CN111850370A - A kind of preparation method of coarse-grained WC-Co cemented carbide - Google Patents

Abstract

The invention discloses a preparation method of coarse-grained WC-Co cemented carbide, comprising the following steps: (1) pretreating WC powder; (2) configuring an activation solution, and then activating the WC powder; (3) filtering, drying Dry the activated WC powder, and perform heat treatment to reduce the WC activated powder with metal Co particles attached to the surface; (4) configure the plating solution; (5) WC activated powder with metal Co particles attached to the surface, C powder and The W powder was placed in the plating solution for electroless plating, filtered, cleaned and vacuum dried to obtain the WC/C/W/Co coarse-grained composite powder; (6) the WC/C/W/Co coarse-grained composite powder was added to the molding agent and pressed Embed and sintered into WC‑Co cemented carbide. The method utilizes in-situ reaction sintering to prepare coarse-grained WC-Co cemented carbide with a grain size greater than 2 μm, and has excellent grain size, hardness, transverse fracture strength and impact toughness.

Description

A kind of preparation method of coarse-grained WC-Co cemented carbide

technical field

The present invention relates to a preparation method of cemented carbide; more particularly, to a preparation method of coarse-grained WC-Co cemented carbide.

Background technique

Cemented carbide is a composite material with high hardness, high wear resistance, excellent red hardness and thermal stability, corrosion resistance, high strength and excellent toughness. Among them, coarse-grained WC-Co cemented carbide has excellent hardness, wear resistance and high toughness, and is widely used in mining tools, tunnel boring tools and other fields. For the preparation of coarse-grained WC-Co cemented carbides, WC powders with an average particle size greater than 20 mm are usually prepared by wet milling with moderate ball milling strength to obtain WC/Co composite powders with consistent particle sizes and uniform dispersion. The particle size is difficult to control, resulting in the distribution of WC particles in the fired alloy below or beyond the range of 2-5mm coarse grain standard, and finally only WC-Co cemented carbide with broad-peak grain distribution is obtained. When the grain size is the same , the strength and toughness of coarse-grained WC-Co cemented carbides with broad peak distribution are lower than those of narrow peak distribution alloys. In addition, the high uniformity of composite powder obtained by ball milling will bring high residual stress to the WC particles, which is not conducive to the improvement of alloy properties.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide a preparation method capable of preparing coarse-grained WC-Co cemented carbide with good narrow peak distribution, hardness, transverse fracture strength and impact toughness.

Technical scheme: the preparation method of coarse-grained WC-Co cemented carbide according to the present invention comprises the following steps:

(1) Ball milling the coarse-grained WC powder, cleaning and vacuum drying to obtain pretreated WC powder;

(2) Dissolving CoSO ₄ ·7H ₂ O and NaH ₂ PO ₂ ·7H ₂ O in the medium to prepare an activation solution, and then adding the WC powder treated in step 1 into the activation solution for activation;

(3) filtering, drying the activated WC powder, and performing heat treatment to reduce the WC activated powder with metallic Co particles attached to the surface;

(4) Dissolving CoSO ₄ ·7H ₂ O and Na ₂ C ₆ H ₅ O ₇ ·2H ₂ O in water to fully complex, adding H ₃ BO ₃ and NaH ₂ PO ₂ ·7H ₂ O in turn to configure a plating solution;

(5) Place the WC activated powder, C powder and W powder with metal Co particles attached to the surface in the plating solution, stir in a water bath, adjust the pH of the plating solution to 10-12, and carry out the process at 70-90 °C Electroless plating, filtering, cleaning and vacuum drying to obtain WC/C/W/Co coarse-grained composite powder;

(6) The WC/C/W/Co coarse-grained composite powder is added into the molding agent, pressed into embryos, and sintered into WC-Co cemented carbide.

Among them, in step 1, alloy balls with a diameter of 10-13 mm are used for ball milling, and the ratio of ball to material is 1-3:1; in step 2, CoSO ₄ ·7H ₂ O and Na ₂ C ₆ H ₅ O ₇ ·2H ₂ in the activation solution The O concentration is 50～60g/L, the volume ratio is 1:1～2, the activation temperature is 50～60℃, and the activation time is 20～30min; in step 3, the heat treatment temperature is 300～400℃, and the time is 2～3h In step 4, the concentration of CoSO ₄ 7H ₂ O is 45～60g/L, the concentration of Na ₂ C ₆ H ₅ O ₇ 2H ₂ O is 50～60g/L, the concentration of H ₃ BO ₃ is 25～30g/L, The concentration of NaH ₂ PO ₂ ·7H ₂ O is 30-40g/L; in step 5, the plating solution is preheated to 70-90 ℃ before adjusting the pH value of the plating solution; in step 5, WC/C/W/Co coarse-grain composite The total proportion of C powder and W powder in the powder is 5-10wt.%, the mass ratio of C powder and W powder is 1:15-16, and the Co coating is 5-10wt.%; in step 6, the molding agent is SD-E The content of rubber and molding agent accounts for 1.5-2.5wt.% of the total powder. The pressing pressure of the green compact is 20-100MPa. During sintering, under vacuum conditions, the sintering temperature is 1400-1450℃, and after sintering, the pressure is 1-10Pa. Keep warm for 1 to 2 hours.

