WO2018120980A1

WO2018120980A1 - Self-lubricating ceramic cutting tool material added with nickel-phosphorus-alloy-coated calcium fluoride composite powder and preparation method therefor

Info

Publication number: WO2018120980A1
Application number: PCT/CN2017/105471
Authority: WO
Inventors: 许崇海; 李智亮; 吴光永; 衣明东; 肖光春; 陈照强
Original assignee: 齐鲁工业大学
Priority date: 2016-12-28
Filing date: 2017-10-10
Publication date: 2018-07-05
Also published as: CN106810259A; CN106810259B; AU2017386460B2; AU2017386460A1

Abstract

A self-lubricating ceramic cutting tool material added with nickel-phosphorus-alloy-coated calcium fluoride composite powder and a preparation method therefor. The self-lubricating ceramic cutting tool material consists of: 30‑48% of α‑Al₂O₃, 42‑66.5% of (W,Ti)C, 3‑12% of CaF₂@Ni‑P by mass of CaF₂, and 0.4‑1.5% of MgO. The preparation method of CaF₂@Ni‑P comprises: coarsening CaF₂ powders after being cleaned, adding the coarsened CaF₂ powders with a sensitizing-activating liquid and performing ultrasonic vibration, and then performing chemical plating under conditions of a pH value of 8.5‑9.5, a temperature of 35‑45 °C and ultrasonic vibration.

Description

Self-lubricating ceramic tool material with nickel-phosphorus alloy coated calcium fluoride composite powder and preparation method thereof

Technical field

The invention relates to a self-lubricating ceramic tool material with a nickel-phosphorus alloy coated calcium fluoride composite powder and a preparation method thereof, and belongs to the technical field of ceramic tool materials.

Background technique

With the advancement of industrial manufacturing technology, machining technology is developing in the direction of high efficiency, high precision and greening. Tools are one of the key factors affecting the efficiency, precision and cost of machining. Compared with traditional tool materials such as high-speed steel and hard alloy, ceramic tool materials have the advantages of high hardness, wear resistance, high temperature resistance and good chemical stability. However, due to the inherent low toughness and low thermal shock resistance of ceramic materials, it is not suitable for the ceramic tool to use the cutting fluid for cooling and lubrication during high-speed machining, resulting in high cutting temperature and serious thermal wear of the tool, resulting in low tool life. The development and application of self-lubricating ceramic tool materials is an effective way to solve this problem.

The traditional self-lubricating ceramic tool material is prepared by directly mixing ceramic powder and solid lubricant powder, and then forming a block material through a certain molding and sintering process. The direct addition of solid lubricants has two effects on the ceramic tool material: on the one hand, the solid lubricant in the tool material forms a self-lubricating film on the tool surface during the cutting process, thereby reducing the friction between the tool and the chip. Coefficients; on the other hand, solid lubricants have low strength and hardness, and dispersion in the tool material results in a decrease in mechanical properties, which in turn reduces the wear resistance of the tool. Al ₂ O ₃ /TiC-based self-lubricating ceramic materials with three solid lubricants of MoS ₂ , h-BN and CaF ₂ have been reported in the literature. For Al ₂ O ₃ /TiC/MoS ₂ self-lubricating ceramic materials, MoS ₂ decomposes during hot pressing and causes the material to generate more pores, resulting in very low mechanical properties; for Al ₂ O ₃ /TiC/ h-BN self-lubricating ceramic material, h-BN chemically reacts with Al ₂ O ₃ to form AlN during hot pressing, resulting in a large number of cracks, greatly reducing the mechanical properties of the material; for Al ₂ O ₃ /TiC/CaF ₂ Self-lubricating ceramic materials, CaF ₂ did not undergo obvious chemical reaction during sintering, but its mechanical properties were still significantly lower than those of Al ₂ O ₃ /TiC ceramic materials without solid lubricant. See Materials Science and Technology, 2006, 14(1): 5-8. It can be seen that the traditional self-lubricating ceramic tool material directly adding a solid lubricant is difficult to achieve uniformity of self-lubricating properties and mechanical properties.

In order to overcome the defects of solid lubricants, research on the improvement of coated calcium fluoride solid lubricant materials has been continuously disclosed in recent years. For example, CN104045351A discloses alumina-coated calcium fluoride powder for self-lubricating tool materials, The aluminum nitrate and CaF ₂ are used as raw materials, and are prepared by non-uniform nucleation method and vacuum calcination method for preparing self-lubricating tool materials; CN104045325A discloses a self-lubricating tool material for adding coated calcium fluoride powder, which is Self-lubricating of Al ₂ O ₃ /(W,Ti)C/CaF ₂ prepared by ball-milling aluminum hydroxide-coated calcium fluoride powder with alumina, tungsten carbide, nickel oxide and magnesium oxide powder by ball milling and hot pressing sintering Tool material. However, the coating materials of the coated calcium fluoride powder disclosed in CN104045351A and CN104045325A above are ceramics, and the improvement of the hardness and bending strength of the prepared self-lubricating ceramic cutter is large (increased by 21.7% and 10.7, respectively). %), the improvement of fracture toughness is less (increased by 8%). Compared with the flexural strength and hardness, the fracture toughness of ceramic tool materials is a more important factor restricting its popularization and application. Improving the fracture toughness of ceramic tool materials has become a major technical problem in the industry.

Chinese patent document CN104962110A provides a nickel-boron-coated calcium fluoride composite powder for self-lubricating tool materials for preparing Al ₂ O ₃ /TiB ₂ /CaF ₂ self-lubricating tool materials. Although the invention achieves an improvement in the fracture toughness of the ceramic tool material, the improvement in bending strength and hardness is not satisfactory. In addition, the patent document adopts ultrasonic electroless plating method to prepare nickel-boron-coated calcium fluoride composite powder. The following disadvantages exist: First, the calcium sensitization and activation process before electroless plating adopts a two-step method. More complicated, and the number of cleaning after sensitization has a great influence on the subsequent activation and electroless plating effects, it is difficult to control the quality consistency of different batches of products, and is not suitable for mass production. Secondly, the electroless plating reducing agent sodium borohydride has a high price, and it is necessary to keep the pH of the plating solution at 12 or more, otherwise the decomposition will be deactivated, resulting in difficulty in maintaining the plating solution and high production cost; third, the electroless plating solution The pH value is between 13-14, and the electroless plating temperature is between 55-75 °C. The high pH value and high temperature of the plating solution make the operating environment worse, and the treatment of the waste liquid after electroless plating is more difficult, which is not good for personnel health and environmental protection. .

