CN110171975B

CN110171975B - Large-size high-density binderless tungsten carbide target material and preparation method thereof

Info

Publication number: CN110171975B
Application number: CN201910450038.1A
Authority: CN
Inventors: 盛利文; 谢志鹏; 盛建华; 安迪; 戴金宁
Original assignee: Zhuzhou Xinrongli Industry Co ltd
Current assignee: ZHUZHOU WANRONG NEW MATERIAL TECHNOLOGY Co.,Ltd.; Zhuzhou xinrongli Industrial Co., Ltd
Priority date: 2019-05-28
Filing date: 2019-05-28
Publication date: 2021-09-07
Anticipated expiration: 2039-05-28
Also published as: CN110171975A

Abstract

The invention provides a preparation method of a large-size high-density binderless tungsten carbide target material, which comprises the following steps of: s1, preparing materials; s2, ball milling and screening; s3, sintering treatment; s4, post-processing; the raw material consists of tungsten carbide powder and free carbon, and dynamic oscillation pressure is applied simultaneously in the sintering treatment process. According to the invention, free carbon is introduced into pure tungsten carbide powder, and a traditional metal binding phase is abandoned, so that the purity of the target material is ensured, and the quality of the magnetron sputtering coating is favorably improved. According to the invention, dynamic oscillation pressure is introduced in the sintering process, particle rearrangement is promoted in the early stage of sintering of the tungsten carbide powder, residual pores are promoted to be eliminated in the later stage of sintering, and grains are refined while the sintering density is improved; the sintering-assisted high-pressure oscillation method can reduce the sintering temperature by 50-200 ℃ on the basis of the traditional hot-pressing sintering process, prepare the high-density fine-grain tungsten carbide target material and improve the coating quality.

Description

Large-size high-density binderless tungsten carbide target material and preparation method thereof

Technical Field

The invention belongs to the technical field of sintering of ceramics and hard alloys, and particularly relates to a large-size high-density binderless tungsten carbide target and a preparation method thereof.

Background

The tungsten carbide coating prepared by the magnetron sputtering process has good comprehensive properties, such as high hardness, high elastic modulus, corrosion resistance, high temperature resistance, low friction coefficient and the like, and is widely applied to wear resistance and friction reduction of surfaces of industrial dies and key parts of equipment. However, the magnetron sputtering process has strict requirements on the performance of the used tungsten carbide target, and the biggest problem to be faced is how to ensure the uniformity of the microstructure and the structure of the large-size sputtering target and avoid generating defects. This is because when the microstructure and the grain size distribution of the tungsten carbide target material are not uniform, the thickness of the deposited film is difficult to be uniformly distributed, and the high-purity tungsten carbide powder is difficult to be sintered, and the tungsten carbide target material sintered by the existing sintering process has low compactness and the relative density is difficult to reach 99%. In addition, during the sputtering coating process, the gas existing in the inner pores of the target material can be suddenly released, and the surface quality of the coating is affected. Therefore, the optimization of powder and sintering process to obtain high-purity tungsten carbide target material with high density, fine grains and uniform microstructure is always the continuous pursuit target in the industrial field.

In order to achieve the aim, the sintering preparation process scheme of the high-purity tungsten carbide is mainly improved from the following aspects: firstly, doping trace active elements in tungsten carbide raw material powder, activating and sintering, and reducing the sintering temperature of the tungsten carbide powder, but doping a second phase can influence the purity of a target material; secondly, a special pressure auxiliary sintering means is adopted, and relevant sintering process conditions are optimized. The commonly used pressure-assisted sintering techniques mainly include three types, hot-pressing sintering, hot isostatic pressing sintering and spark plasma sintering. In the sintering process, the introduction of mechanical pressure can promote the discharge of air holes and reduce the content of defects in the microstructure, thereby improving the density of the tungsten carbide and the uniformity of the microstructure to a certain extent. However, the sintering process using static constant pressure still has certain limitations for the desired high density fine grains. The reason is that the static constant pressure can not promote the rearrangement of particles in the early stage of sintering to obtain higher bulk density, and the driving force such as grain boundary diffusion and the like provided by the constant pressure in the middle stage of sintering is small, so that the rapid densification of the material is difficult to realize; in the later stage of sintering, the discharge of residual pores cannot be realized by constant pressure.

