A sintering anti-sticking coating for cemented carbide and its preparation method and application

Abstract

The present application belongs to the field of coating, and relates to a hard alloy sintering anti-sticking coating and a sintering device, and a preparation method and application thereof. The hard alloy sintering anti-sticking coating contains a graphite material, carbon black, a silicate mineral, a dispersion medium and a solvent, and the silicate mineral contains more than 50 wt% of one-dimensional structure silicate. The hard alloy sintering anti-sticking coating provided by the present application has good stability and is beneficial to the improvement of the insulation effect of the coating.

Description

Technical Field

[0001] This invention belongs to the field of coatings, specifically relating to a cemented carbide sintering anti-stick coating, its preparation method, sintering device, and its application. Background Technology

[0002] Cemented carbide is an alloy composite material formed by powder metallurgy sintering using refractory metal carbides (such as tungsten carbide) as the hard phase and metal binders (such as cobalt, nickel, and iron) as the binder phase. During the sintering process, cemented carbide requires the use of anti-stick coatings to ensure that it does not react with the graphite support plate, thus preventing performance degradation and "sticking" phenomena.

[0003] Existing anti-stick coatings mainly contain carbon materials, inorganic particles, additives, and solvents. The carbon materials primarily provide a carbon atmosphere and enhance the adhesion strength between the coating and the graphite substrate; these can be graphite and / or carbon black. The inorganic particles mainly act as a barrier, and can be silicon dioxide, zirconium oxide, alumina, etc. The additives mainly increase the stability and adhesion of the coating, and can be organic thickeners, surfactants, etc.

[0004] Because of the significant difference in specific gravity between carbon materials, especially graphite, and inorganic particles, coatings are prone to phase separation during storage, making it difficult to form a stable system in aqueous solutions. This leads to easy sedimentation, affecting application and coating uniformity. To achieve a stable, non-stick coating while maintaining good dispersibility between carbon materials and inorganic particles, large amounts of organic thickeners, such as methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, and carboxymethylcellulose, are added as additives. However, this can cause the coating to deteriorate easily during storage, lead to the decomposition of large amounts of organic debris during sintering, and cause unpredictable side reactions with the cemented carbide surface under high temperatures, resulting in reduced mechanical strength and deformation of the cemented carbide parts. Furthermore, excessive use of organic thickeners can increase coating shrinkage during sintering, causing layer cracking and even peeling, significantly reducing coating adhesion strength and thus reducing the barrier effect. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing cemented carbide sintering anti-stick coatings, such as poor stability and poor barrier effect of the coatings formed by them, and to provide a cemented carbide sintering anti-stick coating with good stability and a sintering device, as well as its preparation method and application.

[0006] Specifically, the present invention provides a cemented carbide sintering anti-stick coating, wherein the cemented carbide sintering anti-stick coating contains graphite material, carbon black, silicate minerals, dispersion medium and solvent, wherein the silicate minerals contain more than 50 wt% one-dimensional silicate.

[0007] The present invention also provides a method for preparing the hard alloy sintering anti-stick coating, the method comprising uniformly mixing graphite material, carbon black, silicate minerals, dispersion medium and solvent.

[0008] The present invention also provides a firing device, the surface of which has an anti-stick coating formed by the above-mentioned hard alloy sintering anti-stick coating.

[0009] Furthermore, the present invention also provides the application of the aforementioned sintering device in the sintering of cemented carbide.

[0010] The key to this invention lies in using one-dimensional silicates as inorganic additives. The filamentous structure of one-dimensional silicates not only imparts thickening properties and improves the stability of coatings while reducing or avoiding the use of organic thickeners, but also enhances the film-forming properties of the coatings. At the same time, during the high-temperature sintering process, these silicates also generate submicron silicon carbide whiskers, as well as alumina and silica particles in situ. Among them, silicon carbide whiskers can act as a support and film binder, which can alleviate the direct reaction between the alloy and carbon in the coating. Meanwhile, silicon carbide, alumina, and silica are all inorganic insulating materials. The in-situ generation of metal oxide particles can improve the adhesion strength between the coating and the graphite substrate, and enhance the insulating properties of the coating.

