Chemical enhanced shear thickening polishing solution suitable for WC-Co alloy and polishing method

Abstract

The invention discloses a chemically enhanced shear thickening polishing solution suitable for a WC-Co alloy and a polishing method, and aims to solve the problem of loss of a Co phase on the surface of the WC-Co alloy in a traditional polishing method. The polishing solution comprises K3 [Fe (CN) 6], KOH, diamond abrasive particles, dispersed phase particles and deionized water, a WC phase and a Co phase of a WC-Co alloy react with [Fe (CN) 6] 3 <-> and OH <-> in the polishing solution respectively, and a soft oxidation film WO3-x and a stable Co3O4 oxidation film are generated on the surface of the alloy. Through the shear thickening effect, the polishing solution forms a particle cluster wrapping the abrasive particles when the relative speed reaches a threshold value, a surface oxidation film is removed through the micro-cutting effect of the diamond abrasive particles, and efficient, high-quality and Co-loss-free WC-Co alloy surface polishing is achieved. The method obviously inhibits the loss of the Co phase at the same time, maintains the hardness and the use performance of the alloy surface, and is especially suitable for precision machining of the hard alloy blade.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultra-precision polishing processing, and particularly relates to a chemical enhanced shear thickening polishing liquid suitable for WC-Co alloy and a polishing method. BACKGROUND

[0002] Surface coating treatment can effectively improve the mechanical and tribological properties of the tool and prolong the service life of the tool. Before coating, the tool substrate surface needs to be polished to obtain higher surface quality and improve the adhesion between the coating and the substrate.

[0003] WC-Co alloy (tungsten carbide-cobalt alloy) is a typical hard alloy material that is difficult to polish. In the prior art, chemical enhanced shear thickening polishing is used for efficient polishing of WC-Co alloy blades with complex shapes. For example, in the existing paper "Mechanism of material removal in tungsten carbide-cobalt alloy during chemistry enhanced shear thickening polishing", Fenton reagent with the highest corrosion potential is added to the polishing liquid to prepare a shear thickening polishing liquid with high removal efficiency. However, Fenton reagent not only reacts with WC, but also reacts with Co (and preferentially reacts with Co), which causes Co to be lost on the surface of the polished WC-Co alloy, resulting in a significant decrease in the surface hardness of the hard alloy, affecting the performance of the tool, especially micro-drills made of hard alloy. Low surface Co content makes the micro-drill more prone to breakage.

[0004] In order to overcome the problem of Co loss, Chinese patent application CN116770409A provides a high-efficiency electrolytic force rheological passivation polishing liquid and passivation polishing method for inhibiting Co loss. The method uses a Co loss inhibitor and controls the electrolysis voltage to inhibit the preferential electrolysis of Co and the chemical reaction of Co during electrolysis. However, the process of this method is relatively complex. On the one hand, the generation and removal of the oxide film of WC phase are achieved through electrolysis reaction. In addition, the polishing liquid contains a large amount of chemical reagents, making it very difficult to prepare the polishing liquid. The inhibiting effect of Co is achieved by coating the Co with insulating nano-magnetic powder. However, during the polishing process, part of the coating layer is easily removed by shear thickening polishing, exposing the Co to the electrolyte, and eventually causing Co loss on the surface of the hard alloy due to electrolysis reaction. This does not completely solve the problem of Co loss inhibition.

[0005] Therefore, there is an urgent need to develop a new shear thickening polishing liquid and polishing method for WC-Co alloy to achieve high-efficiency and high-quality surface without loss of surface Co content. SUMMARY

[0006] The present application aims at the defects and deficiencies of the prior art, and provides a chemical enhanced shear thickening polishing liquid for WC-Co alloy with Co loss inhibition effect and a polishing method.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the technical scheme as follows: The present application provides a chemical enhanced shear thickening polishing liquid for WC-Co alloy, raw materials of which include K3[Fe(CN)6], KOH, diamond abrasive particles, dispersed phase particles and deionized water. 3- and OH - react to generate soft oxide film WO 3-x and stable Co3O4 oxide film, respectively, and the generated oxide film is removed by shear thickening to achieve efficient polishing of the surface of WC-Co alloy.

