Method for prolonging service life of bearing by forming oxide layer on surface of metal bearing

Abstract

The invention belongs to the field of metal material surface strengthening, and relates to a surface wear resistance and rolling contact fatigue protection method of a metal transmission component, in particular to a method for prolonging the service life of a bearing by forming an oxide layer on the surface of the metal bearing. The method comprises the steps of metal surface grinding, polishing treatment, cleaning and drying. Lubricating oil containing additives is used; a dense micro-convex oxide layer is formed, and the oxide layer is composed of a metal oxide containing a large number of fine metal particles. The method can be carried out in the using process of the bearing, the cyclic contact stress damaging the surface of the bearing is converted into a method for strengthening the surface of the bearing, the rolling contact fatigue performance of the bearing is improved, the service life of the bearing is prolonged, and the method can be widely applied to various bearings.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of surface strengthening of metal materials, and relates to a surface wear-resistant and rolling contact fatigue prevention method for metal transmission components, in particular to a method for forming an oxide layer on the surface of a metal bearing to improve the service life of the bearing, which is particularly suitable for surface protection and life improvement of large heavy-duty bearings. BACKGROUND

[0002] As an important transmission component in mechanical equipment, bearings mainly function to support the rotating body of a machine and reduce the friction coefficient during its movement. However, bearings are subjected to complex working conditions such as high load, high speed, and high temperature for a long time, and the local area is subjected to complex alternating stress and shear stress, which can cause various failures such as wear, cracking, plastic deformation, and rolling contact fatigue. Among them, rolling contact fatigue failure is the main failure mode of bearings. These damages occur within a certain range of the contact surface or subsurface. In order to prevent these tribological damages, various surface engineering methods are currently being considered to strengthen or protect the surface of such contact transmission components, thereby improving the service life.

[0003] Currently, there are many types of existing surface thin film coatings, such as manganese phosphate, diamond-like carbon, titanium nitride, etc., which mainly improve the cage resistance to sliding wear, electrical insulation, anti-creeper corrosion, corrosion resistance, and raceway wear resistance of bearings. The implementation techniques of these coatings mainly include gaseous coating, liquid coating, and melting coating, which need to be formed in a specific device. Bearings in large equipment are often larger in size and difficult to implement through such techniques.

[0004] Patent No. CN119546865A proposes a rolling bearing and a manufacturing method thereof, which forms a Fe3O4 oxide film with a thickness of 0.6-2.0 μm and a microcrystalline size of 2.5-3.2 nm through blackening treatment (immersing the bearing component in a NaOH-based treatment solution) during the manufacturing stage. However, the film is formed before the bearing is used, relies on an immersion device, cannot strengthen the metal organization through the surface morphology, and has limited improvement effect on rolling contact fatigue failure. Patent No. CN203067530U proposes a corrosion-resistant supporting roller bearing, which realizes corrosion resistance through oxidation treatment layers on the outer ring raceway and the inner ring surface and chrome plating layers on other parts. However, the film formation stage is still during the manufacturing process, and an additional chrome plating process is needed to assist, which cannot improve the wear resistance and cracking resistance through surface organization strengthening. Patent No. CN207261465U proposes a blackened cylindrical roller bearing, which sets a 0.15-0.80 mm thick blackened oxide layer on the surface of the roller to improve corrosion resistance and lubrication adhesion. However, the oxide layer is relatively thick and can easily affect the running accuracy of the bearing; the oxide layer can only passively resist corrosion and cannot balance wear and protection through dynamic film formation, so it has weak effect on improving the rolling contact fatigue life.

[0005] In order to break through the above limitations, it is necessary to develop a method without special equipment, which can form an oxidation layer with protection and strengthening functions in service, to adapt to large heavy-duty bearings and improve their rolling contact fatigue life. SUMMARY

[0006] The purpose of the present application is to provide a method for improving the service life of bearings by forming an oxidation layer on the metal bearing surface, which can form a coating through the reaction of lubricating oil and metal surface during the service of bearings, generate an oxidation layer during the stress cycle contact of the metal bearing surface to improve its performance and rolling contact fatigue life, and reduce the surface origin failure of large heavy-duty bearings.

