Polycrystalline diamond sintered material tool excellent in interfacial bonding strength and method of producing same

Abstract

A polycrystalline diamond sintered material tool includes: a cemented carbide substrate, which is mainly composed of WC and includes Co; and a diamond layer containing a metal catalyst made of Co provided on the cemented carbide substrate. The average layer thickness of a Co rich layer formed in an interface between the cemented carbide substrate and the diamond layer is 30 μm or less. C.sub.MAX/C.sub.DIA is 2 or less when C.sub.DIA is an average content of Co included in the diamond layer and C.sub.MAX is a peak value of a Co content in the Co rich layer. D/D.sub.O is less than 2 when D is an average grain size of WC particles in a region from the interface between the cemented carbide substrate and the diamond layer to 50 μm toward an inside of the cemented carbide substrate; and D.sub.O is an average grain size of WC particles.

Claims

1. A polycrystalline diamond sintered material tool comprising: a cemented carbide substrate, which is mainly composed of WC and includes Co; and a diamond layer containing a metal catalyst made of Co provided on the cemented carbide substrate, wherein an average layer thickness of a Co rich formed in an interface between the cemented carbide substrate and the diamond layer is 30 μm or less, and an average layer thickness of the diamond layer is from 2.0 mm to 15 mm.

2. The polycrystalline diamond sintered material tool according to claim 1, wherein a value of C.sub.MAX/C.sub.DIA is 2 or less when C.sub.DIA is defined as an average content of Co included in the diamond layer and C.sub.MAX is defined as a peak value of a Co content in the Co rich layer.

3. The polycrystalline diamond sintered material tool according to claim 1, wherein a value of D/D.sub.O is less than 2 when D is defined as average grain size of WC particles in a region from the interface between the cemented carbide substrate and the diamond layer to 50 μm toward an inside of the diamond layer; and D.sub.O is defined as an average grain size of WC particles in the inside of the cemented carbide substrate.

4. The polycrystalline diamond sintered material tool according to claim 1, wherein a value, in which an average content of Co in the cemented carbide substrate is subtracted from a Co mixed amount, is from 1% by mass to 30% by mass, the Co mixed amount being a Co amount mixed in the diamond layer prior to sintering.

5. The polycrystalline diamond sintered material tool according to claim 4, wherein a value, in which an average content of Co in the cemented carbide substrate is subtracted from a Co mixed amount, is from 10% by mass to 30% by mass, the Co mixed amount being a Co amount mixed in the diamond layer prior to sintering.

6. The polycrystalline diamond sintered material tool according to claim 5, wherein a value, in which an average content of Co in the cemented carbide substrate is subtracted from a Co mixed amount, is from 16% by mass to 28% by mass, the Co mixed amount being a Co amount mixed in the diamond layer prior to sintering.

7. The polycrystalline diamond sintered material tool according to claim 4, further comprising a buffer layer with an average layer thickness of 5 μm or more and 15 μm or less at the interface between the Co rich layer and the cemented carbide substrate.

8. The polycrystalline diamond sintered material tool according to claim 4, further comprising a buffer layer with an average layer thickness of 8 μm or more and 15 μm or less at the interface between the Co rich layer and the cemented carbide substrate.

9. The polycrystalline diamond sintered material tool according to claim 8, wherein the average layer thickness of the Co rich layer is 21 μm or more.

10. The polycrystalline diamond sintered material tool according to claim 7, wherein the diamond layer is formed directly on the Co rich layer, the Co rich layer is formed directly on the buffer layer, and the buffer layer is formed directly on the cemented carbide substrate.

11. The polycrystalline diamond sintered material tool according to claim 1, wherein the polycrystalline diamond sintered material tool exhibits impact shearing strength in a range of 7.3 J/cm.sup.2 to 12.1 J/cm.sup.2, said impact shear strength being obtained by dividing a drop weight energy by a breakage/testing piece cross-sectional area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic diagram of an ultra-high pressure and high temperature apparatus for producing a PCD tool.

(2) FIG. 2 shows an example of SEM images of the interface between the cemented carbide substrate and the diamond layer in PCD tools. The panels (A) to (D) show PCD tools of Comparative Examples, and the panels (E) and (F) show the PCD tools of Example of the present invention.

