A chromium plating process for nickel-based superalloys

Abstract

The application discloses a chromium plating process for nickel-based high-temperature alloy, which comprises the following steps: S1, electrolytic oil removal; S2, pickling; S3, sulfuric acid activation: the pickled parts are soaked in a sulfuric acid solution with a concentration of 20-30 g / L for 0.5-1.5 min; S4, current activation and chromium plating: the sulfuric acid-activated parts are directly immersed in a chromium plating solution with a temperature of 50-55 DEG C without water washing, and cathode activation is first carried out on the parts by using a cathode current with a current density of 5-8 A / dm 2 2 for 4.5-5.5 min, and then the current density is slowly increased to 45-50 A / dm 2 2 within 5 min for chromium plating. The process provided by the application can completely remove the surface oxide layer of the nickel-based high-temperature alloy parts, so that the parts expose the metal matrix with high activity, the chromium plating effect of the parts is remarkably improved, the qualified rate of the part products is improved, the process has the advantages of simple operation, easy mastering, stable and reliable quality and the like, and the bonding force of the plating layer meets the requirements of relevant standards.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy chromium plating technology, specifically a nickel-based high-temperature alloy chromium plating process. Background Technology

[0002] In the aerospace field, there are many high-temperature alloy chromium-plated parts. During the chromium plating process of these parts, the high-temperature alloy is very easy to passivate, which brings great difficulties to the chromium plating process, and it is difficult to guarantee the adhesion of the chromium layer.

[0003] Currently, there are two main methods for chromium plating of nickel-based superalloys: one is to perform impact nickel plating before chromium plating, creating a functional coating. Impact nickel plating requires high operator skill; improper operation can cause the coating to peel. Furthermore, impact nickel plating increases the internal stress between the coating and the substrate, especially when the coating thickness is required to be ≥20μm; after hydrogen removal, the coating will peel directly. The other method involves adding anodic activation followed by cathodic activation in the pretreatment process. Anodic activation involves a bath solution containing highly corrosive hydrofluoric acid, which significantly affects the roughness of the substrate during anodic activation. Simultaneously, the cathodic activation time is difficult to determine, requiring the absence of visible surface dust, making operation challenging. Additionally, nickel-based superalloys are easily oxidized during pretreatment before chromium plating, generating nickel oxide that is difficult to remove, severely affecting the adhesion of the electroplated layer and significantly reducing its bonding performance and other properties. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a nickel-based high-temperature alloy chromium plating process that can completely remove the oxide layer on the surface of nickel-based high-temperature alloy parts, exposing the parts to a highly active metal substrate, significantly improving the chromium plating effect and increasing the product qualification rate. It has the advantages of simple operation, easy to master, and stable and reliable quality. The adhesion of the plating layer meets the relevant standard requirements and can effectively solve the problems in the background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a nickel-based high-temperature alloy chromium plating process, comprising the following steps:

[0006] S1. Electrolytic degreasing: Immerse the parts in the degreasing solution to remove oil. After the degreasing time is up, take the parts out of the degreasing solution, wash them with hot water first, and then wash them with cold water to remove the degreasing solution from the parts.

[0007] The degreasing solution is composed of the following components: NaOH 10-30 g / L, Na2SiO3 5-10 g / L, Na3PO4·12H2O 30-70 g / L, Na2CO3 20-30 g / L, and the remainder is water;

[0008] S2. Pickling: Immerse the degreased parts in a hydrochloric acid solution at ambient temperature, then remove them and rinse with cold water to remove the hydrochloric acid from the parts.

[0009] The concentration of hydrochloric acid in the hydrochloric acid aqueous solution is 100-150 g / L;

[0010] S3. Sulfuric acid activation: Immerse the pickled parts in an aqueous sulfuric acid solution at ambient temperature for 0.5 to 1.5 minutes.

[0011] The sulfuric acid in the aqueous solution has a concentration of 20–30 g / L.

[0012] S4. Current Activation and Chromium Plating: The sulfuric acid-activated parts are directly immersed in a chromium plating solution at a temperature of 50-55℃ without rinsing with water. Initially, an current of 5-8 A / dm² is used. 2 The cathode current is used to cathodically activate the parts for 4.5–5.5 minutes, and then the current density is slowly increased to 45–50 A / dm² over 5 minutes. 2 Chromium plating;

[0013] The chromium plating solution consists of the following components: CrO3 200-250 g / L, H2SO4 2-2.5 g / L, and the remainder is water;

[0014] S5. Wash and dry: Place the chrome-plated parts in water at ambient temperature and wash for 1-3 minutes. Then use clean compressed air to blow the surface of the parts until there are no obvious water marks.