[0011] In a preferred embodiment, the graphite material is a graphite composite material, comprising graphite and inorganic particles coupled to the graphite surface via an organic coupling agent, wherein the organic coupling agent is a fatty acid and / or aliphatic amine. After in-depth and extensive research, the inventors of this invention discovered that modifying graphite with inorganic particles using fatty acids and aliphatic amines (two specific organic coupling agents) before compounding it with other raw materials results in a cemented carbide sintering anti-stick coating with better stability. The reason for this is speculated to be that fatty acids and aliphatic amines can couple inorganic particles to the surrounding graphite, causing the inorganic particles to adhere to the graphite surface rather than be essentially isolated and suspended in the solution. The resulting graphite composite material particles form an organic whole, and the specific gravity of different graphite composite material particles is similar, making them less prone to sedimentation, thereby imparting better stability to the cemented carbide sintering anti-stick coating. Furthermore, since the use of fatty acids and / or fatty amines fundamentally endows the cemented carbide sintering anti-stick coating with good stability, the amount of thickener used is reduced or avoided, thus avoiding the adverse effects of excessive use of thickener on the mechanical strength, deformation, and yield of cemented carbide parts. Attached Figure Description

[0012] Figure 1 Here is a SEM image of the surface of the cemented carbide sintered anti-stick coating obtained in Example 1 after film formation;

[0013] Figure 2 This is a cross-sectional SEM image of the cemented carbide sintered anti-stick coating obtained in Example 1 after film formation;

[0014] Figure 3 A view of the surface of a graphite plate coated with the cemented carbide sintered anti-stick coating of Example 1;

[0015] Figure 4 A view of the sintered surface of a graphite plate coated with the cemented carbide sintering anti-stick coating of Example 1;

[0016] Figure 5 A surface view of a cemented carbide part after sintering, which is coated with the cemented carbide sintering anti-stick coating of Example 1.

[0017] Figure 6 This is a scanning electron microscope (SEM) image of the surface of the graphite / zirconia composite material obtained in Example 4;

[0018] Figure 7 SEM image of the surface of the cemented carbide sintered anti-stick coating obtained in Example 4;

[0019] Figure 8 SEM image of the cross section of the cemented carbide sintered anti-stick coating obtained in Example 4;

[0020] Figure 9 This is a schematic diagram illustrating the mechanism of action of the cemented carbide sintering anti-stick coating provided by the present invention. Detailed Implementation

[0021] The cemented carbide sintering anti-sticking coating provided by this invention contains graphite material, carbon black, silicate minerals, dispersion medium, and solvent. Specifically, based on the total weight of the cemented carbide sintering anti-sticking coating, the content of the graphite material is preferably 5-30%, such as 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any value between them; the content of the carbon black is preferably 2-20%, such as 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, or any value between them; the silicate minerals... The mineral content is preferably 1-12%, such as 1%, 2%, 4%, 6%, 8%, 10%, 12% or any value therein; the dispersion medium content is preferably 0.5-10%, such as 0.5%, 2%, 5%, 8%, 10% or any value therein; the solvent content is preferably 50-85%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or any value therein.

[0022] In this invention, the silicate mineral contains at least a one-dimensional silicate structure. For example... Figure 9As shown, during high-temperature sintering, one-dimensional silicates generate submicron-sized silicon carbide whiskers, alumina, and silica particles in situ. The silicon carbide whiskers act as a support and film binder, mitigating the direct reaction between the alloy and carbon in the coating. Simultaneously, silicon carbide, alumina, and silica are all inorganic insulating materials, which enhance the coating's insulating effect. Besides one-dimensional silicates, the silicate minerals may also contain silicates with other structures, such as layered silicates, island silicates, and cyclic silicates. The proportion of one-dimensional silicates in the silicate minerals is not less than 50 wt% (e.g., 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 100 wt%, or any value between them), more preferably 100 wt%. The aspect ratio of the one-dimensional silicate is preferably 2.5:1 or higher, more preferably (2.5 to 400):1, such as 2.5:1, 4:1, 5:1, 7:1, 10:1, 30:1, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1 or any value between them. The length of the one-dimensional silicate is preferably 500 nm to 200,000 nm, such as 500 nm, 1000 nm, 2000 nm, 5000 nm, 8000 nm, 10000 nm, 15000 nm, 20000 nm or any value between them. The one-dimensional silicate is preferably selected from at least one of halloysite, attapulgite, and sepiolite. The one-dimensional silicate can be a natural silicate mineral or a modified silicate mineral obtained by acid washing, proton exchange, or ion exchange.

