Surface treatment method for steel parts based on ultrasonic nano-strengthening

Abstract

This invention provides a surface treatment method for steel parts based on ultrasonic nano-strengthening, comprising the following steps: Step a: performing carbonitriding treatment on the steel parts; Step b: performing ultrasonic nano-strengthening treatment on the carbonitriding treated steel parts obtained in Step a; In Step a, the carbonitriding agent for carbonitriding treatment includes a boronizing agent and a carbonitriding agent, wherein the carbonitriding agent comprises the following components by mass percentage: 40-50% carbon black and 30-40% modified nitrogen-doped carbon material; The preparation method of the modified nitrogen-doped carbon material includes: adding sodium carboxymethyl cellulose to water, stirring to obtain sodium carboxymethyl cellulose hydrogel, adding NH4Cl to obtain NH4Cl / sodium carboxymethyl cellulose gel, drying, calcining, cooling to obtain nitrogen-doped carbon material, adding nitrogen-doped carbon material to a rare earth chloride aqueous solution, stirring, centrifuging, drying to obtain modified nitrogen-doped carbon material. This surface treatment method can significantly improve the fatigue resistance of steel parts.

Description

Technical Field

[0001] This invention patent relates to the field of metal surface treatment technology, and in particular to a method for surface treatment of steel parts based on ultrasonic nano-strengthening. Background Technology

[0002] Steel is one of the most widely used structural materials globally, with applications spanning almost all industrial and civil sectors, including construction, automotive, shipbuilding, machinery manufacturing, home appliances, infrastructure, and aerospace. Steel plays a crucial role in these fields due to its high strength, ductility, toughness, and cost-effectiveness. With technological advancements, the application areas of steel continue to expand. The performance of steel directly affects the safety, reliability, and economy of products. As industrial technology develops, the requirements for steel performance are also increasing. Although existing steel production processes are quite mature, the performance of existing steels remains insufficient for certain specific applications.

[0003] Many industrial applications of steel, such as hot work dies, heat exchangers, and turbine blades, operate in high-temperature environments. These components experience rapid temperature changes during operation, which causes thermal stress within the material, leading to thermal fatigue cracks and affecting their service life.

[0004] Therefore, it is necessary to study a method to improve the thermal fatigue properties of steel parts. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems existing in the prior art. Therefore, in a first aspect, the present invention provides a surface treatment method for steel parts based on ultrasonic nano-strengthening, comprising the following steps:

[0006] Step a: Perform carbonitriding treatment on the steel parts;

[0007] Step b: Perform ultrasonic surface nano-treatment on the carbonitrided steel parts obtained in step a;

[0008] In step a, the percolating agent for the carbon-nitrogen-boron co-diffusion treatment includes a boron percolating agent and a carbon-nitrogen co-diffusion agent. The carbon-nitrogen co-diffusion agent comprises the following components by mass percentage: 40-50% carbon black, 30-40% modified nitrogen-doped carbon material, 6-10% sodium carbonate, 2-6% sodium chloride, and 6-10% sodium acetate.

[0009] The preparation method of the modified nitrogen-doped carbon material includes the following steps:

[0010] Step 1): Add sodium carboxymethyl cellulose to water and stir to obtain sodium carboxymethyl cellulose hydrogel. Then add NH4Cl and disperse to obtain NH4Cl / sodium carboxymethyl cellulose gel.

[0011] Step 2): The NH4Cl / sodium carboxymethyl cellulose gel obtained in Step 1) is dried, calcined, and cooled to obtain nitrogen-doped carbon material;

[0012] Step 3): Add the nitrogen-doped carbon material to the rare earth chloride aqueous solution, stir, centrifuge, and dry to obtain the modified nitrogen-doped carbon material;

[0013] In step 1), the mass ratio of sodium carboxymethyl cellulose to NH4Cl is 5:8-12.

