Tungsten carbide-cubic boron nitride composite material and preparation method thereof

Abstract

A tungsten carbide-cubic boron nitride composite material and preparation method thereof mainly includes WC and cBN, wherein the WC powder is coated with Co nano-layer and the cBN powder is coated with SiO.sub.2 nano-layer, and hardness and toughness of the composition material can be improved by coating. The method for preparing a tungsten carbide-cubic boron nitride composite material adopts chemical vapor deposition method and high temperature sintering method. First nano-layers were coated on the surface of WC and cBN, and then the bulk materials can be obtained via high-temperature sintering.

Claims

1. A method for preparing a tungsten carbide-cubic boron nitride composite material, comprising the following steps of: (1) placing WC powders into a chemical vapor deposition reaction chamber, pumping vacuum, preheating the reaction chamber to 500-700 C., using supplying cobaltocene to the reaction chamber, rotating the reaction chamber and reacting the cobaltocene for 18-50 min for coating the WC powders, after the WC powders are coated, stop rotating the reaction chamber, and stop supplying the cobaltocene to the reaction chamber, and taking out coated WC powders from the reaction chamber after cooling the coated WC powders to room temperature; (2) placing cBN powders into the chemical vapor deposition reaction chamber, pumping vacuum, preheating the reaction chamber to 500-700 C., supplying ethyl orthosilicate to the reaction chamber, rotating the reaction chamber and reacting the ethyl orthosilicate for 15-50 min for coating the cBN powders, after the cBN powders are coated, stop rotating the reaction chamber, and stop supplying the ethyl orthosilicate to the reaction chamber, and taking out coated cBN powders from the reaction chamber after cooling the coated cBN powders to room temperature; (3) mixing the coated WC powders and the coated cBN powders, wherein the content of the coated cBN powders in the mixed powders is 9%-18% by weight, and then performing sieving; (4) placing the sieved and mixed powders into a mould, sintering the sieved and mixed powders to prepare a bulk material of tungsten carbide-cubic boron nitride composite material, the sintering being performed at a temperature of 1200-1500 C., a pressure of 4-8 GPa, and for a time of 0.5-2 h.

2. The preparation method according to claim 1, wherein the coating of WC powders is performed under the protection of a gas flow of argon, and the gas flow of argon is 20-50 sccm.

3. The preparation method according to claim 1, wherein the coating of cBN powders is performed under the protection of a gas flow of argon, and the gas flow of argon is 10-30 sccm.

4. The preparation method according to claim 1, wherein the rotating rate of the reaction chamber is 30-60 r/min in step (1) and (2).

5. The preparation method according to claim 1, wherein the coated WC powders and cBN powders are mixed by a rotating-drum method, and the mixing time is 5-10 h.

6. The preparation method according to claim 1, wherein the sieve pore for sieving the mixed WC and cBN powders is 100-200 mesh, and the powder is sieved 3 times.

7. The preparation method according to claim 1, wherein the mean particle size of WC powders is 2 m in step (1).

8. The preparation method according to claim 1, wherein the mean particle size of cBN powders is 3 m in step (2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates the coating of WC and cBN powders in the tungsten carbide-cubic boron nitride composite material of the present invention.

DETAILED DESCRIPTION

(2) For a better understanding of the invention, preferred embodiments of the invention are described below with reference to the embodiments, but it is to be understood that these descriptions are merely illustrative of the features and advantages of the invention and are not intended to be limiting of the invention as claimed.

(3) The tungsten carbide-cubic boron nitride composite material is prepared by the preparation method of tungsten carbide-cubic boron nitride composite material according to the invention. The material is selected from the metallic materials with the purity of more than 95% and the metal organic materials with the purity of more than 98%, wherein the mean particle size of the WC powder is 2 m and the mean particle size of the cBN powder is 3 m, all the materials have been degassed and dehumidified in vacuum before being subjected to the chemical vapor deposition treatment, and then prepared according to the preparation method provided by the present invention.

Embodiment 1

(4) According to the method for preparing tungsten carbide-cubic boron nitride composite material provided by the invention, the prepared tungsten carbide-cubic boron nitride composite material is prepared as follows:

(5) (1) placing WC powders into chemical vapor deposition reaction chamber, pumping vacuum to 5 Pa, preheating to 500 C., using cobaltocene as raw material, setting the evaporating temperature as 120 C., rotating the reaction chamber at a rotating rate of 30 r/min, with a argon gas flow of 20 sccm, and coating the Co nano-layer over the WC powders by the thermal decomposition of cobaltocene, reacting for 20 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(6) (2) placing cBN powders into the chemical vapor deposition reaction chamber, pumping vacuum to 5 Pa, preheating to 500 C., using ethyl orthosilicate as raw material, heating to 80 C., rotating the reaction chamber at a rotating rate of 30 r/min, the gas flow rate of argon is 10 sccm, and coating the SiO.sub.2 nano-layer over the cBN powders by the thermal decomposition of ethyl orthosilicate and reacting for 20 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(7) determining the particle size and thickness of the nano-layer on the particle surface by combination of FESEM and TEM, the thickness of the SiO.sub.2 nano-layer was 20 nm, the particle size of the Co powder on the WC powder surface was 20 nm, and the thickness was 60 nm;

