Corrosion-resistant cold work die steel and preparation method thereof

Abstract

The invention belongs to the technical field of die steel coatings, and provides corrosion-resistant cold work die steel and a preparation method thereof. The preparation method comprises the following steps: (1) treating the surface of a base material; (2) cold zinc spraying treatment is conducted, specifically, a zinc layer is sprayed to the surface of the cold work die steel through a cold zinc spraying coating, then natural drying is conducted, and pretreated cold work die steel is obtained; (3) PVD hard coating treatment, wherein gasified atoms react and deposit on the surface of the pretreated cold work die steel, and a coating of 3-5 microns is formed; and (4) post-treatment: polishing and cleaning. According to the preparation method, dual protection of cathode protection and a hard coating is adopted for the cold work die steel, the cold work die steel treated through the preparation method has high hardness and high abrasion resistance, the corrosion resistance of the cold work die steel can be remarkably improved, meanwhile, the adhesive force, compactness and storage stability of the coating are remarkably improved, and the cold work die steel can be applied to the field of cold work die steel. Therefore, the corrosion resistance of the cold work die steel under complex working conditions is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of die steel coatings, and specifically relates to a corrosion-resistant cold work die steel and a preparation method thereof. Background Art

[0002] Cold work die steels are widely used in the field of industrial manufacturing and play an irreplaceable role in key technological processes such as cold stamping, cold extrusion, and cold heading. However, due to the usually extremely harsh working environment of cold work die steels, the mold surface needs to bear mechanical stress, high-intensity friction, and the erosion of chemical media for a long time, so corrosion is very likely to occur. Corrosion will not only cause the dimensional accuracy of the mold to decrease and the surface quality to deteriorate, leading to premature failure of the mold, but also greatly increase production costs and reduce production efficiency, seriously hindering the development of related industries.

[0003] Currently, as one of the most common means to improve the corrosion resistance of cold work die steels, surface corrosion-resistant treatment is carried out on them. The methods for surface corrosion-resistant treatment of molds include traditional electroplating processes, hot-dip galvanizing processes, organic coating processes, physical vapor deposition (PVD) hard coating processes, etc.

[0004] Although the traditional electroplating process can enhance the corrosion resistance to a certain extent, there are problems such as poor coating adhesion and easy occurrence of hydrogen embrittlement, which limit its application in high-demand scenarios. The hot-dip galvanizing process can form a relatively thick zinc layer with good protective effect. However, this process has limitations on the size and shape of the mold, and the subsequent processing is more difficult. In recent years, some organic coatings have been applied to the surface protection of cold work die steels, but in complex working conditions, their heat resistance and wear resistance often cannot meet the requirements.

[0005] As a new surface protection technology, the cold spray zinc process is based on the principle of aerodynamics. High-pressure gas is used to accelerate zinc powder to supersonic speed, so that zinc powder particles impact the mold surface at an extremely high speed. At the moment of impact, the zinc powder particles undergo severe plastic deformation, forming mechanical occlusion and metallurgical bonding with the mold surface, thereby forming a dense zinc coating on the mold surface. This zinc coating can not only physically isolate the direct contact between external corrosive media such as oxygen, moisture, acids and alkalis and the mold substrate, effectively preventing the occurrence of corrosion reactions; but also because the electrode potential of zinc is lower than that of common metals such as steel, during electrochemical corrosion, the zinc coating can act as a sacrificial anode and be preferentially corroded, thereby protecting the mold substrate from corrosion. This process has the advantages of simple construction, environmental friendliness, strong coating adhesion, etc., and can effectively block the contact between corrosive media and the mold substrate. However, the hardness and wear resistance of the cold spray zinc coating itself are limited, and it is easily damaged in a high-friction environment.

[0006] The PVD hard coating process is carried out in a high-vacuum environment. By physical methods, coating materials (such as metals, alloys, or ceramics, etc.) are evaporated or sputtered into atomic or ionic states. Under the action of an electric field or magnetic field, these particles migrate directionally to the surface of the mold and deposit and condense on the surface to form a high-hardness and high-wear-resistant coating. The PVD hard coating process can significantly improve the wear resistance of the mold, but has poor adaptability to the complex shape of the mold, and has poor anti-corrosion effect when used alone.