Synthesis principle: In the present invention, the WC/C/W/Co coarse-grained composite powder is obtained by the synergistic coating method of carbon powder and tungsten powder. The two powders will be filled between cobalt particles during the nucleation and growth process of cobalt on the surface of tungsten carbide. The C/W/Co coating makes the dispersion of the two powders more uniform and ensures the uniform growth of the cobalt layer. The WC/C/W/Co coarse-grained composite powder finally obtained by the synergistic coating is composed of W and C particles embedded in the The structure in the Co coating, and finally in the liquid phase sintering process, the carbon powder and tungsten powder react in situ in the cobalt liquid phase, which promotes the rapid growth of coarse-grained WC grains and forms a high-performance WC and high-strength phase interface. , and finally obtain a coarse-grained WC-Co cemented carbide with high comprehensive properties.

Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the coarse-grained WC-Co cemented carbide with grain size greater than 2 μm is prepared by in-situ reaction sintering, and its grain size, hardness, transverse fracture strength and Excellent impact toughness.

Detailed ways

Example 1

(1) 500g of coarse WC powder with a particle size of 10 to 15 μm was ball-milled in a drum ball mill with anhydrous alcohol as the wet grinding medium. 3:1; vacuum-drying to obtain pretreated WC powder after ball milling for 12 hours;

(2) Dissolve 50 g of CoSO ₄ ·7H ₂ O and 50 g of NaH ₂ PO ₂ ·7H ₂ O in distilled water to prepare 1 L of activation solution, and then take 100 g of pretreated WC powder and place it in 1 L of activation solution with mechanical stirring, Activation was carried out at 50 °C, and the activation time was 30 min;

(3) Filtering and drying the activated WC powder, and heat treatment in a muffle furnace at 400° C. for 2 h to obtain WC activated powder with metallic Co particles attached to the surface;

(4) Dissolve 55g CoSO ₄ ·7H ₂ O and 50g Na ₂ C ₆ H ₅ O ₇ ·2H ₂ O in 800 mL of distilled water to fully complex, then add 25g H ₃ BO ₃ and 40g NaH ₂ PO ₂ ·7H in turn ₂ O is configured into 900mL plating solution;

(5) Then 24.82g WC activated powder, 2.9g C powder and 0.19g W powder were placed in the above-mentioned plating solution, mechanically stirred in a water bath at 80°C, pH was adjusted to 11 with NaOH, and distilled water was added to make the plating solution 1L , and electroless plating was carried out at 80°C for 60min. After electroless plating, 31.04g WC/0.614wt.%C/9.386wt.%W/10wt.%Co composite powder was obtained by filtration, cleaning and vacuum drying.

(6) Add 2.5wt.% SD-E molding agent to the WC/0.614wt.%C/9.386wt.%W/10wt.%Co composite powder, and granulate, and pass through an 80-mesh sieve after granulation , press and form under the pressure of 20MPa; sinter the green compact under vacuum conditions, the sintering temperature is 1400℃, and the holding time is 1h to obtain WC-Co cemented carbide.

Example 2

(1) 500g of coarse WC powder with a particle size of 10-15μm was ball-milled in a drum ball mill with anhydrous alcohol as a wet grinding medium, the content of anhydrous alcohol was 200mL/kg, the diameter of the grinding ball was 13mm, and the ball material The ratio is 3:1; the pretreated WC powder is obtained by vacuum drying after ball milling for 12 hours;

(2) Dissolve 50 g of CoSO ₄ ·7H ₂ O and 50 g of NaH ₂ PO ₂ ·7H ₂ O in distilled water to prepare 1 L of activation solution, and then take 100 g of pretreated WC powder and place it in 1 L of activation solution with mechanical stirring, Activation was carried out at 50 °C, and the activation time was 30 min;

(3) Filtering and drying the activated WC powder, and heat-treating at 300°C for 3 hours in a muffle furnace to obtain WC activated powder with metallic Co particles attached to the surface;

(4) Dissolve 50g CoSO ₄ ·7H ₂ O and 50g Na ₂ C ₆ H ₅ O ₇ ·2H ₂ O in 800 mL of distilled water to fully complex, then add 25g H ₃ BO ₃ and 30g NaH ₂ PO ₂ ·7H in turn ₂ O is configured into 900mL plating solution;

(5) Then 15.6g of WC activated powder, 0.12g of C powder and 1.83g of W powder were placed in the above-mentioned plating solution, mechanically stirred in a water bath at 70°C, adjusted to pH 11 with NaOH, and distilled water was added to make the plating solution 1L , and electroless plating was carried out at 70 °C for 60 min. After electroless plating, 19.48g WC/0.307wt.%C/4.693wt.%W/8wt.%Co composite powder was obtained by filtration, cleaning and vacuum drying.