[0023] In this invention, the graphite material can be unmodified graphite or modified graphite, such as at least one of natural graphite, flake graphite and expanded graphite.

[0024] In a preferred embodiment, the graphite material is a graphite composite material, comprising graphite and inorganic particles coupled to the graphite surface via an organic coupling agent, wherein the organic coupling agent is a fatty acid and / or a fatty amine. The fatty acid may be a saturated fatty acid, an unsaturated fatty acid, or a mixture of both, preferably C2-C4. 20 saturated fatty acids and / or C2-C 20 Unsaturated fatty acids. The C2-C... 20 Specific examples of saturated fatty acids include, but are not limited to, at least one of: butyric acid, hexanoic acid, caprylic acid, capric acid, lauric acid (dorsodic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), stearic acid (octadecanoic acid), and arachidic acid (eicosanoic acid). The C2-C 20Specific examples of unsaturated fatty acids include, but are not limited to, at least one of oleic acid, linoleic acid, and linolenic acid. That is, the fatty acid is preferably selected from at least one of oleic acid, linoleic acid, linolenic acid, butyric acid, hexanoic acid, caprylic acid, caprylic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid. From the perspective of readily available raw materials, the fatty acid is more preferably selected from at least one of oleic acid, linoleic acid, linolenic acid, caprylic acid, and caprylic acid. The fatty amine can be a short-chain fatty amine, a long-chain fatty amine, or a mixture of both, preferably C8-C9. 10 Short-chain fatty amines and / or C 11 ~C 22 Long-chain fatty amines. The C8-C8... 10 Specific examples of short-chain fatty amines include, but are not limited to, at least one of octylamine, nonylamine, decylamine, and 1,10-decanediamine. The C 11 ~C 22 Specific examples of long-chain fatty amines include, but are not limited to, at least one of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine. That is, the fatty amine is preferably selected from at least one of octylamine, nonylamine, decylamine, 1,10-decanediamine, dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine, and from the perspective of the availability of raw materials, the fatty amine is more preferably octylamine and / or dodecylamine.

[0025] In this invention, the preferred mass ratio of graphite to inorganic particles in the graphite composite material is 100:(50-150), such as 100:50, 100:60, 100:70, 100:80, 100:90, 100:100, 100:110, 100:120, 100:130, 100:140, 100:150, or any value between them. The preferred content of the organic coupling agent in the graphite composite material is 0.1% to 10% of the mass of the inorganic particles, such as 0.1%, 2%, 4%, 6%, 8%, 10%, or any value between them.

[0026] In this invention, the graphite composite material can be obtained by ball milling graphite, an organic coupling agent, and inorganic particles in the presence of a solvent. The ball milling conditions preferably include a temperature of 20–40°C, such as 20°C, 22°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, or any value between them; and a time preferably of 1–10 hours, such as 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or any value between them. Furthermore, the graphite composite material can be directly mixed uniformly with other components to obtain a cemented carbide sintering anti-stick coating, or the solvent can be removed before uniform mixing with other components to obtain a cemented carbide sintering anti-stick coating. The solvent removal method can be, for example, natural air drying, forced-air drying, or oven drying.

[0027] In this invention, the average particle size of the carbon black is preferably 20nm to 500nm, such as 20nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm or any value between them.

[0028] In this invention, specific examples of the inorganic particles include, but are not limited to, at least one of silicon oxide, zirconium oxide, aluminum oxide, calcium fluoride, titanium dioxide, magnesium oxide, and rare earth oxides. The rare earth elements in the rare earth oxides can be the 15 lanthanide elements with atomic numbers 57-71 in the periodic table, as well as scandium (Sc) and yttrium (Y), which have similar chemical properties to the lanthanides. Specific examples of the lanthanides include, but are not limited to, at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Furthermore, the average particle size of the inorganic particles is preferably 50 to 10000 nm, such as 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 500 nm, 1000 nm, 2000 nm, 5000 nm, 10000 nm or any value between them.

