A friction-reducing and wear-resistant coupling layer on a metal surface and a preparation method thereof

Abstract

The present invention discloses a friction-reducing and wear-resistant coupling layer on a metal surface and a preparation method thereof, comprising the following steps: Step 1: constructing a nitride layer on the metal surface using a laser; Step 2: constructing an array of groove microtextures on the surface of the nitride layer in Step 1; Step 3: constructing a lamellar lubrication layer on the surface of the groove microtexture in Step 2 to obtain a lamellar lubrication / microtexture / nitride coupling layer on the metal surface. The present invention sequentially performs laser nitridation, surface microtexturing, and solid lubrication treatment on the surface of a metal substrate to construct a nano-lubrication / microtexture / nitride friction-reducing and wear-resistant coupling layer on the metal substrate surface. This layer imparts long-lasting friction reduction, wear resistance, and corrosion resistance to the metal substrate surface, thus providing an excellent metal substrate surface protection technology.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface wear-resistant functional modification, in particular to a metal surface friction-reducing and wear-resistant coupling layer and a preparation method thereof. Background Art

[0002] At present, the commonly used methods in the field of metal surface wear-resistant functional modification include metal surface coating treatment, metal surface alloying treatment, metal surface structure design and other technologies.

[0003] Metal surface coating treatment generally involves coating the metal surface with relatively stable organic polymer materials or inorganic lubricating materials, such as epoxy resin, molybdenum disulfide, etc. This technology is convenient and fast, and can quickly form a protective cushion layer on the metal surface to prevent external punching friction from causing wear on the metal substrate. However, since organic polymer materials generally contain a large number of active groups such as hydroxyl or carbonyl groups, the coating is prone to aging during use, and in the complex wear process, it is very easy to fall off from the metal surface, eventually leading to protection failure. Although the lamellar sliding effect of inorganic lubricating materials can effectively reduce the friction coefficient, it often needs to reach a certain thickness to exert a stable friction reduction effect. Under severe vibration conditions, it is difficult for it to exist stably on the surface of the metal substrate for a long time.

[0004] Metal surface alloying treatment refers to the use of laser surface alloying, pulsed laser deposition, magnetron sputtering and other technologies to melt or deposit a layer of alloying elements on the metal surface to provide protection for the metal surface. The alloy coating formed by this technology has relatively good bonding with the metal substrate and has an ideal metal protection effect. However, the conditions required for metal surface alloying treatment are relatively harsh. Some technologies need to be operated under a specific inert gas environment and pressure, which places high demands on equipment and operators, limits efficiency, and has high operating costs. In addition, it is difficult to effectively reduce friction on metal uranium by forming only a micron-sized alloying layer on the metal surface. Under long-term wear conditions, the alloying layer is easily damaged by wear.

[0005] Metal surface structure design utilizes technologies such as pulsed lasers, ultrasonic rolling, or heat treatment to create a specific microstructure on the metal surface or to achieve phase transformation strengthening through grain refinement. This design cleverly utilizes the friction reduction mechanism of microtexture or the metal's inherent phase transformation strengthening to provide excellent wear protection without affecting the metal's surface composition. However, this type of technology has limited protective performance. While the modified metal surface exhibits improved wear resistance, the hardness of the substrate itself will largely determine the structural stability of the structure. Under strong punching friction, the surface structure is easily damaged by wear.

[0006] The surface wear resistance of high-value-added precision metal devices will greatly affect their reliability in engineering applications, such as precision bearings in aerospace, artificial joints and bones in the medical field, or uranium materials in the nuclear industry. Among them, metallic uranium is widely used in the nuclear industry and other fields due to its unique nuclear properties. However, due to the complexity and diversity of the use environment, it is very easy to suffer from problems such as oxidation corrosion and friction and wear during service, resulting in damage to its surface structure, which will threaten its application reliability in severe cases. Constructing a surface passivation layer can effectively reduce the oxidation corrosion of the metal. However, during service, the passivation layer is easily damaged by friction and wear and fails. Based on this, the development of a friction-reducing and wear-resistant functional layer will greatly improve the reliability of metallic uranium applications. Summary of the Invention

[0007] The present invention aims to solve the problems of oxidation corrosion and friction wear that easily occur to metals during use, and provides a friction-reducing and wear-resistant coupling layer on a metal surface and a preparation method thereof.

