阅读说明：本技术 一种冷压-热压烧结制备wc-y2o3无粘结相硬质合金的方法 (Method for preparing WC-Y2O3 binderless hard alloy by cold pressing-hot pressing sintering ) 是由 朱流 王金芳 吴意囡 林霄 涂志标 邵建地 刘孟辉 王蓉辉 林奇群 吴明威 朱海 于 2020-07-29 设计创作，主要内容包括：本发明涉及无粘结相硬质合金的制备技术领域,尤其涉及一种冷压-热压烧结制备WC-Y<Sub>2</Sub>O<Sub>3</Sub>无粘结相硬质合金的方法。本发明的方法包括以下步骤：将WC粉体和Y<Sub>2</Sub>O<Sub>3</Sub>粉体进行球磨混合,得到WC-Y<Sub>2</Sub>O<Sub>3</Sub>粉体；向所述WC-Y<Sub>2</Sub>O<Sub>3</Sub>粉体中加入饱和草酸溶液至完全润湿,将润湿后的WC-Y<Sub>2</Sub>O<Sub>3</Sub>粉体进行冷压烧结,得到烧结体；所述冷压烧结的压力为200～400MPa；所述冷压烧结的升温程序为：先升温至100～150℃保温1h,继续升温至200～300℃保温1～2h；将所述烧结体进行热压烧结,得到WC-Y<Sub>2</Sub>O<Sub>3</Sub>无粘结相硬质合金。本发明能显著降低无粘结相WC基硬质合金的烧结温度,同时提高合金的致密度和综合力学性能。(The invention relates to the technical field of preparation of cemented carbide without binding phase, in particular to a method for preparing WC-Y by cold pressing-hot pressing sintering 2 O 3 A method for preparing cemented carbide without binding phase. The method of the invention comprises the following steps: mixing WC powder with Y 2 O 3 Ball milling and mixing the powder to obtain WC-Y 2 O 3 Powder; to the WC-Y 2 O 3 Adding saturated oxalic acid solution into the powder until the powder is completely wetted, and adding the wetted WC-Y 2 O 3 Performing cold-pressing sintering on the powder to obtain a sintered body; the pressure of the cold pressing sintering is 200-400 MPa; the temperature rising procedure of the cold pressing sintering is as follows: firstly heating to 100-150 ℃ and keeping the temperature for 1h, and continuing to heatHeating to 200-300 ℃, and preserving heat for 1-2 h; carrying out hot-pressing sintering on the sintered body to obtain WC-Y 2 O 3 Cemented carbide without binding phase. The invention can obviously reduce the sintering temperature of the WC-based hard alloy without the binding phase and simultaneously improve the compactness and the comprehensive mechanical property of the alloy.)

1. Preparation of WC-Y by cold pressing-hot pressing sintering₂O₃A method of cemented carbide without binder phase comprising the steps of:

mixing WC powder with Y₂O₃Ball milling and mixing the powder to obtain WC-Y₂O₃Powder;

to the WC-Y₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, and adding the wetted WC-Y₂O₃Performing cold-pressing sintering on the powder to obtain a sintered body; the pressure of the cold pressing sintering is 200-400 MPa; the temperature rising procedure of the cold pressing sintering is as follows: firstly heating to 100-150 ℃ and preserving heat for 1h, and continuously heating to 200-300 ℃ and preserving heat for 1-2 h;

carrying out hot-pressing sintering on the sintered body to obtain WC-Y₂O₃Cemented carbide without binding phase.

2. The method of claim 1, wherein the WC-Y is₂O₃Of powders and saturated oxalic acid solutionsThe solid-liquid ratio is 10g (1-1.5) mL.

3. The method of claim 1, wherein Y is₂O₃The mass of the powder is WC powder and Y₂O₃1-3% of the total mass of the powder.

4. The method according to claim 1, wherein the average grain size of the WC powder is 200-400 nm.

5. The method of claim 1, wherein Y is₂O₃The average grain size of the powder is 50 nm-200 nm.

6. The method according to claim 1, wherein the temperature rise procedure of the hot press sintering is as follows: keeping the temperature at 150 ℃ for 20min, then heating to 250 ℃ for 20min, continuing heating to 800 ℃ for 60min, and finally heating to 1400-1650 ℃ for 90 min.

7. The method of claim 6, wherein the pressure of the hot press sintering is 40 MPa.

8. The method according to claim 1, wherein the temperature rise rate in the cold-pressing sintering process and the hot-pressing sintering process is 10-15 ℃/min independently.

9. The method of claim 1, wherein the ball milling mixing conditions comprise: the ball material mass ratio is (5-15): 1, the ball milling medium is absolute ethyl alcohol, the ball milling speed is 200-250 r/min, and the ball milling time is 6-12 h.