Summary of the invention

In order to overcome the above deficiencies of the prior art, the present invention provides a self-lubricating ceramic tool material which is coated with a nickel-phosphorus alloy coated calcium fluoride composite powder and a preparation method thereof.

The invention is achieved by the following technical solutions:

A self-lubricating ceramic tool material with nickel-phosphorus alloy coated calcium fluoride composite powder is made of α-phase alumina (α-Al ₂ O ₃ ) as matrix and tungsten carbide tungsten ((W, Ti) C) As a reinforcing phase, a nickel-phosphorus alloy coated calcium fluoride (CaF ₂ @Ni-P) composite powder is used as a solid lubricant, and magnesium oxide (MgO) is used as a sintering aid, which is formed by ball milling and hot pressing sintering. The mass percentage of each component is: α-Al ₂ O ₃ 30-48%, (W, Ti) C 42-66.5%, CaF ₂ @Ni-P is based on the mass of CaF ₂ in the composite powder 3 -12%, MgO 0.4-1.5%; among them,

Nickel-phosphorus alloy coated calcium fluoride is prepared as follows:

The CaF ₂ powder is washed with a sodium hydroxide solution, and then a mixed solution of hydrofluoric acid and ammonium fluoride is added for coarsening, and the coarsened CaF ₂ powder is ultrasonically oscillated by adding a sensitizing-activating solution, the sensitizing-activating solution The composition is: palladium chloride (PdCl ₂ ) 0.5-1g / L, stannous chloride dihydrate (SnCl ₂ · 2H ₂ O) 30-60g / L, sodium chloride (NaCl) 160-250g / L, a mass fraction of 35-37% concentrated hydrochloric acid 60-100ml / L, the balance is distilled water;

The sensitized-activated CaF ₂ powder is added to the electroless plating solution, and is applied under ultrasonic vibration at 35-45 ° C, and the concentrated ammonia water with a mass fraction of 25-28% is added at any time to maintain the pH of the plating solution at 8.5. -9.5; the composition of the electroless plating solution is: nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) 20-30 g / L, sodium citrate dihydrate (Na ₃ C ₆ H ₅ O ₇ · 2H ₂ O) 40-60g/L, ammonium chloride (NH ₄ Cl) 25-40g/L, sodium hypophosphite monohydrate (NaH ₂ PO ₂ ·H ₂ O) 25-35g/L, mass fraction 25-28% The pH of the ammonia water is adjusted to 8.5-9.5, and the balance is distilled water; after plating, separation, washing and drying are performed to obtain a nickel-phosphorus alloy coated calcium fluoride (CaF ₂ @Ni-P).

According to the preferred embodiment of the present invention, the raw material powders of the above components are all commercially available products, and the average particle diameters of the α-Al ₂ O ₃ powder, the (W, Ti) C powder, the CaF ₂ powder, and the MgO powder. The purity is 0.5-1 μm, 1-3 μm, 1-5 μm, and 1-2 μm, respectively, and the purity is more than 99%.

According to the preferred embodiment of the present invention, the self-lubricating ceramic tool material of the above-mentioned nickel-phosphorus alloy coated calcium fluoride composite powder has a mass percentage of each component: α-Al ₂ O ₃ 31-45%, (W, Ti) C 45-64%, CaF ₂ @Ni-P is 3-9% by mass of CaF ₂ in the composite powder, and MgO is 0.5-1%; the sum of the components is 100%.

Further preferably, the self-lubricating ceramic tool material of the nickel-phosphorus alloy coated calcium fluoride composite powder has a mass percentage of each component: α-Al ₂ O ₃ 31-32%, (W, Ti C 62-63%, CaF ₂ @Ni-P is 5-5.5% by mass of CaF ₂ in the composite powder, and MgO is 0.5%; the sum of the components is 100%.

A method for preparing a self-lubricating ceramic tool material by adding a nickel-phosphorus alloy coated calcium fluoride composite powder comprises the following steps:

(1) Weigh the α-Al ₂ O ₃ and (W, Ti) C powders in proportion, add them to an appropriate amount of absolute ethanol, ultrasonically disperse and mechanically stir for 20-30 min to form α-Al ₂ O ₃ suspension. And (W, Ti) C suspension;

(2) mixing the above two suspensions, then adding MgO powder in proportion, ultrasonically dispersing and mechanically stirring for 20-30 min to obtain a multiphase suspension;

(3) Pour the multiphase suspension obtained in the step (2) into a ball mill tank, add the cemented carbide grinding ball at a weight ratio of 8-10:1, and perform ball milling with a nitrogen or argon atmosphere for 45-50 hours. ;

(4) Weigh CaF ₂ raw material powder in proportion and add it to sodium hydroxide solution for cleaning, ultrasonically shake for 5-10min, centrifuge and wash with distilled water until neutral;

(5) The washed CaF ₂ powder is added to a hydrofluoric acid-ammonium fluoride roughening solution for coarsening, ultrasonically shaken for 10-20 min, centrifuged and washed with distilled water until neutral;

(6) The roughened CaF ₂ powder is added to the sensitization-activation solution, ultrasonically shaken for 10-20 min, centrifuged and washed with distilled water until neutral, and dried in a vacuum drying oven at 100-110 ° C for 5-8 h;

The components of the sensitization-activation solution are: palladium chloride (PdCl ₂ ) 0.5-1 g/L, stannous chloride dihydrate (SnCl ₂ · 2H ₂ O) 30-60 g/L, sodium chloride (NaCl) 160-250g / L, the mass fraction of 35-37% concentrated hydrochloric acid 60-100ml / L, the balance is distilled water.

