阅读说明：本技术 铝合金保持架和铝合金保持架的加工方法 (Aluminum alloy retainer and processing method thereof ) 是由 叶胜华 章桢彦 韦剑飞 于 2019-04-29 设计创作，主要内容包括：提供一种铝合金保持架及其生产方法。铝合金保持架包括喷丸铝合金保持架基体和形成在喷丸铝合金保持架基体的表面上的涂层,涂层包括至少一层含镍层。根据本公开的铝合金保持架具有高疲劳强度、优异的耐腐蚀性、高表面硬度和低表面摩擦系数,并且显示优异的表面润滑性和耐磨耗性。(An aluminum alloy cage and a method for producing the same are provided. The aluminum alloy cage comprises a shot-blasted aluminum alloy cage base body and a coating formed on the surface of the shot-blasted aluminum alloy cage base body, wherein the coating comprises at least one layer containing nickel. The aluminum alloy cage according to the present disclosure has high fatigue strength, excellent corrosion resistance, high surface hardness, and a low surface friction coefficient, and exhibits excellent surface lubricity and wear resistance.)

1. An aluminum alloy cage comprising a shot-peened aluminum alloy cage base and a coating formed on a surface of the shot-peened aluminum alloy cage base, the coating comprising at least one nickel-containing layer.

2. The aluminum alloy cage according to claim 1, wherein the shot-peened aluminum alloy cage matrix has a residual compressive stress of 50MPa to 280MPa at a depth of 50 μm to 200 μm from the surface.

3. The aluminum alloy cage of claim 1, wherein the coating further comprises an intermediate layer on the base, the nickel-containing layer being formed on the intermediate layer.

4. The aluminum alloy cage according to claim 1, wherein the intermediate layer is a zinc-containing layer.

5. The aluminum alloy cage of claim 1, wherein the coating comprises an inner nickel-containing layer and an outer nickel-containing layer.

6. The aluminum alloy cage of claim 5, wherein the nickel-inclusive layer is a single or multiple layer electroless nickel layer, or a single or multiple layer composite electroless nickel layer, or a combination of multiple layer electroless nickel layer and composite electroless nickel layer.

7. The aluminum alloy cage of claim 5 or 6, wherein the outer nickel-containing layer is a Ni-P-PTFE layer for further friction reduction in a bath comprising PTFE, a nickel-containing compound, and a phosphorus-containing compound.

8. A processing method of an aluminum alloy cage according to any one of claims 1 to 7, comprising the steps of:

(1) shot blasting is carried out on the surface of the aluminum alloy retainer substrate;

(2) pre-treating the surface of the shot blast;

(3) forming a coating comprising at least one nickel-containing layer.

9. The process of claim 8, wherein forming a coating comprises:

(1) forming at least one nickel-containing layer on the pretreated surface;

alternatively, the method comprises the following steps:

(2) forming an intermediate layer on the pretreated surface;

(3) at least one nickel-containing layer is formed on the intermediate layer.

10. The processing method according to claim 9, wherein the residual compressive stress at a depth of 50 μm to 200 μm from the surface caused by the shot blasting step is 50MPa to 280 MPa.

Technical Field

The present disclosure relates to aluminum alloy cages and methods of making the same. In particular, the present disclosure relates to aluminum alloy cages having good fatigue strength, corrosion resistance, surface lubricity, and wear resistance, and methods of making the same.

Background

In the field of bearings, the part of the bearing that is partially wrapped around the rolling elements and moves with it is called the cage (or cage). The main function of the rolling bearing cage is the separation and distribution of the rolling elements. The other function is generally to prevent the rolling elements from falling out of the separable bearing and to guide the rolling elements in the unloading zone of the bearing. Currently, brass retainers are widely used. However, brass cages have the following drawbacks or disadvantages: the high density of brass makes it difficult to obtain a light weight bearing; the raw material price is high, which leads to high production cost; brass contains lead which causes environmental problems.

In particular, when the lubricating oil is contaminated with hard particles, the hard particles may become embedded in the soft brass cage. And then the hard particles will wear the roller in contact with the cage pocket bar, causing bearing failure. Furthermore, if lead is removed from brass, the machining efficiency of the brass will be significantly reduced, which increases the machining cost.