Therefore, the problems of over-fast grain growth, low density rate, high required sintering temperature, limited sample size, poor stability and the like still exist in the sintering process, so that the performance of the tungsten carbide target material is influenced, and the method has limitation on preparing the large-size high-density fine-grain tungsten carbide target material by using pure tungsten carbide powder.

Disclosure of Invention

The invention aims to provide a preparation method of a large-size high-density binderless tungsten carbide target, and aims to solve the technical problems of large grains, low density, higher sintering temperature, limited sample size and poor stability in the sintering process of the tungsten carbide target in the prior art.

Another object of the present invention is to provide a large-sized high-density binderless tungsten carbide target.

The purpose of the invention is realized by the following technical scheme:

the preparation method of the large-size high-density binderless tungsten carbide target material comprises the following steps:

s1, material preparation: weighing the raw materials according to the mass fraction ratio for later use;

s2, ball milling and screening: performing ball milling treatment on the raw materials weighed in the step S1 to obtain slurry, drying the uniformly mixed slurry, and finally performing screening treatment to obtain mixed powder with uniform particle size;

s3, sintering treatment: putting the mixed powder obtained in the step S2 into a mold, placing the mold into a sintering furnace, performing high-pressure oscillation auxiliary sintering treatment, and cooling and demolding to obtain a tungsten carbide target blank;

s4, post-processing: and (5) cutting and surface processing the tungsten carbide target blank obtained in the step (S3) to obtain the tungsten carbide target.

The invention can effectively overcome the defect that carbon-deficient phase (WC) is generated in the sintering preparation process of the high-purity tungsten carbide target material by introducing a certain amount of free carbon into the pure tungsten carbide powder and applying dynamic high-pressure oscillation pressure in the sintering process_1-xAnd W₂C) Low density, high sintering temperature, large crystal grains and the like.

Further, in step S1, the raw material is composed of the following components in percentage by mass: 99-99.95% of tungsten carbide powder and 0.05-0.5% of free carbon.

Further, the purity of the tungsten carbide powder is more than 99.9%, and the particle size is 0.4-4 μm; the free carbon is graphite powder.

Further, in step S2, the ball milling process includes: putting the raw materials into a polyurethane mixing tank under vacuum or argon protection, adding grinding media of tungsten carbide balls and absolute ethyl alcohol, and carrying out ball milling treatment for 20-24 hours at the rotating speed of 300-900 r/min.

Further preferably, the drying manner of the mixed slurry is rotary drying.

In order to keep the particle size of the powder uniform, the sieving treatment is preferably performed by sieving the powder with a 60-100 mesh sieve.

Further, in step S3, the high-pressure auxiliary sintering process includes a pre-pressing stage, a pressure increasing and maintaining stage, and a pressure decreasing stage; the oscillating pressure is applied to the whole process of the pressure boosting and pressure maintaining stage or the whole process of the sintering treatment.

Further, the technological process of the pre-pressing stage is as follows: pre-pressing the mixed powder at a constant pressure of 5-10 MPa, and heating to 500 ℃ at a heating rate of 15-30 ℃/min.

Further, the technological process of the pressure increasing and maintaining stage is as follows: after the temperature is increased to 500 ℃, the constant pressure is increased to 25-50 MPa, the pressure is maintained, and meanwhile, the temperature is increased to the sintering temperature at the heating rate of 10-20 ℃/min and the temperature is kept.

Further, the process of the pressure reduction stage comprises the following steps: and after the heat preservation is finished, firstly removing the oscillation pressure, then cooling to 900 ℃ at the cooling rate of 6-12 ℃/min, finally unloading the constant pressure, and cooling to room temperature along with the furnace.

Further, in step S3, the process parameters of the high-pressure oscillation assisted sintering treatment are as follows: the amplitude of the oscillating pressure is 1-10 MPa, the frequency of the oscillating pressure is 1-10 Hz, the sintering temperature is 1700-2200 ℃, and the heat preservation time is 0-2 h.