[0014] Through the above technical solution, modified nitrogen-doped carbon material is added to the carbonitriding agent. The addition of this modified nitrogen-doped carbon material facilitates the co-diffusion of carbon and nitrogen with iron to form iron-carbon-nitrogen compounds. Using sodium carboxymethyl cellulose and NH4Cl as carbon and nitrogen sources, the modified nitrogen-doped carbon material effectively inhibits dislocation movement, significantly improving the hardness of the carbonitriding layer. More importantly, it makes the hardness of the surface layer, carbonitriding layer, and boron-doped layer more similar, resulting in a gentler hardness gradient and increased deformation resistance. Furthermore, it generates more iron-nitrogen active sites in the steel, forming a more uniform and dense nitrogen-containing cementite, homogenizing micro-deformation and effectively preventing the formation and propagation of fatigue cracks. The addition of rare earth modification to the nitrogen-doped carbon material further promotes carbon and nitrogen infiltration, eliminating gaps between the carbonitriding layer and the boron-doped layer. Furthermore, when the mass ratio of sodium carboxymethyl cellulose to NH4Cl is too low, the nitrogen-containing cementite structure has defects, resulting in reduced hardness and the inability to form a uniform hardness gradient, thus reducing the thermal fatigue performance of the steel. When the mass ratio of sodium carboxymethyl cellulose to NH4Cl is too high, the diffusion rate is affected, the thickness of the carbonitriding layer becomes smaller, and the thermal fatigue performance of the steel is affected.

[0015] Preferably, in the carbonitriding agent, the mass ratio of the carbon black to the modified nitrogen-doped carbon material is 1-1.67:1.

[0016] The above technical solutions can control the carbon-nitrogen ratio in the carbonitriding agent to ensure the thickness of the carbonitriding layer. On the other hand, they can form a carbonitriding layer with higher hardness and a more uniform hardness gradient, thereby making the hardness gradient of the steel parts more moderate and the thermal fatigue performance better.

[0017] Preferably, in step 2), the calcination temperature is 800-1000℃.

[0018] By controlling the calcination temperature through the above technical solutions, the activity and diffusion rate of carbon can be improved, thereby improving the hardness and fatigue resistance of steel.

[0019] Preferably, in step 3), the mass concentration of the rare earth chloride aqueous solution is 10-20%, and the mass-volume ratio of the nitrogen-doped carbon material to the rare earth chloride aqueous solution is 1:30-50mL.

[0020] Preferably, in step 3), the rare earth chloride aqueous solution is a lanthanum chloride aqueous solution or a cerium chloride aqueous solution.

[0021] Preferably, the weight ratio of the boronizing agent to the carbonitriding agent is 0.9-1.1:1.

[0022] Preferably, in step a, the co-infiltration temperature is 700-900℃ and the co-infiltration time is 3-5h.

[0023] Preferably, the boronizing agent comprises the following components by mass percentage: 2-8% cerium chloride, 35-45% borax, 30-40% ferroboron alloy, 15-20% sodium fluorosilicate, and 1-5% ammonium chloride.

[0024] Preferably, the ultrasonic surface nano-treatment is ultrasonic surface rolling, wherein the static pressure of ultrasonic surface rolling is 200-400N, the ultrasonic frequency is 18-19kHz, the amplitude of the ultrasonic rolling head is 16-18μm, and the transverse feed rate is 0.2-0.8mm / min.

[0025] Ultrasonic surface rolling is an impact-pressure finishing method that cleverly and rationally improves traditional surface finishing processes by introducing high-power ultrasonic frequency mechanical vibration. It involves applying ultrasonic frequency mechanical vibration of a certain amplitude to the workpiece using an ultrasonic surface nano-processing tool head. Under certain static pressure and feed speed, the tool head transmits pressure and ultrasonic impact vibration to the surface of the mechanical parts. Utilizing the cold contraction properties of metals at room temperature, the material undergoes elastic and plastic deformation. This application combines ultrasonic surface rolling with carbonitriding treatment to improve the fatigue resistance of steel parts.

