Method for plating copper alloy part with complex profile with thick chromium

Abstract

The invention provides a method for plating a copper alloy part with a complex profile with thick chromium. The method comprises the following steps: cleaning a to-be-plated part; performing shielding protection on the non-chromium-plated surface of the cleaned part; local cleaning is conducted on the to-be-chromium-plated face of the part subjected to shielding protection; ion chromium plating is conducted on the part with the to-be-chromium-plated face cleaned up; the shielding protection of a non-chromium-plated surface is removed, and a part locally plated with thick chromium is obtained; wherein the part to be plated is the inner bottom of the injector of the combustion chamber of the engine, the outer wall of the part is of a milling groove structure, and a plurality of through holes for mounting nozzles are formed in the bottom surface of the part. The coating which is resistant to high temperature, free of volatility and easy to clean and remove after being cured at high temperature is selected, the protective coating is sprayed before plating to shield a non-chromium-plated surface, and the chromium plating layer which is well combined with a base body and meets the use requirement is obtained by adopting the proper technological methods of pretreatment, shielding, ion chromium plating and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of physical vapor deposition for surface treatment, and particularly relates to a method for locally plating thick chromium on the surface of a complex-shaped copper alloy part with a porous structure; the average thickness of the chromium layer is about 50-100 μm, which can meet the requirement of high-temperature gas erosion resistance. Background Art

[0002] The material of the inner bottom of the injector in the rocket engine combustion chamber is copper alloy, and its structure is shown in Figure 1 , the outer wall of which is a milled groove structure, and there are about two hundred through holes (including threaded holes and non-threaded holes) on the bottom surface for installing nozzles. To meet the requirements of high-temperature gas erosion resistance of the inner bottom and subsequent processing, the part within a set range (such as 30 mm) starting from the root of the inner wall cylindrical surface and the inner bottom surface are plated with thick chromium, and there is no plating layer allowed on the part outside the set range starting from the root of the inner wall cylindrical surface, the outer wall, the outer bottom surface and the through holes. The positions are shown in Figure 1 Positions A and B shown. The average thickness of the plating layer is 50-100 μm. Due to the structural characteristics of the part, nodules will form at the hole edges during electroplating, so the electroplating method cannot be used to prepare the thick chromium layer. When using the vacuum ion chromium plating method, due to the complex shape of the part, the commonly used coating and shielding protection in vacuum plating cannot ensure complete shielding of the non-plated surface or ensure the integrity of the plated surface. There are mainly three risks as follows: (1) If a chromium plating layer is deposited in the hole, the hole size will be changed, affecting subsequent assembly; (2) If a chromium plating layer is deposited on the milled groove surface of the outer wall, it will affect subsequent processes and reduce the brazing strength; (3) If there is no chromium layer in the local area that needs to be chromium-plated on the inner wall and the inner bottom surface, it will reduce the high-temperature gas erosion resistance of the part and there is a risk of local ablation.

[0003] Therefore, a method for plating thick chromium on a complex-shaped copper alloy part is needed to ensure the integrity of the plating layer inside the chromium-plated surface and avoid the formation of a plating layer inside the non-chromium-plated surface. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the inventor of the present invention has conducted intensive research and provided a method for plating thick chromium on a complex-shaped copper alloy part. By selecting a coating material with high temperature resistance, no volatility and easy to clean and remove after high-temperature curing, spraying a protective coating before plating to shield the non-chromium-plated surface, and adopting appropriate pretreatment, shielding, ion chromium plating and other process methods, a chromium plating layer with good bonding to the substrate and meeting the use requirements is obtained.

[0005] The technical solution provided by the present invention is as follows:

[0006] A method for plating thick chromium on a complex-shaped copper alloy part, comprising the following steps:

[0007] Clean the part to be plated;

[0008] Perform shielding protection on the non-chromium-plated surface of the part after cleaning;

[0009] Perform local cleaning on the chromium-plating surface of the parts after masking protection;

[0010] Perform ion chromium plating on the parts with the chromium-plating surface cleaned;

[0011] Remove the masking protection on the non-chromium-plating surfaces to obtain parts with locally thick chromium plating;

[0012] Among them, the parts to be plated are the inner bottom of the injector in the engine combustion chamber, the outer wall has a milled groove structure, and there are multiple through holes for installing nozzles on the bottom surface.