[0007] In summary, the existing methods for improving the corrosion resistance of cold work die steel all have certain limitations. Therefore, developing a new surface treatment technology to effectively improve the corrosion resistance of cold work die steel under complex working conditions has become an urgent problem to be solved in this field. Summary of the Invention

[0008] Aiming at the above deficiencies in the prior art, the purpose of the present invention is to provide a corrosion-resistant cold work die steel and its preparation method. The preparation method adopts double protection of cathodic protection and hard coating for the cold work die steel. After being treated by the preparation method of the present application, the cold work die steel not only has high hardness and high wear resistance, but also its anti-corrosion performance can be significantly improved. At the same time, the adhesion of its coating, the denseness of the coating and the storage stability are all significantly improved to effectively improve the corrosion resistance of the cold work die steel under complex working conditions.

[0009] To achieve the above purpose, the solution adopted by the present invention is:

[0010] A preparation method of a corrosion-resistant cold work die steel, comprising: (1) Substrate surface treatment: After removing the surface contaminants of the cold work die steel, shot peening or sandblasting treatment is carried out; (2) Cold spray zinc treatment: A zinc layer is sprayed on the surface of the cold work die steel with cold spray zinc coating and then dried naturally to obtain a pretreated cold work die steel; By weight, the raw materials of the cold spray zinc coating include 12-18 parts of graphene-modified epoxy resin, 70-78 parts of zinc powder, 1.2-1.5 parts of ethylene glycol monomethyl ether, 0.6-0.8 parts of methyl pentanol, 0.1-0.3 parts of ethylene oxide, 1.5-2.5 parts of ethylenediamine and 3-5 parts of water; (3) PVD hard coating treatment: The pretreated cold work die steel is placed in a closed and vacuum PVD device, and high-energy electron beam is used to evaporate the target material into a gaseous state, and the vaporized atoms react and deposit on the surface of the pretreated cold work die steel to form a 3-5 μm coating; (4) Post-treatment: Polishing and cleaning.

[0011] Further, in a preferred embodiment of the present invention, in step (2), the thickness of the dried zinc layer is 45-55 μm.

[0012] Further, in a preferred embodiment of the present invention, in step (2), the preparation of the graphene-modified epoxy resin includes: dispersing graphene oxide in deionized water by ultrasonic dispersion according to a mass ratio of 6 - 8:400 - 600 to obtain a graphene oxide solution; mixing the graphene oxide solution and a bisphenol A epoxy resin E-44 solution according to a volume ratio of 0.2 - 0.4:10 - 12 to obtain a mixture; the concentration of the bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; carrying out an in-situ polymerization reaction on the mixture at 80 - 120 °C; after the reaction ends, cooling the reaction product and curing it at 120 - 150 °C for 1 - 2 h.

[0013] Further, in a preferred embodiment of the present invention, before the graphene oxide solution is mixed with the bisphenol A epoxy resin E-44 solution, triethylenetetramine is added to the graphene oxide solution, and the mass ratio of graphene oxide to triethylenetetramine is 2:0.8 - 1.2, and ultrasonic dispersion is continued to obtain a triethylenetetramine-modified graphene oxide dispersion; the bisphenol A epoxy resin E-44 solution is added to the triethylenetetramine-modified graphene oxide dispersion according to a volume ratio of 0.2 - 0.4:10 - 12, and stirred at a stirring speed of 200 - 500 rpm at room temperature for 2 - 3 h.

[0014] Further, in a preferred embodiment of the present invention, in step (2), the ultrasonic power is 380 - 430 W, the first ultrasonic time is 35 - 45 min, and the second ultrasonic time is 50 - 70 min.

[0015] Further, in a preferred embodiment of the present invention, in step (2), the mixture is stirred at a stirring speed of 100 - 300 rpm for 4 - 6 h.

[0016] Further, in a preferred embodiment of the present invention, in step (2), the particle size of the zinc powder is 25 - 35 μm.

