CN102560216A - Preparation method of dense coated composite powder and super coarse and extra coarse grained cemented carbide - Google Patents

Abstract

The invention discloses a preparation method of dense coated composite powder and super coarse and extra coarse grained cemented carbide, which is characterized in that: mechanical activated powder mainly comprising WC, and a Co/Ni hydroxide alkaline pulp material are used as raw materials, and by utilizing the self catalytic activity and the heterogeneous nucleation effect of the mechanical activated powder, without adding a sensitizing agent, an activating agent, a catalyst, and other foreign substances, Co/Ni coated WC composite powder with a nano-assembled structure is prepared by a hydrothermal high-pressure hydrogen reduction process; and the thermal diffusion homogenization treatment of the composite powder is carried out in a hydrogen atmosphere by utilizing a nano-diffusion sintering effect to obtain the dense Co/Ni coated WC composite powder, and the composite powder is used as a raw material to prepare the high-quality super coarse and extra coarse-grained cemented carbide. The preparation method has the characteristics of environmental protection, low cost and the like.

Description

Preparation method of dense coated composite powder and ultra-coarse and ultra-coarse grained cemented carbide

technical field

The invention relates to a preparation method of cemented carbide, in particular to a preparation method of densely coated composite powder and ultra-coarse and ultra-coarse-grained cemented carbide.

Background technique

Cemented carbide is produced by powder metallurgy and consists of transition group refractory metal compounds (WC, TiC, TaC, NbC, etc.) and bonding metals (Co, Ni, Fe, etc.), with a hard phase + bonding Engineering composites with phase structure characteristics. During the sintering process, the cemented carbide forms a liquid phase through eutectic reaction, and the sintering of cemented carbide is a typical liquid phase sintering. The binder phase of cemented carbide is a solid solution of transition metals such as C and W, which is based on the binder metal.

According to the classification standards of cemented carbides of Sandvik, the largest cemented carbide manufacturer in the world, cemented carbides with WC grain sizes of 3.5 μm to 4.9 μm, 5.0 μm to 7.9 μm, and 8.0 μm to 14 μm are coarse grained respectively. , Ultra-coarse-grained and extra-coarse-grained cemented carbide. Under the condition of the same binder metal content, compared with traditional medium and coarse-grained cemented carbides, ultra-coarse-grained and extra-coarse-grained cemented carbides have extremely high thermal conductivity, high fracture toughness and red hardness, and are relatively Good thermal fatigue and thermal shock resistance, mainly used for continuous mining of soft rocks under extreme working conditions (such as coal mining, subway and tunnel construction) and continuous operations of modern roads and bridges (such as road digging and paving), Stamping dies, cold heading dies, rolls, etc. that require high toughness, thermal fatigue resistance, and thermal shock resistance have very broad market prospects.

There have been patent reports on the preparation method of ultra-coarse-grained cemented carbide. Such as: a preparation method of ultra-coarse-grained cemented carbide (201010172891.0); ultra-coarse-grained cemented carbide material for picks or road digging teeth and its preparation method (201110136199.7); high-toughness ultra-coarse-grained tungsten-cobalt Preparation method of cemented carbide (201010553047.2), etc. Coarse-grained, ultra-coarse or extra-coarse-grained WC raw materials must be used to prepare ultra-coarse or extra-coarse-grained cemented carbide. Due to the coarse initial grains of WC, the dissolution of WC in the binder metal during sintering usually has a strong energy selectivity, and the bonding between the WC secondary grains formed by precipitation and the coarse initial grains of WC is very prone to weak regions . Therefore, using the existing ultra-coarse-grained cemented carbide preparation process, it is very easy to appear the WC grain fragmentation defect at the WC/binder phase boundary as shown in Figure 1 . This kind of defect is difficult to be observed after corroding the bonding phase; even if only the WC phase is corroded without corroding the bonding phase, it is difficult to be observed under a metallographic microscope. The WC grain fragmentation defect at the WC/binder phase boundary is an important reason for the low strength and wear resistance of the alloy. The existence of this defect will seriously affect the popularization and application of ultra-coarse and ultra-coarse-grained cemented carbide.

