ALUMINUM ALLOY HUB AND METHOD FOR COATING SURFACE OF ALUMINUM ALLOY HUB

Abstract

The application relates to an aluminum alloy hub and a method for coating the surface of the aluminum alloy hub. The aluminum alloy hub is provided with an aluminum alloy matrix and a coating attached to the surface of the aluminum alloy matrix, and the coating sequentially includes a pre-coating layer formed by nickel-coated aluminum or aluminum-coated nickel powder, a Cr.sub.3C.sub.2 layer and a varnish layer on the surface of the aluminum alloy matrix. According to the aluminum alloy hub disclosed by the invention, more excellent corrosion resistance is obtained by spraying the Cr.sub.3C.sub.2 layer on the surface of the aluminum alloy hub.

Claims

1. An aluminum alloy hub provided with an aluminum alloy matrix and a coating attached to the surface of the aluminum alloy matrix, characterized in that the coating sequentially comprises a pre-coating layer formed by nickel-coated aluminum or aluminum-coated nickel powder, a Cr.sub.3C.sub.2 layer and a varnish layer on the surface of the aluminum alloy matrix.

2. The aluminum alloy hub surface coating according to claim 1, characterized in that the thickness of the pre-coating layer is 0.05-0.08 mm.

3. The aluminum alloy hub surface coating according to claim 1, characterized in that the thickness of the Cr.sub.3C.sub.2 layer is 0.10-0.06 mm, preferably 0.08 mm.

4. The aluminum alloy hub surface coating according to claim 1, characterized in that the porosity of the Cr.sub.3C.sub.2 layer is 1.5-2.5%, preferably 1.8-2.0%.

5. The aluminum alloy hub surface coating according to claim 1, characterized in that the thickness of the varnish layer is 0.40-0.08 mm.

6. A method for coating the surface of an aluminum alloy hub, characterized in that the method comprises the steps of pretreating the surface of the aluminum alloy hub, spraying a pre-coating layer, spraying a Cr.sub.3C.sub.2 layer, and conducting aftertreatment, wherein the step of spraying the Cr.sub.3C.sub.2 layer comprises forming the Cr.sub.3C.sub.2 layer with a thickness greater than or equal to 0.15 mm on the surface of the aluminum alloy hub by adopting a high-speed flame spraying method, and conducting finish turning to a predetermined thickness.

7. The method for coating the surface of the aluminum alloy hub according to claim 6, characterized in that the step of pretreating comprises conducting cleaning of degreasing, decontaminating and derusting, roughening and preheating on the surface of the aluminum alloy hub.

8. The method for coating the surface of the aluminum alloy hub according to claim 6, characterized in that the step of spraying the pre-coating layer comprises: forming the pre-coating layer with a thickness of 0.12-0.13 mm on the surface of the aluminum alloy hub by adopting a high-speed flame spraying method, and turning and roughening the pre-coating layer to be 0.05-0.08 mm, and preferably, the pre-coating layer is formed by nickel-coated aluminum or aluminum-coated nickel powder.

9. The method for coating the surface of the aluminum alloy hub according to claim 6, characterized in that the step of aftertreatment comprises: carrying out sand blasting treatment by using silica sand with a particle size of 0.5-1.0 mm, and then spraying finishing varnish for decoration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a partial cross-sectional schematic diagram of an aluminum alloy hub according to the present invention.

DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the invention are clearly and completely described in combination with the embodiments of the invention and an accompanying drawing of the invention, and obviously, the described embodiments are only a part of the embodiments of the invention, but not all the embodiments of the invention. Based on the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without creative work all belong to the scope of protection of the present invention.

[0019] The drawing in the invention is only a schematic structure diagram, wherein the size and the shape do not represent the real size and shape.

[0020] As shown in FIG. 1, an aluminum alloy hub is provided with an aluminum alloy matrix 100 and a coating 200 attached to the surface of the aluminum alloy matrix, and the coating 200 sequentially includes a pre-coating 210 formed by nickel-coated aluminum or aluminum-coated nickel powder, a Cr.sub.3C.sub.2 layer 220 and a varnish layer 230 on the surface of the aluminum alloy matrix 100. Preferably, the thickness of the pre-coating layer 210 may be 0.05-0.08 mm. Preferably, the thickness of the Cr.sub.3C.sub.2 layer 220 may be 0.10-0.06 mm, more preferably 0.08 mm. Preferably, the porosity of the Cr.sub.3C.sub.2 layer 220 may be 1.5-2.5%, more preferably 1.8-2.0%. Preferably, the thickness of the varnish layer 230 may be 0.40-0.08 mm.

