CERAMIC FORGING METHOD

Abstract

The present disclosure relates to a ceramic forging method, and belongs to the technical field of ceramic preparation. The ceramic forging method comprises a step of applying an oscillatory pressure to to-be-forged ceramic at a forging temperature to perform forging, In accordance with the ceramic forging method provided by the present disclosures, the deformation capacity and the deformation rate of a ceramic material are improved by changing a deformation mechanism of a ceramic material at the high temperature through oscillatory pressure, such that generation of micro fatigues inside the ceramic material and the deformation process of the material are greatly improved, then the ceramic material can reach the higher deformation rate and the larger deformation amount at lower temperature and pressure, and therefore ceramic forging can be achieved, and the cost is greatly reduced.

Claims

1. A ceramic forging method, comprising a step of applying an oscillatory pressure to to-be-forged ceramic at a forging temperature to perform forging.

2. The ceramic forging method according to claim 1, wherein, the oscillatory pressure and the forging temperature are configured to meet the following condition that the to-be-forged ceramic has a stress exponent greater than or equal to 2 when deformed at a median pressure of the oscillatory pressure and under the forging temperature.

3. The ceramic forging method according to claim 1, wherein an amplitude of the oscillatory pressure is 8% to 100% of the median pressure of the oscillatory pressure.

4. The ceramic forging method according to claim 2, wherein an amplitude of the oscillatory pressure is 8% to 100% of the median pressure of the oscillatory pressure.

5. The ceramic forging method according to claim 1, wherein the median pressure of the oscillatory pressure is 40 MPa to 120 MPa.

6. The ceramic forging method according to claim 2, wherein the median pressure of the oscillatory pressure is 40 MPa to 120 MPa.

7. The ceramic forging method according to claim 1, wherein the frequency of the oscillatory pressure is 1 Hz to 20 Hz.

8. The ceramic forging method according to claim 2, wherein the frequency of the oscillatory pressure is 1 Hz to 20 Hz.

9. The ceramic forging method according to claim 1, wherein the waveform of the oscillatory pressure is a sine wave or a cosine wave.

10. The ceramic forging method according to claim 2, wherein the waveform of the oscillatory pressure is a sine wave or a cosine, wave.

11. The ceramic forging method according to claim 1, wherein the to-be-forged ceramic has a relative density of 60% to 100%.

12. The ceramic forging method according to claim 2, wherein the to-be-forged ceramic has a relative density of 60% to 100%.

13. The ceramic forging method according to claim 1, wherein the forging time is 0.5 h to 2 h.

14. The ceramic forging method according to claim 2, wherein the forging time is 0.5 h to 2 h.

15. The ceramic forging method according to claim 1, wherein the to-be-forged ceramic is liquid-phase sintered ceramic or solid-phase sintered ceramic.

16. The ceramic forging method according to claim 2, wherein the to-be-forged ceramic is liquid-phase sintered ceramic or solid-phase sintered ceramic.

17. The ceramic forging method according to claim 1,wherein when the to-be-forged ceramic is boron carbide ceramic, the forging temperature is 1800° C. to 2000° C., and the median pressure of the oscillatory pressure is 50 MPa to 70 MPa; when the to-be-forged ceramic is silicon nitride ceramic, the forging temperature is 1600° C. to 1800° C., and the median pressure of the oscillatory pressure is 40 MPa to 70 MPa; when the to-be-forged ceramic is alumina ceramic, the forging temperature is 1500° C. to 1800° C., and the median pressure of the oscillatory pressure is 70 MPa to 120 MPa.

18. The ceramic forging method according to claim 2, therein when the to-be-forged ceramic is boron carbide ceramic, the forging temperature is 1800° C. to 2000° C., and the median pressure of the oscillatory pressure is 50 MPa to 70 MPa; when the to-be-forged ceramic is silicon nitride ceramic, the forging temperature is 1600° C. to 1800° C., and the median pressure of the oscillatory pressure is 40 MPa to 70 MPa; when the to-be-forged ceramic is alumina ceramic, the forging temperature is 1500° C. to 1800° C., and the median pressure of the oscillatory pressure is 70 MPa to 120 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a morphological diagram of to-be-forged ceramic and forged ceramic an embodiment 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions of the present disclosure are further described below with reference to specific embodiments.

Embodiment 1

[0023] A ceramic forging method of this embodiment, using hot-pressed sintered boron carbide ceramic (in a shape of a cylinder having a diameter of 30 mm and a height of 4.61 mm, and having a relative density of 98%) without the addition of a sintering aid as to-be-forged ceramic, comprises the following steps:

[0024] placing the to-be-forged ceramic in a graphite mold having a diameter of 40 mm, and putting the graphite mold filled with the to-be-forged ceramic into a high-temperature furnace, heating to a forging temperature of 1900° C. under a vacuum condition, and preserving heat for 1 hour; loading oscillatory pressure in the heat preservation stage, wherein the oscillatory pressure has a waveform of a sine wave, a frequency of 5 Hz, the median pressure of 70 MPa, and an amplitude of 10 MPa; and obtaining a boron carbide forged part having a diameter of 40 mm and a height of 2.78 mm after performing oscillatory forging for 1 hour, wherein the to-be-forged ceramic has a stress exponent n=3.38 when deformed at 1900° C. and 70 MPa.