[0008] According to the above scheme, the mass ratio of K3[Fe(CN)6] to KOH is 1:1; the particle size of the diamond abrasive particles is #3000-#8000; the dispersed phase particles are selected from polyhydroxy polymers, the particle size of the dispersed phase particles is 5-30 microns, the polyhydroxy polymer is a micron-level material that is degradable and can stably form shear thickening effect of non-Newtonian fluid with deionized water; the content of K3[Fe(CN)6] is 0.25-1.25 wt.%, the content of diamond abrasive particles is 2-9 wt.%, the content of dispersed phase particles is 45-60 wt.%, and the balance is deionized water.

[0009] According to the above scheme, the preparation process of the chemical enhanced shear thickening polishing liquid for WC-Co alloy includes the following steps: 1) adding deionized water and diamond abrasive particles into a batching cylinder; 2) adding all KOH solids into the batching cylinder and stirring for 5-10 min until all KOH solids are completely dissolved and the diamond abrasive particles are uniformly dispersed in the solution; 3) adding K3[Fe(CN)6] solid particles with the same mass into the batching cylinder and stirring for 5-10 min until complete dissolution; 4) adding the dispersed phase particles in small amounts and multiple times into the batching cylinder and stirring for 5-10 min until uniform mixing.

[0010] The present application also provides a polishing method using the chemical enhanced shear thickening polishing liquid for WC-Co alloy, and the chemical reaction equation involved in the polishing method is: WC+OH - +[Fe(CN)6]3- → WO 3-x + CO↑ + [Fe(CN)6] 4- ; 3Co + 8[Fe(CN)6] 3- + 8OH - → Co3O4 + 8[Fe(CN)6] 4- + 4H2O; wherein x = 0 ~ 1 in the above chemical reaction equation.

[0011] The specific chemical enhanced shear thickening polishing principle is as follows: in the polishing process, the WC phase and the Co phase in the WC-Co alloy respectively react with [Fe(CN)6] 3- and OH - in the polishing liquid to respectively generate soft oxide films WO 3-x (x = 0 ~ 1) and Co3O4 on the surface of the WC-Co alloy. The C atoms in the WC lattice are oxidized into CO gas, resulting in the formation of bubbles and pores on the surface of the WC-Co alloy, increasing the surface area and accelerating the corrosion process, until the WC phase surface is completely covered by the WO 3-x oxide film. The Co3O4 oxide film is relatively stable under alkaline conditions and is not easily dissolved, so that the Co phase in the WC-Co alloy is retained on the surface under the isolation of the Co3O4 oxide film. Since the WC phase has a higher reaction rate than the Co phase, the Co concentration on the surface of the WC-Co alloy after corrosion increases. The two oxide films generated subsequently inhibit the further progress of the reaction. When the relative speed of the polishing area of the polishing liquid and the WC-Co alloy workpiece reaches a threshold value, the polishing liquid produces a shear thickening phenomenon, forming a large number of particle clusters wrapped around diamond abrasive grains. Through the micro-cutting action of the diamond abrasive grains in the particle clusters, the soft oxide film WO 3-x and the stable Co3O4 oxide film and the excess Co phase on the surface of the WC-Co alloy workpiece are removed. When the oxide film and the excess Co phase are removed by the abrasive grains, the new substrate is exposed and participates in the new chemical reaction. Through the continuous balance of oxide film generation and oxide film shear thickening polishing, the ultra-precision surface processing of the WC-Co alloy workpiece is realized.

[0012] According to the above scheme, the polishing method comprises the following steps: 1) configuring the chemical enhanced shear thickening polishing liquid suitable for the WC-Co alloy and adding it to the polishing tank; 2) mounting the WC-Co alloy workpiece on the workpiece shaft of the shear thickening polishing device; 3) adjusting the polishing position of the WC-Co alloy workpiece so that the WC-Co alloy workpiece is immersed in the polishing liquid and the included angle between the WC-Co alloy workpiece and the horizontal line is 2 ~ 6°.

[0013] 4) Start the device, make the workpiece shaft rotate to drive the WC-Co alloy workpiece to rotate forward, at the same time, the polishing tank rotates in the opposite direction, the polishing liquid generates relative shearing with the WC-Co alloy workpiece due to inertia, and high-efficiency and high-quality polishing of the surface of the WC-Co alloy workpiece is realized.