(7) Adding the sensitized-activated CaF ₂ powder to the electroless plating solution in step (6), performing electroless plating in a constant temperature water bath at 35-45 ° C, maintaining ultrasonic vibration during the plating process and dropping the mass at any time. The concentration of 25-28% concentrated ammonia water keeps the pH of the plating solution at 8.5-9.5; the composition of the electroless plating solution is: nickel sulfate hexahydrate (NiSO ₄ ·6H ₂ O) 20-30g/L, dihydrate Sodium citrate (Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O) 40-60 g/L, ammonium chloride (NH ₄ Cl) 25-40 g/L, sodium monophosphite monohydrate (NaH ₂ PO ₂ ·H ₂ O) 25-35g / L, the mass fraction of 25-28% concentrated ammonia water adjusted pH 8.5-9.5, the balance is distilled water.

After the plating is completed, the solid particles are centrifuged and washed with distilled water until neutral, and then dried in a vacuum drying oven at 100-110 ° C for 8-10 h to obtain a CaF ₂ @Ni-P composite powder;

(8) The CaF ₂ @Ni-P composite powder obtained in the step (7) is added to the ball mill tank of the step (3), and ball milling is continued for 1-3 hours with nitrogen or argon as a protective atmosphere to obtain a ball mill liquid;

(9) The ball mill obtained in the step (8) is dried at 80-100 ° C for 20-30 h, and then passed through a 100-200 mesh sieve to obtain a mixed powder, which is sealed for use;

(10) The mixed powder obtained in the step (9) is placed in a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering.

Preferably, the sintering process parameters of the step (10) are: a heating rate of 10-20 ° C / min, a holding temperature of 1500-1600 ° C, a holding time of 10-20 min, and a hot pressing pressure of 25-30 MPa.

According to the preferred embodiment of the present invention, the sodium hydroxide solution for washing according to the step (4) is a sodium hydroxide solution having a mass fraction of 10% to 15%, and more preferably, the addition of CaF ₂ powder per liter of the sodium hydroxide solution during the cleaning is added. The amount is 30-70 g, which is recorded as 30-70 g/L.

According to the preferred embodiment of the present invention, the hydrofluoric acid-ammonium fluoride crude solution according to the step (5) is a mixed solution of ammonium fluoride and a hydrofluoric acid having a mass fraction of 35-40%, wherein the ammonium fluoride is 2-4 g. /L, the mass fraction of 35-40% hydrofluoric acid is 90-120ml / L. The preparation of the hydrofluoric acid-ammonium fluoride roughening liquid and the coarsening of the CaF ₂ powder should be carried out in a plastic container; further preferably, when coarsening, the CaF ₂ powder is added in an amount of 30-70 g/L, that is, each The hydrofluoric acid-ammonium fluoride crude solution was added to 30-70 g of CaF ₂ powder.

According to a preferred embodiment of the present invention, in the sensitization-activation step (6), the CaF ₂ powder is added in an amount of 30 to 60 g/L. That is, 30-60 g of CaF ₂ powder is added per liter of the sensitization-activation solution.

Preferably, the sensitizing-activation liquid preparation step described in the step (6) is as follows:

1) Weigh PdCl ₂ in proportion, add 1/3 amount of concentrated hydrochloric acid, stir and dissolve, and add distilled water to 1/10 of the total volume of sensitized-activated solution to obtain solution A.

2) Weigh NaCl in proportion, add an appropriate amount of distilled water, stir and dissolve, and add distilled water to 1/2 of the total volume of the sensitizing-activating solution to obtain solution B.

3) Mix solution A with solution B and stir to obtain solution C.

4) Weigh SnCl ₂ · 2H ₂ O in proportion, add 2/3 of concentrated hydrochloric acid, stir and dissolve, add distilled water to 2/5 of the total volume of sensitized-activated solution to obtain solution D.

5) The solution D is slowly added to the solution C while stirring, and aged at 3-5 hours at 60-70 ° C in a water bath to obtain a sensitization-activation solution.

According to the preferred embodiment of the present invention, the CaF ₂ powder is added in an amount of 4 to 9 g/L during the electroless plating in the step (7), that is, 4 to 9 g of CaF ₂ powder is added per liter of the electroless plating solution.

Preferably, the step of preparing the electroless plating solution described in the step (7) is as follows:

1 NiSO ₄ ·6H ₂ O, Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O, NH ₄ Cl, NaH ₂ PO ₂ ·H ₂ O were weighed in proportion, and dissolved in an appropriate amount of distilled water to obtain a clear solution.

2 A solution of NiSO ₄ ·6H ₂ O was slowly added to a solution of Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O, and stirred while stirring to obtain a solution a.

3 The NH ₄ Cl solution was slowly added to the solution a, and stirred while stirring to obtain a solution b.

4 The NaH ₂ PO ₂ ·H ₂ O solution was slowly added to the solution b, and stirred while stirring to obtain a solution c.

5 Slowly add 25-28% concentrated ammonia water to solution c, and stir while stirring to make the pH value of the solution reach 8.5-9.5. Then add distilled water to the total volume of the electroless plating solution and stir evenly to obtain electroless plating solution. .

Preferably, the chemical reagents such as sodium hydroxide and hydrofluoric acid used in the present invention are all commercially available products and are analytically pure, wherein the concentration of hydrofluoric acid is 35-40% by mass, and the concentration of concentrated hydrochloric acid is 35-37. %, the concentration of concentrated ammonia is 25-28% by mass.

The present invention has the following advantages over the prior art:

1. The invention prepares a self-lubricating ceramic tool material by adding a nickel-phosphorus alloy coated calcium fluoride composite powder (CaF ₂ @Ni-P) instead of the CaF ₂ powder as a solid lubricant, on the one hand, the coating layer Ni-P The alloy can accelerate the sintering densification process of the solid lubricant and the ceramic matrix, prevent the abnormal growth of the crystal grains, and improve the microstructure of the self-lubricating ceramic tool material; on the other hand, the coating Ni-P alloy can be used for the self-lubricating ceramic tool The material is toughened and strengthened, and at the same time, its mechanical properties are improved, thereby improving the wear resistance of the self-lubricating ceramic tool.