[0007] In order to achieve the above purpose, the technical scheme of the present application is:

[0008] A method for improving the service life of bearings by forming an oxidation layer on the metal bearing surface, comprising the following steps:

[0009] (1) Metal surface pretreatment:

[0010] ① Polishing: polish the metal bearing surface to a roughness Ra>0.1 μm;

[0011] ② Polishing: polish the surface after polishing with anhydrous ethanol or deionized water as lubricant on the polishing cloth until the surface is mirror-like and no visible scratches, and the roughness Ra<0.01 μm;

[0012] ③ Cleaning and drying: rinse the polished metal surface with anhydrous ethanol, and then dry;

[0013] (2) Oxidation layer formation during service:

[0014] The pretreated bearing is serviced using lubricating oil containing antioxidants, corrosion inhibitors and abrasion resistant agents, and an oxidation layer is formed on the metal contact surface through high cycle contact of the bearing; the oxidation layer is in the form of dense micro-bumps, with a thickness of 100-500 nm, and is composed of a large number of fine granular metal particles wrapped in metal oxide, and the formation of oxidation layer and wear maintains a dynamic balance during service.

[0015] The method for improving the service life of bearings by forming an oxidation layer on the metal bearing surface, in step (1)-①, the roughness Ra of the polished metal bearing surface is 0.2-0.4 μm.

[0016] The method for improving the service life of bearings by forming an oxidation layer on the metal bearing surface, in step (1)-②, the polishing cloth is a wool polishing cloth, and the polishing paste with a particle size of W2.5 is used during polishing.

[0017] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0018] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0019] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0020] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0021] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0022] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0023] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0024] The design idea of the present application is:

[0025] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0026] The method for improving the service life of bearings by forming an oxide layer on the surface of a metal bearing comprises the following steps: (1) preparing a metal bearing; (2) forming an oxide layer on the surface of the metal bearing; and (3) using the metal bearing.

[0027] 1. Unlike the existing surface coating strengthening technology, the present application provides a method for forming an oxide layer coating on the surface of a bearing, which is not completed before the bearing is used, but relies on the lubricating oil to form a film through cyclic contact during the service of the bearing, and can be directly applied to large heavy-duty bearings. For large heavy-duty bearings that are difficult to use specific equipment, this method is more universal, overcoming the size limitations of existing immersion and coating technologies.

[0028] 2. The method of the present application not only protects the metal surface as a coating, but also strengthens the microstructure of the metal surface layer. The structure of the metal oxide wrapped around the metal particles improves the wear resistance. The thin oxide layer with a thickness of 100-500 nm balances the protection function and running accuracy, and can comprehensively improve the rolling contact fatigue performance.

[0029] 3. The present application processes metal with low surface roughness. In the process of cyclic contact, lubricating oil containing additives is used, and dense micro-protrusion-shaped oxide layers are formed on the metal contact surface through high-frequency cyclic contact. The oxide layer is in the form of dense micro-protrusions, which is continuously formed during stress cyclic contact, and also wears out. The formation and wear of the oxide layer reach a dynamic balance, which can continuously inhibit the initiation and propagation of surface cracks, reduce surface-originated failures, and significantly improve the rolling contact fatigue life. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure is a schematic diagram of a rolling contact fatigue testing machine used in the embodiments of the present application. In the figure, 1 is a rotating shaft, 2 is an oil tank, 3 is a steel ball and a retainer, 4 is lubricating oil, 5 is a metal test piece, 6 is a load, and 7 is a bearing ring.

[0031] Figure 2 The figure is a schematic diagram of the morphology and structure of the oxide layer in the present application. In the figure, 5 is a metal test piece, 51 is an oxide layer, 52 is a metal oxide, and 53 is a metal particle.

[0032] Figure 3 The figure is a morphology diagram of the dense micro-protrusion oxide layer in Example 1.