(8) (3) mixing 9.1 g coated WC and 0.9 g coated cBN powders by rotating-drum method for 5 h, and then sieving though 100 mesh sieve for 3 times;

(9) (4) placing the sieved and mixed powders into a mould, sintering to prepare bulk material to obtain tungsten carbide-cubic boron nitride composite material, the sintering temperature is 1200 C., and the sintering time is 2 h, the pressure is 4 GPa while sintering, after sintering, the content of cBN phase is 30% by volume, the diameter of the prepared sample is 30 mm, and the thickness is 5 mm.

Embodiment 2

(10) According to the method for preparing tungsten carbide-cubic boron nitride composite material provided by the invention, the prepared tungsten carbide-cubic boron nitride composite material is prepared as follows:

(11) (1) placing WC powders into chemical vapor deposition reaction chamber, pumping vacuum to 10 Pa, preheating to 500 C., using cobaltocene as raw material, setting the evaporating temperature as 130 C., rotating the reaction chamber at a rotating rate of 45 r/min, with a argon gas flow of 30 sccm, and coating the Co nano-layer over the WC powders by the thermal decomposition of cobaltocene, reacting for 18 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(12) (2) placing cBN powders into the chemical vapor deposition reaction chamber, pumping vacuum to 10 Pa, preheating to 500 C., using ethyl orthosilicate as raw material, heating to 120 C., rotating the reaction chamber at a rotating rate of 50 r0/min, the gas flow rate of argon is 20 sccm, and coating the SiO.sub.2 nano-layer over the cBN powders by the thermal decomposition of ethyl orthosilicate and reacting for 15 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(13) determining the particle size and thickness of the nano-layer on the particle surface by combination of FESEM and TEM, the thickness of the SiO.sub.2 nano-layer was 20 nm, the particle size of the Co powder on the WC powder surface was 20 nm, and the thickness was 60 nm;

(14) (3) mixing 8.9 g coated WC and 1.1 g coated cBN powders by rotating-drum method for 10 h, and then sieving though 200 mesh sieve for 3 times;

(15) (4) placing the sieved and mixed powders into a mould, sintering to prepare bulk material to obtain tungsten carbide-cubic boron nitride composite material, the sintering temperature is 1300 C., and the sintering time is 1.5 h, the pressure is 6 GPa while sintering, after sintering, the content of cBN phase is 35% by volume, the diameter of the prepared sample is 30 mm, and the thickness is 5 mm.

Embodiment 3

(16) According to the method for preparing tungsten carbide-cubic boron nitride composite material provided by the invention, the prepared tungsten carbide-cubic boron nitride composite material is prepared as follows:

(17) (1) placing WC powders into chemical vapor deposition reaction chamber, pumping vacuum to 20 Pa, preheating to 500 C., using cobaltocene as raw material, setting the evaporating temperature as 140 C., rotating the reaction chamber at a rotating rate of 60 r/min, with a argon gas flow of 40 sccm, and coating the Co nano-layer over the WC powders by the thermal decomposition of cobaltocene, reacting for 50 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(18) (2) placing cBN powders into the chemical vapor deposition reaction chamber, pumping vacuum to 20 Pa, preheating to 500 C., using ethyl orthosilicate as raw material, heating to 90 C., rotating the reaction chamber at a rotating rate of 40 r/min, the gas flow rate of argon is 30 sccm, and coating the SiO.sub.2 nano-layer over the cBN powders by the thermal decomposition of ethyl orthosilicate and reacting for 50 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(19) determining the particle size and thickness of the nano-layer on the particle surface by combination of FESEM and TEM, the thickness of the SiO.sub.2 nano-layer was 50 nm, the particle size of the Co powder on the WC powder surface was 40 nm, and the thickness was 120 nm;

(20) (3) mixing 8.7 g coated WC and 1.3 g coated cBN powders by rotating-drum method for 10 h, and then sieving though 200 mesh sieve for 3 times;

(21) (4) placing the sieved and mixed powders into a mould, sintering to prepare bulk material to obtain tungsten carbide-cubic boron nitride composite material, the sintering temperature is 1400 C., and the sintering time is 0.5 h, the pressure is 5 GPa while sintering, after sintering, the content of cBN phase is 40% by volume, the diameter of the prepared sample is 30 mm, and the thickness is 5 mm.