Currently, aluminum alloy cages may be used instead of brass cages. However, most existing aluminum alloy cages have no coating on the surface, resulting in unsatisfactory fatigue strength, corrosion resistance, lubricity, and wear resistance. Some companies perform hard anodizing to treat the surface of the aluminum alloy cage. However, the fatigue strength of the aluminum alloy cage after such treatment is deteriorated.

Disclosure of Invention

Problems to be solved by the invention

It is an object of the present disclosure to overcome or at least alleviate the above-mentioned deficiencies of the prior art and to provide an aluminium alloy cage having good fatigue strength, corrosion resistance, surface lubricity and wear resistance, and a method of manufacturing the same.

Means for solving the problems

The processing method of the aluminum alloy retainer comprises the following steps:

(1) shot blasting is carried out on the surface of the aluminum alloy retainer substrate;

(2) pretreating the surface of the shot blasting;

(3) optionally forming an intermediate layer on the pretreated surface;

(4) at least one nickel-containing layer is formed on the substrate or on the intermediate layer.

ADVANTAGEOUS EFFECTS OF INVENTION

The aluminum alloy cage according to the present disclosure has high fatigue strength, excellent corrosion resistance, high surface hardness, and a low surface friction coefficient, and exhibits excellent surface lubricity and wear resistance.

Drawings

FIG. 1 shows the results of the test of shot peening and Ni-P-PTFE coated aluminum alloy holder of example 1 under accelerated conditions.

FIG. 2 shows the results of the test of the uncoated aluminum alloy holder of comparative example 1 under the same acceleration conditions.

Fig. 3 shows the results of the test of the conventional brass holder of comparative example 2 under the same acceleration condition.

Detailed Description

The present disclosure relates to an aluminum alloy cage including a shot-peened aluminum alloy cage base body and a coating layer formed on a surface of the shot-peened aluminum alloy cage base body. The coating comprises an intermediate layer on the substrate and at least one nickel-containing layer formed on the intermediate layer, or at least one nickel-containing layer formed on the substrate, wherein the intermediate layer is preferably a zinc intermediate layer. The intermediate layer is firmly bonded to the aluminum alloy holder base body and the nickel-containing layer, respectively, to ensure good adhesion.

Preferably, the coating comprises an inner nickel containing layer (inner nickel containing layer) and an outer nickel containing layer (outer nickel containing layer). The nickel layer is a single-layer or multi-layer chemical nickel plating layer (or a single-layer or multi-layer composite chemical nickel plating layer), or a combination of the multi-layer chemical nickel plating layer and the composite chemical nickel plating layer.

Preferably, the coating further comprises a layer of Ni-P-PTFE. The Ni-P-PTFE layer contains PTFE (polytetrafluoroethylene) particles that reduce the coefficient of friction of the aluminum alloy cage. In addition, the Ni — P-PTFE layer has a relatively high hardness, which improves the wear resistance of the aluminum alloy holder in use.

The present disclosure further provides a method of making an aluminum alloy cage comprising the steps of:

(1) shot blasting is carried out on the surface of the aluminum alloy retainer substrate;

(2) pretreating the surface of the shot blasting;

(3) optionally forming an intermediate layer on the pretreated surface;

(4) at least one nickel-containing layer is formed on the substrate or on the intermediate layer.

(1)Shot blasting

Shot blasting to full coverage with an Almen intensity of 0.2-0.5mmA results in a residual compressive stress of 50-280 MPa at a depth of 50-200 μm from the surface.

(2)Pretreatment of

The pretreatment step of the present disclosure includes, but is not limited to, a step of chemical degreasing, and a step of surface activation. More preferably, the step of organic degreasing is performed before the step of chemical degreasing. Each of the above steps is described in detail in the following paragraphs.

(2.1)Organic degreasing

Optionally, the surface of the aluminum alloy cage is subjected to a step of organic degreasing. The organic degreasing is to dissolve the grease on the surface of the aluminum alloy holder in an organic solvent and remove the grease. Organic degreasing is particularly preferred when the grease on the surface of the aluminum alloy cage is relatively thick. The organic solvent is one or more than two of the group consisting of ethanol, kerosene, and gasoline or other environment-friendly organic solvents. However, in general, organic degreasing is not thorough because, when the organic solvent on the surface of the base material is volatilized, the grease dissolved in the solvent will remain on the surface of the aluminum alloy holder. Therefore, it is preferable that the step of organic degreasing is followed by a step of chemical degreasing.

