Preparation method of metal surface oxide film

Abstract

The present invention relates to the technical field of metal surface treatment, and provides a method for preparing a metal surface oxide film, comprising: performing water jet shot peening on the metal to form a deformation layer on the metal surface; performing surface ultrasonic rolling on the metal that has completed the water jet shot peening to form a gradient lamellar structure based on the deformation layer; detecting and analyzing whether the gradient lamellar structure meets the preset film forming standards, and if so, continuing the film forming process; if not, re-performing the above steps; and reacting the gradient lamellar structure with oxygen to form an oxide film. According to the solution of the present invention, high-strength quenched and tempered steel can quickly produce an oxide layer with good self-lubricity and high stability during the friction process, greatly improving the ability of high-strength quenched and tempered steel to resist friction and wear.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, in particular to a method for preparing a metal surface oxide film. Background Art

[0002] In the aerospace, automotive, and energy sectors, wear caused by micro-motion or sliding contact of metal parts remains a major industrial problem. Energy losses associated with friction and wear account for more than 20% of global energy consumption, with an estimated annual cost of more than €2.5 trillion, and the most widely used metal structural materials bear the brunt of this problem. Producing a continuous lubrication effect during the friction process of metal materials without the addition of a lubricating medium has become a hot topic and an important approach to solving their anti-wear problems. Improving the friction-reducing and wear-resistant properties of materials by forming a lubricating friction oxide layer can be promoted for their application in high-reliability and long-life service of key components of high-end equipment such as bearing bushings, high-speed train wheels / rails, and cylinder liners.

[0003] Self-lubrication has garnered widespread attention from researchers in the field of materials friction. Through new material development or alloy design, researchers aim to induce physical and chemical reactions and microstructural evolution during friction, thereby achieving a lubricating effect that reduces friction coefficients and wear. However, both material upgrades and component design face significant challenges in terms of timeliness and cost. For example, laser deposition can be used to add aluminum and nickel to metal surfaces to promote their reaction with oxygen, forming an oxide film. However, this requires the addition of additional powders, which require a high powder ratio and are difficult to control. Another approach, using supersonic particle bombardment to produce nanocrystals on metal surfaces, can increase the oxidation rate and rapidly form an oxide film. However, this method relies on a single, strong plastic deformation method, which lacks the ability to better control the formation of gradient structures and enhance the stability of the oxide film. Furthermore, compared to nanosheets, nanosheets are more likely to form nano-oxide particles, which are smaller in size. Existing methods also employ methods such as magnetron sputtering or chemical deposition to directly preform oxides on surfaces. However, this can alter the composition of the original material, affecting mechanical properties or other performance characteristics. On the other hand, the oxides produced by magnetron sputtering or chemical deposition methods have weak bonding with the substrate, making them prone to cracking at the interface during service. Therefore, in the field of metal surface treatment, methods that can effectively reduce time and cost while improving the stability and wear resistance of self-lubricating layer structures need further research. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one technical problem in the background technology and provide a method for preparing an oxide film on a metal surface.

[0005] To achieve the above object, the present invention provides a method for preparing a metal surface oxide film, comprising:

[0006] Perform water jet shot peening on the metal to form a deformation layer on the metal surface;

[0007] Performing surface ultrasonic rolling on the metal that has undergone the water jet shot peening treatment to form a gradient laminar structure on the basis of the deformed layer;

[0008] Detecting and analyzing whether the gradient layer structure meets the preset film forming standards, if so, continuing the film forming process, if not, re-performing the above steps;

[0009] The gradient layer structure reacts with oxygen to form an oxide film.

[0010] According to one aspect of the present invention, the gradient lamellar structure includes nano-lamellae, martensite lamellars supporting the nano-lamellae, and matrix coarse grains supporting the martensite lamellars.

[0011] According to one aspect of the present invention, the preset film forming standards include:

[0012] There are no cracks in the gradient laminar structure;

[0013] The size of the nanosheets is within a threshold range;

[0014] The thickness of the nanosheets is within a threshold range.

[0015] According to one aspect of the present invention, the scale of the nanosheet is ≤10 nm.

[0016] According to one aspect of the present invention, the thickness of the nanosheet is ≤1 μm.

[0017] According to one aspect of the present invention, the process parameters of the water jet shot peening include: shot peening angle 90°, target distance 6-15 mm, water pressure 80-160 MPa, nozzle linear speed 400-800 mm / min, and jet abrasive is steel shot.

[0018] According to one aspect of the present invention, the process parameters of the surface ultrasonic rolling include: static pressure 0.1-0.2 MPa, frequency 20-30 KHz, feed amount 0.02-0.1 mm, and rolling times 4-10 times.