(3) FIG. 3 shows a schematic explanatory view and analytical result of a line analysis of the Co content carried out on the PCD tool (H) of Example of the present invention.

(4) FIG. 4 shows a schematic explanatory view and analytical result of a line analysis of the Co content performed on the PCD tool (G) of Comparative Example.

(5) FIG. 5 shows SEM images of the diamond layer (upper layer), the cemented carbide substrate, and the diamond layer near the interface (lower layer) after performing a heat treatment test on the PCD tool. The panels (C) and (D) are SEM images of the PCD tools (C) and (D) of Comparative Examples after being subjected to heat treatment at 750° C. The panel (F) is a SEM image of the PCD tool (F) of Example of the present invention after being subjected to heat treatment at 850° C.

(6) FIG. 6 shows a schematic vertical sectional view of a PCD tool according to an embodiment of the present invention.

(7) FIG. 7 is a schematic vertical sectional view of a PCD tool according to another embodiment of the present invention.

(8) FIG. 8 shows a front view and a side view of a test piece used for evaluation of impact shear strength.

(9) FIG. 9 shows a schematic cross-sectional view of a measuring apparatus used for evaluating impact shear strength. The state before dropping the weight is shown.

(10) FIG. 10 shows a schematic cross-sectional view of a measuring apparatus used for evaluating impact shear strength. The state after dropping the weight is shown.

DETAILED DESCRIPTION OF THE INVENTION

(11) The present invention will be described in detail below by way of examples.

Example

(12) Table 1 shows combinations of cemented carbide and diamond raw material powders used in Examples. As representative Examples of the present invention, the PCD tools (E), (F), (H), (I) and (J), each of which was made of one of combinations of the cemented carbide and diamond raw material powders shown in Table 1 as (E), (F) and (H), were prepared.

(13) Specifically, the PCD tool (E) was prepared by mixing diamond raw material powder in which 17% by mass of Co powder was mixed in the diamond powder having the average grain size of 9 μm; and the diamond raw material powder having the Co content of 16% by mass. As shown in FIG. 1, the cemented carbide substrate (see Table 1 (E) composed of WC particles of 2.2 μm was packed in the Ta capsule and sintered at the pressure of 5.8 GPa and the sintering temperature of 1500° C. in the ultra-high pressure and high temperature apparatus.

(14) The PCD tool (F) was prepared by: inserting the diamond raw material powder, in which 31% by mass of the Co powder was mixed in the diamond powder having the average grain size of 9 μm, and the cemented carbide substrate (refer (F) in Table 1), which has the Co content of 16% by mass and was made of WC particles having the average grain size of 2.2 μm, in the state where they were laminated in the Ta capsule as shown in FIG. 1; and sintering the laminate in the sintering pressure of 5.8 GPa at the sintering temperature of 1500° C. in the ultra-high pressure and high temperature apparatus.

(15) In addition, the PCD tool (H) was prepared by: inserting the diamond raw material powder, in which 33% by mass of the Co powder was mixed in the diamond powder having the average grain size of 3 μm, and the cemented carbide substrate (refer (H) in Table 1), which has the Co content of 10% by mass and was made of WC particles having the average grain size of 2.2 μm, in the state where they were laminated in the Ta capsule as shown in FIG. 1; and sintering the laminate in the sintering pressure of 5.8 GPa at the sintering temperature of 1500° C. in the ultra-high pressure and high temperature apparatus.

(16) In addition, the PCD tool (I) was prepared by: inserting the diamond raw material powder, in which 33% by mass of the Co powder was mixed in the diamond powder having the average grain size of 6 μm, and the cemented carbide substrate (refer (I) in Table 1), which has the Co content of 10% by mass and was made of WC particles having the average grain size of 2.2 μm, in the state where they were laminated in the Ta capsule as shown in FIG. 1; and sintering the laminate in the sintering pressure of 5.8 GPa at the sintering temperature of 1500° C. in the ultra-high pressure and high temperature apparatus.