(2.2)Chemical degreasing

A chemical degreasing process is employed to degrease the surface of the aluminum alloy cage at an operating temperature range of 60 ℃ to 80 ℃. The chemical degreasing solution may be alkaline or acidic. The alkaline degreasing solution comprises one or more than two of the group consisting of sodium carbonate, sodium hydroxide, sodium phosphate dodecahydrate, sodium silicate and sodium borate, wherein the typical composition is 15-20 g/L of sodium carbonate, 20-30 g/L of sodium dodecahydrate and 10-15 g/L of sodium silicate.

Acid degreasing is increasingly prevalent, the bath solution containing H₂SO₄Or H₃PO₄Adding HF, Fe, H₂O₂NO and a nonionic surfactant, and operating at room temperature for 3-5 minutes. It is highly efficient and pollution free, better than alkali degreasing for aluminum alloys and more widely used.

The method of performing chemical degreasing is not limited thereto. For example, it may be acid degreasing or alkali degreasing, also by dipping, spraying, steam, or the like, or by a combination thereof.

After the step of chemical degreasing, the necessary rinsing is carried out to avoid contamination of the metal surface by residual chemical degreasing solution. For example, rinsing with clean water is performed to achieve a very low concentration of chemical degreasing solution in the rinsing liquid. Preferably, the rinsing is stopped when the concentration of the chemical degreasing solution in the rinsing solution is less than 2% of the initial concentration of the chemical degreasing solution.

(2.3)Activation of

And activating the surface of the aluminum alloy retainer. Preferably, the aluminum alloy retainer is immersed in a 50% nitric acid solution for 20-30 seconds at room temperature to activate the surface of the aluminum alloy retainer.

After activation, the necessary rinsing is performed to avoid corrosion of the metal surface by the residual acidic solution. For example, rinsing with clean water is performed to achieve a very low concentration of acidic solution in the rinsing liquid.

(3)Forming an intermediate layer

After the step of pretreating the surface of the aluminum alloy cage, an intermediate layer is optionally formed on the pretreated surface. Preferably, the pretreated surface is immersed in a zinc salt solution to form an intermediate layer. This step is described in detail in the following paragraphs.

In order to bond the aluminum alloy holder base body to the later-described nickel-containing layer tightly, an intermediate layer is preferably formed on the pretreated surface of the aluminum alloy holder base body. Preferably, the pretreated surface is immersed in a zinc salt solution to form an intermediate layer. The oxide film on the pretreated surface is effectively removed during immersion in the zinc salt solution. The intermediate layer formed can prevent the surface of the aluminum alloy holder base from being oxidized again while tightly bonding between the surface and the nickel plated layer.

In order to improve the quality of the intermediate layer, the intermediate layer is preferably formed by a method including the steps of:

(3.1) dipping the pretreated surface in a zinc salt solution to form a first zinc plating layer;

(3.2) removing the first zinc plating layer;

(3.3) immersing the pretreated surface in a zinc salt solution again to form a second zinc plating layer.

Preferably, the zinc content in the zinc salt solution, for example in the form of zinc oxide, is in the range of 10 to 100 g/L. More preferably, the nitric acid solution in step (3.2) is used to remove the first zinc plating layer, and the residual nitric acid solution is removed by washing with water.

The second zinc coating is washed with water after formation, and finally a denser and integral intermediate layer is obtained, which has outstanding properties in terms of bonding to the surface of the aluminium alloy cage.

(4)Forming at least one layer containing nickel

A nickel pre-plating layer is formed on the substrate or on the intermediate layer by an alkaline bath. Then, the nickel pre-plating layer is thickened by an acid bath to obtain a nickel plating layer.

Preferably, the alkaline bath has a pH of 8.0 to 12.0. The pre-nickel plating layer formed by the alkaline bath effectively prevents the newly formed intermediate layer from dissolving in the bath. More preferably, the alkaline bath comprises a nickel content of about 3.0-7.0 g/L.