[0025] The obtained to-be-forged ceramic and the forged part after forging are as shown in FIG. 1. The obtained boron carbide ceramic forged part has a relative density of 99.5%, a Vickers hardness increased from the 28 GPa of the to-be-forged ceramic to 36 GPa of the forged part, and a bending strength increased from 270 MPa of the to-be-forged ceramic to 620 MPa of the forged part.

Embodiment 2

[0026] A ceramic forging method of this embodiment, using hot-pressed sintered boron carbide ceramic (in a shape of a cylinder having a diameter of 30 mm and a height of 5 mm, and having a relative density of 99.7%) without addition of a sintering aid as to-be-forged ceramic, comprises the following steps:

[0027] placing the to-be-forged ceramic in a graphite mold having a diameter of 40 mm, and putting the graphite mold filled with the to-be-forged ceramic into a high-temperature furnace, heating to a forging temperature of 2000° C. under a vacuum condition, and preserving heat for 1 hour; loading oscillatory pressure in the heat preservation stage, wherein the oscillatory pressure has a waveform of a sine wave, a frequency of 20 Hz, the median pressure of 50 MPa, and an amplitude of 10 MPa; and obtaining a boron carbide forged part having a diameter of 40 mm after performing oscillatory forging for 1 hour, wherein the to-be-forged ceramic has a stress exponent n=3.63 when deformed at 2000° C. and 50 MPa.

[0028] The obtained boron carbide ceramic forged part has a relative density of 99.7%, a Vickers hardness increased from the 30 GPa of the to-be-forged ceramic to 36 GPa of the forged part, and a bending strength increased from 315 MPa of the to-be-forged ceramic to 670 MPa of the forged part.

Embodiment 3

[0029] A ceramic forging method of this embodiment, using silicon nitride carbide ceramic (liquid-phase sintered silicon nitride ceramic, having a relative density of 80%) added with Y.sub.2O.sub.3 in a mass ratio of 10% as a sintering aid as to-be-forged ceramic, comprises the following steps:

[0030] placing the to-be-forged ceramic in a graphite mold, heating to 1800° C. under a nitrogen atmosphere for heat preservation; loading oscillatory pressure, wherein the oscillatory pressure has an oscillatory waveform of a sine wave, a frequency of 5 Hz, the median pressure of 70 MPa, and an amplitude of 10 MPa; and obtaining a deformed silicon nitride ceramic forged part by performing oscillatory forging for 1 hour, wherein the to-be-forged ceramic has a stress exponent n=2.2 at 1800° C. and 70 MPa.

[0031] The obtained silicon nitride ceramic forged part has a relative density of 98%, a Vickers hardness increased from the original 9 GPa to 14 GPa, and a bending strength increased from 320 MPa to 710 MPa.

Embodiment 4

[0032] A ceramic forging method of this embodiment, using silicon nitride ceramic (liquid-phase sintered silicon nitride ceramic, having a relative density of 72%) added with Li.sub.2O in a mass ratio of 2% and Y.sub.2O.sub.3 in a mass ratio of 10% as sintering aids and sintered without pressure at 1500° C. as to-be-forged ceramic, comprises the following steps:

[0033] placing the to-be-forged ceramic in a graphite mold, heating to 1600° C. under a nitrogen atmosphere for heat preservation; loading oscillatory pressure, wherein the oscillatory pressure has an oscillatory waveform of a sine wave, a frequency of 5 Hz, the median pressure of 40 MPa, and an amplitude of 30 MPa; and obtaining a deformed silicon nitride ceramic forged part after performing oscillatory forging for 1 hour, wherein the to-be-forged ceramic has a stress exponent n=2.1 at 1600° C. and 40 MPa.

[0034] The obtained silicon nitride ceramic forged part has a relative density of 96%, a Vickers hardness increased from the original 6 GPa to 12 GPa, and a bending strength increased from 230 MPa to 640 MPa.

Embodiment 5

[0035] A ceramic forging method of this embodiment, using solid-phase sintered alumina ceramic (having a relative density of 99.4%) without the addition of a sintering aid as to-be-forged ceramic, comprises the following steps:

[0036] placing the to-be-forged ceramic in a graphite mold, heating to 1600° C. for heat preservation; loading oscillatory pressure, wherein the oscillatory pressure has an oscillatory waveform of a sine wave, a frequency of 1 Hz, the median pressure of 120 MPa, and an amplitude of 10 MPa; and obtaining a deformed alumina ceramic forged part by performing oscillatory forging for 1 hour, wherein the to-be-forged ceramic has a stress exponent n=3.12 when deformed at 1600° C. and 120 MPa.

[0037] The obtained alumina ceramic forged part has a relative density of 99.8%, a Vickers hardness increased from the original 14 GPa to 16 GPa, and a bending strength increased from 330 MPa to 400 MPa.