[0015] S6. Hydrogen Removal: Determine the hydrogen removal parameters based on the tensile strength of the part material to perform hydrogen removal.

[0016] Preferably, the temperature of the degreasing fluid in S1 is 60–90°C, and the current density is 4–10 A / dm³. 2 The degreasing time is 3 to 5 minutes.

[0017] Preferably, in step S1, the hot water temperature is 60–90°C and the washing time is 0.5–5 minutes; the cold water temperature is ambient temperature and the washing time is 10–180 seconds. For parts with simple structures, the washing time is 10–60 seconds, and for parts with complex structures, the washing time is 60–180 seconds.

[0018] Preferably, in step S2, the parts are immersed in hydrochloric acid aqueous solution for 0.5 to 2 minutes, and the cold water washing temperature is the ambient temperature. The washing time is 10 to 180 seconds, with 10 to 60 seconds for parts with simple structures and 60 to 180 seconds for parts with complex structures.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) After activation with sulfuric acid, the parts are directly immersed in the chromium plating bath without water rinsing. The chromium plating solution in the chromium plating bath is composed of chromium anhydride and sulfuric acid. The sulfuric acid in the parts will not introduce impurities into the chromium plating bath (the sulfuric acid content can also be kept stable through regular analysis and adjustment of the bath solution). This ensures that the nickel-based superalloy is always in an activated state before entering the chromium plating bath. This solves the problem that after the activated substrate is rinsed with water following traditional acid pickling, the dissolved oxygen in the water will passivate the nickel-based superalloy (reaction equation: Ni + O2 → NiO), which will bring difficulties to the subsequent chromium plating process. When the metal substrate is oxidized, the acid on the surface of the parts can also reactivate the parts (reaction equation: NiO + H2). + →Ni 2+ +H2↑);

[0021] (2) Low-current cathode activation is employed, utilizing the side reactions during chromium plating. When the given current density is 5–8 A / dm³, 2 When the chromium plating solution temperature is 50-55℃, no plating layer is deposited on the surface of the part; only hydrogen is released (reaction equation: H). + +e→H 2H→H2↑), while the hydrogen atoms H that have not yet combined into hydrogen gas have a strong reducing ability, which can reduce the passivation film (the reaction equation is NiO+2H→Ni+H2O), so that the passivated metal surface can be electrolytically activated, exposing a highly active metal substrate, and then chromium plating is performed by upflow.

[0022] By using sulfuric acid activation and low-current cathode activation, the oxide layer on the surface of the parts can be completely removed, exposing the highly active metal substrate of the nickel-based superalloy. This significantly improves the chromium plating effect of the nickel-based superalloy, increases the product qualification rate, and has the advantages of simple operation, easy mastery, stable and reliable quality. The adhesion of the plating layer meets the relevant standard requirements. Attached Figure Description

[0023] Figure 1 This is a flowchart of the process steps of the present invention;

[0024] Figure 2 This is a graph showing the relationship between current density and time in step S4 of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will now be described with reference to the accompanying drawings of the embodiments of the present invention. In the description, it should be understood that the terms "upper," "lower," "front," "rear," "left," and "right," etc., indicating directions or positional relationships, are only used to correspond to the accompanying drawings of the present invention for the purpose of facilitating the description of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation.

[0026] Please see Figure 1-2 The present invention provides a technical solution.

[0027] Example 1

[0028] A process for chromium plating on a nickel-based superalloy includes the following steps:

[0029] S1. Electrolytic degreasing: The parts are immersed in a degreasing solution at a temperature of 60℃ and a current density of 5A / dm³. 2 The degreasing time is 3 minutes. After the degreasing time is reached, the parts are taken out of the degreasing solution. First, wash with hot water and then wash with cold water to remove the degreasing solution from the parts. The hot water temperature is 60℃ and the washing time is 2 minutes. The cold water temperature is ambient temperature and the washing time is 40 seconds.

[0030] The degreasing solution consists of the following components: NaOH 15g / L, Na2SiO3 6g / L, Na3PO4·12H2O 40g / L, Na2CO3 20g / L, and the remainder is water;

[0031] S2. Pickling: Immerse the degreased parts in a hydrochloric acid solution at ambient temperature with a concentration of 100g / L. Then remove the parts and rinse them with cold water to remove the hydrochloric acid. Immerse the parts in the hydrochloric acid solution for 1 minute and rinse with cold water at ambient temperature for 60 seconds.

[0032] S3. Sulfuric acid activation: Immerse the pickled parts in an aqueous sulfuric acid solution at ambient temperature for 0.5 min. The concentration of sulfuric acid is 20 g / L.

