub.1/I.sub.2 I.sub.3/I.sub.1 (W/m .Math. K) S2/S1 Present product 1 0.4 15.2 1.4 75 0.988 Present product 2 0.4 13.4 0.8 65 0.991 Present product 3 0.4 14.2 1.7 93 0.981 Present product 4 0.4 35.0 1.0 79 0.989 Present product 5 1.2 17.8 1.2 81 0.992 Present product 6 0.4 10.3 0.9 63 0.987 Present product 7 0.4 8.3 1.8 74 0.998 Comparative product 1 0.4 9.5 3.2 55 0.908 Comparative product 2 0.4 7.5 1.7 42 0.885 Comparative product 3 0.4 5.6 1.6 61 0.966 Comparative product 4 0.4 5.0 4.2 53 0.989 Comparative product 5 0.4 50.0 0.6 57 0.982 Comparative product 6 2.0 19.5 1.1 57 0.920 Comparative product 7 0.4 10.3 1.2 52 0.902 Comparative product 8 0.4 26.0 1.5 56 0.974

(26) Present products and Comparative products were processed to a cutting tool with an insert shape determined by the ISO standard CNGA120408. By using the obtained cutting tools, the following mentioned Cutting tests (1) and (2) were carried out. The results are shown in Table 4.

(27) Cutting Test (1) External continuous dry Cutting (Turning), Work piece material: SCM415H (HRC 60.9 to 61.7), Shape of work piece material: Columnar shape having 48 mmL 200 mm with 90 two V-grooves, Cutting speed: 100 m/min, Depth of cut: 0.15 mm, Feed rate: 0.15 mm/rev, Tool life: Cutting time until fractured.

(28) Cutting Test (2) Face interrupted dry Cutting (Turning), Work piece material: SCM415H (HRC 60.9 to 61.7), Shape of work piece material: A disc having 180 mmL 20 mm with two grooves having a width of 15 mm (Work piece material has a hole with 45 mm at the center of the disc), Cutting speed: 100 m/min, Depth of cut: 0.2 mm, Feed rate: 0.1 mm/rev, Tool life: Cutting time until fractured.

(29) TABLE-US-00004 TABLE 4 Cutting test (1) Cutting test (2) Tool life Tool life Sample number (min) (min) Present product 1 18 26 Present product 2 14 21 Present product 3 17 23 Present product 4 19 25 Present product 5 19 23 Present product 6 14 19 Present product 7 16 24 Comparative product 1 9 11 Comparative product 2 7 9 Comparative product 3 10 11 Comparative product 4 7 16 Comparative product 5 8 15 Comparative product 6 10 10 Comparative product 7 9 12 Comparative product 8 8 11

(30) The cubic boron nitride sintered bodies of Present products have higher thermal conductivity as compared with those of the cubic boron nitride sintered bodies of Comparative products, and progress of the chemical reaction wear at the time of cutting has been suppressed. In addition, Present products were improved in fracture resistance, and had longer tool life as compared with those of Comparative products.

EXAMPLE 2

(31) A coating treatment was carried out onto the surface of Present products 1 to 7 of Example 1 using a PVD device.

(32) A TiN film with an average film thickness of 3 m was each coated onto the surface of the cubic boron nitride sintered bodies of Present products 1 to 4. Present products 1 to 4 onto which the TiN film had been coated are called to as Present products 8 to 11, respectively.

(33) A TiAlN film with an average film thickness 3 m was each coated onto the surface of the cubic boron nitride sintered bodies of Present products 5 to 7. Present products 5 to 7 onto which the TiAlN film had been coated are called to as Present products 12 to 14, respectively.

(34) The same Cutting tests (1) and (2) as in Example 1 were carried out by using Present products 8 to 14. The results are shown in Table 5.

(35) TABLE-US-00005 TABLE 5 Cutting test (1) Cutting test (2) Tool life Tool life Sample number (min) (min) Present product 8 28 31 Present product 9 24 26 Present product 10 27 28 Present product 11 29 30 Present product 12 27 33 Present product 13 22 29 Present product 14 24 34

(36) Present products 8 to 14 in which a film (a TiN film, a TiAlN film) has been coated had longer tool lives than those of Present products 1 to 7 to which no film has been coated.

UTILIZABILITY IN INDUSTRY

(37) The cubic boron nitride sintered body and the coated cubic boron nitride sintered body of the present invention are excellent in fracture resistance, in particular, when they are used as a cutting tool or a wear resistant tool, tool life can be elongated so that they have high utilizability in industry.