2. Compared with the prior art of adding aluminum hydroxide coated calcium fluoride composite powder to prepare self-lubricating ceramic tool material, the invention has a great improvement on the fracture toughness of the self-lubricating ceramic tool material, and is more beneficial to Popularization and application of ceramic tool materials.

3. Compared with the prior art technique of adding a nickel-boron-coated calcium fluoride composite powder to prepare a self-lubricating ceramic tool material, the present invention first cleans and roughens the calcium fluoride powder prior to electroless plating, especially the roughening step. It is beneficial to increase the bonding force between the metal plating layer and the calcium fluoride powder, thereby improving the strengthening effect of the plating metal on the calcium fluoride; on the other hand, the invention simplifies the sensitization-activation one-step method for the calcium fluoride powder. Sensitization and activation process ensure the consistency of quality of different batches of products, which is suitable for mass production. Furthermore, in the electroless plating of calcium fluoride powder, the pH of the electroless plating solution is controlled at 8.5-9.5. The temperature is controlled at 35-45 ° C. The lower pH and temperature of the electroless plating solution improve the operating environment of the electroless plating, reduce the difficulty of processing the waste liquid after electroless plating, and lower the production cost, which is beneficial to health and environmental protection.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a scanning electron microscope (SEM) photograph of a CaF ₂ raw material powder used in an embodiment of the present invention.

2 is a SEM photograph of a CaF ₂ @Ni-P composite powder prepared in Example 1 of the present invention.

Fig. 3 is an X-ray diffraction spectrum of a CaF ₂ @Ni-P composite powder and a CaF ₂ raw material powder prepared in Example 1 of the present invention.

Fig. 4 is an X-ray energy spectrum of a CaF ₂ @Ni-P composite powder prepared in Example 1 of the present invention.

Figure 5 is a cross-sectional SEM photograph of a self-lubricating ceramic tool material added with CaF ₂ @Ni-P composite powder prepared in Example 1 of the present invention.

Figure 6 is a cross-sectional SEM photograph of a self-lubricating ceramic tool material prepared by adding a CaF ₂ powder prepared in a comparative example of Example 1 of the present invention.

detailed description

The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

The raw material powders used in the examples are all commercially available products, and the average particle diameters of α-Al ₂ O ₃ powder, (W, Ti) C powder, CaF ₂ powder, and MgO powder are 0.5 μm and 2.5, respectively. Μm, 5 μm and 2 μm, all of which are more than 99% pure. The chemical reagents used in the examples were all commercially available products and analyzed analytically, wherein the concentration of hydrofluoric acid was 40% by mass, the concentration of concentrated hydrochloric acid was 37% by mass, and the concentration of concentrated ammonia was 28% by mass.

Example 1: A self-lubricating ceramic tool material to which CaF ₂ @Ni-P composite powder was added, the mass percentage of each component was: α-Al ₂ O ₃ 31.8%, (W, Ti) C 62.5%, CaF ₂ @Ni-P is 5.2% by mass of CaF ₂ in the composite powder, and MgO is 0.5%. The preparation method is as follows:

(1) Weigh 31.8g α-Al ₂ O ₃ and 62.5g (W, Ti) C powder, add an appropriate amount of absolute ethanol, ultrasonically disperse and mechanically stir for 20min, and prepare α-Al ₂ O ₃ suspension and (W, Ti) C suspension.

(2) The above two suspensions were mixed, and then 0.5 g of MgO powder was added, ultrasonically dispersed and mechanically stirred for 20 minutes to obtain a multiphase suspension.

(3) The multiphase suspension obtained in the step (2) was poured into a ball mill tank, 900 g of a cemented carbide grinding ball was added, and ball milling was carried out for 48 hours under a nitrogen atmosphere.

(4) Prepare 100ml of 10% sodium hydroxide solution as the cleaning solution, weigh 5.2g of CaF ₂ raw material powder into the cleaning solution, shake it for 10min, centrifuge and wash it with distilled water until neutral.

(5) Preparing 100 ml of a mixed solution of hydrofluoric acid and ammonium fluoride as a roughening liquid in a plastic container, the concentrations of which are 100 ml/L and 2 g/L, respectively, and adding the washed CaF ₂ powder to the roughening In the solution, ultrasonically shake for 15 min, centrifuge and rinse to neutral with distilled water.

(6) Add 0.05g of PdCl ₂ to 2ml of concentrated hydrochloric acid, stir and dissolve, add distilled water to 10ml to obtain solution A; add 16g of NaCl to 50ml of distilled water, stir to dissolve to obtain solution B; mix solution A and solution B, stir well The solution C was obtained; 3 g of SnCl ₂ ·2H ₂ O was dissolved in 4 ml of concentrated hydrochloric acid, stirred and dissolved, and distilled water was added to 40 ml to obtain a solution D; the solution D was slowly added to the solution C while stirring, and the mixture was aged at 60 ° C in a water bath. 3h, 100ml sensitization-activation solution was obtained. The coarsened CaF ₂ powder was added to the sensitization-activation solution, ultrasonically shaken for 15 min, centrifuged and washed with distilled water until neutral, and dried in a vacuum oven at 100 ° C for 7 h.

(7) Dissolving 25 g of NiSO ₄ ·6H ₂ O, 50 g of Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O, 30 g of NH ₄ Cl, and 25 g of NaH ₂ PO ₂ ·H ₂ O in 150-200 ml of distilled water, respectively. The solution was clarified; the NiSO ₄ ·6H ₂ O solution was slowly added to the Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O solution, and stirred while stirring to obtain a solution a; the NH ₄ Cl solution was slowly added to the solution a while adding While stirring, the solution b is obtained; the NaH ₂ PO ₂ ·H ₂ O solution is slowly added to the solution b, and stirred while stirring to obtain a solution c; the concentrated ammonia water is slowly added dropwise to the solution c, and the solution is stirred while stirring. The pH reached 9.5, and then distilled water was added to 1000 ml and stirred to obtain an electroless plating solution. The sensitized-activated CaF ₂ powder was added to an electroless plating solution, and electroless plating was performed in a constant temperature water bath at 45 °C. The ultrasonic vibration was maintained during the plating process and concentrated ammonia was added dropwise at any time to maintain the pH of the plating solution at 9.5. After the plating was completed, the solid particles were centrifuged and washed with distilled water until neutral, and then dried in a vacuum oven at 100 ° C for 10 hours to obtain a CaF ₂ @Ni-P composite powder.