[0008] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0009] A method for preparing a friction-reducing and wear-resistant coupling layer on a metal surface comprises the following steps:

[0010] Step 1: Use laser to build a nitride layer on the metal surface;

[0011] Step 2: constructing a groove micro-texture arranged in an array on the surface of the nitride layer in step 1;

[0012] Step 3: construct a lamellar lubrication layer on the surface of the groove microtexture in step 2 to obtain a metal surface lamellar lubrication / microtexture / nitridation coupling layer.

[0013] Furthermore, in step 1, the specific steps include: constructing a nitride layer on the uranium surface using a laser in a nitrogen atmosphere.

[0014] Furthermore, the nitrogen atmosphere is 1 to 3 atmospheres, the laser output power is 10 to 60 W, the scanning speed is 50 to 100 mm / s, and the scanning step length is 0.3 to 1.0 mm.

[0015] Furthermore, in step 2, the specific steps include: using a marking machine to construct a groove micro-texture on the metal surface by regulating the laser beam efficiency, frequency, scanning speed, and path.

[0016] Furthermore, the laser beam efficiency is 10% to 30%, the frequency is 15 to 40 kHz, and the scanning speed is 500 to 15000 mm / s.

[0017] Furthermore, the groove has a diameter of 100 to 150 μm and a depth of 0.2 to 1.0 μm.

[0018] Furthermore, the lamellar lubricating layer adopts a solid lubricant, and the solid lubricant is any one of molybdenum disulfide, tungsten disulfide, and graphene.

[0019] Furthermore, the solid lubricant powder is evenly coated on the surface of the uranium substrate, with a coating amount of 0.01 to 0.05 g / cm 2 .

[0020] The present invention also provides a metal surface friction-reducing and wear-resistant coupling layer, which is prepared by the above method.

[0021] The present invention has the following beneficial effects:

[0022] 1. It is difficult to make the metal substrate chemically inert due to metal surface coating treatment and metal surface structure design, and it is easy to suffer from corrosion and wear during the wear process. The coupling layer prepared by the present invention has good wear resistance and corrosion resistance. The reason is that the bottom layer of the prepared coupling layer is a nitride layer with high hardness, so it can effectively protect the microtexture. In addition, the nitride layer has stable chemical properties and has extremely strong corrosion resistance in the atmospheric environment.

[0023] 2. The metal surface alloying technology and surface structure design have limited friction reduction properties for the substrate, which is easily worn out and fails during use, thereby accelerating the corrosion and wear of the uranium substrate. The coupling layer prepared by the present invention has excellent friction reduction properties because the solid lubricating material on the surface of the coupling layer can effectively reduce the friction coefficient, thereby reducing the damage caused by punching friction and improving the anti-friction and wear performance of the substrate.

[0024] 3. The friction-reducing and wear-resistant protective layer prepared by metal surface coating treatment is difficult to stably exist on the surface of the uranium substrate and is likely to deteriorate the physical and chemical properties of the uranium substrate; the metal surface structure design is difficult to give the surface an extremely low friction coefficient, and the hardness improvement value is limited; the friction-reducing performance provided by the metal surface alloying technology is limited. The coupling layer prepared by the present invention has stable friction-reducing and wear-resistant performance. The solid lubricating material on the surface of the prepared coupling layer is stored in large quantities in the surface microtexture. During the friction and wear process, it can be continuously replenished from the microtexture grooves between the friction pairs. In addition, the harder nitride layer can also effectively protect the microtexture. Therefore, the coupling layer has stable friction-reducing and wear-resistant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the wear-reducing and coupling-resistant layer on the surface of metallic uranium and its preparation process;

[0026] Figure 2 is the wear resistance diagram of the sample after only laser nitriding and microtexturing treatment;

[0027] Figure 3Scanning electron micrographs of uranium samples after modification (a) untreated; U, (b) laser nitriding: U-LSN, (c) nitriding / microtexture: U-LSN / T, (d) nitriding / microtexture / solid lubrication: U-LSN / TL; (e) data on the change in friction coefficient of the uranium substrate surface under different conditions under a 2N load;

[0028] Figure 4 Scanning electron microscopy and energy spectrum scanning data after wear experiments. (a) Original uranium sample, (b) Surface nitriding / microtexture: U-LSN / T, (d) Surface nitriding / microtexture / solid lubrication: U-LSN / TL. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described clearly and completely below with reference to the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] like Figure 1 As shown, a method for preparing a friction-reducing and wear-resistant coupling layer on a metal surface comprises the following steps:

[0032] Step 1: Use a laser to build a nitride layer on the metal surface.