10. The method of claim 1, further comprising drying the ball milled material after said ball milling and mixing, said drying being vacuum drying.

Technical Field

The invention relates to the technical field of preparation of cemented carbide without binding phase, in particular to a method for preparing WC-Y by cold pressing-hot pressing sintering₂O₃A method for preparing cemented carbide without binding phase.

Background

Tungsten carbide (WC) -based cemented carbides are widely used in cutting tools, dies, wear-resistant and high-pressure resistant parts, etc. because of their high strength, hardness and high young's modulus. Pure WC has a high melting point (2785 ℃), so that the sintering temperature is high, sintering densification is difficult, and fracture toughness of a sintered body is poor, and a generally adopted method is to add a metal binder phase such as cobalt (Co) and nickel (Ni) to prepare WC-M (metal phase) cemented carbide. However, under the harsh working conditions of high-speed and high-efficiency dry cutting, compared with WC hard phase, the metal bonding is more easily oxidized, corroded and worn out, and the application of the metal bonding in the field of difficult-to-process materials such as titanium alloy, high-temperature alloy and the like is limited. At high temperature, the metal phase in the WC-M hard alloy mold is easy to oxidize and diffuse to the glass product, and becomes a material bottleneck which needs to be broken through urgently in manufacturing of high-precision optical glass molds. In addition, metal binding phases such as Co and Ni enter the environment in the form of dust, steam and the like along with abrasion of cutters and parts, so that the health of workers is greatly deterred. Therefore, the technology and the method for preparing the WC non-bonded phase hard alloy with high hardness, high fracture toughness and more excellent wear resistance, corrosion resistance and high-temperature oxidation resistance compared with the traditional WC-M (metal phase) alloy are developed, and the technology and the method have very important significance for the development of the technology of the labor cutting tool and the green manufacture.

The binderless WC-based hard alloy has more excellent wear resistance, corrosion resistance and high-temperature oxidation resistance than the traditional hard alloy, and is a research hot point and development direction in the field of international hard alloys at present. However, the WC melting point is as high as 2785 ℃, the sintering temperature of the non-bonding phase WC-based hard alloy is high, the prepared material is poor in compactness, the comprehensive mechanical property is poor, and the use is influenced. Although the discharge plasma (SPS) sintering technology can greatly reduce the sintering temperature, and the prepared WC-based hard alloy without the binding phase has better comprehensive performance, the equipment is expensive, the preparation cost is high, and the sintering size is limited, so the industrial popularization and application of the WC-based hard alloy without the binding phase are greatly limited.

Disclosure of Invention

The invention aims to provide a method for preparing WC-Y by cold pressing-hot pressing sintering₂O₃The method of the binderless hard alloy can obviously reduce the sintering temperature of the binderless WC-based hard alloy, simultaneously improve the density and the comprehensive mechanical property of the alloy and has low cost.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a method for preparing WC-Y by cold pressing-hot pressing sintering₂O₃A method of cemented carbide without binder phase comprising the steps of:

mixing WC powder with Y₂O₃Ball milling and mixing the powder to obtain WC-Y₂O₃Powder;

to the WC-Y₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, and adding the wetted WC-Y₂O₃Performing cold-pressing sintering on the powder to obtain a sintered body; the pressure of the cold pressing sintering is 200-400 MPa; the temperature rising procedure of the cold pressing sintering is as follows: firstly heating to 100-150 ℃ and preserving heat for 1h, and continuously heating to 200-300 ℃ and preserving heat for 1-2 h;

carrying out hot-pressing sintering on the sintered body to obtain WC-Y₂O₃Cemented carbide without binding phase.

Preferably, the WC-Y₂O₃The solid-liquid ratio of the powder to the saturated oxalic acid solution is 10g (1-1.5) mL.

Preferably, said Y is₂O₃The mass of the powder is WC powder and Y₂O₃1-3% of the total mass of the powder.

Preferably, the average grain size of the WC powder is 200nm to 400 nm.

Preferably, said Y is₂O₃The average grain size of the powder is 50 nm-200 nm.

Preferably, the temperature rise procedure of the hot-pressing sintering is as follows: keeping the temperature at 150 ℃ for 20min, then heating to 250 ℃ for 20min, continuing heating to 800 ℃ for 60min, and finally heating to 1400-1650 ℃ for 90 min.

Preferably, the pressure of the hot-pressing sintering is 40 MPa.

Preferably, the heating rate in the cold-pressing sintering process and the heating rate in the hot-pressing sintering process are independently 10-15 ℃/min.

Preferably, the conditions for ball milling and mixing include: the ball material mass ratio is (5-15): 1, the ball milling medium is absolute ethyl alcohol, the ball milling speed is 200-250 r/min, and the ball milling time is 6-12 h.