There have been patent reports on the preparation method of coated WC-Co composite powder. Such as: preparation method of rare earth modified cobalt-coated tungsten carbide cemented carbide composite powder (201010286211.8). The patented technology is to solve the problems of long time consumption, easy introduction of impurities, and easy segregation of Co in the ball milling process of cemented carbide mixture preparation (ball milling powder mixing). This patented technology uses ethanol as a solvent to prepare composite powder through the aqueous phase reduction reaction of organic matter, and the cost is relatively high. Preparation method of carbide-Co/Ni composite powder and cemented carbide (200910042940.6). This patented technology prepares Co/Ni-coated WC type composite powder through hydrothermal high-pressure hydrogen reduction of cobalt/nickel-ammonia complex solution. The problem to be solved is : To develop the hydrometallurgical preparation process of high-purity MC-Co/Ni composite powder for cemented carbide production without fouling by foreign impurity elements, to replace the traditional MC-Co/Ni mixture wet grinding process, so as to avoid the damage caused by the wet grinding process The problem of excessive crushing of WC particles; on this basis, the preparation of coarse-grained, ultra-coarse-grained, and extra-coarse-grained cemented carbides is solved. The above-mentioned patent technology does not pay attention to the coating state of Co on WC and the physical properties of the Co coating layer, and it is difficult to achieve dense coating of Co on WC.

There are many reports on the preparation of WC-Co composite powder, and the research on coated composite powder is also reported in the literature. The preparation methods of coated composite powder mainly include electroless plating, electroplating, chemical vapor deposition (CVD), Sol-Gel, polyol liquid phase reduction and hydrothermal hydrogen reduction, etc. Methods such as CVD, Sol-Gel, and polyol liquid phase reduction have problems such as high preparation costs. Electroless plating and electroplating have problems such as easy introduction of foreign impurities, and as raw materials for cemented carbide production, they must meet the requirements of high purity. In addition, there are many reports on the precipitation of tungsten-cobalt double salt, the preparation of tungsten-cobalt composite oxide by spray drying, and the preparation of WC-Co composite powder by direct reduction carbonization, but this composite powder is only suitable for the preparation of ultrafine cemented carbide.

The preparation of Co/Ni powder by hydrothermal high-pressure hydrogen reduction of Co/Ni hydroxide slurry (slurry hydrogen reduction) has been reported. Such as: (1) Yu Kening, Mao Minghua, Liang Huanzhen, Xu Ju. Preparation of ultrafine Co powder by hydrogen reduction of cobalt hydroxide alkaline slurry. Chinese Journal of Process Engineering, 2001, 1(1): 62-65. (2) Xu Ju, Yu Kening, Liang Huanzhen, et al. Reaction mechanism of nano-metal nickel powder prepared by nickel hydroxide slurry hydrogen reduction method. Journal of Materials Research, 2002, 16(2): 158-163. In existing reports, catalysts such as noble metals (such as PdCl ₂ ) must be added to carry out the hydrogen reduction reaction.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method to eliminate the phenomenon of WC grain fragmentation at the phase boundary of ultra-coarse and ultra-coarse-grained hard alloys, improve the performance of ultra-coarse and ultra-coarse-grained hard alloys, and improve the compactness of the service life of the alloy. The preparation method of coated composite powder and ultra-coarse and ultra-coarse-grained hard alloy.

In order to solve the above-mentioned technical problems, the preparation method of dense coated composite powder and ultra-coarse and ultra-coarse-grained cemented carbide provided by the present invention is carried out by WC raw material powder containing C content > 6.12% and grain size > 4.5 μm The mechanical activation treatment realizes the activation of WC and the peeling off of the fragile area of WC particles; according to the composition ratio of cemented carbide, the self-catalytic activity and heterogeneous nucleation effect of mechanical activation treatment WC powder can be used without adding sensitizer, Under the condition of activator and catalyst foreign substances, the nano-assembly structure Co/Ni coated WC type composite powder was prepared by hydrothermal high-pressure hydrogen reduction of Co/Ni hydroxide alkaline slurry, and then the composite powder was sintered by nano-diffusion sintering effect. Thermal diffusion homogenization treatment to prepare dense Co/Ni-coated WC type composite powder, using this composite powder as raw material to prepare high-quality ultra-coarse and ultra-coarse-grained cemented carbide; the Co/Ni refers to Co or Ni or Co +Ni.