[0033] S4. Current Activation and Chromium Plating: The parts activated with sulfuric acid are directly immersed in a chromium plating solution at 50°C without rinsing with water. First, a current of 6A / dm² is applied. 2 The cathode current was used to cathodically activate the part for 4.5 minutes, and then the current density was slowly increased to 45 A / dm³ over 5 minutes. 2 Chromium plating;

[0034] The chromium plating solution consists of the following components: CrO3 200g / L, H2SO4 2g / L, and the remainder is water;

[0035] S5. Wash and dry: Immerse the chrome-plated parts in water at ambient temperature for 1 minute, and then use clean compressed air to blow the surface of the parts until there are no obvious water marks.

[0036] S6. Hydrogen Removal: Determine the hydrogen removal parameters based on the tensile strength of the part material to perform hydrogen removal.

[0037] Example 2

[0038] S1. Electrolytic degreasing: The parts are immersed in a degreasing solution at a temperature of 80℃ and a current density of 8A / dm³. 2The degreasing time is 4 minutes. After the degreasing time is up, the parts are taken out of the degreasing solution. First, wash with hot water and then wash with cold water to remove the degreasing solution from the parts. The hot water temperature is 80℃ and the washing time is 3.5 minutes. The cold water temperature is ambient temperature and the washing time is 120 seconds.

[0039] The degreasing solution consists of the following components: NaOH 20g / L, Na2SiO3 8g / L, Na3PO4·12H2O 50g / L, Na2CO3 25g / L, and the remainder is water;

[0040] S2. Pickling: Immerse the degreased parts in a hydrochloric acid solution at ambient temperature with a concentration of 120 g / L. Then remove the parts and rinse them with cold water to remove the hydrochloric acid. Immerse the parts in the hydrochloric acid solution for 1.5 min and rinse with cold water at ambient temperature for 120 s.

[0041] S3. Sulfuric acid activation: Immerse the pickled parts in an aqueous sulfuric acid solution at ambient temperature for 1 minute. The concentration of sulfuric acid is 25 g / L.

[0042] S4. Current Activation and Chromium Plating: The parts activated with sulfuric acid are directly immersed in a chromium plating solution at 52°C without rinsing with water. First, a 7A / dm² current is applied. 2 The cathode current was used to cathodically activate the part for 5 minutes, and then the current density was slowly increased to 48 A / dm³ over 5 minutes. 2 Chromium plating;

[0043] The chromium plating solution consists of the following components: CrO3 230 g / L, H2SO4 2.2 g / L, and the remainder is water;

[0044] S5. Wash and dry: Immerse the chrome-plated parts in water at ambient temperature for 2 minutes, and then use clean compressed air to blow the surface of the parts until there are no obvious water marks.

[0045] S6. Hydrogen Removal: Determine the hydrogen removal parameters based on the tensile strength of the part material to perform hydrogen removal.

[0046] Example 3

[0047] S1. Electrolytic degreasing: The parts are immersed in a degreasing solution at a temperature of 90℃ and a current density of 10A / dm³. 2 The degreasing time is 5 minutes. After the degreasing time is reached, the parts are taken out of the degreasing solution. First, wash with hot water and then wash with cold water to remove the degreasing solution from the parts. The hot water temperature is 90℃ and the washing time is 5 minutes. The cold water temperature is ambient temperature and the washing time is 180 seconds.

[0048] The degreasing solution consists of the following components: NaOH 30g / L, Na2SiO3 10g / L, Na3PO4·12H2O 70g / L, Na2CO3 30g / L, and the remainder is water;

[0049] S2. Pickling: Immerse the degreased parts in a hydrochloric acid solution at ambient temperature with a concentration of 150 g / L. Then remove the parts and rinse them with cold water to remove the hydrochloric acid. Immerse the parts in the hydrochloric acid solution for 2 minutes and rinse with cold water at ambient temperature for 180 seconds.

[0050] S3. Sulfuric acid activation: Immerse the pickled parts in an aqueous sulfuric acid solution at ambient temperature for 1.5 minutes. The concentration of sulfuric acid is 30 g / L.

[0051] S4. Current Activation and Chromium Plating: The parts activated with sulfuric acid are directly immersed in a chromium plating solution at 55°C without rinsing with water. First, an 8A / dm² current is applied. 2 The cathode current was used to cathodically activate the part for 5.5 minutes, and then the current density was slowly increased to 50 A / dm³ over 5 minutes. 2 Chromium plating;

[0052] The chromium plating solution consists of the following components: CrO3 250g / L, H2SO4 2.5g / L, and the remainder is water;

[0053] S5. Wash and dry: Place the chrome-plated parts in water at ambient temperature and wash for 3 minutes. Then use clean compressed air to blow the surface of the parts until there are no obvious water marks.