(17) In addition, the PCD tool (J) was prepared by: inserting the diamond raw material powder, in which 33% by mass of the Co powder was mixed in the diamond powder having the average grain size of 9 μm, and the cemented carbide substrate (refer (J) in Table 1), which has the Co content of 10% by mass and was made of WC particles having the average grain size of 2.2 μm, in the state where they were laminated in the Ta capsule as shown in FIG. 1; and sintering the laminate in the sintering pressure of 5.8 GPa at the sintering temperature of 1500° C. in the ultra-high pressure and high temperature apparatus.

(18) TABLE-US-00001 TABLE 1 Diamond layer WC-Co layer Average grain Mixed amount Average grain Co content Sample size of diamond of Co (% by size of WC (% by name (μm) mass) (μm) mass) A 3 — 0.9 10 B 3 — 3.3 10 C 3 — 2.2 16 D 9 — 2.2 16 E 9 17 2.2 16 F 9 31 2.2 16 G 3 — 2.2 16 H 3 33 2.2 10 I 6 33 2.2 10 J 9 33 2.2 10

(19) Among the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention which were prepared as described above, the PCD tools (E) and (F) were chosen, subjected to scanning electron microscope (SEM) observation, and the vicinity of the interfaces between the cemented carbide substrates and the diamond layers were observed. The obtained SEM images are shown in FIG. 2 in the panels (E) and (F), respectively.

(20) As apparent from the panel (E) and (F) in FIG. 2, in the PCD tool (E) of Example of the present invention, the average layer thickness of the Co rich layer formed at the interface between the cemented carbide substrate and the diamond layer was less than 10 μm or less; and the existence of the Co rich layer was not confirmed at the interface between the cemented carbide substrate and the diamond layer in the PCD tool (F) of Example of the present invention.

(21) Table 2 shows the average layer thickness values of the Co rich layers measured in the PCD tools (E), (F), (H), (I) and (J) of Example of the present invention.

(22) The average layer thickness of the Co rich layer was obtained as explained below. First, the Co content (C.sub.DIA) was measured on the distance of about 100 μm from the diamond layer toward the cemented carbide substrate (about 50 μm for each of the diamond layer and the cemented carbide substrate) by performing a line analysis with EPMA (Electron Probe MicroAnalyzer) with 20 μm of the beam diameter and 0.5 μm of the measurement intervals, as shown in FIG. 3 (corresponding to the PCD tool (H) of Example of the present invention), for example. Then, the region having the value of the Co content of 1.1×C.sub.DIA or more was defined as the Co rich layer and the layer thickness of the region was measured. After measuring the layer thickness of the Co rich layer at multiple different points, by averaging the obtained multiple values, the average layer thickness of the Co rich layer was obtained.

(23) C.sub.DIA is the Co content resided in the diamond layer as metal catalysts after sintering. In addition, the peak value C.sub.MAX of the Co content in the Co rich layer was measured; and the value of C.sub.MAX/C.sub.DIA, which was the ratio of C.sub.MAX to the average Co content in the diamond layer C.sub.DIA was calculated.

(24) From Table 2, it was demonstrate that the average layer thickness of the Co rich layer was 30 μm or less and the value of C.sub.MAX/C.sub.DIA was 2 or less in all of the PCD tools (E), (F) and (H) of Examples of the present invention. In addition, from FIG. 3, it was demonstrated that the layer thickness of the Co rich layer was about 28 μm and the value of C.sub.MAX/C.sub.DIA was 1.7.

(25) The average layer thickness of the diamond layer was obtained by measuring the distance from the boundary line between the diamond layer and the Co rich layer to the outermost surface of the diamond layer at multiple points in the layer thickness direction and calculating the average value from the measured values.

(26) The average layer thicknesses of the diamond layer of the PCD tools (E), (F), (H), (I) and (J) of Example of the present invention were within the range of 5.0 mm to 8.0 mm.

(27) The values of the average layer thicknesses of the buffer layers measured in the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention were also shown.

(28) The average layer thickness of the buffer layer was obtained by measuring the distance between the boundary lines of the buffer layer at multiple points in the layer thickness direction and calculating the average value from the measured values.

(29) The average layer thicknesses of the buffer layers of the PCD tools (E), (F), (H), (I) and (J) of Examples of the present invention were within the range of 5 μm to 9 μm.