[0014] The beneficial effects of the present application are: The present application introduces K3[Fe(CN)6] and KOH as core reaction components for the chemical enhanced shear thickening polishing liquid suitable for WC-Co alloy. The system can precisely control the oxidation process of WC phase and Co phase through synergistic effect, and in-situ generates an oxidation film (WO 3-x and Co3O4) with excellent removability on the alloy surface. 3-x During the polishing process, the oxidation film (WO 3-x and Co3O4) can be efficiently and selectively removed by the shear thickening polishing liquid, so as to realize the chemical mechanical polishing of the WC-Co alloy.

[0015] Especially crucially, the Co3O4 oxidation film shows excellent chemical stability in an alkaline environment and can effectively block the erosion of corrosive media. This property enables the Co phase in the WC-Co alloy to be completely retained on the surface, thereby significantly inhibiting the loss of Co element. Through the technical scheme, not only high-precision polishing is realized, but also the mechanical properties of the WC-Co alloy are fundamentally guaranteed, thereby providing an efficient and reliable solution for the ultra-precision machining of the hard alloy workpiece. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of the polishing of a workpiece by the chemical enhanced shear thickening polishing liquid suitable for WC-Co alloy of the present application; Figure 2 is a polishing principle diagram of the chemical enhanced shear thickening polishing liquid suitable for WC-Co alloy of the present application; Figure 3 is a pure chemical corrosion principle diagram of the WC-Co alloy of the present application; Figure 4 is a surface morphology and roughness change diagram of the WC-Co alloy workpiece after polishing by the polishing liquid of Example 1 and Comparative Examples 1-2; Figure 5 is a SEM and EDS diagram of the WC-Co alloy workpiece after polishing by the polishing liquid of Example 1 and Comparative Examples 1-2.

[0017] In the figure: 1-polishing tank; 2-workpiece shaft; 3-WC-Co alloy workpiece; 4-chemical enhanced shear thickening polishing liquid; 5-main drive shaft; 6-Co3O4 oxidation film; 7-diamond abrasive particles; 8-dispersed phase particles; 9-particle clusters; 10-WO 3-x oxidation film; 31-Co phase; 32-WC phase. DETAILED DESCRIPTION

[0018] The technical solutions of the present application are further specifically described below through specific examples and comparative examples.

[0019] Example 1 (see Figures 1-3 ) This example is a chemical enhanced shear thickening polishing solution suitable for WC-Co alloy, diamond abrasive particles are selected as #5000, and the dispersing phase particles are selected as polyhydroxy polymers with a particle size of 5-30 microns. The mass percentages of the raw materials are shown in Table 1.

[0020] Table 1 Batch parameters Values Abrasive grain concentration 3 wt.% [K3[Fe(CN)6]] 0.5 wt.% KOH 0.5 wt.% Dispersed phase particles 53 wt.% Deionized water 43 wt.% The preparation process of the chemical enhanced shear thickening polishing solution suitable for WC-Co alloy described in this example includes the following steps: 1) Add deionized water and diamond abrasive particles to the batching cylinder; 2) Add all KOH solids to the batching cylinder and stir for 5-10 min until all KOH solids are completely dissolved and the diamond abrasive particles are uniformly dispersed in the solution; 3) Add the same mass of K3[Fe(CN)6] solid particles to the batching cylinder and stir for 5-10 min until complete dissolution; 4) Add the dispersing phase particles in small amounts and multiple times to the batching cylinder and stir for 5-10 min until uniform mixing, and finally obtain the polishing solution.

[0021] The polishing solution of this example is used for polishing processing of WC-Co alloy workpieces, and the polishing parameters are shown in Table 2.

