A method for improving the bonding strength of nickel plating on the molybdenum surface of a rocket engine thrust chamber

Abstract

The present invention discloses a method for improving the bonding strength of a nickel coating on a molybdenum surface of a rocket engine thrust chamber. The method comprises: forming a metallic titanium layer as a transition layer on a molybdenum substrate; activating the surface of the titanium transition layer; pre-plating nickel on the activated titanium transition layer to serve as a base coat for the nickel coating; and forming a nickel coating on the base coat. The method can meet the requirements of the product under service conditions of 800-900°C gas erosion, without causing any undesirable phenomena such as shedding or peeling of the coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of molybdenum surface plating, and in particular relates to a method for improving the bonding strength of a nickel plating on the molybdenum surface of a rocket engine thrust chamber. Background Art

[0002] During the development of a titanium alloy nozzle for a certain type of aerospace liquid rocket engine, a nickel coating was required on the molybdenum surface to ensure an effective diffusion brazing connection between copper, steel, and molybdenum. Therefore, the quality of the nickel coating not only affects the spread of the brazing material on the product surface but also directly influences the strength of the brazed connection.

[0003] Conventional electroplating is commonly used to deposit nickel coatings on molybdenum surfaces in engine thrust chambers. However, because molybdenum is a self-passivating metal, it is chemically active and easily oxidized in air. Directly depositing nickel coatings on molybdenum surfaces through electroplating can easily lead to poor adhesion, such as peeling, shedding, and blistering, resulting in products that fail to meet brazing requirements.

[0004] Coatings produced using cathodic arc plasma deposition (CATP) technology are widely used in molds, tooling, and aerospace applications due to their high density and excellent film-substrate adhesion. This provides a solution to the problem of poor adhesion of nickel coatings on molybdenum surfaces. However, due to the inherent magnetic properties of nickel, this influences the magnetic field during CATP deposition, making the arc motion on the nickel target difficult to control. Therefore, it is difficult to directly deposit nickel coatings on molybdenum surfaces using CATP alone.

[0005] In view of the problem that the existing single electroplating or cathode arc plasma deposition technology cannot directly prepare a nickel coating with excellent adhesion on the molybdenum surface, there is an urgent need for a suitable method for preparing nickel coating on the molybdenum surface to meet the development requirements of rocket engine thrust chambers. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects and provide a method for improving the bonding strength of the nickel plating on the molybdenum surface of the rocket engine thrust chamber, thereby solving the technical problem of poor bonding strength of the plating when nickel is directly plated on the molybdenum surface. The present invention can meet the use requirements of the product under the service conditions of 800-900°C gas flushing, and the plating does not produce any undesirable phenomena such as falling off and peeling.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] A method for improving the bonding strength of a nickel plating layer on a molybdenum surface of a rocket engine thrust chamber, comprising:

[0009] S1 prepares a metal titanium layer on the surface of a molybdenum substrate as a transition layer;

[0010] S2 activates the surface of the titanium transition layer;

[0011] S3 pre-plating nickel on the surface of the activated titanium transition layer as a base layer for the nickel plating layer;

[0012] S4 prepares a nickel plating layer on the surface of the base layer.

[0013] Furthermore, in step S1, a metal titanium layer is prepared on the surface of the molybdenum substrate as a titanium transition layer by using a cathode arc plasma deposition method;

[0014] The thickness of the titanium transition layer is 3 to 5 microns.

[0015] Furthermore, in step S1, the target material deposited by cathode arc plasma is a metal Ti target with a purity of 99.99%;

[0016] The deposition conditions include: target current 70-80A, deposition gas pressure 0.8-1.2Pa, bias voltage 40-60V, target-substrate distance 15-30cm, and time 2-3h.

[0017] Furthermore, in step S2, the method for activating the surface of the titanium transition layer includes:

[0018] The molybdenum substrate with a titanium layer on its surface is placed in an activation solution and activated for 10 to 15 minutes;

[0019] The activation solution contains the following components:

[0020] Sulfuric acid 300-400ml / L;

[0021] OP-10 2~3g / L.

[0022] Furthermore, in step S3, nickel is pre-plated on the surface of the activated titanium transition layer by electroplating;

[0023] The thickness of the pre-nickel plating layer is 1 to 3 microns.