[0017] Further, in a preferred embodiment of the present invention, in step (3), the vacuum degree is 10 -3 -10 -5 Pa, nitrogen is introduced, the deposition temperature is 390 - 410 °C, the target is a CrN target, the target power is 200 - 400 W, and the deposition is carried out for 3 - 4 h.

[0018] Further, in a preferred embodiment of the present invention, in step (1), after the surface treatment of the substrate, the surface cleanliness of the cold work die steel is greater than Sa2.5, and the surface roughness of the cold work die steel is 55 - 70 μm.

[0019] A corrosion-resistant cold work die steel is prepared by using the preparation method of the corrosion-resistant cold work die steel according to any one of claims 1 - 8.

[0020] The beneficial effects of a corrosion-resistant cold work die steel and its preparation method provided by the present invention are as follows:

[0021] (1) In the preparation method of the corrosion-resistant cold work die steel provided by the present invention, by combining the cold spray zinc process and the PVD hard coating process, double protection is provided, showing significant advantages in many aspects, and thus adapting to harsh environments. Specifically, in terms of corrosion resistance, the zinc coating formed by cold spray zinc can serve as a sacrificial anode, preferentially corroding itself to protect the die steel substrate. Even if the coating is locally damaged, it can still provide electrochemical protection; the PVD hard coating can further isolate the corrosion medium and enhance the overall protection effect, thereby significantly improving the corrosion resistance of the cold work die steel; in terms of wear resistance, the high hardness of the PVD hard coating greatly improves the wear resistance of the die surface and reduces friction loss. Although the hardness of the cold spray zinc coating is limited, it can cooperate with the PVD coating to buffer the friction impact to a certain extent and extend the service life of the die; in addition, based on the cold spray zinc coating, the PVD process can better exert its deposition advantages, and the combination of the two can broaden the scope of process application.

[0022] (2) In the preparation method of the corrosion-resistant cold work die steel provided by the present invention, through further improvement of the cold spray zinc coating formula, a cold spray zinc coating obtained by using graphene-modified epoxy resin in combination with zinc powder, a slow-release agent, a dispersant, an antifoaming agent, and a curing agent under specific conditions: Since graphene has excellent electrical conductivity, it can improve the conductive network of epoxy resin, promote electron transfer between zinc powder particles, and make the cathodic protection effect of zinc more efficient, thereby enhancing its electrical conductivity; the two-dimensional sheet structure of graphene can form a physical barrier to effectively block the penetration of water, oxygen, and corrosive ions (such as Cl-), thereby reducing the corrosion rate of the substrate and achieving the purpose of long-term corrosion protection; the strength of graphene is more than 100 times that of steel, so it can significantly enhance the toughness and crack resistance of epoxy resin and reduce mechanical damage to the coating during cold spraying construction or service; since the functional groups (such as hydroxyl groups and carboxyl groups) on the surface of graphene can form chemical bonds with epoxy resin, the interfacial bonding force between the coating and the metal substrate can be improved, and the chemical inertness of graphene can also slow down the aging of epoxy resin in ultraviolet, humid heat, or acid-base environments, further avoiding coating powdering or peeling; in addition, through the synergistic anti-corrosion effect of graphene, the consumption of zinc powder can be significantly reduced (the zinc content of traditional cold spray zinc coatings needs to be ≥96%), reducing zinc resource waste and subsequent environmental treatment pressure; at the same time, the thixotropy of graphene-modified epoxy resin is better, which is suitable for the atomization and deposition requirements of the cold spraying process and improves the coating uniformity.