[0019] According to one aspect of the present invention, a transmission electron microscope is used to detect and analyze whether the gradient layer structure meets the preset film forming standard.

[0020] According to one aspect of the present invention, the thickness of the oxide film is less than 1 μm.

[0021] According to one aspect of the present invention, the oxide film is composed of iron-based nano-oxide particles.

[0022] According to one solution of the present invention, high-strength quenched and tempered steel is fixed on a high-pressure water jet shot peening machine to complete the water jet shot peening process, thereby forming a deformation layer with good surface integrity and a large thickness.

[0023] According to one solution of the present invention, high-strength quenched and tempered steel that has undergone water jet shot peening is clamped on a surface ultrasonic rolling machine to complete the surface ultrasonic rolling process. Based on the formed large thickness deformation layer, a gradient laminar structure can be formed on the surface of the quenched and tempered steel through multiple ultrasonic rolling passes.

[0024] According to one embodiment of the present invention, high-strength quenched and tempered steel treated with a composite surface deformation strengthening process (water jet shot peening and surface ultrasonic rolling) can be directly used in dry sliding friction or micro-friction conditions. During the friction process, its friction surface can react in situ with oxygen in the air, and the outermost nano-layers are transformed into an oxide film with lubricating properties.

[0025] According to the present invention, a method employs a composite surface deformation strengthening process combining high-pressure water jets and ultrasonic rolling to create a unique gradient lamellar structure on the surface of quenched and tempered steel. The surface of this gradient lamellar structure comprises ultrafine and fragmented nano-lamellae. These ultrafine and fragmented nano-lamellae promote friction-oxidation reactions, rapidly forming an oxide film that protects the worn surface. The high-gradient martensitic lamellae beneath the nano-lamellae support the lubricating oxide film produced by the oxidation reaction of the nano-lamellae, making it less susceptible to detachment during sustained friction. This method enables high-strength quenched and tempered steel to rapidly produce a highly stable, self-lubricating oxide layer during friction, significantly enhancing its resistance to friction and wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart schematically showing a method for preparing a metal surface oxide film according to one embodiment of the present invention;

[0027] Figure 2 Shows the wear scar image of metal without any surface treatment;

[0028] Figure 3 Shows the wear scar image of metal treated by water jet;

[0029] Figure 4 Shows the metal wear scar image after being processed by the method of the present invention;

[0030] Figure 5 Shows the use of Figure 2-Figure 4 Figure 2 shows the metal friction coefficient corresponding to different treatment methods;

[0031] Figure 6 Shows the use of Figure 2-Figure 4Metal wear rate diagram corresponding to different treatment methods;

[0032] Figure 7 The figure shows that the oxide layer formed by friction after metal surface modification is supported by gradient martensite lamellae;

[0033] Figure 8 A diagram showing the distribution of lamellar sizes for a gradient lamellar structure;

[0034] Figure 9 Figure 2 shows an oxide film supported by martensite lamellae and matrix coarse grains. DETAILED DESCRIPTION

[0035] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only intended to enable those skilled in the art to better understand and implement the present invention, rather than to imply any limitation on the scope of the present invention.

[0036] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0037] Figure 1 Schematically showing a flow chart of a method for preparing a metal surface oxide film according to one embodiment of the present invention. Figure 1 As shown, the method for preparing a metal surface oxide film according to the present invention comprises the following steps:

[0038] S1. Perform water jet shot peening on the metal to form a deformation layer on the metal surface;

[0039] S2. The metal surface is subjected to ultrasonic rolling treatment after water jet shot peening to form a gradient laminar structure on the basis of the deformed layer;

[0040] S3. Detection and analysis of the gradient layer structure to see if it meets the preset film forming standards. If so, continue the film forming process. If not, re-execute the above steps.

[0041] S4. Make the gradient layer structure react with oxygen to form an oxide film.

[0042] According to one embodiment of the present invention, in step S1, the metal is a tempered steel material with a tempered martensite microstructure and a medium carbon content, such as 40CrNiMoA. By varying the composite surface deformation strengthening process parameters, the quenched and tempered steel material can achieve different deformation layer thicknesses, nano-martensite lamellae sizes, and gradient ranges on the surface of the material, thereby achieving different lubrication effects. In this embodiment, high-strength quenched and tempered steel is secured to a high-pressure water jet shot peening machine to perform the water jet shot peening process. This step can form a deformation layer with good surface integrity and a large thickness.