[0029] In this invention, specific examples of the dispersion medium include, but are not limited to, at least one of: polyoxyethylene fatty alcohol ether, alkylphenol polyoxyethylene ether, sorbitan fatty acid ester, sorbitan fatty acid ester-ethylene oxide condensate, ethylene oxide-propylene oxide copolymer, polyethylene glycol, polyvinylpyrrolidone, polydimethylsiloxane, polyether-modified organosiloxane, polyester-modified organosiloxane, alkyl-modified organosiloxane, and polyacrylic acid. The polyoxyethylene fatty alcohol ether may, for example, be at least one of O-3, O-8, O-9, O-10, O-15, O-20, O-25, O-30, and O-35. The alkylphenol polyoxyethylene ether may, for example, be at least one of octylphenol polyoxyethylene ether (OP, such as at least one of OP-4, OP-7, OP-10, OP-15, and OP-20) and / or nonylphenol polyoxyethylene ether. ( TX-10). The sorbitan fatty acid ester may be, for example, at least one of Span-20, Span-40, Span-60 and Span-80. The sorbitan fatty acid ester-ethylene oxide condensate may be, for example, at least one of Tween 20, 21, 40, 60, 61, 80, 81 and 85.

[0030] In this invention, the solvent may be selected from at least one of water, C1-C8 alcohols, C2-C8 ethers, C3-C8 esters, C3-C8 ketones, and C3-C8 saturated alkanes. Specific examples of the C1-C8 alcohols include, but are not limited to, at least one of methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-butanol, 1-pentanol, 1-hexanol, 1-octanol, 1-decanol, cyclopentanol, cyclohexanol, benzyl alcohol, and glycerol. Specific examples of the C2-C8 ethers include, but are not limited to, at least one of diethyl ether, cyclopentyl methyl ether, and propylene oxide. Specific examples of the C3-C8 esters include, but are not limited to, at least one of methyl acetate, ethyl acetate, and propyl acetate. Specific examples of the C3-C8 ketones include, but are not limited to, at least one of acetone, methyl butyl ketone, and methyl isobutyl ketone. 10 Saturated alkanes can be C3 to C4. 10 Aromatic hydrocarbons (such as benzene, toluene, xylene, etc.), C3~C 10 Aliphatic hydrocarbons (such as pentane, hexane, octane, etc.), C3~C 10 Alicyclic hydrocarbons (such as cyclohexane, cyclohexanone, methylcyclohexanone, etc.) and C3~C 10 At least one of the halogenated hydrocarbons (such as chlorobenzene, dichlorobenzene, dichloromethane, trichloromethane, etc.).

[0031] The method for preparing the cemented carbide sintering anti-stick coating provided by this invention includes uniformly mixing graphite material, carbon black, silicate minerals, dispersion medium, and solvent. The mixing method can be ball milling or stirring. The mixing conditions generally include a temperature of 0–50°C, preferably 20–30°C, such as 20°C, 22°C, 25°C, 28°C, 30°C, or any value between them; and a time of 0.5–48 h, preferably 10–30 h, such as 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 25 h, 28 h, 30 h, or any value between them.

[0032] The surface of the firing device provided by the present invention has an anti-stick coating formed by the above-mentioned hard alloy sintering anti-stick coating.

[0033] Furthermore, the present invention also provides the application of the above-mentioned sintering device in the sintering of cemented carbide.

[0034] The present invention will be described in detail below through embodiments.

[0035] In the following examples and comparative examples, natural graphite was purchased from Shanghai Jixiang Industrial Co., Ltd., with grade JXF-2; flake graphite was purchased from Shanghai Jixiang Industrial Co., Ltd., with grade JXF-6; and expanded graphite was purchased from Shanghai Jixiang Industrial Co., Ltd., with grade JXFH-50.

[0036] Example 1

[0037] S1. Take 2.4g of Tween-80 and add it to 37.6mL of water to prepare a dispersion. Add 6.6g of 100nm graphite and stir to disperse for 10min.

[0038] S2. Add 10.6g of carbon black and stir to disperse for 10 minutes;

[0039] S3. Add 5.7g halloysite and stir to disperse for 24h to obtain a hard alloy anti-stick coating.

[0040] The prepared cemented carbide anti-stick coating was brushed onto a graphite plate. After the coating dried, the surface and cross-sectional SEM images of the cemented carbide anti-stick coating film were shown below. Figure 1 and Figure 2 As shown. From Figure 1 and Figure 2 It can be seen that the prepared cemented carbide anti-stick coating is uniform and flat, with a dense cross-section and uniform distribution of each component.