[0033] Specifically, in step 1, the specific steps include: using a laser to construct a nitride layer on the uranium surface under a nitrogen pressure range of 1 to 3 atmospheres (0.1 atm ≈ 1 atmosphere), wherein the laser output power is 10 to 60 W, the scanning speed is 50 to 100 mm / s, and the scanning step length is 0.3 to 1.0 mm.

[0034] Step 2: Constructing an array of groove micro-textures on the surface of the nitride layer in step 1.

[0035] Specifically, in step 2, the specific steps include: using a marking machine to construct a groove micro-texture on the metal surface by regulating the laser beam efficiency, frequency, scanning speed, and path; wherein the laser beam efficiency is 10% to 30%, the frequency is 15 to 40 kHz, and the scanning speed is 500 to 15000 mm / s. The groove diameter is 100 to 150 μm, the depth is 0.2 to 1.0 μm, and the groove shape is a concave pit, including but not limited to other surface micro-textures that can store a certain amount of mesoporous silicon balls and lubricants, such as grooves, triangles, rectangles, grids, etc.; in addition, according to Figure 2As shown in the figure, after micro-texturing treatment, the highest point of the edge of the micro-dimple does not exceed 3μm, thereby avoiding the increase of metal surface roughness caused by edge protrusion and ensuring that the micro-dimple can store a large amount of lubricating materials and abrasive particles and debris.

[0036] Step 3: construct a lamellar lubrication layer on the surface of the groove microtexture in step 2 to obtain a uranium surface lamellar lubrication / microtexture / nitridation coupling layer.

[0037] Specifically, the lamellar lubricating layer adopts a solid lubricant, which is any one of molybdenum disulfide, tungsten disulfide, and graphene. The solid lubricant powder is evenly coated on the surface of the uranium substrate, and the coating amount is 0.01 to 0.05 g / cm 2 .

[0038] Example 1

[0039] Step 1: First, the uranium substrate is cleaned with acetone and ethanol and placed in a sealed chamber. Then, in a 0.1atm nitrogen atmosphere, the laser output power is controlled to 60W, the scanning speed is 100mm / s, and the scanning step length is 0.5mm to construct a nitride layer on the surface of the uranium substrate.

[0040] Step 2: After cleaning the laser nitrided uranium sample, place it in a sealed chamber. In a low-oxygen and low-humidity atmosphere, control the marking machine efficiency to 10%, the frequency to 25kHz, the scanning speed to 10,000mm / s, and perform zigzag scanning to construct a groove microtexture on the surface of the nitrided layer.

[0041] Step 3: After the surface micro-textured uranium sample was polished with 1200 mesh and 2500 mesh sandpaper, it was cleaned and dried. Then, molybdenum disulfide powder was evenly applied on the surface of the uranium substrate (0.01 g / cm 2 ).

[0042] Example 2

[0043] Step 1: First, the uranium substrate is cleaned with acetone and ethanol and placed in a sealed chamber. Then, in a 0.3atm nitrogen atmosphere, the laser output power is controlled to 10W, the scanning speed is 50mm / s, and the scanning step length is 0.3mm to construct a nitride layer on the surface of the uranium substrate.

[0044] Step 2: After cleaning, place the laser nitrided uranium sample in a sealed chamber. In a low-oxygen and low-humidity atmosphere, control the marking machine efficiency to 30%, the frequency to 15 kHz, the scanning speed to 500 mm / s, and perform reciprocating scanning to construct a groove microtexture on the surface of the nitrided layer.

[0045] Step 3: After the surface micro-textured uranium sample is polished with 1200 mesh and 2500 mesh sandpaper, it is cleaned and dried. Then, tungsten disulfide powder is evenly applied on the surface of the uranium substrate by rubbing method (0.03g / cm2 ).

[0046] Example 3

[0047] Step 1: First, the uranium substrate is cleaned with acetone and ethanol and placed in a sealed chamber. Then, in a 0.3atm nitrogen atmosphere, the laser output power is controlled to 30W, the scanning speed is 70mm / s, and the scanning step length is 0.6mm to construct a nitride layer on the surface of the uranium substrate.

[0048] Step 2: After cleaning the laser nitrided uranium sample, place it in a sealed chamber. In a low-oxygen and low-humidity atmosphere, control the marking machine efficiency to 30%, the frequency to 15 kHz, the scanning speed to 500 mm / s, and perform reciprocating scanning to construct a groove microtexture on the surface of the nitrided layer.