The mechanical activation treatment of the coated powder: select the WC raw material containing C content > 6.12%, grain size > 4.5 μm as the raw material of ultra-coarse or ultra-coarse grained hard alloy, according to the mass ratio of ball: material 3:1~5:1, mechanically activate the WC raw material powder in the mechanical activation machine for 8h~14h, the material of the grinding ball is WC-Co cemented carbide, and the total carbon content of the composite powder is adjusted by adding W . According to the alloy type, application and carbon content of WC raw material powder, transition metal carbide and W powder are added at the same time when WC powder is mechanically activated. The mechanically activated powder does not need to be graded and sieved, and is directly subjected to subsequent coating treatment. The mechanical activation treatment can realize the activation of WC and the peeling off of the brittle area of WC particles, which is beneficial to the improvement of the coating strength of Co/Ni on WC and the sintering activity of WC.

The preparation of the Co/Ni hydroxide alkaline slurry: Co/Ni chloride or sulfate and NaOH are used as raw materials to prepare through aqueous phase reaction; the reaction temperature is controlled at 60°C to 70°C to improve the reaction form. Nuclear efficiency; according to the size of the reaction volume and the loading capacity of the material, the aqueous solution of Co/Ni salt is added dropwise to the aqueous NaOH solution in the form of a single tube or multiple tubes to control the crystal growth rate of the reaction product Co/Ni hydroxide; using stirring Diffusion and dispersion of cations and reaction products in the solution are realized by means of the method; the molar concentration of (Co/Ni) ²⁺ is 0.5mol/L～1.5mol/L, and the molar concentration of NaOH is 2mol/L～4mol/L; according to NaOH: The (Co/Ni) ²⁺ molar ratio is 95% to 100% of the stoichiometric ratio of 2:1. The addition amount of NaOH is calculated to make the reaction product Co/Ni hydroxide slurry alkaline; Co/Ni salt The amount of NaOH added is adjusted according to the required Co:Ni ratio and the total content of Co/Ni in the composite powder, and the amount of NaOH added is determined accordingly; no other external substances are added during the preparation of Co/Ni hydroxide alkaline slurry. supplies.

The hydrothermal high-pressure hydrogen reduction: add WC powder or WC-based raw material powder and Co/Ni hydroxide alkaline slurry into the high-pressure reactor, and stir the WC or WC-based raw material The powder is suspended in the slurry, and the reduction conditions are as follows: the reaction temperature is 150°C-180°C, the holding time is 2h-8h, and the hydrogen pressure is 2.5MPa-4.5MPa. The reaction process does not add foreign substances such as sensitizers, activators and catalysts.

The thermal diffusion homogenization treatment: After washing, dehydration and drying, the nano-assembled structure Co/Ni coated WC type composite powder is subjected to diffusion homogenization, deoxidation, and residual anion treatment at 600 ° C to 700 ° C in a hydrogen atmosphere , so that the nano-assembly structure Co/Ni coating layer is transformed into a smooth and dense coating layer through the nano-diffusion sintering effect, preventing the nano-assembly structure Co/Ni from falling off during the subsequent mixing of the forming agent and the compacting process, and reducing the composite powder. Improve the wettability of Co/Ni bonding metal to WC in the sintering process of cemented carbide, and realize the regulation of WC dissolution and precipitation behavior in the liquid phase sintering process of WC-Co/Ni alloy.

The preparation of the hard alloy: adding PEG or paraffin wax-based forming agent with a mass ratio of 2.0% to 2.5% to the dense Co/Ni coated WC type composite powder obtained after thermal diffusion homogenization treatment, Dry and granulate the composite powder of the agent, shape the composite powder mixed with the forming agent, and carry out liquid phase sintering in a pressure sintering furnace at 1430 ° C to 1480 ° C.