[0033] Figure 4 The figure is a morphology diagram of the dense micro-protrusion oxide layer in Example 2. DETAILED DESCRIPTION

[0034] In the specific implementation process, the present application provides a method for forming an oxide layer coating on the surface of a bearing during service. The technical solution adopted is: polishing, polishing treatment and cleaning and drying of the metal surface; using lubricating oil containing additives; forming a dense micro-protrusion-shaped oxide layer morphology.

[0035] Next, each step will be described in detail.

[0036] S1: metal surface grinding. The metal surface is coarsely ground to a roughness Ra of 0.2-0.4 μm.

[0037] S2: metal surface polishing. The metal surface is polished using a polishing paste with a particle size W2.5 on a polishing cloth, lubricated with anhydrous ethanol, until the metal surface is mirror-like, with no visible scratches, and the roughness Ra is less than 0.01 μm.

[0038] S3: metal surface cleaning and drying. The metal surface after polishing is rinsed with anhydrous ethanol and then dried.

[0039] S4: the bearing is subjected to high-cycle rolling contact using a lubricating oil composed of neopentyl polyol ester as base oil and additives; the composition of the lubricating oil is as follows by weight percentage: 2-4% additives, and the rest is base oil; the additives include antioxidants, corrosion inhibitors and anti-wear agents, the proportion of the antioxidants is 1-2%, the proportion of the corrosion inhibitors is 0.08-0.10%, and the proportion of the anti-wear agents is 1-2%; the antioxidants can be diisooctyl diphenylamine, N-phenyl-α-naphthylamine or octyl butyl diphenylamine, the corrosion inhibitors can be triazol, and the anti-wear agents can be trimethylphenyl phosphite, triphenyl phosphite or trimethyl phosphate.

[0040] S5: formation of a dense micro-protrusion oxide layer.

[0041] Specifically, the formation mechanism and influence of the oxide layer coating in the present application are described in detail: the oxide layer coating is wrapped with a large number of fine metal particles by a dense iron oxide, avoiding the initiation and expansion of surface cracks, and the dense micro-protrusion morphology of the oxide layer produces a high stress strengthening surface layer structure.

[0042] In actual application, the inner ring raceway and the outer ring raceway of a large heavy-duty bearing (the inner diameter is greater than or equal to 200 mm, the weight of a single set is greater than or equal to 50 kg, and the bearing needs to bear a radial load greater than or equal to 100 kN, such as a wind turbine main shaft bearing and a rolling mill bearing) are polished, polished and cleaned and dried by a device matched with its size and load characteristics.

[0043] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the drawings and examples, but the listed examples are not intended to limit the protection scope of the present application.

[0044] It should be noted that, unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials used, unless otherwise specified, can be purchased on the market.

[0045] Referring to Fig. 1, the following embodiment of the present application uses a TRF-1000 / 1H rolling contact fatigue tester, which includes a rotating shaft 1, an oil tank 2, a steel ball and retainer 3, lubricating oil 4, a metal test piece 5, a load 6, a bearing ring 7, and the metal test piece 5 is immersed in the oil tank 2 filled with lubricating oil 4, and the top of the metal test piece 5 is sequentially provided with the steel ball and retainer 3, the bearing ring 7, and the rotating shaft 1, and a constant load 6 is applied at the bottom of the oil tank 2.

[0046] In use, the rotating shaft 1 rotates at a constant speed around its own axis, and the rotating speed of the rotating shaft 1 is set according to the test target of high frequency, and when the cycle frequency reaches 1.0x10 8 ~ 1.3x10 8 r / min, the rotating speed of the rotating shaft is controlled at 500~2200r / min, the power of the rotating shaft is converted into the mechanical energy required for rolling contact, and the load 6 is matched to form the contact stress required for the test.