[0024] Furthermore, in step S3, the electroplating process parameters include:

[0025] Current density 10~15A / dm 2 , power on for 5 to 10 minutes.

[0026] Furthermore, in step S3, the pre-nickel plating solution used for electroplating contains the following components:

[0027] Nickel chloride 200-250g / L;

[0028] Hydrochloric acid 50-150g / L.

[0029] Furthermore, step S1 further includes:

[0030] Before preparing the metal titanium layer as a transition layer on the surface of the molybdenum substrate, the surface of the molybdenum substrate is degreased with an organic solvent or chemically.

[0031] Furthermore, the temperature of chemical degreasing is 60-90°C and the time is 10-15 minutes;

[0032] The degreasing agent used for chemical degreasing contains the following components:

[0033]

[0034] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0035] (1) The present invention provides a method for improving the bonding strength of the nickel coating on the molybdenum surface of the thrust chamber of a rocket engine. The method prepares a titanium coating on the metal molybdenum surface as a transition layer and pre-plates nickel as a base layer to solve the problem of poor coating bonding strength when the molybdenum surface is directly nickel-plated. The method can meet the use requirements of the product under the service conditions of 800-900°C gas flushing, and the coating does not produce any undesirable phenomena such as shedding and peeling.

[0036] (2) In a method for improving the bonding strength of a nickel coating on a molybdenum surface of a rocket engine thrust chamber provided by the present invention, titanium having a lattice constant similar to that of the molybdenum substrate is provided as a transition layer to ensure the interfacial bonding strength between the coating and the substrate. The titanium surface is activated by an activation solution to produce an anti-oxidation, conductive titanium hydride film on the surface, thereby improving the bonding strength between the titanium transition layer and the subsequent coating. Simultaneously, a pre-nickel coating is prepared before nickel plating, and a high current density is used to cause nickel ions in the solution to impact the titanium surface at high speed, further improving the bonding strength between the titanium overcoat and the nickel coating.

[0037] (3) The present invention adopts a combination of cathode arc plasma deposition and electroplating technology. First, a metal titanium layer is prepared on the molybdenum surface by cathode arc plasma deposition technology, and then a pre-nickel plating layer is prepared on the titanium surface by electroplating. This solves the problem that a single technology cannot directly prepare a nickel plating layer with excellent bonding strength on the molybdenum surface. DETAILED DESCRIPTION

[0038] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0039] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0040] The present invention provides a method for improving the bonding strength of a nickel plating layer on a molybdenum surface of a rocket engine thrust chamber, comprising the following steps:

[0041] Step 1: preparing a metallic titanium layer as a transition layer on the surface of a molybdenum substrate;

[0042] Step 2, activating the surface of the titanium transition layer;

[0043] Step 3, pre-plating nickel on the surface of the activated titanium coating as a base layer for the nickel coating;

[0044] Step 4: preparing a nickel plating layer on the surface of the base layer.

[0045] Preferably, the metal titanium transition layer is prepared by cathode arc plasma deposition, and the coating thickness is 3 to 5 microns.

[0046] More preferably, the target material of the cathode plasma deposition is a metal Ti target (99.99%), and the deposition conditions include: target current 70-80A, deposition gas pressure 0.8-1.2Pa, bias voltage 40-60V, target-substrate distance 15-30cm, and time 2-3h.

[0047] Preferably, the surface activation of the titanium transition layer is to place the substrate coated with the metal titanium layer into an activation solution for activation for 10 to 15 minutes, and the activation solution contains the following components:

[0048] Sulfuric acid 300~400ml / L

[0049] OP-10 2~3g / L

[0050] Preferably, the pre-nickel plating layer on the surface of the activated titanium plating layer is prepared by electroplating and serves as a base layer for the nickel plating layer.

[0051] More preferably, the nickel pre-plating process parameters include: current density 10 to 15 A / dm 2 , power on for 5 to 10 minutes, and the thickness of the pre-plated nickel layer is 1 to 3 microns. The pre-plated nickel solution contains the following components:

[0052] Nickel chloride 200~250g / L

[0053] Hydrochloric acid 50-150g / L

[0054] Preferably, before preparing the titanium transition layer on the molybdenum surface, the method further comprises the following step: removing oil from the product surface by organic solvent or chemically removing oil.