[0023] (3) In the preparation method of the corrosion-resistant cold working die steel provided by the present invention, triethylenetetramine (TETA) is used to modify graphene oxide (GO) in the graphene-modified epoxy resin. Through the improvement of chemical activity and interface optimization brought by the introduction of amino groups, the coating formed by the cold spray zinc coating prepared under the above specific technical conditions of this application can show significant advantages in the fields of anti-corrosion, adsorption, intelligent coatings, etc., specifically reflected in: Multiple amino groups (-NH 2 ) in the TETA molecule can react with the oxygen-containing functional groups (such as carboxyl groups and hydroxyl groups) on the surface of GO, and improve the dispersion of GO in the solvent or polymer matrix through covalent bonds or hydrogen bond interactions, reducing sheet agglomeration; in the composite material, the compatibility between TETA-modified GO (TETA-GO) and the resin matrix is better, and a more uniform composite structure can be formed, thereby enhancing the mechanical properties and stability of the material; the amino and imino groups of TETA have strong coordination ability, can selectively adsorb heavy metal ions, and form stable complexes; TETA-modified GO combines the high specific surface area of graphene and the chemical activity of amine groups, and the adsorption capacity is significantly higher than that of unmodified GO; TETA-GO can form a dense physical barrier in the anti-corrosion coating, effectively blocking the penetration of corrosion media such as water, oxygen and Cl - ; TETA can react with GO and the resin matrix as a cross-linking agent to form a three-dimensional network structure, significantly improving the cross-linking density of the coating, enhancing the mechanical strength and chemical resistance of the coating; the cross-linked structure can also inhibit the movement of molecular segments, improve the thermal stability of the material, and further ensure that the composite coating can still maintain high anti-corrosion performance at high temperatures. Detailed implementation manners

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0025] The following specifically describes a corrosion-resistant cold working die steel and its preparation method provided by the embodiments of the present invention.

[0026] The features and performance of the present invention will be further described in detail below in combination with the embodiments.

[0027] Example 1

[0028] This example provides a preparation method of a corrosion-resistant cold working die steel, including:

[0029] (1) Substrate surface treatment: After removing the surface contaminants of Cr12MoV cold work die steel, shot peening or sandblasting is carried out. After the substrate surface treatment, the surface cleanliness of the cold work die steel is greater than Sa2.5, and the surface roughness of the cold work die steel is 60 μm;

[0030] (2) Cold spray zinc treatment: A layer of zinc layer is sprayed on the surface of the cold work die steel with cold spray zinc coating and then dried naturally to obtain pretreated cold work die steel; Spraying process parameter settings: Use an Oerlikon PQP6038A pneumatic airless spraying machine, the spraying pressure is 16 MPa, the distance between the spray gun and the cold work die steel is 250 mm, the moving speed of the spray gun is 45 cm / s, and the thickness of the dried zinc layer is 50 μm.

[0031] By weight, the raw materials of the cold spray zinc coating include 15 parts of graphene-modified epoxy resin, 75 parts of zinc powder (the particle size of zinc powder is 30 μm), 1.4 parts of ethylene glycol monomethyl ether, 0.7 part of methyl amyl alcohol, 0.2 part of ethylene oxide, 2 parts of ethylenediamine and 4 parts of water;

[0032] The preparation of graphene-modified epoxy resin includes: Ultrasonic dispersing graphene oxide in deionized water according to a mass ratio of 7:500, the ultrasonic power is 400 W, and the first ultrasonic time is 40 min to obtain a graphene oxide solution; Then add triethylenetetramine to the graphene oxide solution, and the mass ratio of graphene oxide to triethylenetetramine is 2:1, continue ultrasonic dispersion, the ultrasonic power is 400 W, and the second ultrasonic time is 60 min to obtain a triethylenetetramine-modified graphene oxide dispersion; Add bisphenol A epoxy resin E-44 solution to the triethylenetetramine-modified graphene oxide dispersion according to a volume ratio of 0.3:11, and stir at a stirring speed of 300 rpm at room temperature for 2.5 h; The concentration of bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; Carry out in-situ polymerization reaction on the mixture at 100 °C, and stir the mixture at a stirring speed of 200 rpm for 5 h; After the reaction is completed, cool the reaction product and cure it at 130 °C for 1.5 h;

[0033] The preparation of the cold spray zinc coating includes: Weighing the above raw materials according to weight; Adding graphene-modified epoxy resin, ethylene glycol monomethyl ether, methyl amyl alcohol, ethylene oxide, ethylenediamine and water into a stirring kettle, and stirring at a low speed until the graphene-modified epoxy resin is completely dissolved; Then gradually add zinc powder, stir evenly at a high speed and filter to obtain the cold spray zinc coating; The viscosity of the cold spray zinc coating is 28 s (measured by Ford Cup #4, 25 °C);

[0034] (3) PVD hard coating treatment: Put the pretreated cold work die steel into a closed and vacuum PVD equipment (JEOL, BS-72050ICE), and set the vacuum degree to 10 -4Pa, introduce nitrogen gas, use a high-energy electron beam to evaporate the target material into a gaseous state, and the vaporized atoms react and deposit on the surface of the pre-treated cold work die steel. The deposition temperature is 400 °C, the target material is a CrN target, the target power is 300 W, and the deposition is carried out for 3.5 h until a 4-μm coating is formed;

[0035] (4) Post-treatment: polishing and cleaning.

