阅读说明：本技术 一种陶瓷的锻造方法 (Forging method of ceramic ) 是由 樊磊 安立楠 于 2021-09-13 设计创作，主要内容包括：本发明涉及一种陶瓷的锻造方法,属于陶瓷制备技术领域。本发明的陶瓷的锻造方法,包括以下步骤：将待锻造陶瓷在锻造温度下施加振荡压力进行锻造。本发明的陶瓷的锻造方法,通过振荡压力下改变陶瓷材料高温下的变形机制,提升陶瓷材料变形能力和变形速率,使陶瓷材料内部微观疲劳的产生和材料变形历程的大幅提升,进而使陶瓷材料能够在更低的温度和压力下达到更高的变形速率并达到更大的变形量,从而使得陶瓷锻造得以实现并大幅降低成本。此外,利用振荡压力锻造所产生的变形过程可以实现陶瓷材料相对密度的提升和性能的强化,也可以实现一定形状和尺寸陶瓷构件的锻造成形。(The invention relates to a forging method of ceramics, belonging to the technical field of ceramic preparation. The forging method of the ceramic comprises the following steps: and forging the ceramic to be forged by applying oscillating pressure at the forging temperature. According to the ceramic forging method, the deformation mechanism of the ceramic material at high temperature is changed under the oscillating pressure, so that the deformation capacity and the deformation rate of the ceramic material are improved, the generation of the internal micro fatigue of the ceramic material and the deformation process of the material are greatly improved, the ceramic material can reach higher deformation rate and larger deformation amount at lower temperature and pressure, and the ceramic forging is realized and the cost is greatly reduced. In addition, the deformation process generated by the oscillating pressure forging can realize the promotion of the relative density and the performance strengthening of the ceramic material, and also can realize the forging forming of the ceramic component with certain shape and size.)

1. A method for forging ceramics is characterized in that: the method comprises the following steps: and forging the ceramic to be forged by applying oscillating pressure at the forging temperature.

2. The method for forging ceramics according to claim 1, wherein: the oscillating pressure and forging temperature should satisfy the following conditions: and the pressure index of the ceramic to be forged when the ceramic is deformed at the median pressure of the oscillation pressure and the forging temperature is more than or equal to 2.

3. The forging method of ceramics according to claim 1 or 2, wherein: the amplitude of the oscillating pressure is 8-100% of the median pressure of the oscillating pressure.

4. The forging method of ceramics according to claim 1 or 2, wherein: the median pressure value of the oscillating pressure is 40-120 MPa.

5. The forging method of ceramics according to claim 1 or 2, wherein: the frequency of the oscillating pressure is 1-20 Hz.

6. The forging method of ceramic as recited in claim 1 or 2, wherein a waveform of the oscillating pressure is a sine wave or a cosine wave.

7. The forging method of ceramics according to claim 1 or 2, wherein: the relative density of the ceramic to be forged is 60-100%.

8. The forging method of ceramics according to claim 1 or 2, wherein: the forging time is 0.5-2 h.

9. The forging method of ceramics according to claim 1 or 2, wherein: the ceramic to be forged is liquid phase sintered ceramic or solid phase sintered ceramic.

10. The forging method of ceramics according to claim 1 or 2, wherein: when the ceramic to be forged is boron carbide ceramic, the forging temperature is 1800-2000 ℃, and the pressure median value of the oscillation pressure is 50-70 MPa; when the ceramic to be forged is silicon nitride ceramic, the forging temperature is 1600-1800 ℃, and the pressure median value of the oscillation pressure is 40-70 MPa; when the ceramic to be forged is alumina ceramic, the forging temperature is 1500-1800 ℃, and the pressure median value of the oscillation pressure is 70-120 MPa.

Technical Field

The invention relates to a forging method of ceramics, belonging to the technical field of ceramic preparation.

Background

Forging is a process of plastically deforming a material by pressure to obtain a certain shape, size and properties. Forging is often used for forming metal materials, and in the case of ceramic materials, forging is difficult because of difficulty in sliding and poor plasticity. The preparation method of the commonly used high-performance ceramic component is mainly hot-pressing sintering, and compared with the hot-pressing sintering, the forging process generates larger shear stress in the material, so that the material generates larger deformation, the pore structure in the material can be greatly eliminated, and the texture structure and the work hardening can be generated, thereby greatly improving the material performance.

Ceramic materials are often bound by ionic and covalent bonds, which makes dislocation generation and movement of the ceramic material difficult. Although the stress required to create deformation at high temperatures decreases with increasing atomic mobility, higher temperatures and pressures are still required to achieve ceramic forging. Under the existing static pressure condition, the high-temperature creep mechanism of the ceramic material mainly takes a ble and Naborro-Herring diffusion mechanism as a main mechanism, the strain amount is small, the strain rate is low, and if the deformation mechanism is promoted to a power law deformation mechanism of slip or dislocation control so as to achieve the effect of improving the strain amount and the strain rate, very high temperature and very high static pressure are needed, which often exceeds the bearing range of equipment and high-temperature molds such as graphite molds. This makes ceramic forging difficult to achieve or requires extremely high costs.