[0021] The invention provides a method for coating the surface of an aluminum alloy hub. According to the method, a compact chromium carbide layer is formed on the surface of an aluminum alloy matrix through a high-speed flame spraying method, so that the cost of surface treatment of the aluminum alloy hub is reduced, and improved corrosion resistance is obtained.

[0022] According to one specific embodiment of the invention, the method disclosed by the invention is described in detail below in combination with FIG. 1.

[0023] Firstly, the surface of an aluminum alloy matrix 100 is pretreated. The pretreatment step includes the steps that the surface of the aluminum alloy hub is cleaned by degreasing, decontaminating and derusting, and oxide skin on the surface of the aluminum alloy hub is removed, so that the surface of a workpiece shows metallic luster; then, the surface is roughened through turning, so that the surface quality is further guaranteed, the bonding strength is improved, and the thickness of the coating is reserved; and then the aluminum alloy hub is preheated at 120-140° C. through a resistance furnace, so that the temperature of the workpiece is uniform, and water vapor is not generated on the surface.

[0024] Then the pre-coating layer 210 is sprayed by adopting a high-speed flame spray gun. The process parameters are shown in the following table, the thickness of the sprayed pre-coating layer is 0.12-0.13 mm, the thickness of the pre-coating layer after turning and roughening is 0.05-0.08 mm, and preferably, the pre-coating layer 210 may be formed by nickel-coated aluminum or aluminum-coated nickel powder.

[0025] Then, the high-speed flame spray gun is still adopted for spraying the Cr.sub.3C.sub.2 layer 220. The process parameters are shown in the following table, and the thickness of the sprayed Cr.sub.3C.sub.2 layer 220 is greater than or equal to 0.15 mm.

TABLE-US-00001 Oxygen Compressed Acetylene Spraying Spraying pressure air pressure pressure distance angle (MPa) (MPa) (MPa) (mm) (°) 0.45-0.48 0.42-0.44 0.55-0.58 160-170 26-28 0.42-0.49 0.40-0.45 0.52-0.60 150-180 26-28

[0026] Finally, the surface of the aluminum alloy hub is subjected to aftertreatment, and sand blasting is conducted by using silica sand of 0.5-1.0 mm; after finish turning, the thickness of the Cr.sub.3C.sub.2 layer 220 is about 0.08 mm; and finally, finishing varnish 230 is sprayed for decoration, the thickness of the varnish layer is 0.40-0.08 mm, and the thickness of the varnish layer in specific production is within a range value.

[0027] The present invention is further described hereinafter with specific embodiments. The reagents used in the following embodiments are all commercially available and purchased.

[0028] Embodiment Spraying Cr3C2 powder on the surface of an aluminum alloy sample block by adopting a high-speed flame spraying method

[0029] 1. Test Equipment:

[0030] Equipment: SQP-1 type flame spray gun (manufacturer: Shanghai Ouya spraying machinery Co., Ltd.)

[0031] Workpiece: aluminum alloy hub base material sample block

[0032] Priming layer material: aluminum-coated nickel powder (particle size No.: 230-240, and particle size: 15 μm)

[0033] Spraying material: Cr.sub.3C.sub.2 powder (particle size: 10 μm)

[0034] 2. Test Method

[0035] The surface of an aluminum alloy sample block is degreased, decontaminated and derusted. Then roughening treatment is carried out by adopting a turning process. A resistance furnace is adopted for preheating at 120-140° C. for 5 min.

[0036] A high-speed flame spray gun is adopted for spraying a pre-coating layer according to the following conditions, wherein the thickness is 0.12-0.13 mm. Then turning and roughening are conducted again. The remaining thickness is 0.05 mm. Cr.sub.3C.sub.2 powder with a thickness of 0.15 mm is sprayed by adopting a high-speed flame spray gun according to the following conditions. Then silica sand with a particle size of 0.5-1.0 mm is adopted for conducting sand blasting aftertreatment on the surface of the Cr.sub.3C.sub.2, and after finish turning, the thickness of the Cr.sub.3C.sub.2 layer is 0.08 mm. Finally, finishing varnish is sprayed for decoration.