[0036] Example 2

[0037] This example provides a method for preparing a corrosion-resistant cold work die steel, which is different from Example 1 in that: (2) Cold spray zinc treatment: By weight, the raw materials of the cold spray zinc coating include 12 parts of graphene-modified epoxy resin, 78 parts of zinc powder, 1.2 parts of ethylene glycol monomethyl ether, 0.8 part of methyl pentanol, 0.1 part of ethylene oxide, 2.5 parts of ethylenediamine, and 3 parts of water.

[0038] Example 3

[0039] This example provides a method for preparing a corrosion-resistant cold work die steel, which is different from Example 1 in that: (2) Cold spray zinc treatment: By weight, the raw materials of the cold spray zinc coating include 18 parts of graphene-modified epoxy resin, 70 parts of zinc powder, 1.5 parts of ethylene glycol monomethyl ether, 0.6 part of methyl pentanol, 0.3 part of ethylene oxide, 1.5 parts of ethylenediamine, and 5 parts of water.

[0040] Example 4

[0041] This example provides a method for preparing a corrosion-resistant cold work die steel, which is different from Example 1 in that: (2) Cold spray zinc treatment: The preparation of graphene-modified epoxy resin includes: ultrasonic dispersion of graphene oxide in deionized water according to a mass ratio of 6:600, with an ultrasonic power of 380 W and a first ultrasonic time of 35 min to obtain a graphene oxide solution; then add triethylenetetramine to the graphene oxide solution, and the mass ratio of graphene oxide to triethylenetetramine is 2:0.8, continue ultrasonic dispersion, with an ultrasonic power of 380 W and a second ultrasonic time of 70 min to obtain a triethylenetetramine-modified graphene oxide dispersion; add bisphenol A epoxy resin E-44 solution according to a volume ratio of 0.2:12 to the triethylenetetramine-modified graphene oxide dispersion, and stir at a stirring speed of 200 rpm at room temperature for 3 h; the concentration of bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; carry out in-situ polymerization reaction on the mixture at 80 °C, and stir the mixture at a stirring speed of 100 rpm for 6 h; after the reaction is completed, cool the reaction product and cure it at 120 °C for 2 h.

[0042] Example 5

[0043] This embodiment provides a preparation method of corrosion-resistant cold working die steel, which is different from Embodiment 1 in that: (2) Cold spraying zinc treatment: The preparation of graphene-modified epoxy resin includes: dispersing graphene oxide in deionized water according to a mass ratio of 8:400, with an ultrasonic power of 430 W and a first ultrasonic time of 45 min to obtain a graphene oxide solution; then adding triethylenetetramine to the graphene oxide solution, with a mass ratio of graphene oxide to triethylenetetramine of 2:1.2, and continuing ultrasonic dispersion with an ultrasonic power of 430 W and a second ultrasonic time of 50 min to obtain a triethylenetetramine-modified graphene oxide dispersion; adding bisphenol A epoxy resin E-44 solution to the triethylenetetramine-modified graphene oxide dispersion according to a volume ratio of 0.4:10, and stirring at a stirring speed of 500 rpm at room temperature for 2 h; the concentration of bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; carrying out in-situ polymerization reaction on the mixture at 120 °C, and stirring the mixture at a stirring speed of 300 rpm for 4 h; after the reaction is completed, cooling the reaction product and curing at 150 °C for 1 h.

[0044] Example 6

[0045] This embodiment provides a preparation method of corrosion-resistant cold working die steel, which is different from Embodiment 1 in that: (2) Cold spraying zinc treatment: The particle size of zinc powder is 25 μm, the viscosity of the cold spraying zinc coating is 25 s (measured by Ford Cup #4, 25 °C), and the thickness of the dried zinc layer is 45 μm.