The preparation method of densely coated composite powder and ultra-coarse and ultra-coarse-grained cemented carbide adopts the above-mentioned technical scheme, and utilizes the self-catalytic activity and non-uniform nucleation effect of mechanically activated WC powder to reduce Co/ The preparation of nano-assembly structure Co/Ni coated WC type composite powder with Ni hydroxide alkaline slurry, and then using the nano-diffusion sintering effect to perform thermal diffusion and homogenization treatment on the composite powder, is a kind of preparation of Co/Ni bonded metal dense package. WC-type composite powder is coated to realize the control of WC dissolution and precipitation behavior in the liquid phase sintering process of WC-Co/Ni alloy, eliminate the phenomenon of WC grain fragmentation at the phase boundary of ultra-coarse and ultra-coarse-grained cemented carbide, and improve the ultra-coarse It is an effective method to improve the performance of Hete coarse-grained cemented carbide products and improve the service life of alloys. Since water is used as the medium in the preparation process of the hydrothermal high-pressure hydrogen reduction coated composite powder, hydrogen is used as the reducing agent, and only a cheap NaOH auxiliary material is added, the method has the remarkable characteristics of low cost and environmental protection.

By selecting the grain size of WC raw materials and adjusting the sintering temperature, this method is also suitable for the preparation of high-quality hard alloys with other grain grades.

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) photograph (1000 times) of the ultra-coarse grain WC-12Ni alloy of 5.8 μm that adopts the alloy crystal grain size that adopts the traditional craft to prepare;

Fig. 2 is the SEM photo (1000 times) of Co-coated WC type WC-12Co composite powder after thermal diffusion homogenization treatment;

Figure 3 is the energy spectrum micro-region component analysis map of the surface of the bright-colored WC particle pointed by the arrow in Figure 2

Fig. 4 is the SEM photo (1000 times) of the ultra-coarse-grained WC-12Co alloy with a grain size of 11.8 μm prepared by the preparation method of the present invention;

Fig. 5 is the SEM photograph (20,000 times) of the metallic Co powder that hydrothermal high pressure hydrogen reduces the cobalt hydroxide basic slurry that contains _PdCl catalyzer

Fig. 6 is the SEM photo (3000 times) of the ultra-coarse-grained WC-12Ni-0.5Cr ₃ C ₂ alloy with a grain size of 7.2 μm prepared by the preparation method of the present invention;

Fig. 7 is a SEM photo (1000 times) of an ultra-coarse-grained WC-6Co-6Ni alloy with a grain size of 6.8 μm prepared by the preparation method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments.

Example 1:

Composite powder is prepared according to WC-12% Co (mass ratio) composition. Choose WC with a C content of 6.13% and a grain size of 6.6 μm as the raw material, add W powder to adjust the total carbon content in the WC-12Co composite to 5.36%, and mix WC and The W powder was subjected to mechanical activation treatment for 8 hours in a mechanical activation machine. Cobalt chloride was dissolved in deionized water at a molar concentration of 1.5 mol/L Co ²⁺ . Calculate the amount of NaOH added based on the 100% addition of NaOH: ^Co molar ratio of 2: 1 stoichiometric ratio, and dissolve NaOH in deionized water at a molar concentration of 2 mol/L. The filtered NaOH solution was transferred to a stirring reaction tank, the temperature of the reaction tank was controlled to be 70°C, and the filtered cobalt chloride solution was added dropwise to the NaOH solution through three pipelines. The reaction product cobalt hydroxide alkaline slurry is transferred to a high-pressure reactor, and at the same time, mechanically activated WC and W powder are added. The hydrothermal high-pressure hydrogen reduction conditions are as follows: reaction temperature 180°C, holding time 2h, hydrogen pressure 3.5MPa, WC+W powder is suspended in the slurry by stirring. The reaction product is washed, dehydrated and dried. The reaction products were observed and analyzed under a scanning electron microscope, and it was found that the nano-assembled structure Co was uniformly coated on the surface of the WC+W powder. Diffusion homogenization, deoxidation, and residual anion removal treatments were performed on the nano-assembly structure Co-coated WC composite powder at 650 °C in a hydrogen atmosphere. The results of chemical analysis showed that the Co content in the composite powder was 11.98%, and the O content was 0.09%. Observing and analyzing the Co-coated WC type composite powder after thermal diffusion homogenization treatment under the scanning electron microscope, it is found that a dense coating layer of Co has formed on the surface of the WC+W powder. Figure 2 is a scanning electron microscope photo of Co-coated WC type composite powder after thermal diffusion homogenization treatment, and Figure 3 is an energy spectrum micro-region component analysis map of the surface of the bright-colored WC particle pointed by the arrow in Figure 2. It can be seen from Figure 3 that the presence of Co was detected on the surface of WC particles. Add 2.5% PEG forming agent to the dense coated WC-12Co composite powder obtained after thermal diffusion homogenization treatment. The dried and granulated mixture is pressed into a B-type strip compact, and the compact is sintered at 1480°C in a 6MPa pressure sintering furnace. The flexural strength test results show that the flexural strength of the alloy is 2360MPa. The grain size of the alloy was measured by Image J image processing software and the line intercept method, and the results showed that the grain size of the alloy was 11.8 μm. Figure 4 is a scanning electron micrograph of the alloy. It can be seen from Figure 4 that there is no WC grain fragmentation defect at the WC/binder phase boundary in the alloy. Using the same hydrothermal high-pressure hydrogen reduction process (reaction temperature 180°C, holding time 2h, hydrogen pressure 3.5MPa), reduce the above-mentioned cobalt hydroxide alkaline slurry mixed with _PdCl2 catalyst in a high-pressure reactor, and obtain the flake The specific surface area of the metal Co powder with the nano-assembled structure is 16.14m ² /g, and the specific surface particle size is 41.8nm. The photo of the powder is shown in FIG. 5 .