[0013] A method for thick chromium plating of copper alloy parts with complex surfaces provided by the present invention has the following beneficial effects:

[0014] (1) A method for thick chromium plating of copper alloy parts with complex surfaces provided by the present invention designs a masking method according to the structural characteristics of the product. For the milled grooves and through holes on the outer wall, a tooling protection matching the structure of these parts is adopted. For the parts outside the set range of the outer bottom surface and the root of the inner wall cylindrical surface, spraying coating is used for protection, solving the problem of difficult local protection during vacuum plating of products with complex surfaces;

[0015] (2) A method for thick chromium plating of copper alloy parts with complex surfaces provided by the present invention uses a masking coating that can meet the requirements of local plating, does not affect the quality of the plating layer, and is easy to clean and remove after plating, providing support for realizing local plating of parts with complex surfaces;

[0016] (3) A method for thick chromium plating of copper alloy parts with complex surfaces provided by the present invention optimizes the process parameters of ion chromium plating. Ion chromium plating is carried out at a temperature of 340 - 360 °C, and after the plating is completed, it is kept warm at 340 - 360 °C for 12 - 15 h, effectively avoiding the phenomenon of the plating layer falling off due to excessive internal stress when leaving the furnace. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the inner bottom of the injector in the engine combustion chamber. Detailed Embodiments

[0018] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite with these descriptions.

[0019] The special term "exemplary" here means "serving as an example, embodiment, or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior to or better than other embodiments.

[0020] The present invention provides a method for thick chromium plating of copper alloy parts with complex surfaces, including the following steps:

[0021] The first step is to clean the parts to be plated. The parts to be plated are the inner bottom of the engine combustion chamber injector, with a milled groove structure on the outer wall and multiple through holes for installing nozzles on the bottom surface.

[0022] In this step, according to the oil stain situation on the part surface, one of the methods of degreasing with organic solvents or chemical degreasing is selected for degreasing, or a combined method is used for degreasing. The solvents for degreasing with organic solvents are: aviation washing gasoline, absolute ethanol, acetone or other organic solvents. Chemical degreasing uses an alkaline solution at 60 - 90 °C composed of sodium hydroxide, sodium carbonate, sodium phosphate and sodium silicate.

[0023] The second step is to shield and protect the non-chromium-plated surfaces of the parts after the first-step cleaning.

[0024] The shielding and protection methods for non-chromium-plated surfaces include tooling protection and spraying coating protection.

[0025] For the milled grooves and through holes on the outer wall, tooling protection matching the structures of the above parts is adopted. For example, bolts are used to protect the threaded holes, sheets are used to fill the non-threaded holes, and a structure that fits the concavity and convexity of the milled grooves is used for sealing and filling.

[0026] For the parts outside the set range of the outer bottom surface and the root of the inner wall cylindrical surface, spraying coating protection is adopted. Coating A is a suspension prepared by mixing titanium dioxide and an organic solvent such as acetone in a certain proportion, and the concentration is suitable for spraying with a spray gun.

[0027] Coating B is a coating prepared by mixing silicate and water in a certain proportion. Water-soluble volatile organic solvents such as absolute ethanol or acetone can be added appropriately according to the coating situation to adjust the thickness, and the concentration is suitable for spraying with a spray gun. The silicate is a composition formed by compounding multiple silicates mainly composed of calcium silicate, supplemented by sodium silicate and / or potassium silicate.

[0028] Coating A and / or Coating B is used to spray the non-chromium-plated surfaces. After spraying, it is left to dry naturally or dried in an oven at a temperature of 80 - 120 °C for 5 - 8 h.

[0029] The third step is to locally clean the chromium-plated surfaces in the second step. Specifically: Use a clean white silk cloth to wipe the chromium-plated surfaces successively with absolute ethanol and acetone.

[0030] The fourth step is to perform ion chromium plating on the parts with the chromium-plated surfaces cleaned in the third step.