[0046] Example 7

[0047] This embodiment provides a preparation method of corrosion-resistant cold working die steel, which is different from Embodiment 1 in that: (2) Cold spraying zinc treatment: The particle size of zinc powder is 35 μm, the viscosity of the cold spraying zinc coating is 30 s (measured by Ford Cup #4, 25 °C), and the thickness of the dried zinc layer is 55 μm.

[0048] Example 8

[0049] This embodiment provides a preparation method of corrosion-resistant cold working die steel, which is different from Embodiment 1 in that: (1) Substrate surface treatment: The surface roughness of the cold working die steel is 55 μm.

[0050] Example 9

[0051] This embodiment provides a preparation method of corrosion-resistant cold working die steel, which is different from Embodiment 1 in that: (1) Substrate surface treatment: The surface roughness of the cold working die steel is 70 μm.

[0052] Example 10

[0053] This embodiment provides a preparation method of corrosion-resistant cold work die steel, which is different from Embodiment 1 in that: (3) PVD hard coating treatment: Put the pretreated cold work die steel into a closed and vacuum PVD device, set the vacuum degree to 10 -3 Pa, introduce nitrogen gas, use a high-energy electron beam to evaporate the target material into a gaseous state, and the vaporized atoms react and deposit on the surface of the pretreated cold work die steel. The deposition temperature is 390 °C, the target material is a CrN target, the target power is 200 W, and the deposition is carried out for 4 h until a 3-μm coating is formed.

[0054] Embodiment 11

[0055] This embodiment provides a preparation method of corrosion-resistant cold work die steel, which is different from Embodiment 1 in that: (3) PVD hard coating treatment: Put the pretreated cold work die steel into a closed and vacuum PVD device, set the vacuum degree to 10 -5 Pa, introduce nitrogen gas, use a high-energy electron beam to evaporate the target material into a gaseous state, and the vaporized atoms react and deposit on the surface of the pretreated cold work die steel. The deposition temperature is 410 °C, the target material is a CrN target, the target power is 400 W, and the deposition is carried out for 3 h until a 5-μm coating is formed.

[0056] Comparative Example 1

[0057] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Embodiment 1 in that: there is no (2) cold spraying zinc step.

[0058] Comparative Example 2

[0059] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Embodiment 1 in that: there is no (3) PVD hard coating treatment step.

[0060] Comparative Example 3

[0061] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Embodiment 1 in that: (2) Cold spraying zinc treatment: By weight, the raw materials of the cold spraying zinc coating include 10 parts of graphene-modified epoxy resin, 80 parts of zinc powder, 1 part of ethylene glycol monomethyl ether, 1 part of methyl pentanol, 0.05 part of ethylene oxide, 3 parts of ethylenediamine, and 2 parts of water.

[0062] Comparative Example 4

[0063] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Embodiment 1 in that: (2) Cold spraying zinc treatment: By weight, the raw materials of the cold spraying zinc coating include 15 parts of bisphenol A type epoxy resin E-44, 75 parts of zinc powder (the particle size of zinc powder is 30 μm), 1.4 parts of ethylene glycol monomethyl ether, 0.7 part of methyl pentanol, 0.2 part of ethylene oxide, 2 parts of ethylenediamine, and 4 parts of water.

[0064] Comparative Example 5

[0065] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Example 1 in that: (2) Cold spraying zinc treatment: The preparation of graphene-modified epoxy resin includes: dispersing graphene oxide in deionized water by ultrasonic wave according to a mass ratio of 7:500, with an ultrasonic power of 400 W and an ultrasonic time of 40 min to obtain a graphene oxide solution; adding bisphenol A epoxy resin solution according to a volume ratio of 0.3:11 to the graphene oxide solution, and stirring at a stirring speed of 300 rpm at room temperature for 2.5 h; the concentration of bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; carrying out in-situ polymerization reaction on the mixture at 100 °C, and stirring the mixture at a stirring speed of 200 rpm for 5 h; after the reaction is completed, cooling the reaction product and curing at 130 °C for 1.5 h.