[0043] According to one embodiment of the present invention, in the above-mentioned step S2, the high-strength quenched and tempered steel that has completed water jet shot peening in step S1 is clamped on a surface ultrasonic rolling machine to complete the surface ultrasonic rolling process. In this step, based on the large thickness deformation layer formed in step S1, a gradient laminar structure is formed on the surface of the quenched and tempered steel through multiple ultrasonic rolling passes.

[0044] According to one embodiment of the present invention, in the above-mentioned S4 step, the high-strength quenched and tempered steel treated with a composite surface deformation strengthening process (water jet shot peening and surface ultrasonic rolling) can be directly used in dry sliding friction or micro-friction conditions. During the above-mentioned friction process, its friction surface can react in situ with oxygen in the air, and the outermost nano-layer is transformed into an oxide film with a lubricating effect.

[0045] In this embodiment, the gradient lamellar structure comprises nanolamellae, martensitic lamellae supporting the nanolamellae, and matrix coarse grains supporting the martensitic lamellae. When this structure is formed, the nanolamellae, formed by the movement and proliferation of dislocations, form a high surface energy structure that reacts more readily with oxygen in the air to form a lubricating oxide film than ordinary coarse grains. Within the gradient structure, the scale of the martensitic lamellae varies with depth, and strain gradients are accommodated harmoniously near the interfaces of different depth regions. This deformation-induced process further enhances continuous hardening and load-bearing capacity. This nanolamellae + martensitic lamellae + coarse grain structure coordinates frictional deformation within the friction layer, further supporting surface oxides, maintaining their stability, and promoting their protective properties.

[0046] According to the aforementioned solution of the present invention, the method utilizes a composite surface deformation strengthening process combining high-pressure water jets and ultrasonic rolling to construct a unique gradient lamellar structure on the surface of the tempered steel. The surface of this gradient lamellar structure comprises ultrafine and fragmented nano-lamellae. These ultrafine and fragmented nano-lamellae promote friction-oxidation reactions, rapidly forming an oxide film that protects the worn surface. The high-gradient martensitic lamellae beneath the nano-lamellae support the lubricating oxide film generated by the oxidation reaction of the nano-lamellae, preventing it from falling off during sustained friction. This method enables high-strength tempered steel to rapidly produce a highly stable, self-lubricating oxide layer during friction, significantly enhancing its resistance to friction and wear.

[0047] Furthermore, in this embodiment, the above detection and analysis of whether the gradient layer structure meets the preset film forming standards includes:

[0048] There are no cracks in the gradient laminar structure;

[0049] The scale of the nanosheets is within the threshold range;

[0050] The thickness of the nanosheets is within the threshold range.

[0051] In this embodiment, the scale of the nano-sheet is ≤10 nm. In this embodiment, the scale of the nano-oxide particles in the final oxide film depends on the scale of a single nano-sheet. The oxide particles with a scale less than 10 nanometers formed in the subsequent reaction with oxygen can better lubricate the friction surface.

[0052] The thickness of the nanosheet is ≤ 1 μm. In this embodiment, the thickness of the nanosheet determines the thickness of the lubricating oxide film formed later. When the thickness of the nanosheet is greater than 1 μm, cracks are likely to form at the interface between the nanosheet and the underlying martensite sheet, resulting in the entire oxide film falling off after formation.

[0053] Furthermore, in this embodiment, the process parameters of water jet shot peening include: shot peening angle 90°, target distance 6-15 mm, water pressure 80-160 MPa, nozzle linear speed 400-800 mm / min, and jet abrasive is steel shot. In this embodiment, when the shot peening angle is 90°, the residual stress, surface hardness, and surface roughness are better than when the shot peening angle is less than 90° or greater than 90°. When the target distance is greater than 15mm, the surface residual stress and surface hardness are small, while when the target distance is less than 6mm, the impact force is too large, the material removal amount is too large, and the surface roughness is too large. When the water pressure is less than 80Mpa, the deformation effect is poor, while when the water pressure is greater than 160Mpa, the surface is too rough and prone to cracking. When the nozzle linear speed is less than 400mm / min, the number of local impacts is too high, the distribution is uneven, and the production efficiency is low. When the nozzle linear speed is greater than 800mm / min, the surface residual stress and surface hardness are too low. The jet abrasive is steel shot, which has a greater impact force than glass shot and can achieve a smaller surface roughness. This configuration can form a thicker and more high-performance deformation layer on the metal surface after water jet shot peening.