[0041] The cemented carbide part was placed on a graphite plate coated with the cemented carbide anti-stick coating and then placed in a sintering furnace for sintering. The surface condition of the graphite plate before and after sintering was observed. The surface condition of the graphite plate before sintering is as follows: Figure 3 As shown, the surface condition of the graphite plate after sintering is as follows. Figure 4 As shown, the surface condition of the cemented carbide after sintering is as follows. Figure 5 As shown. From Figures 3-5 It can be seen that there are no obvious sintering marks on the surface of the graphite plate and the surface of the cemented carbide sample after sintering, indicating that the coating of the cemented carbide anti-stick coating has a good isolation effect.

[0042] Example 2

[0043] S1. Take 1.0g of polyethylene glycol and add it to 45mL of water to prepare a dispersion. Add 6.75g of 8000-mesh graphite and stir to disperse for 10min.

[0044] S2. Add 6.75g of carbon black and stir to disperse for 10 minutes;

[0045] S3. Add 2.25g of attapulgite and stir to disperse for 24h to obtain a cemented carbide anti-stick coating.

[0046] Example 3

[0047] S1. Take 1.0g of polyvinylpyrrolidone and add it to 45mL of water to prepare a dispersion. Add 6.75g of 8000-mesh graphite and stir to disperse for 10min.

[0048] S2. Add 6.75g of carbon black and stir to disperse for 10 minutes;

[0049] S3. Add 2.25g of sepiolite and stir to disperse for 24h to obtain a cemented carbide anti-stick coating.

[0050] Example 4

[0051] S1. Preparation of graphite / zirconia composite material: 0.25g of oleic acid was dissolved in 10g of water and stirred thoroughly for 10min. Then, 10g of zirconia powder (average particle size approximately 100nm), 9.5g of natural graphite, and 0.5g of expanded graphite were added to the resulting dispersion and ball-milled for 7h. The sample was then air-dried at room temperature to obtain the graphite / zirconia composite material, the morphology of which is as follows. Figure 6 As shown. From Figure 6 It can be seen that zirconium oxide is uniformly dispersed on the surface of the graphite sheet.

[0052] S2. Preparation of cemented carbide anti-stick coating: 0.12 g Tween-80 and 0.35 g Pingpingjia O-25 were dissolved in 45 mL of aqueous solution. 4.50 g of the graphite / zirconia composite material obtained in step S1 was added to the system and stirred for 30 min. Then, 8.25 g of carbon black (average particle size approximately 100 nm) was added and stirred for 10 min. Next, 4.25 g of attapulgite (with a one-dimensional structure, length 1000 nm–3000 nm, and aspect ratio (10–30):1) was added to the resulting mixture and ball-milled for 16 h to obtain the cemented carbide anti-stick coating. SEM images of the surface and cross-section of the cemented carbide anti-stick coating after coating are shown below. Figure 7 and Figure 8 As shown. From Figure 7 and Figure 8 The results show that the zirconium oxide particles and graphite flakes are uniformly dispersed, and there is no phenomenon of zirconium oxide agglomeration or graphite flakes stacking and separating. This proves that using an organic coupling agent to pre-composite graphite and inorganic particles can improve the dispersibility of graphite and inorganic particles in the coating.

[0053] Example 5

[0054] S1. Preparation of graphite / silicon oxide composite material: 0.25g of oleic acid was dissolved in 10g of water and stirred and dispersed for 10min. Then, 5g of silicon oxide powder (average particle size of about 50nm), 9.5g of natural graphite and 0.5g of flake graphite were added to the resulting dispersion and ball milled for 7h. The sample was then air-dried at room temperature to obtain graphite / silicon oxide composite material.

[0055] S2. Preparation of cemented carbide anti-stick coating: Dissolve 6.25g of polyethylene glycol in 40mL of aqueous solution, add 3.12g of graphite / silica composite material obtained in step S1 to the system and stir for 30min, then add 12.49g of carbon black (average particle size of about 20nm) and stir for 10min, then add 0.63g of halloysite (with a one-dimensional structure, length of 3000nm to 5000nm and aspect ratio of (30 to 50):1) to the resulting mixture, ball mill and disperse for 16h to obtain cemented carbide anti-stick coating.