[0037] Process parameters for spraying the pre-coating layer and a working layer are as follows:

TABLE-US-00002 Oxygen Compressed Acetylene Spraying Spraying Spraying pressure air pressure pressure distance angle material (MPa) (MPa) (MPa) (mm) (°) Aluminum- 0.45-0.48 0.42-0.44 0.55-0.58 160-170 26-28 coated nickel powder Cr.sub.3C.sub.2 powder 0.42-0.49 0.40-0.45 0.52-0.60 150-180 26-28

[0038] Comparative example Electroplating the surface of an aluminum alloy sample block by using an electroplating method

[0039] A conventional electroplating method is adopted, surface electroplating is conducted on an aluminum alloy sample block used for preparing an aluminum alloy hub according to a technological process of polishing, pretreatment, cleaning, activation, oil removal, semi-bright nickel plating, high-sulfur nickel plating, bright nickel plating, chromium plating and inspection, and an electroplated sample block with the following structure is obtained:

[0040] Electroplated layer thickness:

[0041] a chromium layer: 0.25-0.40 μm;

[0042] a microporous nickel layer (without minimum requirements, but STEP requirements must be met);

[0043] a bright nickel layer: 16 μm (minimum);

[0044] a high sulfur nickel layer (without minimum requirements, but STEP requirements must be met);

[0045] a semi-bright nickel layer: 24 μm (minimum);

[0046] the thickness of a copper layer is 10 μm (minimum);

[0047] the total nickel layer thickness is 40 μm (minimum); and

[0048] the total coating thickness is 50 μm (minimum).

[0049] Test example 1 Performance test of coatings in Embodiment and comparative example

[0050] 1. Test Method and Instrument

[0051] Density: detected by a metallographic method (Zeiss metallographic microscope)

[0052] Porosity: detected by a metallographic method (Zeiss metallographic microscope)

[0053] Bonding strength: tested by using a stretcher (German Zwick/Z100)

[0054] A density/porosity detection method: a hub coating section is taken, mounting, grinding and polishing are conducted, the section is viewed under a 200-fold microscope, and checking is conducted.

[0055] A bonding strength detection method: a tensile sample is made of common Q235 steel through turning. Specific test steps are as follows: sand blasting treatment is performed on a sample mating plate A and a sample mating plate B, a coating with a bonding strength to be detected is uniformly sprayed on the end surface of the test piece A, wherein the thickness is about 0.8 mm, the test piece A and the test piece B are bonded by using E-7 glue, wherein the test piece A is placed on the test piece B, and the test piece A and the test piece B are enabled to be coaxial, thermal curing is conducted at 100° C. for 1 h, the test piece is clamped on a clamp of a testing machine, and stretched at a speed of 1 m/min, the magnitude of a load applied is recorded when the test piece is stretched to be broken, and meanwhile, the peeling condition of the coating on the end surface of the test piece is observed when the test piece is stretched to be broken.

[0056] 2. Test Results

TABLE-US-00003 Bonding Structure Density strength Porosity Comparative Epoxy resin/nickel/nickel/  .sup.  76% 66 MPa 3.2% example chromium Embodiment Pre-coating layer: 0.05 mm 90-95% 92 MPa 2.5% Cr.sub.3C.sub.2 layer: 0.08 mm

[0057] Test example 2 Test of corrosion resistance of coatings in embodiment and comparative example

[0058] 1. Test Method

[0059] A copper accelerated acetic acid salt spray (CASS) test (ISO9227-2006) is carried out for 240 h by adopting salt spray chamber equipment (manufacturer: ATLAS, and trade mark: FS-2000).

[0060] 2. Test Results

TABLE-US-00004 First stage Second stage Third stage Comparative No change within Having a corrosion Severe corrosion example 66 h spot at 120 h at 168 h Embodiment No change within No change within No corrosion 66 h 120 h within 240 h

[0061] The above are only the preferred embodiments of the invention, and does not limit the patent range of the invention, and the equivalent structure transformation made by using the contents of the description and the drawing of the invention or the direct/indirect application in other related technical fields under the conception of the invention is included in the patent protection range of the invention.