Embodiment 4

(22) According to the method for preparing tungsten carbide-cubic boron nitride composite material provided by the invention, the prepared tungsten carbide-cubic boron nitride composite material is prepared as follows:

(23) (1) placing WC powders into chemical vapor deposition reaction chamber, pumping vacuum to 15 Pa, preheating to 500 C., using cobaltocene as raw material, setting the evaporating temperature as 150 C., rotating the reaction chamber at a rotating rate of 35 r/min, with a argon gas flow of 40 sccm, and coating the Co nano-layer over the WC powders by the thermal decomposition of cobaltocene, reacting for 40 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(24) (2) placing cBN powders into the chemical vapor deposition reaction chamber, pumping vacuum to 15 Pa, preheating to 500 C., using ethyl orthosilicate as raw material, heating to 130 C., rotating the reaction chamber at a rotating rate of 35 r/min, the gas flow rate of argon is 25 sccm, and coating the SiO.sub.2 nano-layer over the cBN powders by the thermal decomposition of ethyl orthosilicate and reacting for 40 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(25) determining the particle size and thickness of the nano-layer on the particle surface by combination of FESEM and TEM, the thickness of the SiO.sub.2 nano-layer was 100 nm, the particle size of the Co powder on the WC powder surface was 40 nm, and the thickness was 120 nm;

(26) (3) mixing 8.5 g coated WC and 1.5 g coated cBN powders by rotating-drum method for 6 h, and then sieving though 100 mesh sieve for 3 times;

(27) (4) placing the sieved and mixed powders into a mould, sintering to prepare bulk material to obtain tungsten carbide-cubic boron nitride composite material, the sintering temperature is 1400 C., and the sintering time is 1.5 h, the pressure is 5 GPa while sintering, after sintering, the content of cBN phase is 45% by volume, the diameter of the prepared sample is 30 mm, and the thickness is 5 mm.

Embodiment 5

(28) According to the method for preparing tungsten carbide-cubic boron nitride composite material provided by the invention, the prepared tungsten carbide-cubic boron nitride composite material is prepared as follows:

(29) (1) placing WC powders into chemical vapor deposition reaction chamber, pumping vacuum to 10 Pa, preheating to 500 C., using cobaltocene as raw material, setting the evaporating temperature as 150 C., rotating the reaction chamber at a rotating rate of 60 r/min, with a argon gas flow of 25 sccm, and coating the Co nano-layer over the WC powders by the thermal decomposition of cobaltocene, reacting for 20 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(30) (2) placing cBN powders into the chemical vapor deposition reaction chamber, pumping vacuum to 20 Pa, preheating to 500 C., using ethyl orthosilicate as raw material, heating to 130 C., rotating the reaction chamber at a rotating rate of 60 r/min, the gas flow rate of argon is 25 sccm, and coating the SiO.sub.2 nano-layer over the cBN powders by the thermal decomposition of ethyl orthosilicate and reacting for 25 min for coating, after the coating is over, stopping rotating, and stopping to supplying the raw material, and taking out after cooling to room temperature;

(31) determining the particle size and thickness of the nano-layer on the particle surface by combination of FESEM and TEM, the thickness of the SiO.sub.2 nano-layer was 40 nm, the particle size of the Co powder on the WC powder surface was 30 nm, and the thickness was 60 nm;

(32) (3) mixing 8.5 g coated WC and 1.5 g coated cBN powders by rotating-drum method for 6 h, and then sieving though 100 mesh sieve for 3 times,

(33) (4) placing the sieved and mixed powders into a mould, sintering to prepare bulk material to obtain tungsten carbide-cubic boron nitride composite material, the sintering temperature is 1500 C., and the sintering time is 0.5 h, the pressure is 8 GPa while sintering, after sintering, the content of cBN phase is 50% by volume, the diameter of the prepared sample is 30 mm, and the thickness is 5 mm.

(34) The hardness and the fracture toughness of the WC-cBN composite material were measured by Vickers hardness indentation method, and the strength of the material was measured by the tensile method. The results are as follows:

(35) TABLE-US-00001 TABLE 1 density, hardness, toughness and strength of the WC-cBN composite material Hardness/ Toughness/MPa Embodiment Density/% GPa m.sup.1/2 Strength 1 95.2 30 11.8 950 2 96.5 32 12.6 1200 3 95.3 33 13.4 1100 4 98.8 35 13.2 1360 5 97.9 34 11.1 1300

(36) It can be seen from the table that, the WC-cBN composite material prepared by the present invention has high hardness, toughness and strength, and while the volume content of the coated cBN phase is increased from 30% to 50%, the density of the WC-cBN composite material presents fluctuations. When the volume content of the coated cBN phase is 45%, the density reaches the highest point. The hardness index of the composites showed a tendency to increase first and then decrease with the increase of the volume content of the cBN phase after coating. The hardness of the composites was the highest when the content of cBN phase was 45%. The toughness of the composites exhibits a similar trend with the change of the hardness index, and the toughness is the highest when the volume content of the coated cBN phase reaches 40%. The strength of the composites exhibits a similar trend with the change of the density index, and the strength is the highest when the volume content of the coated cBN phase reaches 45%.

(37) The foregoing description of the disclosed embodiments will enable those skilled in the art to make or use the invention. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.