[0056] Example 6

[0057] S1. Preparation of graphite / calcium fluoride composite material: 0.25g of octylamine was dissolved in 10g of water and stirred and dispersed for 10min. Then, 15g of calcium fluoride powder (average particle size of about 200nm) and 10g of natural graphite were added to the resulting dispersion and ball milled for 7h. The sample was then air-dried at room temperature to obtain graphite / calcium fluoride composite material.

[0058] S2. Preparation of cemented carbide anti-stick coating: Dissolve 3.12g of polyacrylic acid in 32mL of aqueous solution, add 18.74g of graphite / calcium fluoride composite material obtained in step S1 to the system and stir for 30min, then add 1.25g of carbon black (average particle size of about 500nm) and stir for 10min, then add 7.50g of sepiolite (with a one-dimensional structure, length of 10000nm~20000nm and aspect ratio of (200~400):1) to the resulting mixture, ball mill and disperse for 16h to obtain cemented carbide anti-stick coating.

[0059] Example 7

[0060] The cemented carbide anti-stick coating was prepared according to the method of Example 1, except that halloysite in Example 1 was replaced by silicate minerals of the same weight. Specifically, the silicate minerals included 3.0g halloysite and 2.7g bentonite. The other conditions were the same as in Example 1, and the cemented carbide anti-stick coating was obtained.

[0061] Example 8

[0062] The cemented carbide anti-stick coating was prepared according to the method of Example 1, except that halloysite in Example 1 was replaced by silicate minerals of the same weight. Specifically, the silicate minerals included 5.0g halloysite and 0.7g montmorillonite. The other conditions were the same as in Example 1, and the cemented carbide anti-stick coating was obtained.

[0063] Comparative Example 1

[0064] A cemented carbide anti-stick coating was prepared according to the method of Example 1, except that halloysite was replaced with the same amount of methyl cellulose by weight, and the other conditions were the same as in Example 1, to obtain a reference cemented carbide anti-stick coating.

[0065] Comparative Example 2

[0066] S1. 5g of silica powder (average particle size of about 50nm), 9.5g of natural graphite, 0.5g of flake graphite and 0.63g of methylcellulose are ball-milled for 7h to obtain mixture A.

[0067] S2. Dissolve 6.25g of polyethylene glycol in 50mL of aqueous solution, add the mixture A obtained in step S1 and stir for 30min to obtain the reference hard alloy anti-stick coating.

[0068] Comparative Example 3

[0069] The cemented carbide anti-stick coating was prepared according to the method of Example 4, except that the amount of graphite / zirconia composite material added was 44.5g (accounting for 43.43%), and the other conditions were the same as in Example 4, to obtain a reference cemented carbide anti-stick coating.

[0070] Comparative Example 4

[0071] The cemented carbide anti-stick coating was prepared according to the method of Example 4, except that the amount of graphite / zirconia composite material added was 2.05 g (accounting for 3.42%), and the other conditions were the same as in Example 4, to obtain a reference cemented carbide anti-stick coating.

[0072] Comparative Example 5

[0073] The cemented carbide anti-stick coating was prepared according to the method of Example 1, except that the amount of halloysite added was 0.25g (accounting for 0.43%), and the other conditions were the same as in Example 1, to obtain a reference cemented carbide anti-stick coating.

[0074] Comparative Example 6

[0075] The cemented carbide anti-stick coating was prepared according to the method of Example 1, except that the amount of halloysite added was 12.49 g (accounting for 17.66%), and the other conditions were the same as in Example 1, to obtain a reference cemented carbide anti-stick coating.

[0076] Comparative Example 7

[0077] The cemented carbide anti-stick coating was prepared according to the method of Example 4, except that the amount of oleic acid added was 0.005 g (the amount of oleic acid added was 0.05% of the mass of the inorganic particles), and the other conditions were the same as in Example 4, to obtain a reference cemented carbide anti-stick coating.

[0078] Comparative Example 8

[0079] The cemented carbide anti-stick coating was prepared according to the method of Example 4, except that the amount of oleic acid added was 3g (the amount of oleic acid added was 30% of the mass of the inorganic particles), and the other conditions were the same as in Example 4, to obtain a reference cemented carbide anti-stick coating.