[0055] More preferably, the chemical degreasing temperature is 60-90°C, the time is 10-15 minutes, and the degreasing agent contains the following components:

[0056]

[0057] In a specific embodiment, the present invention comprises the following steps:

[0058] (1) Degreasing

[0059] Depending on the oil contamination on the surface of the product (such as the nozzle), either organic solvent degreasing or chemical degreasing can be used for degreasing, or a combination of methods can be used for degreasing.

[0060] The commonly used solvents for organic solvent degreasing are: aviation washing gasoline, alcohol or other organic solvents.

[0061] Chemical degreasing is based on the complete removal of oil stains. The specific chemical degreasing process parameters include the following:

[0062] Chemical degreasers contain the following components:

[0063]

[0064] (2) Cathodic arc plasma deposition of titanium transition layer

[0065] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 250-350°C (such as 300°C), and then titanium plating is carried out. The specific parameters are as follows: the titanium target is 99.99% pure titanium, the target current is 70-80A, the deposition pressure is 0.8-1.2Pa, the bias voltage is 40-60V (preferably 50V), the target-substrate distance is 15-30cm, and the plating time is 2-3h.

[0066] The titanium transition layer on the molybdenum surface is 3 to 5 microns.

[0067] (3) Activated titanium coating

[0068] The activation parameters for the titanium over-plating layer on the molybdenum surface of the product are as follows:

[0069] Sulfuric acid 300~400ml / L

[0070] OP-10 2~3g / L

[0071] Activation time: 10 to 15 minutes.

[0072] (4) Pre-nickel plating

[0073] Prepare a pre-nickel-plated base layer on the surface of the titanium transition layer of the product: current density 10-15A / dm 2 , power on for 5 to 10 minutes, the silver plating solution contains the following components:

[0074] Nickel chloride 200~250g / L

[0075] Hydrochloric acid 50-150g / L.

[0076] The prepared pre-nickel plating base layer has a thickness of 1 to 3 microns.

[0077] (5) Formal nickel plating.

[0078] The present invention provides a method for improving the bonding strength of nickel-plated coatings on the molybdenum surface of a rocket engine thrust chamber. Titanium, with a lattice constant similar to that of the molybdenum substrate, is provided as a transition layer to ensure interfacial bonding between the coating and the substrate. However, since titanium is relatively active and easily passivated, direct electroplating results in extremely poor bonding between the coating and the substrate. Therefore, the titanium surface is activated with an activation solution to produce an oxidation-resistant, conductive titanium hydride film, thereby enhancing the bonding strength between the titanium transition layer and subsequent coatings. Furthermore, a pre-nickel-plating primer layer is prepared before nickel plating, and a high current density is used to cause nickel ions in the solution to impact the titanium surface at high speed, further enhancing the bonding strength between the titanium over-plating layer and the nickel coating. This method solves the problems of easy shedding, bubbling, and flaking of the nickel-plated coating on the molybdenum surface of a rocket engine thrust chamber. It ensures the film-based bonding strength between the molybdenum and nickel surfaces of the thrust chamber, ensuring sufficient bonding strength to meet the product's operational requirements under 800-900°C fuel gas erosion, without causing any undesirable phenomena such as shedding or flaking.

[0079] The present invention adopts a combination of cathode arc plasma deposition and electroplating technology. First, a metal titanium layer is prepared on the molybdenum surface by cathode arc plasma deposition technology, and then a pre-nickel plating layer is prepared on the titanium surface by electroplating. This solves the problem that a single technology cannot directly prepare a nickel plating layer with excellent bonding strength on the molybdenum surface.

[0080] Example

[0081] Example 1

[0082] Step (1) Degreasing

[0083] Degrease the product with aviation washing gasoline;

[0084] Step (2) ion plating titanium

[0085] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 300 ° C, and then titanium plating was carried out. The specific parameters were as follows: the titanium target was 99.99% pure titanium, the target current was 70A, the deposition pressure was 1.1Pa, the bias voltage was 50V, the target-substrate distance was 15cm, and the plating time was 2h.

[0086] Step (3) Activation of the titanium coating

[0087] Activation of titanium coating: The time is 10 minutes, and the activation solution contains the following components: 300 ml / L sulfuric acid and 2 g / L OP-10.