[0054] Furthermore, in this embodiment, the process parameters for surface ultrasonic rolling include: static pressure of 0.1-0.2 MPa, frequency of 20-30 kHz, feed rate of 0.02-0.1 mm, and rolling times of 4-10. In this embodiment, when the static pressure is greater than 0.2 MPa, surface cracks are likely to form, while when it is less than 0.1 MPa, the modification effect is not significant. When the frequency is less than 20 kHz, the surface residual stress and surface hardness do not meet the requirements, and the surface roughness is excessive. When the frequency is greater than 30 kHz, cracks are likely to form. When the feed rate is less than 0.02 mm, production efficiency is too low, while when it is greater than 0.1 mm, the surface roughness is excessive. When the rolling times are less than 4, the deformation amount does not meet the requirements and nano-lamellae cannot be formed. When it is greater than 10, cracks appear on the surface and the roughness increases. This configuration allows the surface ultrasonic rolling treatment to form an optimally performing gradient lamellar structure, including nano-lamellae and martensitic lamellars, based on the above-mentioned deformation layer.

[0055] According to one embodiment of the present invention, the water jet shot peening and surface ultrasonic rolling are respectively performed on 40CrNiMoA steel using SQ1313 CNC water jet equipment and VMC500 CNC Hawken ultrasonic rolling system, and the specific process parameters are the above parameters. The surface roughness Ra tested by Olympus OLS4100 laser confocal microscope is 0.3μm, the residual compressive stress is 869MPa using Italian GNR STRESS-X X-ray residual stress analyzer, and the surface microhardness is 590HV using HVS-1000 digital display microhardness tester. Such a scheme combined with the above parameter settings can obtain the above-mentioned crack-free, optimal mechanical properties and microstructure gradient lamellar structure, ensuring the self-lubricating properties, stability and wear resistance of the subsequently formed oxide film.

[0056] According to one embodiment of the present invention, in the above-mentioned step S3, the tempered steel after the composite surface deformation strengthening treatment is detected and analyzed by a projection electron microscope to detect and analyze whether the gradient lamellar structure thereon meets the above-mentioned film-forming standards. If it meets the standards, it is directly used in the actual working conditions of dry sliding friction wear or micro-friction wear. After a certain period of use, the in-situ FIB sampling technology is used to extract the wear scar transmission sample. By observing the cross-section of the wear scar under a high-resolution transmission electron microscope, it can be observed that the tempered steel has formed a self-lubricating protective layer of nano-oxide particles after the friction oxidation reaction.

[0057] Furthermore, in this embodiment, the thickness of the oxide film is less than 1 μm, and the oxide film is composed of iron-based nano-oxide particles. In this embodiment, the thickness of the oxide film is related to the total thickness of the nano-layer sheet. The thicker the oxide film, the better. The formation of a thicker oxide film will cause cracks to easily form at the interface between the oxide film and the martensite layer sheet, and the oxide film will eventually fall off very easily. On the other hand, the formation of the oxide film is, in a sense, the formation of the original surface material after the reaction with oxygen after the damage. The thin oxide film indicates that the degree of material damage is relatively light and can achieve better lubricity. In this embodiment, when the thickness of the oxide film is less than 1 μm, it can be guaranteed not to fall off while having better lubricity.

[0058] Based on the above solution of the present invention, the solution of the present invention is described in detail below in the form of a specific embodiment in conjunction with the accompanying drawings.

[0059] Example 1

[0060] The method for accelerating the in-situ formation of a lubricating oxide film on the surface of 40CrNiMoA steel comprises the following steps:

[0061] (1) Take 40CrNiMoA steel bars with a length of 40 mm and a radius of 6 mm and make several friction pair samples.

[0062] (2) The friction pair sample was fixed to the chuck using a fixture. A CNC machine was programmed to move the chuck and nozzle along a specific trajectory to ensure water jet shot peening coverage. The shot peening process parameters were set as follows: jet angle 90°, water pressure 95 MPa, target distance 7 mm, nozzle linear speed 700 mm / min, and abrasive flow rate 185 ml / min. The abrasive used was steel shot with a diameter of 0.1 mm.

[0063] (3) The friction pair sample that has been treated with water jet shot peening is clamped and fixed on the chuck. The CNC machine tool is programmed to move the chuck and tool head along a certain trajectory to ensure the coverage of the ultrasonic rolling. The ultrasonic rolling process parameters are set as follows: static load pressure 0.18 MPa, ultrasonic frequency 2.5 kHz, rolling times 8 times, and feed rate 0.03 mm.