Disclosure of Invention

The invention aims to provide a method for forging ceramics, which can reduce the forging cost of the ceramics.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

a forging method of ceramics comprises the following steps: and forging the ceramic to be forged by applying oscillating pressure at the forging temperature.

According to the ceramic forging method, the deformation mechanism of the ceramic material at high temperature is changed through the oscillation pressure, the deformation capacity and the deformation rate of the ceramic material are improved, the generation of the internal micro fatigue of the ceramic material and the deformation process of the material are greatly improved, and the high-temperature deformation mechanism of the ceramic material can reach higher deformation rate and larger deformation amount at lower temperature and pressure, so that the ceramic forging is realized and the cost is greatly reduced. In addition, the deformation process generated by the oscillating pressure forging can realize the promotion of the relative density and the performance strengthening of the ceramic material, and also can realize the forging forming of the ceramic component with certain shape and size.

Preferably, the oscillating pressure and the forging temperature should satisfy the following conditions: and the pressure index of the ceramic to be forged when the ceramic is deformed at the median pressure of the oscillation pressure and the forging temperature is more than or equal to 2. When the pressure index is larger than or equal to 2, the deformation mechanism is the power law deformation of grain boundary sliding or dislocation creep control. The forging temperature is above the creep temperature of the ceramic to be forged.

The median pressure of the oscillating pressure is selected in conjunction with the forging temperature. Preferably, the amplitude of the oscillating pressure is 8-100%, such as 12.5%, 14.2% or 20% of the median pressure of the oscillating pressure.

Preferably, the median pressure value of the oscillating pressure is between 40 and 120MPa, for example 50MPa, 70MPa, 80MPa or 100 MPa.

Preferably, the frequency of the oscillating pressure is 1-20Hz, which may be, for example, 5Hz or 10 Hz.

Preferably, the waveform of the oscillating pressure is a sine wave or a cosine wave.

Preferably, the relative density of the ceramic to be forged is 60 to 100%. According to the ceramic forging method, after the ceramic to be forged with the relative density of less than 99% is forged by the forging method, further densification can be realized, so that the relative density is improved; for the ceramic to be forged which is compact (the relative density is more than or equal to 99%) or non-compact (the relative density is less than 99%), the strength and hardness of the ceramic after forging are improved.

Preferably, the forging time is 0.5 to 2 hours, for example 1 hour.

Preferably, the ceramic to be forged is a liquid phase sintered ceramic or a solid phase sintered ceramic. The liquid phase sintered ceramic is a ceramic material containing an intercrystalline glass phase or an amorphous phase. For example, the liquid phase sintered ceramic is a liquid phase sintered silicon nitride ceramic or a liquid phase sintered aluminum nitride ceramic. The solid-phase sintered ceramic is a ceramic with no intercrystalline glass phase or intercrystalline amorphous phase. Preferably, the solid-phase sintered ceramic is a boron carbide ceramic or an alumina ceramic. The ceramic to be forged can be ceramic added with a sintering aid during preparation, and can also be ceramic without using the aid during sintering.

When the ceramic to be forged is boron carbide ceramic, the forging temperature is preferably 1800-2000 ℃, and the pressure median value of the oscillation pressure is 50-70 MPa.

When the ceramic to be forged is silicon nitride ceramic, the forging temperature is preferably 1600-1800 ℃, and the pressure median value of the oscillation pressure is 40-70 MPa.

When the ceramic to be forged is alumina ceramic, the forging temperature is preferably 1500-1800 ℃, and the pressure median value of the oscillation pressure is 70-120 MPa.

The ceramic to be forged is sintered and produces a sintered bond before the oscillating pressure is applied for forging. The sintered and bonded ceramic to be forged may be a ceramic material which is sintered and taken out after cooling before forging, or may be sintered during heating before applying oscillating pressure. The sintering may be either pressure sintering or pressureless sintering. Meanwhile, the sintering can be carried out with or without a sintering aid. Preferably, the ceramic to be forged is obtained by pressure or pressureless sintering, and then is heated to a forging temperature and forged by applying an oscillating pressure at the forging temperature.

Drawings

FIG. 1 is a graph showing the morphology of the ceramic to be forged and the ceramic after forging in example 1.

Detailed Description

The technical solution of the present invention will be further described with reference to the following embodiments.