[0026] Preferably, the steel component is made of 15CrNiMo steel.

[0027] In a second aspect, the present invention provides an application of the above-described surface treatment method in improving the thermal fatigue properties of steel parts.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. This invention provides a surface treatment method for steel parts based on ultrasonic nano-strengthening, including carbonitriding treatment of the steel parts. The carbonitriding agent includes a boronizing agent and a carbonitriding agent. The carbonitriding agent includes carbon black and modified nitrogen-doped carbon material. The modified nitrogen-doped carbon material uses sodium carboxymethyl cellulose and NH4Cl as carbon and nitrogen sources, giving the modified nitrogen-doped carbon material unique electrical conductivity and surface properties. It can effectively prevent dislocation movement, give the steel more effective iron and nitrogen active sites, generate a more uniform and dense nitrogen-containing cementite, improve the hardness of the carbonitriding layer, and more importantly, make the hardness of the surface layer, carbonitriding layer and boronizing layer more similar, with a gentler hardness gradient, uniform micro-deformation, increased deformation resistance, and effective prevention of fatigue crack formation and propagation. Furthermore, when the mass ratio of sodium carboxymethyl cellulose to NH4Cl is too low, the nitrogen-containing cementite structure has defects, leading to reduced hardness and the inability to form a uniform hardness gradient, thus reducing the thermal fatigue performance of the steel. When the mass ratio of sodium carboxymethyl cellulose to NH4Cl is too high, the diffusion rate is affected, the thickness of the carbonitriding layer becomes smaller, and the thermal fatigue performance of the steel is also affected. The surface treatment method of this invention can significantly improve the fatigue resistance of steel parts.

[0030] 2. This invention provides a surface treatment method for steel parts based on ultrasonic nano-strengthening, which combines carbonitriding treatment with ultrasonic surface nano-treatment. The process is simple and greatly improves the fatigue resistance of steel parts. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. However, the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar with the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention. The carbon black was carbon black N110 purchased from Longxing Chemical Co., Ltd. The water-soluble carbon black was water-soluble pigment carbon black purchased from Anyang Wangtai New Materials Co., Ltd.

[0032] Preparation Example 1

[0033] The preparation of modified nitrogen-doped carbon materials includes the following steps:

[0034] Step 1): Add 5g of sodium carboxymethyl cellulose (CMC) to 180mL of ultrapure water and stir to obtain sodium carboxymethyl cellulose hydrogel. Then add 10g of NH4Cl and sonicate for 30min to obtain NH4Cl / sodium carboxymethyl cellulose gel.

[0035] Step 2): Dry the NH4Cl / sodium carboxymethyl cellulose gel obtained in Step 1), transfer it to a tube furnace, purge the air in the tube with nitrogen, then heat the tube furnace to 900℃ at a heating rate of 5℃ / min and calcine it for 2 hours, and then cool it naturally to room temperature to obtain nitrogen-doped carbon material.

[0036] Step 3): Prepare a 15% cerium chloride aqueous solution. Take 200 mL of the cerium chloride aqueous solution and add 5 g of the nitrogen-doped carbon material prepared by the method in step 2). Stir at 80°C for 2 h, centrifuge, and dry to obtain the modified nitrogen-doped carbon material.

[0037] Preparation Example 2

[0038] The difference between Preparation Example 2 and Preparation Example 1 is that the amount of NH4Cl used is different. In Preparation Example 2, the amount of NH4Cl used is 8g.

[0039] Preparation Example 3

[0040] The difference between Preparation Example 3 and Preparation Example 1 is that the amount of NH4Cl used is different. In Preparation Example 3, the amount of NH4Cl used is 12g.

[0041] Preparation Example 4

[0042] The difference between Preparation Example 4 and Preparation Example 1 is that in step 2), the calcination temperature is 800℃.