Example 2:

The composite powder is prepared according to the composition of WC-12%Ni-0.5%Cr ₃ C ₂ (mass ratio). Choose WC with a C content of 6.13% and a grain size of 6.6 μm as the raw material, add W powder to adjust the total carbon content in the WC-12Ni-0.5Cr ₃ C ₂ composite powder to 5.36%, according to the mass ratio of ball: material WC, Cr ₃ C ₂ and W powder were mechanically activated for 11 hours in a mechanical activation machine at a ratio of 3:1. Dissolve nickel sulfate in deionized water at a molar concentration of 1.0mol/L Ni ²⁺ . According to NaOH:Ni ²⁺ molar ratio is the 95% addition amount of 2:1 stoichiometric ratio to calculate the addition amount of NaOH, by 3mol/L molar concentration NaOH is dissolved in deionized water. The filtered NaOH solution was transferred to a stirred reaction tank, and the temperature of the reaction tank was controlled at 60° C., and the filtered nickel sulfate solution was added dropwise to the NaOH solution through three pipes. Transfer the reaction product nickel hydroxide alkaline slurry to a high pressure reactor, and add mechanically activated WC, Cr ₃ C ₂ and W powder at the same time. The hydrothermal high-pressure hydrogen reduction conditions are as follows: reaction temperature 165°C, holding time 8h, hydrogen pressure 4.5MPa, WC+Cr ₃ C ₂ +W powder is suspended in the slurry by stirring. The reaction product is washed, dehydrated and dried. In a hydrogen atmosphere at 600 ° C, the Ni-coated WC type composite powder was treated for diffusion homogenization, deoxidation, and residual anion removal. The results of chemical analysis show that the Ni content in the composite powder is 11.97%, and the O content is 0.07%. Add 2.5% paraffin wax forming agent to the densely coated WC-12Ni-0.5Cr ₃ C ₂ composite powder obtained after thermal diffusion homogenization treatment. The dried and granulated mixture is pressed into a B-type strip compact, and the compact is sintered at 1440°C in a 6MPa pressure sintering furnace. The flexural strength test results show that the flexural strength of the alloy is 2680MPa. The grain size of the alloy was measured by Image J image processing software and the line intercept method, and the results showed that the grain size of the alloy was 7.2 μm. Figure 6 is a scanning electron micrograph of the alloy. It can be seen from Figure 6 that the microstructure of the alloy is uniform, and there is no WC grain fragmentation defect at the WC/binder phase boundary in the alloy.