[0049] Step 3: After the surface micro-textured uranium sample was polished with 1200 mesh and 2500 mesh sandpaper, it was cleaned and dried. Then, the graphene powder was evenly rubbed on the surface of the uranium substrate by rubbing method (0.02g / cm 2 ).

[0050] The results of the other embodiments are similar to those of Example 1. Figure 2 As shown in Figures a, b, and c, the wear resistance of the nitride layer and microtexture was investigated through ring-block wear experiments. The study found that under a relatively low load (1N), the nitride layer experienced a certain degree of wear, and the friction coefficient quickly stabilized at around 0.78. During the experiment, a sharp, piercing sound due to friction lasted for about 10 seconds. However, under a higher load (2N), the nitride layer surface experienced severe wear, and the friction coefficient fluctuated greatly (0.6 to 0.75). During the experiment, a sharp, piercing sound caused by the unstable wear interface lasted for up to 300 seconds, and the nitride layer flakes off. The surface of the uranium nitride sample after wear was analyzed by SEM and EDS. It was found that compared with the large amount of nitrogen in the unworn area (Area2, N: 7.35wt%, O: 2.25wt%), the nitrogen content in the worn area (Area1, N: 2.89wt%, O: 20.23wt%; Area3, N: 2.52wt%, O: 24.4wt%; Area4, N: 2.1wt%, O: 16.14wt%) was significantly reduced, and the mass proportion of oxygen in the worn area was significantly increased, indicating that a certain amount of corrosive wear occurred in the worn area. Compared with wear areas 1 and 3, in wear area 4, it can be found that the silicon and oxygen content are significantly lower. Combined with SEM, it can be judged that the degree of corrosive wear in this area is relatively light. Figure 2 d and Figure 2As shown in Figure e, the U-LSN / T sample was subjected to a wear test under a load of 2N. Through SEM, it can be found that the micro-texture modification did not significantly improve the wear resistance of the substrate. Obvious wear marks can still be seen. Compared with the area without severe wear, there is still a certain nitride layer (Area3, N: 7.54wt%, O: 7.31wt%). The adhesive wear area has more serious corrosive wear (Area2, N: 1.45wt%, O: 28.58wt%). The micro-texture morphology at the wear mark is also destroyed due to wear. There is a certain amount of nitrogen at the center point of the micro-texture area (Area1, N: 3.87wt%, O: 2.78wt%), which also indicates that the prepared micro-texture still has a certain nitride layer in the bottom area of ​​the micro-pits. In addition, since the thickness of the prepared nitride layer is relatively thin, nanoindentation is used to characterize the influence of the nitride layer on the hardness of the substrate. The study found that laser surface nitriding can increase the hardness of the uranium substrate from 4GPa to about 7.5GPa, significantly improving the surface hardness of the substrate ( Figure 2 f). The above experimental results show that although the presence of the nitride layer and microtexture can improve the hardness of the substrate and enhance the wear resistance to a certain extent, under a large load (2N), the modified layer will still suffer relatively severe wear.

[0051] Figure 3 The surface scanning electron micrographs of the uranium substrate after different treatments are shown in Fig. Figure 3 As shown in (a), the surface of the untreated uranium substrate is relatively smooth after sandpaper polishing, but there are still some protrusions; after laser nitriding treatment, the surface is even smoother ( Figure 3 b); After the nitrided sample is treated with micro-texture, regularly arranged micro-dimples appear on the surface ( Figure 3 c); Finally, after coating the surface of the modified uranium substrate with a layer of molybdenum disulfide (black), the micro-dimples appear black, indicating that a certain amount of lamellar lubricating material is stored in them ( Figure 3 c) Pin-on-disc wear test was used to further characterize the friction reduction and wear resistance of the coupling layer. During the experiment, the black friction pair was Si3N4 ball, the load was 2N, the radius was 2.8mm, and the number of friction turns was set to 2000. Figure 3 As shown by the black line in (e), the friction coefficient of the untreated uranium substrate surface increases rapidly to above 0.4 at the beginning of friction, then vibrates violently, and a harsh friction sound is emitted during the experiment. Finally, the friction coefficient remains at around 0.5-0.6; Figure 3 As shown by the red line in (e), the uranium sample after laser nitriding reaches a friction coefficient of more than 0.5 more quickly at the beginning of the friction under a larger load of 2N. During the experiment, a sharp friction sound is also emitted, and the friction coefficient finally stabilizes at around 0.7. Figure 3As shown by the blue line in (e), the sample after nitriding / microtexture has a certain effect of storing wear debris in the early stage due to the presence of microtexture. However, due to the large load, the microtexture is quickly destroyed, thus losing the friction reduction performance, causing the friction coefficient to increase rapidly and finally stabilize at around 0.7. Compared with the wear experiments of the first three, the sample after nitriding / microtexture / solid lubrication has no sharp wear sound during the experiment, as shown in the figure below. Figure 3 As shown by the pink line in (e), the friction coefficient remains consistently below 0.1, demonstrating that the designed coupling layer achieves excellent friction reduction and wear resistance. Furthermore, a comparison confirms the necessity of microtexturing. Samples without microtexturing, consisting solely of nitrided and solid lubricated surfaces, exhibit limited friction reduction performance. During wear, the friction coefficient exceeds 0.1, making them less effective than the coupling layer with microtexture.