Example 1

The method for forging the ceramic of the embodiment, which uses the hot-pressed sintered boron carbide ceramic (the shape is a cylinder with the diameter of 30mm and the height of 4.61mm, and the relative density is 98%) without adding the sintering aid as the ceramic to be forged, comprises the following steps:

putting the ceramic to be forged into a graphite die with the diameter of 40mm, putting the graphite die in which the ceramic to be forged is put into a high-temperature furnace, heating to the forging temperature of 1900 ℃ under a vacuum condition, preserving heat for 1h, loading oscillation pressure in the heat preservation stage, wherein the oscillation pressure is sine wave in waveform, the frequency is 5Hz, the pressure median value is 70MPa, the amplitude is 10MPa, and oscillating and forging for 1h to obtain a boron carbide forged piece with the diameter of 40mm and the height of 2.78 mm; the stress index n of the ceramic to be forged at a deformation of 1900 ℃ and 70MPa is 3.38.

The obtained ceramic to be forged and the forged piece are shown in figure 1, the relative density of the obtained boron carbide ceramic forged piece is 99.5%, the Vickers hardness is improved from 28GPa of the ceramic to be forged to 36GPa of the forged piece, and the bending strength is improved from 270MPa of the ceramic to be forged to 620MPa of the forged piece.

Example 2

The method for forging the ceramic of the embodiment, which uses the hot-pressed sintered boron carbide ceramic (cylinder with the shape of being straight 30mm and with the height of 5mm and the relative density of 99.7%) without adding the sintering aid as the ceramic to be forged, comprises the following steps:

putting the ceramic to be forged into a graphite die with the diameter of 40mm, putting the graphite die in which the ceramic to be forged is put into a high-temperature furnace, heating to the forging temperature of 2000 ℃ under a vacuum condition, preserving heat for 1h, loading oscillation pressure in the heat preservation stage, wherein the oscillation pressure is sine wave in waveform, the frequency is 20Hz, the pressure median value is 50MPa, the amplitude is 10MPa, and oscillating and forging for 1h to obtain a boron carbide forged piece with the diameter of 40 mm; the stress index n of the ceramic to be forged at a deformation of 2000 ℃ and 50MPa is 3.63.

The relative density of the obtained boron carbide ceramic forging piece is 99.7 percent, the Vickers hardness is improved from 30GPa of the ceramic to be forged to 36GPa of the forging piece, and the bending strength is improved from 315MPa of the ceramic to be forged to 670MPa of the forging piece.

Example 3

The method for forging the ceramics of this example was carried out by adding Y in an amount of 10% by mass₂O₃Silicon nitride ceramics (liquid phase sintered silicon nitride ceramics, relative density of 80%) as a sintering aid as ceramics to be forged, comprising the steps of:

putting the ceramic to be forged into a graphite grinding tool, heating to 1800 ℃ in a nitrogen atmosphere, preserving heat, loading oscillation pressure, wherein the oscillation waveform of the oscillation pressure is sine wave, the frequency is 5Hz, the median value of the oscillation pressure is 70MPa, the amplitude is 10MPa, and after oscillation forging for 1 hour, obtaining a deformed silicon nitride ceramic forging; the stress index n of the ceramic to be forged is 2.2 at 1800 ℃ and 70 MPa.

The relative density of the obtained silicon nitride ceramic forged piece is 98%, the Vickers hardness is improved from the original 9GPa to 14GPa, and the bending strength is improved from 320MPa to 710 MPa.

Example 4

The method for forging the ceramics of this example was carried out by adding 2% by mass of Li₂O and 10% Y₂O₃As a sintering aid, silicon nitride ceramic (liquid phase sintered silicon nitride ceramic, relative density of 72%) sintered at 1500 ℃ without pressure is taken as ceramic to be forged, and the method comprises the following steps:

putting the ceramic to be forged into a graphite grinding tool, heating to 1600 ℃ in a nitrogen atmosphere, preserving heat, loading oscillation pressure, wherein the oscillation waveform of the oscillation pressure is sine wave, the frequency is 5Hz, the median value of the oscillation pressure is 40MPa, the amplitude is 30MPa, and oscillating and forging for 1 hour to obtain a deformed silicon nitride ceramic forging; the stress index n of the ceramic to be forged is 2.1 at 1600 ℃ and 40 MPa.

The relative density of the obtained silicon nitride ceramic forged piece is 96 percent, the Vickers hardness is improved from the original 6GPa to 12GPa, and the bending strength is improved from 230MPa to 640 MPa.

Example 5

The method for forging the ceramic of the embodiment uses solid-phase sintered alumina ceramic (with a relative density of 99.4%) without adding a sintering aid as the ceramic to be forged, and comprises the following steps:

putting the ceramic to be forged into a graphite die, heating to 1600 ℃, preserving heat, loading oscillation pressure, wherein the oscillation waveform of the oscillation pressure is sine wave, the frequency is 1Hz, the median value of the oscillation pressure is 120MPa, the amplitude is 10MPa, and after oscillation forging for 1 hour, obtaining a deformed alumina ceramic forging; the stress index n of the ceramic to be forged at 1600 ℃ and 120MPa in deformation is 3.12.

The relative density of the obtained aluminum oxide ceramic forged piece is 99.8 percent, the Vickers hardness is improved from the original 14GPa to 16GPa, and the bending strength is improved from 330GPa to 400 GPa.