Preferably, the ball-milling and mixing process further comprises drying the ball-milled materials, wherein the drying process is vacuum drying.

The invention provides a method for preparing WC-Y by cold pressing-hot pressing sintering₂O₃A method of cemented carbide without binder phase comprising the steps of: mixing WC powder with Y₂O₃Ball milling and mixing the powder to obtain WC-Y₂O₃Powder; to the WC-Y₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, and adding the wetted WC-Y₂O₃Performing cold-pressing sintering on the powder to obtain a sintered body; the pressure of the cold pressing sintering is 200-400 MPa; the temperature rising procedure of the cold pressing sintering is as follows: firstly heating to 100-150 ℃ and preserving heat for 1h, and continuously heating to 200-300 ℃ and preserving heat for 1-2 h; carrying out hot-pressing sintering on the sintered body to obtain WC-Y₂O₃Cemented carbide without binding phase.

In the invention, WC powder and Y are mixed₂O₃Ball milling and mixing the powder to obtain Y₂O₃Fully dispersing the powder in the WC powder; then to the obtained WC-Y₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, Y₂O₃Is slightly soluble in oxalic acid solution, and Y is obtained under the action of pressure and temperature of cold pressing and sintering₂O₃Partial dissolution begins, the oxalic acid solution evaporates with increasing temperature, Y₂O₃Will be precipitated just because of the trace amount of Y₂O₃Dissolution-precipitation in oxalic acid solution to allow WC-Y₂O₃The powder gap reaches a supersaturated state, the chemical potential of the particle contact zone is higher than that of the crystal, and dissolved atoms or ion clusters are separated out at the crystal, so that WC-Y is promoted₂O₃Densification of WC-Y₂O₃The cemented carbide without binding phase obtains a sintered body with the relative density of more than 70 percent at a lower temperature (100-300 ℃), thereby greatly reducing the sintering temperature of the WC-based cemented carbide without binding phase prepared by the following traditional sintering process (hot-pressing sintering), and the obtained WC-Y₂O₃The cemented carbide without binding phase has high compactness and excellent comprehensive performance. The results of the examples show that the invention can be usedThe method can reduce the temperature of the traditional hot-pressing sintering to be less than 1650 ℃, and the prepared bonding-phase-free WC-based hard alloy has high compactness of 97.87-100%, hardness of 2357-2500 HV30 and fracture toughness of 8.2-9.3 MPa-m^1/2And the comprehensive performance is excellent.

Drawings

FIG. 1 is an SEM topography of the material before and after ball milling in example 1;

FIG. 2 is an SEM fracture morphology chart of a sintered body obtained after cold-pressing and sintering of example 1;

FIG. 3 is WC-1 wt.% Y prepared as in example 1₂O₃SEM fracture morphology of cemented carbide without binding phase;

FIG. 4 is WC-2 wt.% Y prepared in example 2₂O₃SEM fracture morphology of cemented carbide without binding phase;

FIG. 5 is WC-3 wt.% Y prepared in example 3₂O₃SEM fracture morphology of cemented carbide without binding phase;

FIG. 6 is WC-3 wt.% Y prepared in example 4₂O₃SEM fracture morphology of cemented carbide without binding phase;

FIG. 7 is WC-2 wt.% Y of comparative example preparation₂O₃SEM fracture morphology of cemented carbide without binding phase.

Detailed Description

The invention provides a method for preparing WC-Y by cold pressing-hot pressing sintering₂O₃A method of cemented carbide without binder phase comprising the steps of:

mixing WC powder with Y₂O₃Ball milling and mixing the powder to obtain WC-Y₂O₃Powder;

to the WC-Y₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, and adding the wetted WC-Y₂O₃Performing cold-pressing sintering on the powder to obtain a sintered body; the pressure of the cold pressing sintering is 200-400 MPa; the temperature rising procedure of the cold pressing sintering is as follows: firstly heating to 100-150 ℃ and preserving heat for 1h, and continuously heating to 200-300 ℃ and preserving heat for 1-2 h;

carrying out hot-pressing sintering on the sintered body to obtain WC-Y₂O₃Cemented carbide without binding phase.

In the present invention, the starting materials used are all commercially available products well known in the art, unless otherwise specified.

In the invention, WC powder and Y are mixed₂O₃Ball milling and mixing the powder to obtain WC-Y₂O₃And (3) powder. In the present invention, the average grain size of the WC powder is preferably 200nm to 400nm, more preferably 200nm to 300nm, and in an embodiment of the present invention, specifically 200 nm. In the present invention, said Y is₂O₃The average grain size of the powder is preferably 50nm to 200nm, more preferably 100 nm to 150nm, and in the embodiment of the present invention, specifically 50 nm. In the present invention, said Y is₂O₃The mass of the powder is preferably WC powder and Y₂O₃1 to 3% by mass of the total powder, more preferably 1.5 to 2.5% by mass.