[0066] Comparative Example 6

[0067] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Example 1 in that: (2) Cold spraying zinc treatment: The preparation of graphene-modified epoxy resin includes: dispersing graphene oxide in deionized water by ultrasonic wave according to a mass ratio of 5:700, with an ultrasonic power of 350 W and the first ultrasonic time of 50 min to obtain a graphene oxide solution; then adding triethylenetetramine to the graphene oxide solution, and the mass ratio of graphene oxide to triethylenetetramine is 2:0.5, and continuing ultrasonic dispersion with an ultrasonic power of 350 W and the second ultrasonic time of 80 min to obtain a triethylenetetramine-modified graphene oxide dispersion; adding bisphenol A epoxy resin E-44 solution according to a volume ratio of 0.5:8 to the triethylenetetramine-modified graphene oxide dispersion, and stirring at a stirring speed of 100 rpm at room temperature for 4 h; the concentration of bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; carrying out in-situ polymerization reaction on the mixture at 150 °C, and stirring the mixture at a stirring speed of 300 rpm for 3 h; after the reaction is completed, cooling the reaction product and curing at 160 °C for 0.8 h.

[0068] Comparative Example 7

[0069] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Example 1 in that: (2) Cold spraying zinc treatment: The particle size of zinc powder is 20 μm, the viscosity of the cold spraying zinc coating is 20 s (measured by Ford Cup #4, 25 °C), and the thickness of the dried zinc layer is 60 μm.

[0070] Comparative Example 8

[0071] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Example 1 in that: (1) Substrate surface treatment: The surface roughness of the cold work die steel is 50 μm.

[0072] Comparative Example 9

[0073] This comparative example provides a preparation method of corrosion-resistant cold work die steel, which is different from Example 1 in that: (3) PVD hard coating treatment: The pretreated cold work die steel is placed in a closed and vacuum PVD device, the vacuum degree is set to 10 -6 Pa, nitrogen is introduced, the target material is evaporated into a gaseous state by using a high-energy electron beam, and the vaporized atoms react and deposit on the surface of the pretreated cold work die steel. The deposition temperature is 430 °C, the target material is a CrN target, the target power is 180 W, and the deposition is carried out for 5 h until a 4-μm coating is formed.

[0074] Experimental Example 1

[0075] For the corrosion-resistant cold work die steels prepared in Examples 1-11 and Comparative Examples 1-9, mechanical property tests are carried out, including:

[0076] Mechanical property test: Test according to "GB / T 4340.1-2024 Metallic materials - Vickers hardness test - Part 1: Test method" to obtain the Vickers hardness (HV);

[0077] Wear resistance test: Test according to GB / T 12444-2006 "Test method for wear of metallic materials - Ring-on-block sliding wear test" to obtain the wear rate (mm 3 / (N·m));

[0078] Corrosion resistance test: Carry out tests according to salt spray test: ASTM B117 (neutral salt spray), ISO 9227, and electrochemical test: ASTM G5 (potentiodynamic polarization), ASTM G59 (electrochemical impedance spectroscopy) to obtain the time (h) when rust first appears and the corrosion current density (Icorr, unit: μA / cm 2 );

[0079] Coating adhesion test: Test according to ASTM C1624-05 (Standard test method for adhesion strength of coatings by the scratch test) by using a scratch test to obtain the adhesion strength (MPa).

[0080] The above test result data are shown in Table 1:

[0081] Table 1

[0082]

[0083]

[0084] As can be seen from the data in Table 1, for the corrosion-resistant cold work die steel prepared by Examples 1-11 of the present application, its anti-corrosion performance can be significantly improved, and at the same time, the adhesion, hardness and wear resistance of its coating are all significantly improved.

[0085] In summary, the corrosion-resistant cold work die steel and its preparation method provided by the present invention are adopted. The preparation method adopts double protection of cathodic protection and hard coating for the cold work die steel. After being treated by the preparation method of the present application, the cold work die steel not only has high hardness and high wear resistance, but also its anti-corrosion performance can be significantly improved. At the same time, the adhesion of its coating, the compactness of the coating and the storage stability are all significantly improved, so as to effectively improve the corrosion resistance of the cold work die steel under complex working conditions.