(8) The CaF ₂ @Ni-P composite powder obtained in the step (7) is added to the ball mill tank of the step (3), and ball milling is continued for 1 hour with nitrogen as a protective atmosphere to obtain a ball mill liquid.

(9) The ball mill obtained in the step (8) is dried in a vacuum drying oven at 100 ° C for 24 hours, and then passed through a 120 mesh sieve to obtain a mixed powder, which is sealed for use.

(10) The mixed powder obtained in the step (9) is placed in a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering. The sintering process parameters are: heating rate 15 ° C / min, holding temperature 1550 ° C, holding time 15 min, hot pressing pressure 25 MPa.

Comparative Example 1: A self-lubricating ceramic tool material to which CaF ₂ powder was added, the mass percentage of each component was: α-Al ₂ O ₃ 31.8%, (W, Ti) C 62.5%, CaF ₂ 5.2%, MgO 0.5%. The preparation method is as follows:

(4) Weigh 5.2 g of CaF ₂ raw material powder into the ball-milling tank of the step (3), and continue ball milling for 1 h with nitrogen as a protective atmosphere to obtain a ball-milling liquid.

(5) The ball mill obtained in the step (4) is dried in a vacuum drying oven at 100 ° C for 24 hours, and then passed through a 120 mesh sieve to obtain a mixed powder, which is sealed for use.

(6) The mixed powder obtained in the step (5) is charged into a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering. The sintering process parameters are: heating rate 15 ° C / min, holding temperature 1550 ° C, holding time 15 min, hot pressing pressure 25 MPa.

It can be seen from Fig. 1 that the CaF ₂ raw material powder is an irregular polyhedron with sharp edges and a smooth surface. It can be seen from Fig. 2 that the CaF ₂ @Ni-P composite powder is round and blunt, and the surface is rough due to the coating of closely arranged spherical particles. In the X-ray diffraction pattern of the CaF ₂ @Ni-P composite powder in Fig. 3, in addition to the diffraction peak of CaF ₂ , there is a monotonically broadened diffraction peak in the range of 2θ = 40-50° (ie, "Taro peak" , the rectangular dotted line in the figure is indicated), indicating that the cladding layer is an amorphous alloy of Ni. The X-ray energy spectrum of the CaF ₂ @Ni-P composite powder in Fig. 4 has only Ni and P elements except for the F and Ca elements, indicating that the above amorphous alloy is a Ni-P alloy. 2, 3 and 4, it can be seen that the composite powder of Ni-P alloy coated CaF ₂ can be successfully prepared according to the method of the present invention. It can be seen from Fig. 5 that the self-lubricating ceramic tool material with CaF ₂ @Ni-P composite powder has uniform grain size and tight arrangement. It can be seen from Fig. 6 that the self-lubricating ceramic tool material with CaF ₂ powder has uneven grain size. There is an abnormal growth. Figures 5 and 6 show that the addition of a nickel-phosphorus alloy coated calcium fluoride composite powder instead of the calcium fluoride powder as a solid lubricant can improve the microstructure of the self-lubricating ceramic tool material.

The mechanical properties of the self-lubricating ceramic tool material prepared by adding the CaF ₂ @Ni-P composite powder prepared in Example 1 were: bending strength 582 MPa, hardness 14.1 GPa, fracture toughness 4.3 MPa·m ^1/2 ; The mechanical properties of the self-lubricating ceramic tool material prepared by adding CaF ₂ powder are: bending strength 506 MPa, hardness 13.4 GPa, and fracture toughness 3.6 MPa·m ^1/2 . It can be seen that the flexural strength, hardness and fracture toughness of the former are increased by 15.0%, 5.2% and 19.4%, respectively.

Example 2: Self-lubricating ceramic tool material with CaF ₂ @Ni-P composite powder added, the mass percentage of each component is: α-Al ₂ O ₃ 32.6%, (W, Ti) C 63.9%, CaF ₂ @Ni-P is 3% by mass of CaF ₂ in the composite powder, and MgO is 0.5%. The preparation method is as follows:

(1) Weigh 32.6g α-Al ₂ O ₃ and 63.9g (W, Ti) C powder, add an appropriate amount of absolute ethanol, ultrasonically disperse and mechanically stir for 20min, and prepare α-Al ₂ O ₃ suspension and (W, Ti) C suspension.

(2) The above two suspensions were mixed, and then 0.5 g of MgO powder was added, ultrasonically dispersed and mechanically stirred for 25 minutes to obtain a multiphase suspension.

(3) The multiphase suspension obtained in the step (2) was poured into a ball mill tank, and 950 g of a cemented carbide grinding ball was added, and ball milling was carried out for 45 hours under a nitrogen atmosphere.

(4) Prepare 100ml of sodium hydroxide solution with a mass fraction of 15% as the cleaning solution, weigh 3g of CaF ₂ raw material powder into the cleaning solution, shake it for 5min, centrifuge and wash it with distilled water until neutral.

(5) Preparing 100 ml of a mixed solution of hydrofluoric acid and ammonium fluoride as a roughening liquid in a plastic container, the concentration of which is 90 ml/L and 2 g/L, respectively, and adding the washed CaF ₂ powder to the roughening In the solution, ultrasonically shake for 15 min, centrifuge and rinse to neutral with distilled water.

(6) Add 0.05g of PdCl ₂ to 2ml of concentrated hydrochloric acid, stir and dissolve, add distilled water to 10ml to obtain solution A; add 16g of NaCl to 50ml of distilled water, stir to dissolve to obtain solution B; mix solution A and solution B, stir well Solution C was obtained; 3 g of SnCl ₂ ·2H ₂ O was dissolved in 4 ml of concentrated hydrochloric acid, stirred and dissolved, and distilled water was added to 40 ml to obtain a solution D; the solution D was slowly added to the solution C while stirring, and the mixture was aged at 65 ° C in a water bath. 3h, 100ml sensitization-activation solution was obtained. The coarsened CaF ₂ powder was added to the sensitization-activation solution, ultrasonically shaken for 10 min, centrifuged and washed with distilled water until neutral, and dried in a vacuum oven at 110 ° C for 5 h.