(30) Further, with respect to the PCD tools (E), (F), (H), (I) and (J) of Examples of the present invention, the average grain size D of the WC particles in the region from the interface to 50 μm inside of the diamond layer were obtained by: observing the region from the interface between each of the cemented carbide substrates and the diamond layers to 50 μm inside of the diamond layer by SEM (scanning electron microscope) with a magnification of 500 to 3000 times; measuring the grain sizes of WC particles in the region using the image processing of the observed SEM pictures (using software, ImageJ Ver: 1.49, provided by the National Institute of Health, USA); and averaging the measurement values obtained in different multiple points.

(31) In addition, the average grain size D.sub.O of the WC particles inside the cemented carbide substrate was obtained in the same manner, and the value of D/DO was calculated.

(32) Table 2 shows the results obtained from the interface between the respective cemented carbide substrates and the diamond layers obtained in the PCD tools (E), (F), (H), (I) and (J) of Examples of the present invention. The value of the average particle diameter D of the WC particles in the region from the interface between each of the cemented carbide substrates and the diamond layers to 50 μm inside of the diamond layer; the value of the average particle diameter D.sub.O of the WC particles inside the cemented carbide substrate; and the value of D/D.sub.O were shown.

(33) From Table 2, it was demonstrated that the value of D/D.sub.O was less than 2 in all of the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention.

(34) For comparison, PCD tools (A) to (D) and (G) of Comparative Examples were produced by combining the cemented carbide and the diamond raw material powder shown as (A) to (D) and (G) in Table 1.

(35) The sintering pressure and the sintering temperature of the PCD tools (A) to (D) and (G) of Comparative Examples were 5.8 GPa and 1500° C., respectively, The same sintering conditions as the PCD tools of (E), (F) and (H) of Examples of the present invention were used.

(36) Among the PCD tools (A) to (D) and (G) of Comparative Examples, which were prepared as described above, the PCD tools (A) to (D) were chosen, subjected to scanning electron microscope (SEM) observation, and the vicinity of the interfaces between the cemented carbide substrates and the diamond layers were observed. The obtained SEM images are shown in FIG. 2 in the panels (A) to (D), respectively.

(37) From the panels (A) to (D) in FIG. 2, it was demonstrated that the Co rich layer having the average layer thickness of 50 μm or more (FIG. 1, (A) and (B); or the Co rich layer having the average layer thickness more than 30 μm (FIG. 1, (C) and (D), was formed at the interface between the cemented carbide substrate and the diamond layer in the PCD tools (A) to (D) of Comparative Examples, in which the Co powder was not premixed in the diamond powder.

(38) Further, in the PCD tools (A) to (D), (G) of Comparative Examples, WC particles, in which the grain sizes were abnormally grown, were observed in the region form the interface between the cemented carbide substrate and the diamond layer to 50 μm inside of the diamond layer.

(39) From comparison between panels (A) to (D) in FIG. 2, it was demonstrated that: the layer thickness of the Co rich layer was thickened for the WC particles to grow abnormally in the PCD tools (A) to (C), in which the average grain sizes of the diamond powders used were relatively small (3 μm), compared to the PCD tool (D), in which the average grain size of the diamond powder was relatively large (9 μm); and the layer thickness of the Co rich layer was thickened in the PCD tools (A) and (B), in which the Co contents in the cemented carbide substrates used were relatively less (10% by mass), compared to the PCD tools (C) and (D), in which the Co contents in the cemented carbide substrates used were relatively high (16% by mass).

(40) Table 2 shows the average layer thicknesses of the diamond layers; the average layer thicknesses of the Co rich layers; the average grain sizes D of the WC particles in the region from the interface between the cemented carbide substrate and the diamond layer to 50 μm inside of the diamond layer; the average grain sizes of the WC particles in the inside of the cemented carbide substrate; the values of D/D.sub.O; and the average layer thickness of the buffer layer, of the PCD tools (A) to (D) and (G) of Comparative Examples, all of which were measured as in the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention.