[0080] Comparative Example 9

[0081] The cemented carbide anti-stick coating was prepared according to the method of Example 1, except that halloysite was replaced by montmorillonite with the same weight ratio of layered structure, and the other conditions were the same as in Example 1, to obtain a reference cemented carbide anti-stick coating.

[0082] Test case

[0083] (1) Stability: The hard alloy anti-stick coatings of the examples and comparative examples were left to stand for 24 hours to observe whether there was sedimentation in order to judge the stability of the hard alloy anti-stick coatings. The results are shown in Table 1. No sedimentation indicates that the coating is stable. If sedimentation occurs, it means that the coating itself is too unstable and no further tests will be conducted.

[0084] (2) Isolation Effect: The anti-stick coatings for cemented carbide used in the examples and comparative examples were brushed onto graphite plates. After the coatings dried, the cemented carbide parts were placed on the graphite plates and sintered in a sintering furnace. The isolation effect of the coating was judged based on whether the cemented carbide parts adhered to the graphite support plate after sintering (referred to as "plate adhesion"), whether the coating adhered to the surface of the cemented carbide parts after sintering, and whether pores and carburization appeared on the cemented carbide parts after sintering. The results are shown in Table 1. No coating adhesion indicates good adhesion between the coating and the graphite plate and the coating is stable. The presence of pores and carburization suggests that it may be related to the smoothness of the coating and the uniform distribution of the various components in the coating. The smoothness is related to the viscosity and stability of the coating itself. If it is too sticky, the smoothness is poor. If the coating is unstable, the distribution of the various components in the coating will be uneven. If plate adhesion occurs, it indicates that the isolation effect of the coating is too poor, and no further testing will be conducted.

[0085] Table 1

[0086] Example 1 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 2 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 3 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 4 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 5 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 6 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 7 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Example 8 No sediment Unglued board Non-stick coating No pores were observed. No carburization observed Comparative Example 1 No sediment Sticker - - - Comparative Example 2 No sediment Sticker - - - Comparative Example 3 No sediment Unglued board Adhesive coating No pores were observed. No carburization observed Comparative Example 4 No sediment Sticker - - - Comparative Example 5 There is sediment - - - - Comparative Example 6 No sediment Unglued board Non-stick coating Porous Carburization Comparative Example 7 No sediment Sticker - - - Comparative Example 8 No sediment Sticker - - - Comparative Example 9 There is sediment - - - -

[0087] As can be seen from Examples 1-3 and 7-8 in the table above, adding an appropriate amount of one-dimensional silicate minerals can improve the stability and film-forming properties of the coating, as well as enhance its barrier properties. The filamentous structure of one-dimensional silicates not only imparts thickening properties, improving coating stability while reducing or avoiding the use of organic thickeners, but also enhances film-forming properties. Furthermore, during high-temperature sintering, these silicates also generate submicron silicon carbide whiskers, as well as alumina and silica particles in situ (see reference). Figure 9Among them, silicon carbide whiskers can act as a support and film binder, which can alleviate the direct reaction between the alloy and carbon in the coating. Meanwhile, silicon carbide, alumina and silicon dioxide are all inorganic insulating materials. The in-situ generation of metal oxide particles can improve the adhesion strength between the coating and the graphite substrate, and improve the insulating performance of the coating.

[0088] As can be seen from Examples 4 to 6 in the table above, adding an organic coupling agent to combine graphite and inorganic particles can further improve the stability of the coating.

[0089] Compared to Example 1, Comparative Example 1 replaced the one-dimensional silicate mineral with a traditional cellulose-based thickener, which resulted in a poorer barrier effect of the coating and "sticking". This is because the one-dimensional silicate mineral has both a thickening effect, which is beneficial to improving the stability of the coating, and a toughening effect. After sintering, it will form silicon carbide whiskers, as well as alumina and silica particles in situ, which is beneficial to improving the barrier effect of the coating.

[0090] Compared to Example 1, the amount of halloysite added in Comparative Example 5 was too low, which reduced the stability of the coating and caused precipitation after standing. The amount of halloysite added in Comparative Example 6 was too high, which made the coating viscosity too high. The coating smoothness was poor when brushing, and it could not be sprayed. The poor coating smoothness led to the appearance of pores and carburization on the surface of the cemented carbide parts after sintering.