Further preferably, the mold is a graphite mold, and an inner cavity of the graphite mold is circular or rectangular.

In order to facilitate demolding, it is further preferable that graphite paper is further disposed between the graphite mold and the mixed powder.

Further preferably, the sintering furnace is a hot-pressing sintering furnace with bidirectional oscillating pressurization.

Further preferably, the sintering atmosphere is vacuum or argon protective atmosphere.

Further preferably, the vacuum degree of the vacuum sintering is less than 10 Pa.

Further preferably, the pressure in the furnace for sintering in the argon protective atmosphere is-0.01 to-0.002 MPa.

The invention also provides a large-size high-density binderless tungsten carbide target material prepared by the preparation method of the large-size high-density binderless tungsten carbide target material. The tungsten carbide target material prepared by the method does not contain a binding phase, the maximum size of the tungsten carbide target material can reach phi 200 multiplied by 100mm, the maximum size of a square product can reach 200 multiplied by 80mm, the tungsten carbide target material has the characteristic of high-density fine grains, the average grain size is about 0.6 mu m, and the relative density can reach more than 99.9%.

The large-size high-density binderless tungsten carbide target material and the preparation method thereof provided by the invention have the beneficial effects that:

the method creatively introduces a certain amount of free carbon into the pure tungsten carbide powder, abandons the traditional metal binding phase, not only ensures the purity of the target material, but also is beneficial to improving the quality of the magnetron sputtering coating.

According to the invention, high-pressure oscillation auxiliary sintering is introduced in the sintering process, particle rearrangement is promoted in the early stage of sintering of the tungsten carbide powder, residual pores are promoted to be eliminated in the later stage of sintering, and grains are refined while the sintering density is improved; meanwhile, the sintering-assisted high-pressure oscillation method can reduce the sintering temperature by 50-200 ℃ on the basis of the traditional hot-pressing sintering process, is favorable for saving energy consumption, prepares the high-density fine-grain tungsten carbide target material and improves the film coating quality.

By optimizing the powder component proportion and the sintering technology, the uniformity of the temperature in the furnace is ensured, the density of the pure tungsten carbide target material is improved, and the microstructure is optimized; by adopting the method, a plurality of high-quality tungsten carbide target products can be produced by simple sintering at one time, the sintering cost of the tungsten carbide target is reduced, and the method is easy for industrial production.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a process flow chart of the present invention for preparing large-size high-density binderless tungsten carbide target.

FIG. 2 is a schematic diagram of high pressure vibration assisted sintering in accordance with the present invention.

Fig. 3 is a graph of the variation of the oscillating pressure used in the present invention.

FIG. 4 is a digital photograph of a sample of a large-size high-density binderless tungsten carbide target prepared in example 1 of the present invention.

Fig. 5 is a cross-sectional microscopic structure diagram of a large-sized high-density binderless tungsten carbide target prepared in example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It is to be understood that the terms "upper", "lower", "left", "right", and the like, as used herein, refer to an orientation or positional relationship based on that shown in the drawings, which is for convenience of description only, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be considered limiting of this patent. The terms "first", "second" and "first" are used merely for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "plurality" is two or more unless specifically limited otherwise. Furthermore, the terms "horizontal", "vertical", "overhang" and the like do not imply that the components are required to be absolutely horizontal or overhang, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

It should also be noted that, unless expressly stated or limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and may for example be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In order to explain the technical solution of the present invention, the following detailed description is made with reference to the specific drawings and examples.