[0022] Table 2 Polishing parameters Values Workpiece shaft tilt angle 4° Polishing bath rotation speed 80 rpm Workpiece shaft rotation speed 15 rpm Polishing time 35 min The specific workpiece polishing processing is shown in Figure 1 , and the workpiece is a WC-Co alloy workpiece 3 composed of a WC phase 32 and a Co phase 31. The shear thickening polishing device used for processing includes a polishing tank 1, a workpiece shaft 2, and a main drive shaft 5. The main drive shaft 5 is arranged below the polishing tank 1 to drive the polishing tank 1 to rotate, and the workpiece shaft 2 is arranged inside the polishing tank 1. The detailed polishing processing steps include: 1) Configure the chemical enhanced shear thickening polishing solution 4 suitable for WC-Co alloy described in Example 1 and add it to the polishing tank 1; 2) Install the WC-Co alloy workpiece 3 on the workpiece shaft 2 of the shear thickening polishing device; 3) Adjust the polishing position of the WC-Co alloy workpiece so that the WC-Co alloy workpiece is immersed in the polishing solution, and the included angle between the WC-Co alloy workpiece and the horizontal line is 4°.

[0023] 4) Start the device to rotate the workpiece shaft 2 to rotate the WC-Co alloy workpiece 3, at the same time, the polishing tank 1 rotates in the opposite direction, the polishing liquid generates relative shear with the WC-Co alloy workpiece 3 due to inertia, and high-efficiency and high-quality polishing of the surface of the WC-Co alloy workpiece 3 is realized.

[0024] Comparative Example 1 The comparative example is a shear thickening polishing liquid, diamond abrasive grains #5000 are selected, and the dispersed phase particles are selected to be polyhydroxy polymers with a particle size of 5-30 microns, and the mass percentages of the raw materials are shown in Table 3.

[0025] Table 3 Batch parameters Values Abrasive grain concentration 3 wt.% Dispersed phase particles 53 wt.% Deionized water 44 wt.% The preparation steps of the comparative example are basically the same, except that the addition steps of KOH and K3[Fe(CN)6] are not included.

[0026] The polishing parameters and polishing steps for polishing by using the comparative example are the same as those of Example 1, and are not described in detail here.

[0027] Comparative Example 2 The comparative example is a shear thickening polishing liquid based on Fenton reaction, diamond abrasive grains #5000 are selected, and the dispersed phase particles are selected to be polyhydroxy polymers with a particle size of 5-30 microns, and the mass percentages of the raw materials are shown in Table 3.

[0028] Table 3 Batch parameters Values Abrasive grain concentration 3 wt.% FeSO4 0.6 wt.% H2O2 0.1 wt.% Dispersed phase particles 53 wt.% Deionized water 43.3 wt.% The preparation steps of the comparative example include: 1) Fenton solution is prepared according to the mass percentages of FeSO4 and H2O2 above; 2) The remaining deionized water is added to the batching cylinder, and the dispersed phase particles are added to the batching cylinder in small amounts and multiple times, and stirred for 5-10 min until mixed uniformly; 3) The prepared Fenton solution is added to the batching cylinder, and stirred for 5-10 min until mixed uniformly; 4) Finally, diamond abrasive grains are added and stirred uniformly to obtain the polishing liquid.

[0029] The polishing parameters and polishing steps for polishing by using the comparative example are the same as those of Example 1, and are not described in detail here.

[0030] As Figure 4As shown, the surface roughness of the WC-Co alloy workpiece after treatment with three different polishing liquids (Comparative Example 1: shear thickening polishing liquid; Comparative Example 2: shear thickening polishing liquid based on Fenton reaction; Example 1: polishing liquid of the present application) presents significant differences. Example 1 exhibits excellent polishing performance, with the surface roughness Sa value significantly reduced from the initial 306.73 ± 25 nm to 2.36 ± 0.16 nm, with lower surface roughness than existing methods (shear thickening polishing and shear thickening polishing based on Fenton reaction). More notably, the polishing efficiency of Example 1 is significantly improved, with the surface roughness reduced to below Sa 10 nm in only 15 minutes, while completely eliminating scratches.

[0031] Figure 5 The SEM and EDS images reveal the effect of polishing treatment on the microstructure of the surface of the WC-Co alloy. All workpieces present a typical composite structure composed of WC particles and Co binder, but obvious gaps between WC particles are observed in the workpiece treated with the shear thickening polishing liquid based on Fenton reaction (Comparative Example 2), indicating that the surface layer of Co metal is selectively removed. This phenomenon is further confirmed by the Co element distribution map (yellow area): the Co element distribution on the surface of the workpiece of Comparative Example 2 is significantly reduced.