[0047] The upper end of the rotating shaft 1 is connected with an external driving system (such as a servo motor), and the driving system drives the rotating shaft to rotate at a constant speed; the lower end of the rotating shaft 1 is tightly connected with the bearing ring 7, and under the action of the bottom load 6, the bearing ring 7 is pressed on the three steel balls of the steel ball and retainer 3. When the rotating shaft 1 rotates, it will synchronously drive the bearing ring 7 to rotate, and the bearing ring 7 drives the steel ball and retainer 3 to rotate through friction, and the three steel balls in the retainer contact the metal test piece 5 to generate friction, and the three steel balls form rolling contact on the contact interface of the metal test piece, simulating the relative movement of the rolling elements and the raceway in the actual service of the bearing.

[0048] The applied load 6 (a constant 5.0~5.5GPa contact load is loaded by hanging weights on the other end of the lever) is along the axial direction of the rotating shaft 1, and the load is uniformly transmitted to the metal test piece 5, and then transmitted to the bearing ring 7 and the rotating shaft 1 through the three steel balls of the steel ball and retainer 3 in turn, and the load will form a local high-pressure contact stress at the contact point of the steel ball and the metal test piece, and this stress induces the surface of the metal test piece 5 to react with the lubricating oil additive to form a dense micro-protrusion oxide layer.

[0049] The oil tank 2 surrounds the outside of the steel ball and retainer 3 and the metal test piece 5, and is filled with lubricating oil 4 containing antioxidants, corrosion inhibitors, and abrasion resistant agents. When the rotating shaft 1 rotates, it will drive the steel ball to roll in the lubricating oil, on the one hand, the lubricating oil can lubricate the contact interface of the steel ball and the metal test piece, avoiding dry friction leading to excessive wear of the metal surface (ensuring the dynamic balance of oxidation layer formation and wear); on the other hand, the additives in the lubricating oil will react with the surface of the metal test piece to form an oxide layer under the action of high-pressure contact stress and friction heat generated by the rotation of the rotating shaft.

[0050] As Figure 2As shown in the figure, from the morphology and structure of the oxide layer, it can be seen that the oxide layer 51 is not flatly covered on the surface of the metal test piece 5 (i.e. the substrate), but presents a densely distributed platform-like micro-protrusion form. The skeleton structure of the oxide layer 51 is composed of metal oxides 52, which are uniformly distributed in the oxide layer 51, and their role is to provide the oxide layer with basic wear resistance and corrosion resistance to avoid direct exposure of the metal substrate to the friction interface. Inside the metal oxides 52, a large number of fine-grained metal particles 53 are uniformly wrapped, which come from the alloy particles of the metal test piece 5, and the volume proportion of the metal particles 53 in the oxide layer is 10% to 30%. Under the stress action of high-cycle cyclic contact, the fine metal particles (particle size is 1 to 100 nm) on the surface layer of the metal test piece 5 are not completely oxidized, are wrapped by newly generated metal oxides and are retained inside the oxide layer 51, and their role is to improve the toughness and structural strength of the oxide layer to avoid cracking or peeling of the oxide layer due to excessive brittleness.

[0051] The application will be further described in detail below through examples and drawings.

[0052] Example 1

[0053] In this embodiment, a method for improving the service life of a bearing by forming an oxide layer on the surface of a metal bearing, the metal test piece uses a metal material of GCr15SiMn, and includes the following steps:

[0054] S1: The surface of the metal test piece simulating the bearing raceway is machined and polished, and the initial surface roughness Ra is 0.2 to 0.4 μm.

[0055] S2: The surface of the metal test piece is polished on a polishing cloth using a polishing paste with a particle size of W2.5, and anhydrous ethanol is used for lubrication until the surface of the metal test piece is mirror-like, there are no visible scratches on the surface, and the roughness Ra is less than 0.01 μm.

[0056] S3: The metal that has completed the polishing step is washed with anhydrous ethanol and then dried in air.

[0057] S4: 4050 aviation lubricating oil composed of neopentyl polyol ester as base oil and additives is used.