[0043] Preparation Example 5

[0044] The difference between Preparation Example 5 and Preparation Example 1 is that in step 2), the calcination temperature is 1000℃.

[0045] Preparation Example 6

[0046] The difference between Preparation Example 6 and Preparation Example 1 is that, in step 3), lanthanum chloride of equal mass is used instead of cerium chloride.

[0047] Preparation Example 7

[0048] The difference between Preparation Example 7 and Preparation Example 1 is that, in step 1), NH4Cl is replaced with an equal mass of urea.

[0049] Preparation Example 8

[0050] The difference between Preparation Example 8 and Preparation Example 1 is that, in step 1), sodium carboxymethyl cellulose (CMC) is replaced with an equal mass of water-soluble carbon black.

[0051] Preparation Example 9

[0052] The difference between Preparation Example 9 and Preparation Example 1 is that, excluding step 3), the nitrogen-doped carbon material prepared in this preparation example is the same as that prepared in step 2) of Preparation Example 1.

[0053] Preparation Example 10

[0054] The difference between Preparation Example 10 and Preparation Example 1 is that the amount of NH4Cl used is different. In Preparation Example 10, the amount of NH4Cl used is 6g.

[0055] Preparation Example 11

[0056] The difference between Preparation Example 11 and Preparation Example 1 is that the amount of NH4Cl used is different. In Preparation Example 11, the amount of NH4Cl used is 15g.

[0057] Example 1

[0058] Step a: Place 15CrNiMo steel in a temperature-controlled furnace, add a carburizing agent, and perform carbonitriding treatment at 800℃ for 4 hours. After heating, remove the steel while it is cooling in the furnace.

[0059] The penetrant is composed of boronizing agent and carbonitriding agent in a weight ratio of 1:1.

[0060] Boronizing agent (by weight): 5% cerium chloride, 40% borax, 36% ferroborone alloy, 17% sodium fluorosilicate, and 2% ammonium chloride.

[0061] Carbonitriding agent (mass percentage): carbon black 45%, modified nitrogen-doped carbon material 35%, anhydrous sodium carbonate 8%, sodium chloride 4%, anhydrous sodium acetate 8%. The modified nitrogen-doped carbon material was prepared using the method described in Preparation Example 1.

[0062] Step b: The 15CrNiMo steel treated with carbonitriding in step a was subjected to ultrasonic rolling nano-strengthening using an ultrasonic rolling equipment. The static pressure of the ultrasonic rolling process was 300N, the spindle speed was 200rpm, the frequency of the ultrasonic generator was 18.5kHz, the amplitude of the ultrasonic rolling head was 17μm, the transverse feed rate was 0.5mm / min, and the number of processing times was 10.

[0063] Example 2

[0064] The difference between Example 2 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the preparation method of Example 2.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the preparation method of Example 3.

[0067] Example 4

[0068] The difference between Example 4 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the preparation method of Example 4.

[0069] Example 5

[0070] The difference between Example 5 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the preparation method of Example 5.

[0071] Example 6

[0072] The difference between Example 6 and Example 1 is that the mass percentages of carbon black and modified nitrogen-doped carbon material in the carbonitriding agent are different. In Example 6, carbon black accounts for 50% and modified nitrogen-doped carbon material accounts for 30%.

[0073] Example 7

[0074] The difference between Example 7 and Example 1 is that the mass percentages of carbon black and modified nitrogen-doped carbon material in the carbonitriding agent are different. In Example 7, the carbon black content is 40% and the modified nitrogen-doped carbon material content is 40%.

[0075] Example 8

[0076] The difference between Example 8 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the method of Preparation Example 6.

[0077] Comparative Example 1

[0078] The difference between Comparative Example 1 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the method of Preparation Example 7.

[0079] Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the method of Preparation Example 8.