[0032] The specific content changes of each element after polishing are shown in Table Four, and the data in Table Four shows that although the polishing method based on Fenton reaction can effectively reduce the surface roughness and eliminate scratches, it is accompanied by obvious Co loss problems. In contrast, the Co content of the workpiece treated with the polishing liquid of the present application (Example 1) is stably maintained at 11 wt.%, which is comparable to the workpiece treated with the shear thickening polishing liquid (Comparative Example 1), indicating that it effectively avoids the excessive loss of Co elements while achieving efficient polishing.

[0033] Table Four Element changes on the surface of the polished WC-Co alloy workpiece Elements Co (wt. %) W (wt. %) C (wt. %) Comparative Example 1 11.91 81.24 6.85 Comparative Example 2 0.23 92.60 7.17 Example 1 11.06 81.56 7.38 The above analysis results show that polishing the WC-Co alloy with the polishing liquid of the present application can inhibit the loss of Co content on the surface of the workpiece while ensuring the polishing efficiency and quality. The high-efficiency, high-quality and non-damaging surface quality requirements of the WC-Co alloy material are achieved.

[0034] The above description is only the preferred embodiment of the present application, so equivalent changes or modifications made to the structure, features and principles described in the scope of the present patent application are included in the scope of the present patent application.

Claims

1. A chemical reinforced shear thickening polishing fluid suitable for WC-Co alloys, characterized in that, The raw materials include K3[Fe(CN)6], KOH, diamond abrasive particles, dispersed phase particles and deionized water.

2. The chemically fortified shear thickening polishing fluid for WC-Co alloys according to claim 1, characterized in that, The mass ratio of the K3[Fe(CN)6] to KOH is 1:

1.

3. The chemically fortified shear thickening polishing fluid for WC-Co alloys according to claim 1, characterized in that, The particle size of the diamond abrasive particles is #3000-#8000.

4. The chemically fortified shear thickening polishing fluid for WC-Co alloys according to claim 1, characterized in that, The dispersed phase particles are selected from polyhydroxy polymers.

5. The chemically fortified shear thickening polishing fluid for WC-Co alloys according to claim 2, wherein The K3[Fe(CN)6] is 0.25-1.25 wt.%, the diamond abrasive particles are 2-9 wt.%, the dispersed phase particles are 45-60 wt.%, and the balance is deionized water.

6. The chemically fortified shear thickening polishing fluid for WC-Co alloys according to claim 1, wherein The preparation process includes the following steps: 1) adding deionized water and diamond abrasive particles into a batching cylinder; 2) adding all KOH solids into the batching cylinder and stirring for 5-10 min until all KOH solids are completely dissolved and the diamond abrasive particles are uniformly dispersed in the solution; 3) adding K3[Fe(CN)6] solid particles of the same mass into the batching cylinder and stirring for 5-10 min until complete dissolution; 4) adding the dispersed phase particles in small amounts and multiple times into the batching cylinder and stirring for 5-10 min until uniform mixing.

7. A polishing method using the chemical reinforced shear thickening polishing liquid of the WC-Co alloy according to any one of claims 1 to 6, characterized by, The chemical reaction equation involved in the polishing method is: WC + OH - +[Fe(CN)6] 3- → WO 3-x + CO↑ + [Fe(CN)6] 4- ; 3Co+8[Fe(CN)6] 3- +8OH - →Co3O4+8[Fe(CN)6] 4- +4H2O; wherein x=0-1 in the above chemical reaction equation.

8. The polishing method according to claim 7, wherein The method includes the following steps: 1) configuring the chemical reinforced shear thickening polishing liquid suitable for WC-Co alloy and adding it into a polishing tank; 2) mounting the WC-Co alloy workpiece on a workpiece shaft of a shear thickening polishing device; 3) adjusting the polishing position of the WC-Co alloy workpiece so that the WC-Co alloy workpiece is immersed in the polishing liquid and the included angle between the WC-Co alloy workpiece and the horizontal line is 2-6°; 4) starting the equipment to rotate the workpiece shaft to drive the WC-Co alloy workpiece to rotate in the forward direction, while the polishing tank rotates in the reverse direction, and the polishing liquid generates relative shear with the WC-Co alloy workpiece due to inertia, thereby achieving efficient and high-quality polishing of the surface of the WC-Co alloy workpiece.

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