(41) In the samples (A) to (D) and (G) in Table 1, the Co content in the diamond raw material powder was zero, but by sintering, Co was infiltrated from the cemented carbide into the diamond layer. Thus, the amount of Co indicated as C.sub.DIA in Table 2 was included in the diamond layer.

(42) FIG. 4 shows a schematic explanation and analysis results of the line analysis performed on the PCD tool (G) of Comparative Example. It was demonstrated that the layer thickness of the Co rich layer was about 50 μm, and the value of C.sub.MAX/C.sub.DIA was 4.3.

(43) According to Table 2, in all of the PCD tools (A) to (D), (G) of Comparative Examples, the average layer thicknesses of the Co rich layers exceeded 30 μm. In addition, D/D.sub.O in the region from the interface between the cemented carbide substrate and the diamond layer to 50 μm inside of the diamond layer was 3-12. In addition, in all of the PCD tools (A) to (D), (G) of Comparative Examples, the average layer thicknesses of the diamond layers were less than 0.8 mm; and there was not buffer layer.

(44) TABLE-US-00002 TABLE 2 Average layer Average layer Average layer Impact PCD thickness of the thickness of the thickness of the shear tool diamond layer Co rich layer buffer layer strength type C.sub.DIA C.sub.MAX C.sub.MAX/C.sub.DIA (mm) (μm) D D.sub.o D/D.sub.o (μm) (J/cm.sup.2) Remarks A 4406 17183 3.9 0.5 47 10.8 0.9 12.0 0 3.7 Comparative Example B 3986 12755 3.2 0.5 42 10 3.3 3.0 0 4.0 Comparative Example C 4271 11532 2.7 0.8 36 18 2.2 8.2 0 5.1 Comparative Example D 2885 6347 2.2 0.8 31 16 2.2 7.3 0 4.7 Comparative Example E 3684 4789 1.3 5.0 10 2.6 2.2 1.2 5 7.3 Example of the present invention F 4181 6690 1.6 8.0 20 2.2 2.2 1.0 7 8.9 Example of the present invention G 3907 16800 4.3 0.8 53 22 2.2 10.0 0 2.9 Comparative Example H 5914 10054 1.7 6.0 20 3.2 2.2 1.5 9 10.2 Example of the present invention I 5793 10028 1.7 6.0 21 3.3 2.2 1.5 9 11.4 Example of the present invention J 5821 10721 1.8 6.0 23 3.1 2.2 1.4 9 12.1 Example of the present invention Note: “Co rich layer” means the region from the interface between the diamond layer and the WC-based cemented carbide to the diamond layer and having the Co content of 1.1 × C.sub.DIA or more.

(45) Next, with respect to the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention; and the PCD tools (A) to (D), and (G) of Comparative Examples, heat treatment test was performed at 750° C.-850° C. for 60 minutes in order to evaluate the heat resistance, the cracking resistance and the peeling resistance.

(46) For the PCD tools (A) to (D), and (G), occurrence of cracking and peeling was observed at the interface between the cemented carbide substrate and the diamond layer by heat treatment at 750° C. for 60 minutes.

(47) On the contrary, in the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention, there was no occurrence of cracking or peeling at the interface between the cemented carbide substrate and the diamond layer in the heat treatment at 750° C. for 60 minutes.

(48) In the PCD tools (E), (H), (I) and (J) of Examples of the present invention, the occurrence of cracking was observed for the first time at the interface between the cemented carbide substrate and the diamond layer by heat treatment at 800° C. for 60 minutes.

(49) In the PCD tool (F) of Example of the present invention, cracking did not occur at the interface between the cemented carbide substrate and the diamond layer even by heat treatment at 850° C. for 60 minutes, but the occurrence of fine cracks in the diamond layer was observed.

(50) It is assumed that the fine cracks were formed in the PCD tool (F) of Example of the present invention because: the temperature for heat resistance test was higher than the temperature in the PCD tools (A) to (D), and (G); and the PCD tools of (E), and (H) to (J); the heat stress of Co exceeded the bonding force between diamond particles; and as a result, the fine cracks were formed in the inside of the diamond layer itself

(51) In addition, for the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention; and the PCD tools (A) to (D), and (G) of Comparative Examples, the impact share strength test was performed in order to evaluate the resistance against peeling of the diamond layer due to an instantaneous impact. The results are shown in Table 2.