[0086] The foregoing are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing corrosion-resistant cold-working die steel, characterized in that: include: (1) Substrate surface treatment: removing surface contaminants from the cold working die steel and then subjecting it to shot blasting or sand blasting; (2) Cold-spray zinc treatment: a layer of zinc is sprayed on the surface of the cold-working die steel by cold-spray zinc coating and then dried naturally to obtain a pre-treated cold-working die steel; the raw materials of the cold-spray zinc coating include, by weight, 12-18 parts of graphene-modified epoxy resin, 70-78 parts of zinc powder, 1.2-1.5 parts of ethylene glycol methyl ether, 0.6-0.8 parts of methyl amyl alcohol, 0.1-0.3 parts of ethylene oxide, 1.5-2.5 parts of ethylenediamine and 3-5 parts of water; (3) PVD hard coating treatment: the pretreated cold working die steel is placed in a closed and vacuum PVD device, and a high-energy electron beam is used to evaporate the target material into a gaseous state, and the vaporized atoms react and deposit on the surface of the pretreated cold working die steel to form a coating layer of 3-5 μm; (4) Post-processing: polishing and cleaning.

2. The method for preparing the corrosion-resistant cold-working die steel according to claim 1, characterized in that: In step (2), the thickness of the zinc layer after drying is 45-55 μm.

3. The method for preparing the corrosion-resistant cold-working die steel according to claim 1, characterized in that: In step (2), the preparation of the graphene-modified epoxy resin comprises: Ultrasonic dispersion of graphene oxide in deionized water at a mass ratio of 6-8:400-600 to obtain a graphene oxide solution; The graphene oxide solution and the bisphenol A epoxy resin E-44 solution are mixed in a volume ratio of 0.2-0.4:10-12 to obtain a mixture; the concentration of the bisphenol A epoxy resin E-44 solution is 12%, and the solvent is ethylene glycol; The mixture is subjected to in-situ polymerization at 80-120° C.; After the reaction is completed, the reaction product is cooled and solidified at 120-150° C. for 1-2 hours.

4. The method for preparing the corrosion-resistant cold-working die steel according to claim 3, characterized in that: In step (2), before the graphene oxide solution is mixed with the bisphenol A epoxy resin E-44 solution, triethylenetetramine is added to the graphene oxide solution, the mass ratio of the graphene oxide to the triethylenetetramine is 2:0.8-1.2, and ultrasonic dispersion is continued to obtain a triethylenetetramine-modified graphene oxide dispersion; The bisphenol A epoxy resin E-44 solution is added to the triethylenetetramine modified graphene oxide dispersion at a volume ratio of 0.2-0.4:10-12, and stirred at room temperature at a stirring speed of 200-500 rpm for 2-3 hours.

5. The method for preparing the corrosion-resistant cold-working die steel according to claim 4, characterized in that: In step (2), the ultrasonic power is 380-430 W, the first ultrasonic time is 35-45 min, and the second ultrasonic time is 50-70 min.

6. The method for preparing the corrosion-resistant cold-working die steel according to claim 3, characterized in that: In step (2), the mixture is stirred at a stirring speed of 100-300 rpm for 4-6 hours.

7. The method for preparing the corrosion-resistant cold-working die steel according to claim 3, characterized in that: In step (2), the zinc powder has a particle size of 25-35 μm.

8. The method for preparing the corrosion-resistant cold-working die steel according to claim 1, characterized in that: In step (3), the vacuum degree is 10 -3 -10 -5 Pa, nitrogen is introduced, the deposition temperature is 390-410°C, the target material is CrN target, the power of the target material is 200-400W, and the deposition time is 3-4h.

9. The method for preparing the corrosion-resistant cold-working die steel according to claim 1, characterized in that: In step (1), after the substrate surface is treated, the surface cleanliness of the cold working die steel is greater than Sa2.5, and the surface roughness of the cold working die steel is 55-70 μm.

10. A corrosion-resistant cold working die steel, characterized in that: The corrosion-resistant cold-working die steel is prepared by the preparation method of any one of claims 1 to 9.

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