[0064] (4) In order to study the tribological behavior of materials after different process treatments, the present embodiment carried out tribological behavior tests on 40CrNiMoA quenched and tempered steel without treatment, after water jet shot peening alone, and after water jet shot peening + ultrasonic rolling treatment under the same friction conditions. The experimental results show that the wear resistance of the metal material after the water jet shot peening process alone is improved compared with that of the untreated material, which makes the time when the friction coefficient begins to decrease in the friction process be advanced. However, the combined treatment of water jet shot peening + ultrasonic rolling has the best effect and the corresponding wear rate is the lowest. Figure 2-Figure 6 As shown, Figure 2 The figure shows the wear scar of metal without any surface treatment; Figure 3 Shown is the wear scar image of the metal that has only been treated with water jet; Figure 4 The figure shows the metal wear scars after being processed by the method of the present invention. Figure 2 and Figure 3 It was found that the wear scar depth of the metal treated by the method of the present invention was the shallowest and the overall wear scar volume was the smallest. Figure 5 Shown is the use of Figure 2-Figure 4 The metal friction coefficient diagram corresponding to different treatment methods is shown in FIG. 1 . By comparing, it is found that the metal friction coefficient reduced fastest after being treated by the method of the present invention. Figure 6 Shown is the use of Figure 2-Figure 4 The metal wear rate diagram corresponding to the three different treatment methods is shown in FIG. 1 . By comparison, it is found that the metal wear rate after treatment by the method of the present invention is the lowest.

[0065] (5) Based on the oxide layer structure and element distribution, it can be seen that the oxide layer of the untreated 40CrNiMoA quenched and tempered steel is mainly composed of nano-sized ferric oxide, and the friction layer structure below is mainly martensite lamellae. Cracks will occur in both the oxide and lamellae structure. Although the friction oxide layer after surface deformation strengthening treatment is also composed of nano-sized ferric oxide, the scale of the martensite lamellae below is significantly smaller (average 24.2nm) compared with the untreated steel and has a certain gradient distribution feature. In addition, no cracks will appear in the oxide layer or the martensite lamellae.

[0066] According to the method of the present invention, the following Figure 7-Figure 9 The structure and dimensions shown in Figure 7 The figure shows that the oxide layer formed by friction after metal surface modification is supported by gradient martensite lamellae. From the figure, it can be seen that the surface oxide layer is formed on the metal after surface modification during the friction service process, and the lower part is the martensite lamellae supporting the oxide layer. Figure 8 A diagram showing the distribution of lamellar sizes for a gradient lamellar structure; Figure 9 The figure shows the oxide film supported by martensite lamellae and matrix coarse grains. Based on this, it can be concluded that if different gradient structures are constructed by adjusting the relevant parameters of steps (1)-(3) in the embodiment, the structure will evolve into the following after friction: Figure 7 The microstructure shown will obtain the different tribological performances mentioned in step (4), and can also obtain the different oxide layer structures and element distributions mentioned in step (5), further regulating the speed and stability of forming a lubricating oxide film.

[0067] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a metal surface oxide film, characterized in that: include: The metal is high-strength quenched and tempered medium carbon steel, and its structure is tempered martensite; Perform water jet shot peening on the metal to form a deformation layer on the metal surface; Performing surface ultrasonic rolling on the metal that has undergone the water jet shot peening treatment to form a gradient laminar structure on the basis of the deformed layer; Detecting and analyzing whether the gradient layer structure meets the preset film forming standards, if so, continuing the film forming process, if not, re-performing the above steps; The gradient lamellar structure reacts with oxygen to form an oxide film; The gradient lamellar structure includes nano-lamellae, martensite lamellars supporting the nano-lamellae, and matrix coarse grains supporting the martensite lamellars; The thickness of the oxide film is less than 1 μm; The preset film forming standards include: There are no cracks in the gradient laminar structure; The scale of the nanosheet is ≤10nm; The thickness of the nanosheet is ≤1 μm; The oxide film is composed of iron-based nano-oxide particles.

2. The method for preparing a metal surface oxide film according to claim 1, wherein: The process parameters of the water jet shot peening include: a shot peening angle of 90°, a target distance of 6-15 mm, a water pressure of 80-160 MPa, a nozzle linear speed of 400-800 mm / min, and a jet abrasive is steel shot.

3. The method for preparing a metal surface oxide film according to claim 1, wherein: The process parameters of the surface ultrasonic rolling include: static pressure 0.1-0.2 MPa, frequency 20-30 KHz, feed amount 0.02-0.1 mm, and rolling times 4-10 times.

4. The method for preparing a metal surface oxide film according to claim 1, wherein: Transmission electron microscopy is used to detect and analyze whether the gradient layer structure meets the preset film-forming standards.

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