[0058] S5: The metal test piece is subjected to high-cycle cyclic rolling contact under a load of 5.0 GPa to form a densely micro-protruded oxide layer on the surface of the metal test piece, as shown in the figure. Figure 3

[0059] S6: The final cycle number reaches 1.3×10 8 .

[0060] Example 2

[0061] ​In the embodiment, a method for improving service life of a bearing by forming an oxide layer on a metal bearing surface, the metal test piece uses GCr15SiMn as the metal material, and comprises the following steps.

[0062] S1: machining and grinding the surface of the metal test piece simulating the bearing raceway, so that the initial surface roughness Ra is 0.2-0.4 μm.

[0063] S2: polishing the surface of the metal test piece on a polishing cloth using polishing paste with a particle size of W2.5, and using anhydrous ethanol as lubricant, until the surface of the metal test piece is mirror-finished, no visible scratches are present on the surface, and the surface roughness Ra is less than 0.01 μm.

[0064] S3: rinsing the metal test piece after the polishing step with anhydrous ethanol, and then drying it in air.

[0065] S4: using 4050 aviation lubricating oil composed of neopentyl polyol ester as base oil and additives.

[0066] S5: subjecting the metal test piece to high-cycle rolling contact under a load of 5.5 GPa, so that a dense micro-protrusion oxide layer is formed on the surface of the metal test piece, as shown in Fig. 1. Figure 4

[0067] S6: when the final cycle number reaches 1.0×10 8 .

[0068] The implementation results show that the method can be used during the use of the bearing, and can convert the cycle contact stress damaging the bearing surface into a method for strengthening the bearing surface, improve the rolling contact fatigue performance and service life of the bearing, and can be widely applied to various bearings.

[0069] The above-described embodiments only express the implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.​

Claims

1. A method for improving the service life of a bearing by forming an oxide layer on the surface of a metal bearing, characterized by, The method comprises the following steps: (1) metal surface pretreatment: ① grinding: grinding the surface of the metal bearing to a roughness Ra>0.1 μm; ② polishing: polishing the surface after grinding on a polishing cloth with anhydrous ethanol or deionized water as a lubricant until the surface is mirror-like and free of visible scratches, and the roughness Ra<0.01 μm; ③ cleaning and drying: rinsing the polished metal surface with anhydrous ethanol and then drying; (2) formation of an oxide layer during service: The pretreated bearing is put into service, and a lubricating oil containing antioxidants, corrosion inhibitors and anti-wear agents is used to form an oxide layer on the metal contact surface through high-cycle contact of the bearing; the oxide layer is in the form of dense micro-protrusions, with a thickness of 100-500 nm, and is composed of a large number of fine granular metal particles wrapped in metal oxides, and the formation of the oxide layer and wear maintain a dynamic balance during service.

2. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: In step (1)-①, the roughness Ra of the surface of the metal bearing after grinding is 0.2-0.4 μm.

3. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: In step (1)-②, the polishing cloth is a wool polishing cloth, and a polishing paste with a particle size of W2.5 is used during polishing. ​ 4. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: In step (2), the load of high-cycle contact is 5.0-5.5 GPa. ​ 5. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: In step (2), the surface roughness Ra after the formation of the oxide layer is less than 0.2 μm, and is close to the critical value of the boundary lubrication and mixed lubrication state. ​ 6. The method of claim 5, wherein the metal bearing surface is formed by a process comprising: After the formation of the oxide layer, the low roughness of the surface of the metal bearing, the use of lubricating oil containing additives, and high-cycle contact during the cycle contact form a dense micro-protrusion oxide layer on the metal contact surface.

7. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: In step (2), the lubricating oil is mineral lubricating oil or synthetic lubricating oil. ​ 8. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: In step (2), the lubricating oil is 4050 aviation lubricating oil. ​ 9. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: The metal material of the metal bearing is GCr15SiMn. ​ 10. The method of claim 1, wherein the metal bearing surface is formed by a process comprising: The oxide layer is continuously formed during stress cycle contact, and wear also occurs, and the formation of the oxide layer and wear reaches a dynamic balance. ​

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