[0054] S6. Hydrogen Removal: Determine the hydrogen removal parameters based on the tensile strength of the part material to perform hydrogen removal.

[0055] As is well known, the cathode current efficiency of chromium plating is only about 13%, mainly due to the numerous side reactions and intense hydrogen evolution during the chromium plating process. The main cathode reactions in chromium plating are shown in the following two equations:

[0056] Main reaction: Cr2O7 2- +14H + +12e→2Cr+7H2O

[0057] Side reaction: H + +e→H

[0058] 2H→H2↑

[0059] "Small current cathode activation" is achieved by utilizing the side reactions during chromium plating. The principle is that during chromium plating, when the given current density is 5-8 A / dm³, 2When the chromium plating solution temperature is 50-55℃, only side reactions occur on the surface of the part. That is, no plating layer is deposited on the surface of the part, only active hydrogen atoms are released. The hydrogen atoms H that have not yet combined into hydrogen gas have a strong reducing ability and can reduce the passivation film, so that the passivated metal surface can be electrolytically activated.

[0060] The parts of this invention not described in detail are prior art. It will be apparent to those skilled in the art that this invention is not limited to the details of the above exemplary embodiments, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the above embodiments should be regarded as exemplary and non-limiting in all respects. The scope of this invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended to include all changes that fall within the meaning and scope of the equivalents of the claims within this invention, and no reference numerals in the claims should be regarded as limiting the content of the claims.

Claims

1. A process for chromium plating on nickel-based high-temperature alloys, characterized in that: Includes the following steps: S1. Electrolytic degreasing: Immerse the parts in the degreasing solution to remove oil. After the degreasing time is up, take the parts out of the degreasing solution, wash them with hot water first, and then wash them with cold water to remove the degreasing solution from the parts. The degreasing solution is composed of the following components: NaOH 10-30 g / L, Na2SiO3 5-10 g / L, Na3PO4·12H2O 30-70 g / L, Na2CO3 20-30 g / L, and the remainder is water; S2. Pickling: Immerse the degreased parts in a hydrochloric acid solution at ambient temperature, then remove them and rinse with cold water to remove the hydrochloric acid from the parts. The concentration of hydrochloric acid in the hydrochloric acid aqueous solution is 100-150 g / L; S3. Sulfuric acid activation: Immerse the pickled parts in an aqueous sulfuric acid solution at ambient temperature for 0.5 to 1.5 minutes. The sulfuric acid in the aqueous solution has a concentration of 20–30 g / L. S4. Current Activation and Chromium Plating: The parts activated with sulfuric acid are directly immersed in a chromium plating solution at 50–55°C without rinsing with water. Initially, an current of 5–8 A / dm² is used. 2 The cathode current is used to cathodically activate the parts for 4.5–5.5 minutes, and then the current density is slowly increased to 45–50 A / dm² over 5 minutes. 2 Chromium plating; The chromium plating solution consists of the following components: CrO3 200-250 g / L, H2SO4 2-2.5 g / L, and the remainder is water; S5. Wash and dry: Place the chrome-plated parts in water at ambient temperature and wash for 1-3 minutes. Then use clean compressed air to blow the surface of the parts until there are no obvious water marks. S6. Hydrogen Removal: Determine the hydrogen removal parameters based on the tensile strength of the part material to perform hydrogen removal.

2. The nickel-based high-temperature alloy chromium plating process according to claim 1, characterized in that: The temperature of the degreasing fluid in S1 is 60–90°C, and the current density is 4–10 A / dm³. 2 The degreasing time is 3 to 5 minutes.

3. The nickel-based high-temperature alloy chromium plating process according to claim 1, characterized in that: In S1, the hot water washing temperature is 60-90℃, and the washing time is 0.5-5 minutes. The cold water washing temperature is the ambient temperature, and the washing time is 10-180 seconds. For simple parts, the washing time is 10-60 seconds, and for complex parts, the washing time is 60-180 seconds.

4. The nickel-based high-temperature alloy chromium plating process according to claim 1, characterized in that: In step S2, the parts are immersed in hydrochloric acid aqueous solution for 0.5 to 2 minutes, and the cold water washing temperature is the ambient temperature. The washing time is 10 to 180 seconds. For parts with simple structures, the washing time is 10 to 60 seconds, and for parts with complex structures, the washing time is 60 to 180 seconds.

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