Example 1

The embodiment provides a preparation method of a large-size high-density binderless tungsten carbide target material, which comprises the following steps of:

s1, material preparation: weighing the raw materials according to a certain mass fraction ratio for later use; the raw materials comprise the following components in percentage by mass: 99.6 percent of tungsten carbide powder, 0.4 percent of graphite, more than 99.9 percent of tungsten carbide powder with the purity and the grain diameter of 0.4-4 mu m;

s2, ball milling and screening: placing the raw materials weighed in the step S1 into a vacuum polyurethane mixing tank, adding grinding media of absolute ethyl alcohol and tungsten carbide balls, carrying out vacuum ball milling treatment for 20 hours at the rotating speed of 600r/min, then carrying out rotary drying on the uniformly mixed slurry, and finally sieving by using an 80-mesh sieve to obtain mixed powder with uniform particle size;

s3, sintering treatment: weighing 40kg of mixed powder obtained in the step S2, putting the mixed powder into a graphite die, arranging graphite paper between the graphite die and the mixed powder, putting the graphite die and the mixed powder into an oscillating pressure sintering furnace, pre-pressing the powder at a constant pressure of 8MPa, starting a vacuum pump, keeping vacuum in the furnace during sintering to prevent materials from being oxidized, and raising the temperature to 500 ℃ at a heating rate of 25 ℃/min; then raising the temperature to 1900 ℃ at a heating rate of 15 ℃/min, preserving the temperature for 1h, setting a pressure program, slowly raising the constant pressure applied to the powder to 30MPa, and simultaneously applying an oscillating pressure with the amplitude of 5MPa and the frequency of 2 Hz; stopping heating after the heat preservation is finished, removing the oscillation pressure, maintaining the constant pressure of 30MPa, cooling at the speed of 10 ℃/min until the temperature is reduced to 900 ℃, unloading the constant pressure, cooling to room temperature along with the furnace, cooling and demoulding to obtain a tungsten carbide target blank;

s4, post-processing: and (5) cutting and surface processing the tungsten carbide target blank obtained in the step (S3) to obtain the large-size high-density binderless tungsten carbide target.

In this embodiment, a high-pressure oscillation assisted sintering treatment is adopted, and a schematic structural diagram thereof is shown in fig. 1. As can be seen from fig. 1, the high-pressure oscillation auxiliary sintering device sequentially comprises a hydraulic oil cylinder 1, an upper pressure head 2, a graphite die 3 and a lower pressure head 4 from top to bottom, and mixed powder 5 of tungsten carbide and graphite is placed in the graphite die 3.

Fig. 2 is a graph showing the change of the oscillating pressure applied in the present embodiment. As can be seen from fig. 2, the oscillating pressure employed in the present invention is dynamically variable.

Fig. 3 is a digital photograph of a tungsten carbide target sample prepared in example 1, wherein the thickness of the product is 80 mm.

Fig. 4 is a Scanning Electron Microscope (SEM) photograph of the tungsten carbide target material prepared in example 1, from which it can be seen that the material structure is uniform, the average grain size is 0.6 μm, and the phase compositions in the sample are all WC phases.

Example 2

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the sintering temperature is 1750 ℃.

Example 3

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the sintering temperature is 1800 ℃.

Example 4

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the sintering temperature is 1850 ℃.

Example 5

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the heat retention time is 0 h.

Example 6

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the heat-retaining time is 0.5 h.

Example 7

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the heat-retaining time is 1.5 hours.

Example 8

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the heat retention time is 2 hours.

Example 9

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the amplitude of the oscillation pressure is 1.25 MPa.

Example 10

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the amplitude of the oscillation pressure is 2.5 MPa.

Example 11

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the frequency of the oscillating pressure is 1 Hz.

Example 12

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the frequency of the oscillating pressure is 3 Hz.

Example 13

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S2, the frequency of the oscillating pressure is 4 Hz.

Example 14

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S1, the mass fraction of free carbon is 0.1%.

Example 15

The embodiment provides a method for preparing a large-size high-density binderless tungsten carbide target, which is different from the embodiment 1 in the following point by referring to the operation steps of the embodiment 1: in step S1, the mass fraction of free carbon is 0.2%.

Comparative example 1

The comparative example provides a preparation method of a large-size high-density binderless tungsten carbide target, which is different from the preparation method of the example 1 in the following point by referring to the operation steps of the example 1: in step S1, the raw material does not contain free carbon.