(52) For the evaluation of the impact shear strength, testing pieces corresponding to the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention; and the PCD tools (A) to (D), and (G) of Comparative Examples, were prepared in the dimension shown in FIG. 8 and used.

(53) The testing pieces were fixed to the testing piece fixing jig (25) shown in FIG. 9 via the clamp (24) on the WC-Co layer side. The hammer (21) was set so that its lower end abuts the diamond layer (18) of the test piece. Then, the weight (22) of a predetermined mass (kg) was dropped from a predetermined height on the upper end of the hammer (21). FIG. 10 shows a state in which the diamond layer (18) is broken by the falling of the weight (22).

(54) If the diamond layer (18) does not break (peeled off from the cemented carbide substrate (17), the drop height of the weight (22) was increased and retested. When breaking occurred, the falling weight energy (J) at that time was taken as the impact shear strength.

(55) The falling weight energy is obtained from the formula of falling weight energy (J)=mass of weight (kg)×gravity constant (ms.sup.−2)×height (m).

(56) The shear strength (J/cm.sup.2) was obtained from the equation of shear strength (J/cm.sup.2)=drop weight energy (J) at breakage/testing piece cross-sectional area (cm.sup.2).

(57) From Table 2, it was demonstrated that in the PCD tool (E), (F), (H), and (I) of Example of the present invention, impact shearing strength (J) was 7.3 J/cm.sup.2 to 12.1 J/cm.sup.2. In the PCD tools (H), (I) and (J) of Examples of the present invention including the buffer layer having the average layer thickness of 5 μm or more and 15 μm or less, the impact shear strength exhibited the value of about 10 J/cm.sup.2 or more. In particular, the PCD tools (I) and (J) of Example of the present invention showed high impact shear strength.

(58) On the other hand, in the PCD tools (A) to (D), and (G) of Comparative Examples, the impact shear strength (J/cm.sup.2) against the peeling of the diamond layer (18) due to the instantaneous impact was 2.9 J/cm.sup.2 to 5.1 J/cm.sup.2, which was significantly lower than the impact shear strength in the PCD tools (E), (F), (H), (I), and (J) of Examples of the present invention.

(59) FIG. 3 shows SEM images obtained in the PCD tools (C) and (D) of Comparative Example; and the PCD tool (F) of Example of the present invention after the heat treatment test.

(60) As clearly demonstrated in results shown in Table 3, the PCD tools (E), (F) and (H) of Examples of the present invention, in which the average layer thicknesses of the Co rich layers formed at the interfaces between the cemented carbide substrates and the diamond layers were suppressed to 30 μm or less, and the average grain size D of the WC particles in the region from the interface between the cemented carbide substrate and the diamond layer to 50 μm inside of the diamond layer satisfied the formula D/D.sub.O<2 with respect to the average grain size D.sub.O of the WC particles in the inside of the cemented carbide substrate, had excellent heat resistance and impact resistance; and excellent cracking resistance and peeling resistance.

INDUSTRIAL APPLICABILITY

(61) As described above, the PCD tool of the present invention has excellent interface bonding strength and excellent heat resistance/impact resistance in addition to excellent hardness, thermal conductivity, and chemical stability that ordinary PCD tools have. Thus, it is used as a long-life PCD tool for cutting of non-ferrous metals, cemented carbide, ceramics and the like; or for petroleum/natural gas/geothermal well drilling and the like.

REFERENCE SINGS LIST

(62) 1: WC-Co base material (cemented carbide substrate) 2: Graphite disc 3: Graphite 4: Heater 5: Steel ring 6: Ta foil 7: NaCl-10 wt % ZrO.sub.2 8: Diamond powder or (diamond+Co) mixed powder 9: Ta capsule 10: Co rich layer 11: WC particles (white) 12: Co (gray) 13: Diamond particles (black) 14: Analysis direction 15: Interface crack 16: Crack in diamond layer 17: Cemented carbide substrate 18: Diamond layer 19: Co rich layer 20: Buffer layer 21. Hammer 22: Weight 23: Fall 24: Clamp 25: Test piece fixing jig