[0031] To obtain a thick chromium layer with uniform plating and a qualified thickness, the furnace cavity temperature before ion chromium plating is 340 - 360 °C, such as 350 °C, the ion chromium plating target power is 90 - 150 A / dm 2 , and the plating time is 25 ± 3 h.

[0032] Perform heat preservation treatment on the parts after ion chromium plating. The heat preservation temperature is 340 - 360 °C, such as 350 °C, and the heat preservation time is 12 - 15 h.

[0033] In the fifth step, remove the shielding protective layer on the non-chromium-plated surface in the second step. After removing the tooling or thoroughly cleaning the coating, the parts with locally thick chromium plating are obtained.

[0034] Embodiment

[0035] Embodiment 1

[0036] A method for thick chromium plating of copper alloy parts with complex surfaces includes the following steps:

[0037] In the first step, when cleaning the parts to be plated, according to the oil stain situation on the part surface, select anhydrous ethanol and acetone to degrease in sequence.

[0038] In the second step, shield and protect the non-chromium-plated surface of the parts. For the outer wall milling grooves and through holes, use tooling that matches the structure of the above parts for protection. For example, use bolts to protect the threaded holes, use materials such as cylindrical parts to fill the non-threaded holes, and use a structure that fits the milling groove's concavity and convexity for sealing.

[0039] For the part of the outer bottom surface and the root of the inner wall cylindrical surface outside the set range, use coating A for protection. Coating A is a suspension prepared from titanium dioxide and acetone, and the concentration is suitable for spraying with a spray gun. Coating A is sprayed with a spray gun. After spraying, dry it in an oven at a drying temperature of 80 °C for 5 h.

[0040] In the third step, perform local cleaning on the surface to be chromium-plated in the second step. Use a clean white silk cloth to dip in anhydrous ethanol and acetone in sequence to wipe the surface to be chromium-plated.

[0041] In the fourth step, perform ion chromium plating on the parts with the surface to be chromium-plated cleaned in the third step. Before ion chromium plating, the furnace cavity temperature is 350 °C, and the ion chromium plating target power is 120 A / dm 2 , and the plating time is 25 h.

[0042] In the fifth step, perform heat preservation treatment on the parts after ion chromium plating in the fourth step. After chromium plating, the heat preservation temperature is 350 °C, and the heat preservation time is 12 h.

[0043] In the sixth step, remove the shielding protective layer on the non-chromium-plated surface in the second step. After thoroughly cleaning, the parts with locally thick chromium plating are obtained.

[0044] After plating, the chromium layer on the chromium-plated surface is uniform, flat, has good bonding, the interface with the non-chromium-plated surface is clear, and there is a small amount of chromium layer on the non-chromium-plated surface in individual parts, which can be removed by filing, sanding, etc. The coating thickness is about 50 ± 5 μm.

[0045] Embodiment 2

[0046] A method for electroplating thick chromium on a copper alloy part with a complex surface includes the following steps:

[0047] In the first step, when cleaning the part to be electroplated, according to the oil stain situation on the part surface, select an alkaline solution at 60 °C composed of sodium hydroxide, sodium carbonate, sodium phosphate and sodium silicate for degreasing.

[0048] In the second step, shield and protect the non-chromium-plated surfaces of the part. For the outer wall milling grooves and through holes, use tooling that matches the structure of these parts for protection. For example, use bolts to protect the threaded holes, use cylindrical parts to fill the non-threaded holes, and use a structure that fits the milling grooves to seal and fill.

[0049] For the part of the outer bottom surface and the root of the inner wall cylindrical surface outside the set range, use coating B for protection. Coating B is a coating prepared from silicate (calcium silicate: sodium silicate mass ratio = 2:1) and water. Appropriately add anhydrous ethanol or acetone to adjust the thickness according to the coating situation. After stirring evenly, it should be atomizable by a spray gun. After spraying, let it dry naturally.

[0050] In the third step, locally clean the chromium-plated surface in the second step. Use a clean white silk cloth to wipe the chromium-plated surface successively with anhydrous ethanol and acetone.

[0051] In the fourth step, perform ion chromium plating on the part with the chromium-plated surface cleaned in the third step. Before ion chromium plating, the furnace chamber temperature is 350 °C, the ion chromium plating target power is 100 A / dm 2 , and the plating time is 25 h.