Comparative example 2

The comparative example provides a preparation method of a large-size high-density binderless tungsten carbide target, which is different from the preparation method of the example 1 in the following point by referring to the operation steps of the example 1: in step S3, no dynamic oscillating pressure is applied during the sintering process.

The tungsten carbide targets prepared in examples 1 to 14 and comparative examples 1 to 2 were tested for various properties including relative density, average grain size and phase composition, and the specific test results are shown in table 1.

TABLE 1

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts of the present invention. It should be noted that there are no specific structures but a few objective structures due to the limited character expressions, and that those skilled in the art may make various improvements, decorations or changes without departing from the principle of the invention or may combine the above technical features in a suitable manner; such modifications, variations, combinations, or adaptations of the invention using its spirit and scope, as defined by the claims, may be directed to other uses and embodiments.

Claims

1. A preparation method of a large-size high-density binderless tungsten carbide target material is characterized by comprising the following steps of:

s1, material preparation: weighing raw materials according to a mass fraction ratio for later use, wherein the raw materials comprise the following components in mass fraction ratio: 99-99.95% of tungsten carbide powder and 0.05-0.5% of free carbon;

s3, sintering treatment: putting the mixed powder obtained in the step S2 into a die, placing the die in a sintering furnace for sintering treatment, simultaneously applying dynamic oscillation pressure, cooling and demoulding to obtain a tungsten carbide target blank; the sintering treatment comprises a pre-pressing stage, a pressure boosting and maintaining stage and a pressure reducing stage; applying oscillating pressure to the pressure boosting and maintaining stage or the whole sintering process; the technological parameters of the high-pressure oscillation auxiliary sintering treatment are as follows: the amplitude of the oscillating pressure is 1-10 MPa, the frequency of the oscillating pressure is 1-10 Hz, the sintering temperature is 1700-2200 ℃, and the heat preservation time is 0-2 h; the sintering furnace is a hot-pressing sintering furnace with bidirectional oscillation pressurization; the sintering atmosphere is vacuum or argon protective atmosphere;

2. The method for preparing the large-size high-density binderless tungsten carbide target material according to claim 1, wherein the purity of the tungsten carbide powder is more than 99.9%, and the particle size is 0.4-4 μm; the free carbon is graphite powder.

3. The method for preparing the large-size high-density binderless tungsten carbide target material of claim 1, wherein in step S2, the ball milling process comprises the following steps: putting the raw materials into a polyurethane mixing tank under vacuum or argon protection, adding grinding media of tungsten carbide balls and absolute ethyl alcohol, and carrying out ball milling treatment for 20-24 hours at the rotating speed of 300-900 r/min; the drying mode of the mixed slurry is rotary drying, and the screening treatment is 60-100-mesh screening.

4. The method for preparing the large-size high-density binderless tungsten carbide target material according to claim 1, wherein the pre-pressing step comprises the following steps: pre-pressing the mixed powder at a constant pressure of 5-10 MPa, and heating to 500 ℃ at a heating rate of 15-30 ℃/min.

5. The method for preparing the large-size high-density binderless tungsten carbide target material according to claim 1, wherein the pressure increasing and pressure maintaining stage comprises the following steps: after the temperature is increased to 500 ℃, the constant pressure is increased to 25-50 MPa, the pressure is maintained, and meanwhile, the temperature is increased to the sintering temperature at the heating rate of 10-20 ℃/min and the temperature is kept.

6. The method for preparing the large-size high-density binderless tungsten carbide target material according to claim 1, wherein the step of reducing the pressure comprises the following steps: and after the heat preservation is finished, firstly removing the oscillation pressure, then cooling to 900 ℃ at the cooling rate of 6-12 ℃/min, finally unloading the constant pressure, and cooling to room temperature along with the furnace.

7. The method for preparing the large-size high-density binderless tungsten carbide target according to claim 1, wherein in step S3, the mold is a graphite mold, and graphite paper is further disposed between the graphite mold and the mixed powder.

8. The large-size high-density binderless tungsten carbide target material prepared by the method for preparing the large-size high-density binderless tungsten carbide target material according to any one of claims 1 to 7.