In the present invention, the conditions for ball milling and mixing preferably include: the ball material mass ratio is (5-15): 1, the ball milling medium is absolute ethyl alcohol, the ball milling speed is 200-250 r/min, and the ball milling time is 6-12 h. Further, the mass ratio of the ball materials is more preferably 10:1, the ball milling rotating speed is more preferably 210-230 r/min, and the ball milling time is more preferably 8-10 h. In the present invention, the ball milling mixing process is preferably reversed every 5 minutes. In order to avoid impurities generated in the ball milling process, the hard alloy ball milling tank and the milling balls are preferably adopted in the invention. After the ball milling and mixing, the invention preferably further comprises drying the ball-milled materials, wherein the drying is preferably vacuum drying, the temperature of the vacuum drying is preferably 60 ℃, and the time of the vacuum drying is preferably 24 hours. The invention utilizes ball milling to ensure Y₂O₃The powder was fully dispersed in the WC powder.

Obtaining WC-Y₂O₃After powdering, the invention provides the WC-Y₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, and adding the wetted WC-Y₂O₃And carrying out cold-pressing sintering on the powder to obtain a sintered body.

In the present invention, the WC-Y is reacted with₂O₃Saturated grass for completely wetting powderThe amount of the acid solution is preferably such that: WC-Y₂O₃The solid-to-liquid ratio of the powder to the saturated oxalic acid solution is 10g (1-1.5) mL, and more preferably 10g to 1 mL.

In the invention, the pressure of the cold-pressing sintering is 200-400 MPa, preferably 250-350 MPa; the temperature rising procedure of the cold pressing sintering is preferably as follows: firstly heating to 100-150 ℃ and preserving heat for 1h, and continuously heating to 200-300 ℃ and preserving heat for 1-2 h; more preferably: firstly heating to 150 ℃ and preserving heat for 1h, and then continuously heating to 250 ℃ and preserving heat for 2 h. The temperature of the present invention is preferably raised from room temperature. In the invention, the heating rate in the cold pressing and sintering process is preferably 10-15 ℃/min independently. The invention preferably uses WC-Y₂O₃And placing the powder in a metal mold, installing a heating ring on the outer ring of the metal mold, applying pressure to an upper pressure head of the metal mold, and heating the heating ring according to the temperature-raising program to perform cold-pressing sintering.

WC-Y obtained by the invention₂O₃Adding saturated oxalic acid solution into the powder until the powder is completely wetted, Y₂O₃Is slightly soluble in oxalic acid solution, and Y is obtained under the action of pressure and temperature of cold pressing and sintering₂O₃Partial dissolution begins, the oxalic acid solution evaporates with increasing temperature, Y₂O₃Will be precipitated just because of the trace amount of Y₂O₃Dissolution-precipitation in oxalic acid solution to allow WC-Y₂O₃The powder gap reaches a supersaturated state, the chemical potential of the particle contact zone is higher than that of the crystal, and dissolved atoms or ion clusters are separated out at the crystal, so that WC-Y is promoted₂O₃Densification of WC-Y₂O₃The cemented carbide without binding phase obtains a sintered body with the relative density of more than 70 percent at a lower temperature (100-300 ℃), thereby greatly reducing the sintering temperature of the WC-based cemented carbide without binding phase prepared by the following traditional sintering process (hot-pressing sintering), and the obtained WC-Y₂O₃The cemented carbide without binding phase has high compactness and excellent comprehensive performance.

After obtaining a sintered body, the invention carries out hot-pressing sintering on the sintered body to obtain WC-Y₂O₃Cemented carbide without binding phase. In the present invention, the temperature raising procedure of the hot press sintering is preferably: keeping the temperature at 150 ℃ for 20min, then heating to 250 ℃ for 20min, continuing heating to 800 ℃ for 60min, and finally heating to 1400-1650 ℃ for 90 min; the pressure of the hot-pressing sintering is preferably 40 MPa. The sintered body is preferably placed in a graphite mold for hot-pressing sintering. According to the invention, the residual oxalic acid solution in the hot-pressing sintering process is further decomposed and separated out, WC crystal grains are further rearranged, and gaps and grain boundaries are effectively reduced, so that the compactness of a sintered body is further improved. The temperature of the present invention is preferably raised from room temperature. In the invention, the heating rate in the hot-pressing sintering process is preferably 10-15 ℃/min independently.

The invention provides a method for preparing WC-Y by cold pressing-hot pressing sintering by combining the embodiment₂O₃The methods for cemented carbide without binder phase are described in detail, but they should not be construed as limiting the scope of the invention.