[0081] Comparative Example 3

[0082] The difference between Comparative Example 3 and Example 1 is that the modified nitrogen-doped carbon material was replaced with the nitrogen-doped carbon material prepared by the method of Preparation Example 9.

[0083] Comparative Example 4

[0084] The difference between Comparative Example 4 and Example 1 is that the modified nitrogen-doped carbon material was replaced with carbon black of the same mass.

[0085] Comparative Example 5

[0086] The difference between Comparative Example 5 and Example 1 is that carbon black was replaced by a modified nitrogen-doped carbon material of equal mass.

[0087] Comparative Example 6

[0088] The difference between Comparative Example 6 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the method of Preparation Example 10.

[0089] Comparative Example 7

[0090] The difference between Comparative Example 7 and Example 1 is that the modified nitrogen-doped carbon material is the modified nitrogen-doped carbon material prepared by the method of Preparation Example 11.

[0091] Thermal fatigue tests were conducted on the specimens of Examples 1-8 and Comparative Examples 1-7: A thermal fatigue testing machine was used to cycle the specimens in the temperature range of 20℃-800℃, with the highest temperature held for 120 seconds. The thermal fatigue performance was expressed as the length of the main crack in the steel after 6000 thermal cycles. The results are shown in Table 1.

[0092] Table 1

[0093] Main crack length (μm) Example 1 53 Example 2 98 Example 3 89 Example 4 85 Example 5 76 Example 6 77 Example 7 93 Example 8 73 Comparative Example 1 128 Comparative Example 2 113 Comparative Example 3 243 Comparative Example 4 156 Comparative Example 5 268 Comparative Example 6 171 Comparative Example 7 196

[0094] Comparing Comparative Example 1 with Example 1, it can be seen that the thermal fatigue performance of the steel decreases when the nitrogen source used in preparing the modified nitrogen-doped carbon material is changed. Comparing Comparative Example 2 with Example 1, it can be seen that the thermal fatigue performance of the steel decreases when the carbon source used in preparing the modified nitrogen-doped carbon material is changed. This may be because when the carbon source is sodium carboxymethyl cellulose and the nitrogen source is NH4Cl, it is easier to avoid dislocation movement during carbonitriding, resulting in a thicker carbonitrided layer with higher hardness and a more uniform hardness gradient.

[0095] Comparing Comparative Example 3 with Example 1, it can be seen that when nitrogen-doped carbon materials are not modified with rare earth elements, the thermal fatigue performance of steel deteriorates. This may be because, without the addition of rare earth elements, the diffusion rate of carbonitriding is disordered, resulting in an uneven carbonitriding layer and thus a deterioration in thermal fatigue performance.

[0096] Comparing Comparative Example 4 with Example 1, it can be seen that when the modified nitrogen-doped carbon material is replaced by carbon black or the same mass, the thermal fatigue performance of the steel deteriorates.

[0097] Comparing Comparative Example 5 with Example 1, it can be seen that replacing carbon black with a modified nitrogen-doped carbon material of equal mass results in a deterioration in the thermal fatigue performance of the steel.

[0098] Comparing Comparative Example 6 with Example 1, it can be seen that when the mass ratio of sodium carboxymethyl cellulose to NH4Cl in the raw materials for preparing modified nitrogen-doped carbon materials is too high, the thermal fatigue performance of the steel decreases.

[0099] Comparing Comparative Example 7 with Example 1, it can be seen that when the mass ratio of sodium carboxymethyl cellulose to NH4Cl in the raw materials for preparing modified nitrogen-doped carbon materials is too low, the thermal fatigue performance of the steel decreases.

[0100] A comparison of Examples 2 and 3 with Example 1 shows that the mass ratio of sodium carboxymethyl cellulose and NH4Cl in the raw materials of the modified nitrogen-doped carbon material affects the thermal fatigue properties of the steel.

[0101] A comparison of Examples 4 and 5 with Example 1 shows that the calcination temperature during the preparation of modified nitrogen-doped carbon materials affects the thermal fatigue properties of steel.