(7) 15 g of NiSO ₄ ·6H ₂ O, 30 g of Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O, 20 g of NH ₄ Cl, and 15 g of NaH ₂ PO ₂ ·H ₂ O were respectively dissolved in 80-100 mL of distilled water to obtain Clarify the solution; slowly add NiSO ₄ ·6H ₂ O solution to Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O solution, while stirring, to obtain solution a; slowly add NH ₄ Cl solution to solution a, while adding While stirring, the solution b is obtained; the NaH ₂ PO ₂ ·H ₂ O solution is slowly added to the solution b, and stirred while stirring to obtain a solution c; the concentrated ammonia water is slowly added dropwise to the solution c, and the solution is stirred while stirring. The pH reached 9, and then distilled water was added to 500 ml and stirred to obtain an electroless plating solution. The sensitized-activated CaF ₂ powder was added to an electroless plating solution, and electroless plating was performed in a constant temperature water bath at 35 °C. The ultrasonic vibration was maintained during the plating process and concentrated ammonia was added dropwise at any time to maintain the pH of the plating solution at 9. After the plating was completed, the solid particles were centrifuged and washed with distilled water until neutral, and then dried in a vacuum oven at 110 ° C for 8 hours to obtain a CaF ₂ @Ni-P composite powder.

(8) The CaF ₂ @Ni-P composite powder obtained in the step (7) is added to the ball mill tank of the step (3), and ball milling is continued for 2 hours with nitrogen as a protective atmosphere to obtain a ball mill liquid.

(9) The ball mill obtained in the step (8) is dried in a vacuum drying oven at 100 ° C for 20 h, and then passed through a 120 mesh sieve to obtain a mixed powder, which is sealed for use.

(10) The mixed powder obtained in the step (9) is placed in a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering. The sintering process parameters are: heating rate 10 ° C / min, holding temperature 1500 ° C, holding time 10 min, hot pressing pressure 30 MPa.

Comparative Example 2: A self-lubricating ceramic tool material to which CaF ₂ powder was added, the mass percentage of each component was: α-Al ₂ O ₃ 32.6%, (W, Ti) C 63.9%, CaF ₂ 3%, MgO 0.5%. The preparation method is as follows:

(4) Weigh 3 g of CaF ₂ raw material powder into the ball-milling tank of the step (3), and continue ball milling for 2 h with nitrogen as a protective atmosphere to obtain a ball-milling liquid.

(5) The ball mill obtained in the step (4) is dried in a vacuum drying oven at 100 ° C for 20 h, and then passed through a 120 mesh sieve to obtain a mixed powder, which is sealed for use.

(6) The mixed powder obtained in the step (5) is charged into a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering. The sintering process parameters are: heating rate 10 ° C / min, holding temperature 1500 ° C, holding time 10 min, hot pressing pressure 30 MPa.

The mechanical properties of the self-lubricating ceramic tool material prepared by adding the CaF ₂ @Ni-P composite powder prepared in Example 2 were as follows: bending strength 591 MPa, hardness 15.2 GPa, fracture toughness 4.6 MPa·m ^1/2 ; 2 The mechanical properties of the self-lubricating ceramic tool material prepared by adding CaF ₂ powder are: bending strength 534 MPa, hardness 14.5 GPa, and fracture toughness 3.9 MPa·m ^1/2 . It can be seen that the flexural strength, hardness and fracture toughness of the former are increased by 10.7%, 4.8% and 17.9%, respectively.

Example 3: Self-lubricating ceramic tool material with CaF ₂ @Ni-P composite powder added, the mass percentage of each component is: α-Al ₂ O ₃ 44.4%, (W, Ti) C 45.6%, CaF ₂ @Ni-P is 9% by mass of CaF ₂ in the composite powder, and MgO1%. The preparation method is as follows:

(1) Weigh 44.4g α-Al ₂ O ₃ and 45.6g (W, Ti) C powder, add an appropriate amount of absolute ethanol, ultrasonically disperse and mechanically stir for 25min, and prepare α-Al ₂ O ₃ suspension and (W, Ti) C suspension.

(2) The above two suspensions were mixed, and then 1 g of MgO powder was added, ultrasonically dispersed and mechanically stirred for 30 minutes to obtain a multiphase suspension.

(3) The multiphase suspension obtained in the step (2) was poured into a ball mill tank, and 850 g of a cemented carbide grinding ball was added, and ball milling was carried out for 50 hours under a nitrogen atmosphere.

(4) Prepare 200ml of 15% sodium hydroxide solution as the cleaning solution, weigh 9g of CaF ₂ raw material powder into the cleaning solution, shake it for 10min, centrifuge and wash it with distilled water until neutral.

(5) Preparing 200 ml of a mixed solution of hydrofluoric acid and ammonium fluoride as a roughening liquid in a plastic container, the concentration of which is 110 ml/L and 3 g/L, respectively, and adding the washed CaF ₂ powder to the roughening In the solution, ultrasonically shake for 20 min, centrifuge and rinse with distilled water until neutral.

(6) 0.1 g of PdCl _{2 was} added to 4 ml of concentrated hydrochloric acid, stirred and dissolved, and then distilled water was added to 20 ml to obtain a solution A; 32 g of NaCl was added to 100 ml of distilled water, and stirred to dissolve to obtain a solution B; the solution A and the solution B were mixed and stirred uniformly. Solution C was obtained; 6 g of SnCl ₂ ·2H ₂ O was dissolved in 8 ml of concentrated hydrochloric acid, stirred and dissolved, and distilled water was added to 80 ml to obtain a solution D; the solution D was slowly added to the solution C while stirring, and the mixture was aged at 65 ° C in a water bath. 4h, 200ml sensitization-activation solution was obtained. The coarsened CaF ₂ powder was added to the sensitization-activation solution, ultrasonically shaken for 15 min, centrifuged and washed with distilled water until neutral, and dried in a vacuum oven at 110 ° C for 8 h.