Example 3:

Composite powder is prepared according to WC-6%Co-6%Ni (mass ratio) composition. Choose WC with a C content of 6.13% and a grain size of 6.6 μm as the raw material, add W powder to adjust the total carbon content in the WC-6Co-6Ni composite powder to 5.35%, and the mass ratio of balls: materials is 5:1 WC and W powder were mechanically activated in a mechanical activation machine for 14 hours. Dissolve cobalt chloride and nickel chloride in deionized water at a molar concentration of 0.5 mol/L (Co/Ni) ²⁺ . According to the NaOH: (Co/Ni) ²⁺ molar ratio is 2: 1 stoichiometric ratio of 98% of the added amount of NaOH is calculated, according to 4mol/L molar concentration NaOH is dissolved in deionized water. Transfer the filtered NaOH solution into the stirring reaction tank, control the temperature of the reaction tank at 65°C, and drop the filtered cobalt chloride and nickel chloride mixed solution into the NaOH solution through 3 pipes. Transfer the reaction product cobalt and nickel hydroxide slurry to the autoclave, and add the mechanically activated WC and W powder at the same time. The hydrothermal high-pressure hydrogen reduction conditions are as follows: reaction temperature 150°C, holding time 6h, hydrogen pressure 2.5MPa, WC+W raw material powder is suspended in the slurry by stirring. The reaction product is washed, dehydrated and dried. Co and Ni-coated WC type composite powders were subjected to diffusion homogenization, deoxidation, and residual anion removal treatments at 700°C in a hydrogen atmosphere. The results of chemical analysis show that the content of Co in the composite powder is 5.98%, the content of Ni is 5.96%, and the content of O is 0.06%. Add 2.0% PEG forming agent to the densely coated WC-6Co-6Ni composite powder obtained after thermal diffusion homogenization treatment. The dried and granulated mixture is pressed into a B-type strip compact, and the compact is sintered at 1430°C in a 6MPa pressure sintering furnace. The flexural strength test results show that the flexural strength of the alloy is 2720MPa. The grain size of the alloy was measured by Image J image processing software and the line intercept method, and the results showed that the grain size of the alloy was 6.8 μm. Figure 7 is a scanning electron micrograph of the alloy. It can be seen from Figure 7 that the structure of the alloy is uniform, and there is no WC grain fragmentation defect at the WC/binder phase boundary in the alloy.

Claims (8)

1. the preparation method of fine and close cladded type composite powder and ultra thick and extraordinarily thick cemented carbide is characterized in that: through the WC raw material powder that contains C content＞6.12%, grain fineness number＞4.5 μ m being carried out mechanical activation processing realization to the activation of WC and peeling off of WC particle frangible region; Composition proportion according to wimet; Utilize mechanical activation to handle the active and heterogeneous nucleation effect of autocatalysis of WC powder; Under the condition of not adding sensitizing agent, acvator and catalyzer foreign matter; Co/Ni coats WC type composite powder through hydro-thermal High Pressure Hydrogen reduction Co/Ni oxyhydroxide alkalescence pulp preparation nanometer packaging assembly; Utilizing nanometer diffusion-sintering effect that composite powder is carried out the thermodiffusion homogenizing subsequently and handle, prepare fine and close Co/Ni and coat WC type composite powder, is the ultra thick and extraordinarily thick cemented carbide of feedstock production high quality with this composite powder; Described Co/Ni is meant Co or Ni or Co+Ni.

2. the preparation method of fine and close cladded type composite powder according to claim 1 and ultra thick and extraordinarily thick cemented carbide; It is characterized in that: describedly the WC raw material powder is carried out mechanical activation handle and to be meant by ball: the mass ratio of material is 3: 1～5: 1, and the mechanical activation that in the mechanical activation machine, the WC raw material powder is carried out 8h～14h is handled; The mill ball material is the WC-Co wimet; Adopt the mode of adding W to regulate the total carbon content of composite powder; According to the carbon content of alloy species, purposes and WC raw material powder, WC powder is being carried out add transition metal carbides and W powder when mechanical activation is handled simultaneously; The powder of handling through mechanical activation does not need classification processings of sieving, and directly carries out follow-up coating processing.

3. the preparation method of fine and close cladded type composite powder according to claim 1 and 2 and ultra thick and extraordinarily thick cemented carbide; It is characterized in that: described hydro-thermal High Pressure Hydrogen reduction is in autoclave; Adopt alr mode to make WC or be that the raw material powder of main body is suspended in the slurry with WC; Under 2.5MPa～4.5MPa hydrogen pressure,, form nanometer packaging assembly Co/Ni and coat WC type composite powder in 150 ℃～180 ℃ insulation 2h～8h reduction Co/Ni oxyhydroxide alkalescence slurry.