[0091] Compared to Example 4, both excessive and insufficient addition of graphite composite materials in Comparative Examples 3 and 4 will affect the stability of the coating after sintering. Insufficient addition will result in poor coating isolation effect and "sticking to the plate". Excessive addition will result in poor coating stability and easy peeling of the coating after sintering, resulting in coating sticking to the surface of the hard alloy parts.

[0092] Compared to Example 4, Comparative Examples 7 and 8 showed that adding too little or too much organic coupling agent would affect the dispersion of graphite and inorganic particles in the coating, resulting in uneven coating composition and "sticking" after sintering.

[0093] Compared to Example 1, Comparative Example 9 did not add one-dimensional silicate, which led to poor stability of the coating after sintering and precipitation.

[0094] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A hard alloy sintering anti-stick coating, characterized in that, The cemented carbide sintered anti-stick coating contains graphite material, carbon black, silicate minerals, a dispersion medium, and a solvent. The silicate minerals contain more than 50 wt% one-dimensional silicates. The graphite material is a graphite composite material, comprising graphite and inorganic particles coupled to the graphite surface via an organic coupling agent, which is a fatty acid and / or aliphatic amine. Based on the total weight of the cemented carbide sintered anti-stick coating, the content of graphite material is 5-30%, the content of carbon black is 2-20%, the content of silicate minerals is 1-12%, the content of the dispersion medium is 0.5-10%, and the content of the solvent is 50-85%. The mass ratio of graphite to inorganic particles in the graphite composite material is 100:(50-150). The content of the organic coupling agent in the graphite composite material is 0.1%-10% of the mass of the inorganic particles.

2. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The silicate mineral contains 100 wt% one-dimensional silicate.

3. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The aspect ratio of the one-dimensional silicate structure is 2.5:1 or higher.

4. The cemented carbide sintering anti-stick coating according to claim 3, characterized in that, The aspect ratio of the one-dimensional silicate structure is (2.5~400):

1.

5. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The length of the one-dimensional silicate structure is 500 nm to 20000 nm.

6. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The one-dimensional silicate is selected from at least one of halloysite, attapulgite, and sepiolite.

7. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The fatty acid is selected from at least one of oleic acid, linoleic acid, linolenic acid, butyric acid, hexanoic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid.

8. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The fatty amine is selected from at least one of octylamine, nonylamine, decylamine, 1,10-decanediamine, dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

9. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The graphite is selected from at least one of natural graphite, flake graphite, and expanded graphite.

10. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The inorganic particles are selected from at least one of silicon oxide, zirconium oxide, aluminum oxide, calcium fluoride, titanium dioxide, magnesium oxide, and rare earth oxides.

11. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The average particle size of the inorganic particles is 50~10000nm.

12. The cemented carbide sintering anti-stick coating according to claim 1, characterized in that, The graphite composite material is obtained by ball milling graphite, an organic coupling agent, and inorganic particles in the presence of a solvent.

13. The cemented carbide sintering anti-stick coating according to any one of claims 1 to 12, characterized in that, The average particle size of the carbon black is 20 nm to 500 nm.

14. The cemented carbide sintering anti-stick coating according to any one of claims 1 to 12, characterized in that, The solvent is selected from water, C1-C8 alcohols, C2-C8 ethers, C3-C8 esters, C3-C8 ketones, and C3-C8 esters. 10 At least one of the saturated alkanes.

15. The cemented carbide sintering anti-stick coating according to any one of claims 1 to 12, characterized in that, The dispersion medium is selected from at least one of polyoxyethylene fatty alcohol ether, alkylphenol polyoxyethylene ether, sorbitan fatty acid ester, sorbitan fatty acid ester-ethylene oxide condensate, ethylene oxide-propylene oxide copolymer, polyethylene glycol, polyvinylpyrrolidone, polydimethylsiloxane, polyether-modified organosiloxane, polyester-modified organosiloxane, alkyl-modified organosiloxane, and polyacrylic acid.

16. The method for preparing the cemented carbide sintering anti-stick coating according to any one of claims 1 to 15, characterized in that, The method involves uniformly mixing graphite material, carbon black, silicate minerals, dispersion medium, and solvent.

17. A firing device, characterized in that, The surface of the firing device has an anti-stick coating formed by the hard alloy sintering anti-stick coating as described in any one of claims 1 to 15.

18. The application of the sintering device according to claim 17 in the sintering of cemented carbide.

Images