After the formation of the nickel pre-plating layer, the nickel pre-plating layer is thickened by an acidic bath to obtain a nickel plating layer. Preferably, the acidic bath has a pH of 4.0 to 6.0. More preferably, the acidic bath comprises a nickel content of about 3.0-7.5 g/L.

In a preferred embodiment, after the nickel plating layer is formed, a Ni-P-PTFE layer is formed on the nickel plating layer using a plating bath containing PTFE, a nickel-containing compound, and a phosphorus-containing compound.

Preferably, the PTFE particles are dispersed in a plating bath comprising a nickel-containing compound and a phosphorus-containing compound to form a Ni-P-PTFE layer on the nickel plating layer.

The Ni-P-PTFE layer contains PTFE particles, which reduces the wet coefficient of friction of the surface of the aluminum alloy cage. For example, the wet friction coefficient of the surface of the aluminum alloy cage may be 0.08 or less. Preferably, the content of the polytetrafluoroethylene in the Ni-P-PTFE layer is 10-50% (m/m ratio). The Ni-P-PTFE layer is used to improve the hardness of the surface of the aluminum alloy cage, providing excellent wear resistance.

Examples

Example 1

And sequentially carrying out shot blasting on the surface of the aluminum alloy retainer substrate. A pre-nickel plating layer is formed in an alkaline bath. A nickel plating layer is formed in an acidic solution. A PTFE-phosphorous-nickel layer is formed in the Ni-P-PTFE plating solution. The aluminum alloy cages thus obtained were tested.

The detailed process parameters are as follows:

(1) chemical degreasing: to remove grease and dirt from the surface of the aluminum alloy during processing: the solution contained 35g/L sodium carbonate, 27g/L sodium dodecahydrate, the temperature of the solution was 65 ℃ and the impregnation time was 3 minutes.

(2) Alkaline etching: the surface oxide was removed by soaking in a 10% sodium hydroxide solution at 52 degrees for about 30 seconds.

(3) And (3) activation: the aluminum alloy holder was immersed in a 50% nitric acid solution at room temperature for 20 to 30 seconds to remove residual spots from the alkaline etching, and the surface of the aluminum alloy holder was activated.

(4) Zinc impregnation: the technical conditions are as follows: NaOH 120g/L, ZnO 20g/L, stabilizer: 30ml/L, 20 ℃ for 45 seconds, after the first zinc impregnation, with 50% HNO at room temperature₃The solution treatment for 10 seconds followed by a second zinc dip allows for a more uniform zinc coating, higher density and better adhesion.

(5) Alkaline electroless nickel (alkaline Ni-P): composition of the solution, NiSO₄·7H₂O 27g/L、NaH₂PO₂·H₂O 26g/L、Na₃C₆H₅O₇·H₂O 85g/L、NH₄Cl 35g/L、(HOCH₂CH₂)₃N90 g/L, pH 9.3, temperature 50 ℃.

(6) Acid electroless nickel (acid Ni — P): make up EN plating (HP) DNC 571: ni: 5.7g/L, NaH₂PO₂·H₂O35 g/L, pH 4.9, temperature 90 ℃.

(7) Chemical nickel plating grading Ni-P-PTFE: the composition is ENP 3400A, the pH value is 4.9, and the temperature is 85-90 ℃.

All of the above procedures were washed with water. The total thickness of the coating (Ni-P/Ni-P-PTFE) was 8.1. mu.m, and the PTFE content of the Ni-P-PTFE coating was 13% (m/m).

Performance testing

The same kind of bearings are respectively assembled on an aluminum alloy retainer without/with shot blasting and a Ni-P-PTFE coating and a conventional brass retainer, are installed on a bearing fatigue life capability test device, and then are simultaneously tested under the working conditions of high speed and low load to accelerate the damage to the retainer. The test conditions are listed below.

The test results are shown in fig. 1 to 3. The cage of example 1 was only ground at the area contacting the rollers and had the least amount of wear, whereas the amount of wear was much greater for both comparative examples 1 and 2. The test results show that the coating has good abrasion resistance.