4. the preparation method of fine and close cladded type composite powder according to claim 1 and 2 and ultra thick and extraordinarily thick cemented carbide is characterized in that: the alkaline slurry of described Co/Ni oxyhydroxide is to be that raw material passes through water react and prepares with the muriate of Co/Ni or vitriol and NaOH; Control reaction temperature is 60 ℃～70 ℃, to improve reaction forming core efficient; Adopt the aqueous solution that single tube or multitube form drip Co/Ni salt to the NaOH aqueous solution, according to the tonburden of the size of reaction volume and material with the crystalline growth velocity of control reaction product Co/Ni oxyhydroxide; The diffusion and the dispersion of positively charged ion and reaction product in the employing alr mode realization solution; (Co/Ni) ²⁺Volumetric molar concentration be 0.5mol/L～1.5mol/L, the volumetric molar concentration of NaOH is 2mol/L～4mol/L; Press NaOH: (Co/Ni) ²⁺Mol ratio is the addition that 95%～100% addition of 2: 1 stoichiometric ratios calculates NaOH, makes resultant of reaction Co/Ni hydroxide slurry be alkalescence; The add-on of Co/Ni salt is according to desired Co in the composite powder: Ni regulates than with the Co/Ni total content, and the add-on of NaOH is fixed therefrom.

5. the preparation method of fine and close cladded type composite powder according to claim 3 and ultra thick and extraordinarily thick cemented carbide is characterized in that: the alkaline slurry of described Co/Ni oxyhydroxide is to be that raw material passes through water react and prepares with the muriate of Co/Ni or vitriol and NaOH; Control reaction temperature is 60 ℃～70 ℃, to improve reaction forming core efficient; Adopt the aqueous solution that single tube or multitube form drip Co/Ni salt to the NaOH aqueous solution, according to the tonburden of the size of reaction volume and material with the crystalline growth velocity of control reaction product Co/Ni oxyhydroxide; The diffusion and the dispersion of positively charged ion and reaction product in the employing alr mode realization solution; (Co/Ni) ²⁺Volumetric molar concentration be 0.5mol/L～1.5mol/L, the volumetric molar concentration of NaOH is 2mol/L～4mol/L; Press NaOH: (Co/Ni) ²⁺Mol ratio is the addition that 95%～100% addition of 2: 1 stoichiometric ratios calculates NaOH, makes resultant of reaction Co/Ni hydroxide slurry be alkalescence; The add-on of Co/Ni salt is according to desired Co in the composite powder: Ni regulates than with the Co/Ni total content, and the add-on of NaOH is fixed therefrom.

6. the preparation method of fine and close cladded type composite powder according to claim 1 and 2 and ultra thick and extraordinarily thick cemented carbide is characterized in that: said thermodiffusion homogenizing is handled and is meant nanometer packaging assembly Co/Ni coating WC type composite powder after washing, dehydrate processing is carried out even diffusedization, deoxidation, takes off remaining anionic treatments in 600 ℃～700 ℃ in hydrogen atmosphere.

7. the preparation method of fine and close cladded type composite powder according to claim 3 and ultra thick and extraordinarily thick cemented carbide is characterized in that: said thermodiffusion homogenizing is handled and is meant nanometer packaging assembly Co/Ni coating WC type composite powder after washing, dehydrate processing is carried out even diffusedization, deoxidation, takes off remaining anionic treatments in 600 ℃～700 ℃ in hydrogen atmosphere.

8. the preparation method of fine and close cladded type composite powder according to claim 1 and 2 and ultra thick and extraordinarily thick cemented carbide; It is characterized in that: the adding mass ratio is 2.0%～2.5% PEG or paraffinic base binder in the fine and close Co/Ni coating WC type composite powder that after the thermodiffusion homogenizing is handled, obtains; Composite powder to mixing binder carries out drying and granulating; The composite powder that mixes binder is formed, and in pressure sintering furnace, carry out liquid phase sintering in 1430 ℃～1480 ℃.

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