[0052] In order to further characterize the anti-friction and wear resistance of the coupling layer, the surface morphology and elements after wear were analyzed using scanning electron microscopy and energy spectrum scanning. Figure 4 As shown in (a), the wear scar area is deep and contains a large amount of Si and O elements. This is because the Si element in the grinding pair wears on the surface of the metal uranium substrate, and oxidative wear occurs during the wear process. The uranium substrate treated with nitriding / microtexture / solid lubrication was subjected to a 35m cyclic wear test. Figure 4 As shown in (c), there is no obvious wear at the wear scar, and the micro-dimple structure still exists, with a small amount of molybdenum disulfide inside. There is no silicon element in the wear scar area, but there is a certain amount of N element (the nitride layer is exposed but not damaged by wear), which shows that the coupling layer can effectively reduce wear and exert an excellent friction reduction effect.

[0053] In summary, the present invention constructs a friction-reducing and wear-resistant coupling layer of nano-lubrication / micro-texturing / nitridation on the surface of a uranium substrate by sequentially performing laser nitriding, surface micro-texturing, and solid lubrication treatment on the surface of the uranium substrate. This layer can impart long-term friction-reducing, wear-resistant, and corrosion-resistant properties to the surface of the uranium substrate, and is an excellent uranium substrate surface protection technology.

[0054] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0055] The above specific implementation methods are detailed descriptions of the present invention. It cannot be considered that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions and substitutions without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for preparing a friction-reducing and wear-resistant coupling layer on a metal surface, characterized in that: The steps include: Step 1: Use laser to build a nitride layer on the metal surface; The specific steps include: using a laser to construct a nitride layer on the metal surface in a nitrogen atmosphere; the nitrogen atmosphere is 1 to 3 atmospheres, the laser output power is 10 to 60W, the scanning speed is 50 to 100 mm / s, and the scanning step length is 0.3 to 1.0 mm; Step 2: constructing a groove micro-texture arranged in an array on the surface of the nitride layer in step 1; In step 2, the specific steps include: using a marking machine to construct a groove micro-texture on the metal surface by adjusting the laser beam efficiency, frequency, scanning speed, and path; the laser beam efficiency is 10% to 30%, the frequency is 15 to 40 kHz, and the scanning speed is 500 to 15000 mm / s; Step 3: constructing a lamellar lubrication layer on the surface of the groove micro-texture in step 2 to obtain a metal surface lamellar lubrication / micro-texture / nitridation coupling layer; The metal is uranium.

2. The method for preparing a friction-reducing and wear-resistant coupling layer on a metal surface according to claim 1, characterized in that: The groove has a diameter of 100 to 150 μm and a depth of 0.2 to 1.0 μm.

3. The method for preparing a friction-reducing and wear-resistant coupling layer on a metal surface according to claim 1, characterized in that: The lamellar lubricating layer adopts a solid lubricant, and the solid lubricant is any one of molybdenum disulfide, tungsten disulfide, and graphene.

4. The method for preparing a friction-reducing and wear-resistant coupling layer on a metal surface according to claim 3, characterized in that: The solid lubricant powder is evenly coated on the surface of the metal substrate, and the coating amount is 0.01 to 0.05 g / cm 2 .

5. A friction-reducing and wear-resistant coupling layer on a metal surface, characterized in that: The method is prepared by any one of claims 1 to 4.

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