(7) Dissolving 30 g of NiSO ₄ ·6H ₂ O, 60 g of Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O, 40 g of NH ₄ Cl, and 35 g of NaH ₂ PO ₂ ·H ₂ O in 150-200 ml of distilled water, respectively. Clarify the solution; slowly add NiSO ₄ ·6H ₂ O solution to Na ₃ C ₆ H ₅ O ₇ ·2H ₂ O solution, while stirring, to obtain solution a; slowly add NH ₄ Cl solution to solution a, while adding While stirring, the solution b is obtained; the NaH ₂ PO ₂ ·H ₂ O solution is slowly added to the solution b, and stirred while stirring to obtain a solution c; the concentrated ammonia water is slowly added dropwise to the solution c, and the solution is stirred while stirring. The pH reached 8.5, and then distilled water was added to 1000 ml and stirred to obtain an electroless plating solution. The sensitized-activated CaF ₂ powder was added to an electroless plating solution, and electroless plating was performed in a constant temperature water bath at 40 °C. The ultrasonic vibration was maintained during the plating process and concentrated ammonia was added dropwise at any time to maintain the pH of the plating solution at 8.5. After the plating was completed, the solid particles were centrifuged and washed with distilled water until neutral, and then dried in a vacuum oven at 100 ° C for 10 hours to obtain a CaF ₂ @Ni-P composite powder.

(8) The CaF ₂ @Ni-P composite powder obtained in the step (7) was placed in a ball mill tank of the step (3), and ball milling was continued for 3 hours under a nitrogen atmosphere to obtain a ball mill liquid.

(9) The ball mill obtained in the step (8) is dried in a vacuum drying oven at 90 ° C for 30 hours, and then passed through a 100 mesh sieve to obtain a mixed powder, which is sealed and used.

(10) The mixed powder obtained in the step (9) is placed in a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering. The sintering process parameters are: heating rate 15 ° C / min, holding temperature 1600 ° C, holding time 20 min, hot pressing pressure 30 MPa.

Comparative Example 3: A self-lubricating ceramic tool material to which CaF ₂ powder was added, the mass percentage of each component was: α-Al ₂ O ₃ 44.4%, (W, Ti) C 45.6%, CaF ₂ 9%, MgO 1%. The preparation method is as follows:

(4) Weighing 9 g of CaF ₂ raw material powder into the ball-milling tank of the step (3), and continuing ball milling for 3 hours with nitrogen as a protective atmosphere to obtain a ball-milling liquid.

(5) The ball mill obtained in the step (4) is dried in a vacuum drying oven at 90 ° C for 30 hours, and then passed through a 100 mesh sieve to obtain a mixed powder, which is sealed and used.

(6) The mixed powder obtained in the step (5) is charged into a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering. The sintering process parameters are: heating rate 15 ° C / min, holding temperature 1600 ° C, holding time 20 min, hot pressing pressure 30 MPa.

The mechanical properties of the self-lubricating ceramic tool material prepared by adding the CaF ₂ @Ni-P composite powder prepared in Example 3 were: bending strength 563 MPa, hardness 13.7 GPa, fracture toughness 3.8 MPa·m ^1/2 ; 3 The mechanical properties of the prepared self-lubricating ceramic tool material with CaF ₂ powder are: bending strength 491 MPa, hardness 12.9 GPa, fracture toughness 3.2 MPa·m ^1/2 . It can be seen that the flexural strength, hardness and fracture toughness of the former are increased by 14.7%, 6.2% and 18.8%, respectively.

Claims

Self-lubricating ceramic tool material with nickel-phosphorus alloy coated calcium fluoride composite powder, characterized by α-phase alumina (α-Al 2 O 3 ) as matrix and tungsten carbide tungsten ((W, Ti) C) as a reinforcing phase, a nickel-phosphorus alloy coated calcium fluoride (CaF 2 @Ni-P) composite powder as a solid lubricant, magnesium oxide (MgO) as a sintering aid, ball milled, hot pressed Sintered; the mass percentage of each component is: α-Al 2 O 3 30-48%, (W, Ti) C 42-66.5%, CaF 2 @Ni-P according to CaF 2 in the composite powder 3-12% by mass, 0.4-1.5% of MgO; among them,

Nickel-phosphorus alloy coated calcium fluoride is prepared as follows:

The CaF 2 powder is washed with a sodium hydroxide solution, and then a mixed solution of hydrofluoric acid and ammonium fluoride is added for coarsening, and the coarsened CaF 2 powder is ultrasonically oscillated by adding a sensitizing-activating solution, the sensitizing-activating solution The composition is: palladium chloride (PdCl 2 ) 0.5-1g / L, stannous chloride dihydrate (SnCl 2 · 2H 2 O) 30-60g / L, sodium chloride (NaCl) 160-250g / L, a mass fraction of 35-37% concentrated hydrochloric acid 60-100ml / L, the balance is distilled water;

The sensitized-activated CaF 2 powder is added to the electroless plating solution, and is applied under ultrasonic vibration at 35-45 ° C, and the concentrated ammonia water with a mass fraction of 25-28% is added at any time to maintain the pH of the plating solution at 8.5. -9.5; the composition of the electroless plating solution is: nickel sulfate hexahydrate (NiSO 4 · 6H 2 O) 20-30 g / L, sodium citrate dihydrate (Na 3 C 6 H 5 O 7 · 2H 2 O) 40-60g/L, ammonium chloride (NH 4 Cl) 25-40g/L, sodium hypophosphite monohydrate (NaH 2 PO 2 ·H 2 O) 25-35g/L, mass fraction 25-28% The pH of the ammonia water is adjusted to 8.5-9.5, and the balance is distilled water; after plating, separation, washing and drying are carried out to obtain a nickel-phosphorus alloy coated calcium fluoride.
The self-lubricating ceramic tool material of the nickel-phosphorus alloy-coated calcium fluoride composite powder according to claim 1, wherein the α-Al 2 O 3 powder, the (W, Ti) C powder, and the CaF 2 The average particle diameters of the powder and the MgO powder are 0.5-1 μm, 1-3 μm, 1-5 μm, and 1-2 μm, respectively, and the purity is more than 99%.
The self-lubricating ceramic tool material according to claim 1, wherein the mass percentage of each component is: α-Al 2 O 3 31-45% (W, Ti) C 45-64%, CaF 2 @Ni-P is 3-9% by mass of CaF 2 in the composite powder, and MgO is 0.5-1%; the sum of the components is 100%.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to any one of claims 1 to 3, comprising the following steps:

(1) Weigh the α-Al 2 O 3 and (W, Ti) C powders in proportion, add them to an appropriate amount of absolute ethanol, ultrasonically disperse and mechanically stir for 20-30 min to form α-Al 2 O 3 suspension. And (W, Ti) C suspension;

(2) mixing the above two suspensions, then adding MgO powder in proportion, ultrasonically dispersing and mechanically stirring for 20-30 min to obtain a multiphase suspension;

(3) Pour the multiphase suspension obtained in the step (2) into a ball mill tank, add the cemented carbide grinding ball at a weight ratio of 8-10:1, and perform ball milling with a nitrogen or argon atmosphere for 45-50 hours. ;

(4) Weigh CaF 2 raw material powder in proportion and add it to sodium hydroxide solution for cleaning, ultrasonically shake for 5-10min, centrifuge and wash with distilled water until neutral;

(5) The washed CaF 2 powder is added to a hydrofluoric acid-ammonium fluoride roughening solution for coarsening, ultrasonically shaken for 10-20 min, centrifuged and washed with distilled water until neutral;

(6) The roughened CaF 2 powder is added to the sensitization-activation solution, ultrasonically shaken for 10-20 min, centrifuged and washed with distilled water until neutral, and dried in a vacuum drying oven at 100-110 ° C for 5-8 h;

The components of the sensitization-activation solution are: palladium chloride (PdCl 2 ) 0.5-1 g/L, stannous chloride dihydrate (SnCl 2 · 2H 2 O) 30-60 g/L, sodium chloride (NaCl) 160-250g / L, the mass fraction of 35-37% concentrated hydrochloric acid 60-100ml / L, the balance is distilled water;

(7) Adding the sensitized-activated CaF 2 powder to the electroless plating solution in step (6), performing electroless plating in a constant temperature water bath at 35-45 ° C, maintaining ultrasonic vibration during the plating process and dropping the mass at any time. The concentration of 25-28% concentrated ammonia water keeps the pH of the plating solution at 8.5-9.5; the composition of the electroless plating solution is: nickel sulfate hexahydrate (NiSO 4 ·6H 2 O) 20-30g/L, dihydrate Sodium citrate (Na 3 C 6 H 5 O 7 ·2H 2 O) 40-60 g/L, ammonium chloride (NH 4 Cl) 25-40 g/L, sodium monophosphite monohydrate (NaH 2 PO 2 ·H 2 O) 25-35g / L, the mass fraction of 25-28% concentrated ammonia water adjusted pH 8.5-9.5, the balance is distilled water;

After the plating is completed, the solid particles are centrifuged and washed with distilled water until neutral, and then dried in a vacuum drying oven at 100-110 ° C for 8-10 h to obtain a CaF 2 @Ni-P composite powder;

(8) The CaF 2 @Ni-P composite powder obtained in the step (7) is added to the ball mill tank of the step (3), and ball milling is continued for 1-3 hours with nitrogen or argon as a protective atmosphere to obtain a ball mill liquid;

(9) The ball mill obtained in the step (8) is dried at 80-100 ° C for 20-30 h, and then passed through a 100-200 mesh sieve to obtain a mixed powder, which is sealed for use;

(10) The mixed powder obtained in the step (9) is placed in a graphite mold, and after cold press forming, it is placed in a vacuum hot press sintering furnace for hot press sintering.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to claim 4, wherein the cleaning sodium hydroxide solution according to the step (4) is of mass A sodium hydroxide solution having a fraction of 10% to 15%; preferably, the CaF 2 powder is added in an amount of 30 to 70 g/L at the time of washing.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to claim 4, wherein the hydrofluoric acid-ammonium fluoride roughening liquid according to the step (5) is fluorine. a mixed solution of ammonium and a hydrofluoric acid having a mass fraction of 35-40%, wherein the ammonium fluoride is 2-4 g/L, and the hydrofluoric acid having a mass fraction of 35-40% is 90-120 ml/L; The CaF 2 powder is added in an amount of 30 to 70 g/L.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to claim 4, wherein in the step (6) sensitization-activation, the CaF 2 powder is added in an amount of 30 -60g/L.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to claim 4, wherein the sensitizing-activating liquid preparation step according to the step (6) is as follows:

1) Weigh PdCl 2 proportionally, add 1/3 amount of concentrated hydrochloric acid, stir and dissolve, add distilled water to 1/10 of the total volume of sensitized-activated solution to obtain solution A;

2) weigh NaCl according to the ratio, add appropriate amount of distilled water, stir and dissolve, add distilled water to 1/2 of the total volume of sensitized-activated solution to obtain solution B;

3) Mixing solution A with solution B, stirring to obtain solution C;

4) Weigh SnCl 2 · 2H 2 O proportionally, add 2 / 3 amount of concentrated hydrochloric acid, stir and dissolve, add distilled water to 2 / 5 of the total volume of sensitization - activation solution, to obtain solution D;

5) The solution D is slowly added to the solution C while stirring, and aged at 3-5 hours at 60-70 ° C in a water bath to obtain a sensitization-activation solution.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to claim 4, wherein the step (7) of adding the CaF 2 powder in the electroless plating is 4-9 g/ L, that is, 4-9 g of CaF 2 powder was added per liter of electroless plating solution.
The method for preparing a self-lubricating ceramic tool material for adding a nickel-phosphorus alloy coated calcium fluoride composite powder according to claim 4, wherein the sintering process parameter of the step (10) is: a heating rate of 10-20 ° C /min, holding temperature 1500-1600 ° C, holding time 10-20min, hot pressing pressure 25-30MPa.