[0088] Step (4) pre-nickel plating

[0089] Pre-nickel plating: current density 10A / dm 2 , power on for 5 minutes, the pre-nickel plating solution contains the following components: nickel chloride (NiCl2) 200g / L, hydrochloric acid (HCl) 50g / L.

[0090] The prepared nickel plating was verified by brazing and gas flushing and met the requirements; the strength of the copper-steel brazing seam was 62Mpa.

[0091] Example 2

[0092] Step (1) Degreasing

[0093] The injector was chemically degreased with the following mixture: sodium hydroxide (NaOH) 40 g / L; sodium carbonate (Na2CO3) 40 g / L; sodium phosphate (Na3PO4) 25 g / L; sodium silicate (Na2SiO3) 4 g / L; temperature 80°C; time 12 min;

[0094] Step (2) ion plating titanium

[0095] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 300 ° C, and then titanium plating was carried out. The specific parameters were as follows: the titanium target was 99.99% pure titanium, the target current was 70A, the deposition pressure was 1.1Pa, the bias voltage was 50V, the target-substrate distance was 15cm, and the plating time was 3h.

[0096] Step (3) Activation of the titanium coating

[0097] Activation of titanium coating: The time is 15 minutes, and the activation solution contains the following components: 300 ml / L sulfuric acid and 2 g / L OP-10.

[0098] Step (4) pre-nickel plating

[0099] Pre-nickel plating: current density 15A / dm 2 , power on for 5 minutes, the pre-nickel plating solution contains the following components: nickel chloride (NiCl2) 250g / L, hydrochloric acid (HCl) 50g / L.

[0100] The prepared nickel plating was verified by brazing and gas flushing and met the requirements; the strength of the copper-steel brazing seam was 68Mpa.

[0101] Example 3

[0102] Step (1) Degreasing

[0103] Degrease the injector with aviation washing gasoline;

[0104] Step (2) ion plating titanium

[0105] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 300 ° C, and then titanium plating was carried out. The specific parameters were as follows: the titanium target was 99.99% pure titanium, the target current was 70A, the deposition pressure was 1.1Pa, the bias voltage was 50V, the target-substrate distance was 15cm, and the plating time was 2h.

[0106] Step (3) Activation of the titanium coating

[0107] Activation of titanium coating: The time is 10 minutes, and the activation solution contains the following components: sulfuric acid 400 ml / L, OP-10 content is 3 g / L.

[0108] Step (4) pre-nickel plating

[0109] Pre-nickel plating: current density 10A / dm 2 , power on for 10 minutes, the pre-nickel plating solution contains the following components: nickel chloride (NiCl2) 200g / L, hydrochloric acid (HCl) 150g / L.

[0110] The prepared nickel plating was verified by brazing and gas flushing and met the requirements; the strength of the copper-steel brazing seam was 66Mpa.

[0111] Comparative Example 1

[0112] The remaining steps are the same as those in Example 1, with the following differences:

[0113] After degreasing the product, proceed as follows:

[0114] Step (1) ion plating titanium

[0115] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 300 ° C, and then titanium plating was carried out. The specific parameters were as follows: target current 60 A, deposition pressure 1.1 Pa, bias 50 V, target-substrate distance 15 cm, and plating time 2 h.

[0116] After the product was ion-plated with titanium, the process parameters (target current) of the ion-plated titanium deviated from the process range, and the titanium coating showed obvious peeling, shedding and other poor film adhesion phenomena, which did not meet the product's use requirements.

[0117] Comparative Example 2

[0118] After degreasing the product, proceed as follows:

[0119] Step (1) ion plating titanium

[0120] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 300 ° C, and then titanium plating was carried out. The specific parameters were as follows: the titanium target was 99.99% pure titanium, the target current was 70A, the deposition pressure was 1.1Pa, the bias voltage was 50V, the target-substrate distance was 15cm, and the plating time was 2h.

[0121] Step (2) Activation of the titanium coating

[0122] Activation of titanium coating: The time is 10 minutes, and the activation solution contains the following components: 300 ml / L sulfuric acid and 2 g / L OP-10.

[0123] Step (3) pre-nickel plating

[0124] Pre-nickel plating: current density 5A / dm 2 , power on for 5 minutes, the pre-nickel plating solution contains the following components: nickel chloride (NiCl2) 200g / L, hydrochloric acid (HCl) 50g / L.