(6) Add 2.5wt.% SD-E molding agent to the WC/0.614wt.%C/9.386wt.%W/10wt.%Co composite powder, and granulate, pass through an 80-mesh sieve after granulation, Press molding under the pressure of 20MPa; sinter the green compact under vacuum condition, the sintering temperature is 1450℃, and the holding time is 1h to obtain WC-Co cemented carbide.

Comparative Example 1

The difference between this comparative example and Example 1 is that C powder and W powder are not added in the electroless plating step, and WC/10wt.%Co composite powder is obtained after electroless plating.

Comparative Example 2

The difference between this comparative example and Example 2 is that the coarse WC powder is not subjected to ball milling pretreatment.

The performance tests of Examples 1-2 and Comparative Examples 1-2 are carried out, and the results are shown in Table 1. It can be seen from the table that the pores in the four kinds of coarse-grained cemented carbides are basically the same. The average grain size of the alloy is greater than 2 μm, the coated C/W/Co coating is uniform, and the C and W particles are uniformly dispersed. In Comparative Example 2, the coarse-grained cemented carbide prepared by the former without carbon powder and tungsten powder is slightly lower in grain size, hardness, strength and impact toughness. It is easy to generate aggregated WC grains and cause performance degradation.

Table 1 The performance test results of Examples 1-2 and Comparative Examples 1-2

Claims (10)

1. a preparation method of coarse-grained WC-Co cemented carbide, is characterized in that, comprises the following steps: (1) Ball milling the coarse-grained WC powder, cleaning and vacuum drying to obtain pretreated WC powder; (2) Dissolving CoSO ₄ ·7H ₂ O and NaH ₂ PO ₂ ·7H ₂ O in the medium to prepare an activation solution, and then adding the WC powder treated in step 1 into the activation solution for activation; (3) filtering, drying the activated WC powder, and performing heat treatment to reduce the WC activated powder with metallic Co particles attached to the surface; (4) Dissolving CoSO ₄ ·7H ₂ O and Na ₂ C ₆ H ₅ O ₇ ·2H ₂ O in water to fully complex, adding H ₃ BO ₃ and NaH ₂ PO ₂ ·7H ₂ O in turn to configure a plating solution; (5) Place the WC activated powder, C powder and W powder with metal Co particles attached to the surface in the plating solution, stir in a water bath, adjust the pH of the plating solution to 10-12, and carry out the process at 70-90 °C Electroless plating, filtering, cleaning and vacuum drying to obtain WC/C/W/Co coarse-grained composite powder; (6) The WC/C/W/Co coarse-grained composite powder is added into the molding agent, pressed into embryos, and sintered into WC-Co cemented carbide. 2. The preparation method of coarse-grained WC-Co cemented carbide according to claim 1, characterized in that, in the step 1, alloy balls with a diameter of 10-13 mm are used for ball milling, and the ball-to-material ratio is 1-3:1 . 3. The preparation method of coarse-grained WC-Co cemented carbide according to claim 1, wherein in the step 2, CoSO ₄ ·7H ₂ O and Na ₂ C ₆ H ₅ O ₇ ·2H in the activation solution The ₂ O concentration is 50～60g/L, the volume ratio is 1:1～2, the activation temperature is 50～60℃, and the activation time is 20～30min. 4 . The method for preparing coarse-grained WC-Co cemented carbide according to claim 1 , wherein in the step 3, the heat treatment temperature is 300-400° C., and the time is 2-3 hours. 5 . 5 . The preparation method of coarse-grained WC-Co cemented carbide according to claim 1 , wherein in the step 4, the concentration of CoSO ₄ ·7H ₂ O is 45-60 g/L, Na ₂ C ₆ H ₅ . The concentration of O ₇ ·2H ₂ O is 50-60 g/L, the concentration of H ₃ BO ₃ is 25-30 g/L, and the concentration of NaH ₂ PO ₂ ·7H ₂ O is 30-40 g/L. 6 . The method for preparing coarse-grained WC-Co cemented carbide according to claim 1 , wherein, in the step 5, before adjusting the pH value of the plating solution, the plating solution is preheated to 70-90° C. 7 . 7. The preparation method of coarse-grained WC-Co cemented carbide according to claim 1, wherein in the step 5, the total proportion of C powder and W powder in the WC/C/W/Co coarse-grained composite powder It is 5-10wt.%, the mass ratio of C powder and W powder is 1:15-16, and the Co plating layer is 5-10wt.%. 8. The preparation method of coarse-grained WC-Co cemented carbide according to claim 1, characterized in that, in the step 6, the molding agent is SD-E rubber, and the content of the molding agent accounts for 1.5-2.5% of the total powder. wt.%. 9 . The method for preparing coarse-grained WC-Co cemented carbide according to claim 1 , wherein in the step 6, the pressing pressure of the green sheet is 20-100 MPa. 10 . 10 . The method for preparing coarse-grained WC-Co cemented carbide according to claim 1 , wherein in the step 6, under vacuum conditions during sintering, the sintering temperature is 1400-1450° C., and the sintering temperature is 1-100° C. 11 . Heat preservation under 10Pa pressure for 1-2h.