[0102] A comparison of Examples 6 and 7 with Example 1 shows that the mass ratio of carbon black to modified nitrogen-doped carbon material in carbonitriding agents affects the thermal fatigue properties of steel.

[0103] A comparison of Example 8 and Example 1 shows that the thermal fatigue properties of steel differ when nitrogen-doped carbon materials are modified with different rare earth elements. Cerium chloride shows a better effect, which may be because cerium chloride is more conducive to the infiltration of the nitrogen-doped carbon material.

[0104] 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, all of which should be included within the protection scope of the present invention.

Claims

1. A method for surface treatment of a steel piece based on ultrasonic nanoreinforcement, characterized in that, It comprises the following steps: Step a: carbonitridizing the steel piece; Step b: ultrasonic nanometer strengthening the steel piece treated by carbonitriding in step a; In step a, the carbonitriding agent comprises a boronizing agent and a carbonitriding agent, and the carbonitriding agent comprises the following components in percentage by mass: carbon black 40-50%, modified nitrogen-doped carbon material 30-40%, sodium carbonate 6-10%, sodium chloride 2-6%, and sodium acetate 6-10%. The modified nitrogen-doped carbon material is prepared by the following method: Step 1): adding sodium carboxymethyl cellulose into water, stirring, preparing sodium carboxymethyl cellulose hydrogel, adding NH4Cl, and dispersing to obtain NH4Cl / sodium carboxymethyl cellulose gel; Step 2): drying and calcining the NH4Cl / sodium carboxymethyl cellulose gel obtained in step 1), and cooling to obtain nitrogen-doped carbon material; Step 3): adding the nitrogen-doped carbon material into a rare earth chloride aqueous solution, stirring, centrifuging, and drying to obtain modified nitrogen-doped carbon material; In step 1), the mass ratio of sodium carboxymethyl cellulose to NH4Cl is 5:8-12; In the carbonitriding agent, the mass ratio of the carbon black to the modified nitrogen-doped carbon material is 1-1.67:1; In step 2), the calcination temperature is 800-1000℃.

2. The ultrasonic nanostrengthening-based surface treatment method of a steel piece according to claim 1, characterized in that, In step 3), the mass concentration of the rare earth chloride aqueous solution is 10-20%, and the mass-volume ratio of the nitrogen-doped carbon material to the rare earth chloride aqueous solution is 1:30-50 mL.

3. The ultrasonic nanostrengthening-based surface treatment method for steel pieces according to claim 1, characterized in that, In step 3), the rare earth chloride aqueous solution is lanthanum chloride aqueous solution or cerium chloride aqueous solution.

4. The ultrasonic nanostrengthening-based surface treatment method for steel pieces according to claim 1, characterized in that, The weight ratio of the boronizing agent to the carbonitriding agent is 0.9-1.1:

1.

5. The ultrasonic nanostrengthening-based surface treatment method for steel pieces according to claim 1, characterized in that, In step a, the co-diffusion temperature is 700-900℃, and the co-diffusion time is 3-5h.

6. The ultrasonic nanostrengthening-based surface treatment method for steel pieces according to claim 1, characterized in that, The boronizing agent comprises the following components in percentage by mass: cerium chloride 2-8%, borax 35-45%, boron-iron alloy 30-40%, sodium fluorosilicate 15-20%, and ammonium chloride 1-5%.

7. The ultrasonic nanostrengthening-based surface treatment method for steel pieces according to claim 1, characterized in that, The ultrasonic nanometer strengthening is ultrasonic surface rolling, the static pressure of the ultrasonic surface rolling is 200-400N, the ultrasonic frequency is 18-19 kHz, the amplitude of the ultrasonic rolling processing head is 16-18μm, and the transverse feed amount is 0.2-0.8mm / min.

8. Application of the surface treatment method in any of claims 1-7 in improving the thermal fatigue performance of a steel piece.