[0125] After the product was pre-nickel-plated, the process parameters (current density) of the pre-nickel plating deviated from the process range, and the nickel plating layer showed obvious peeling, shedding and other poor film bonding phenomena, which did not meet the product's use requirements.

[0126] Comparative Example 3

[0127] After degreasing the product, proceed as follows:

[0128] Step (1) ion plating titanium

[0129] The product is placed in the ion plating chamber, and the background vacuum of the coating chamber is pumped to 3.5×10 -3 Pa, heated to 300 ° C, and then titanium plating was carried out. The specific parameters were as follows: the titanium target was 99.99% pure titanium, the target current was 70A, the deposition pressure was 1.1Pa, the bias voltage was 50V, the target-substrate distance was 15cm, and the plating time was 2h.

[0130] Step (2) Activation of the titanium coating

[0131] Activation of titanium coating: The time is 10 minutes, and the activation solution contains the following components: sulfuric acid 100 ml / L, OP-10 content 2 g / L.

[0132] Step (3) Pre-nickel plating

[0133] Pre-nickel plating: current density 10A / dm 2, power on for 5 minutes, the pre-nickel plating solution contains the following components: nickel chloride (NiCl2) 200g / L, hydrochloric acid (HCl) 50g / L.

[0134] After the product was pre-nickel-plated, the process parameters of the activated titanium coating (sulfuric acid content) deviated from the process range, and the nickel coating showed obvious peeling, shedding and other poor film bonding phenomena, which did not meet the product's use requirements.

[0135] Comparative Example 4

[0136] The remaining steps are the same as those in Example 1, but no pre-nickel plating layer is prepared.

[0137] The nickel plating layer showed obvious peeling and falling off, which showed poor film adhesion and did not meet the product's usage requirements.

[0138] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

[0139] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for improving the bonding strength of nickel plating on the molybdenum surface of a rocket engine thrust chamber, characterized in that: include: S1 prepares a metal titanium layer on the surface of a molybdenum substrate as a transition layer; In step S1, the target material deposited by cathode arc plasma is a metal Ti target with a purity of 99.99%; Deposition conditions include: target current 70-80A, deposition gas pressure 0.8-1.2Pa, bias voltage 40-60V, target-substrate distance 15-30cm, and time 2-3h; S2 activates the surface of the titanium transition layer; The method for activating the surface of the titanium transition layer includes: The molybdenum substrate with a titanium layer on its surface is placed in an activation solution and activated for 10 to 15 minutes; The activation solution contains the following components: sulfuric acid 300-400 ml / L, OP-10 2-3 g / L; S3 pre-plating nickel on the surface of the activated titanium transition layer as a base layer for the nickel plating layer; The process parameters of electroplating include: current density 10~15A / dm 2 , power on for 5 to 10 minutes; The pre-nickel plating solution used for electroplating contains the following components: nickel chloride 200-250g / L, hydrochloric acid 50-150g / L; S4 prepares a nickel plating layer on the surface of the base layer.

2. The method for improving the bonding strength of the nickel plating on the molybdenum surface of a rocket engine thrust chamber according to claim 1, characterized in that: In step S1 , the thickness of the transition layer is 3 to 5 microns.

3. The method for improving the bonding strength of the nickel plating on the molybdenum surface of a rocket engine thrust chamber according to claim 1, characterized in that: In step S3, the thickness of the base layer is 1 to 3 microns.

4. The method for improving the bonding strength of the nickel plating on the molybdenum surface of a rocket engine thrust chamber according to claim 1, characterized in that: Step S1 further includes: Before preparing the metal titanium layer as a transition layer on the surface of the molybdenum substrate, the surface of the molybdenum substrate is degreased with an organic solvent or chemically.

5. The method for improving the bonding strength of the nickel plating on the molybdenum surface of a rocket engine thrust chamber according to claim 4, characterized in that: The temperature of chemical degreasing is 60-90℃ and the time is 10-15 minutes; The degreasing agent used for chemical degreasing contains the following components: Sodium hydroxide 30-50g / L; Sodium carbonate 30-50g / L; Sodium phosphate 20-30 g / L; Sodium silicate 3-5g / L.

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