[0052] In the fifth step, perform heat preservation treatment on the part after ion chromium plating in the fourth step. After chromium plating, the heat preservation temperature is 350 °C, and the heat preservation time is 12 h.

[0053] In the sixth step, remove the shielding protection layer on the non-chromium-plated surface in the second step. After thoroughly cleaning, obtain the part with locally electroplated thick chromium.

[0054] After electroplating, the chromium layer on the chromium-plated surface is uniform, flat, with good bonding, the interface with the non-chromium-plated surface is clear, and there is a small amount of chromium layer on the non-chromium-plated surface at individual parts, which can be removed by filing, sanding, etc. The coating thickness is about 50 ± 5 μm. The above has described the present invention in detail in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0055] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for electroplating thick chromium on a copper alloy part with a complex surface, characterized in that, It includes the following steps: Clean the parts to be plated; Mask and protect the non-chromium-plated surfaces of the parts after cleaning; Locally clean the chromium-plated surfaces of the parts after masking and protection; Ion chromium-plate the parts with clean chromium-plated surfaces; Remove the masking protection from the non-chromium-plated surfaces to obtain parts with locally thick chromium plating; Among them, the parts to be plated are the inner bottom of the engine combustion chamber injector, the outer wall has a milling groove structure, and there are multiple through holes for installing nozzles on the bottom surface.

2. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 1, characterized in that, The step of cleaning the parts to be plated is specifically: according to the oil stain situation on the part surface, select one of organic solvent degreasing and chemical degreasing for degreasing or use a combined method for degreasing.

3. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 1, characterized in that, The step of masking and protecting the non-chromium-plated surfaces of the parts after cleaning is specifically: For the outer wall milling grooves and through holes, use tooling that matches the structure of the above parts for protection; For the parts outside the set range starting from the outer bottom surface and the root of the inner wall cylindrical surface, use sprayed coating for protection.

4. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 3, characterized in that, The use of tooling that matches the structure of the above parts for protection for the outer wall milling grooves and through holes includes: using bolts to protect the threaded holes, using materials to fill the non-threaded holes, and using a structure that fits the milling groove concavity and convexity for sealing.

5. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 3, characterized in that, In the step of using sprayed coating for protection for the parts outside the set range starting from the outer bottom surface and the root of the inner wall cylindrical surface, the coating is a suspension prepared from titanium dioxide and an organic solvent, and the concentration is appropriate for spraying with a spray gun.

6. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 3, characterized in that, In the step of using sprayed coating for protection for the parts outside the set range starting from the outer bottom surface and the root of the inner wall cylindrical surface, the coating is a coating prepared from silicate and water, and an appropriate amount of water-soluble volatile organic solvent is added to adjust the thickness according to the coating situation, and the concentration is appropriate for spraying with a spray gun.

7. The method for plating thick chromium on a copper alloy part with a complex surface according to claim 3, characterized in that, In the step of using sprayed coating for protection for the parts outside the set range starting from the outer bottom surface and the root of the inner wall cylindrical surface, spray the non-chromium-plated surface with the coating, and let it dry naturally or dry it in an oven after spraying. The drying temperature is 80-120°C and the time is 5-8h.

8. The method for plating thick chromium on a copper alloy part with a complex surface according to claim 1, characterized in that, The step of locally cleaning the chromium-plated surfaces of the parts after masking and protection includes: using a clean fabric to wipe the chromium-plated surfaces in turn with anhydrous ethanol and acetone.

9. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 1, characterized in that, The step of subjecting the parts with the chrome-plating surface cleaned to ion chrome plating includes: subjecting the parts with the chrome-plating surface cleaned to ion chrome plating, the temperature of the furnace cavity before ion chrome plating is 340-360°C, the power of the ion chrome plating target is 90-150 A / dm 2 , and the plating time is 25±3 h.

10. The method for electroplating thick chromium on a copper alloy part with a complex surface according to claim 1, characterized in that, The step of ion chromium-plating the parts with clean chromium-plated surfaces also includes: performing heat preservation treatment on the parts after ion chromium-plating. The heat preservation temperature is 340-360°C and the heat preservation time is 12-15h.

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