Crn / tin / alin composite film layer on surface of stainless steel welded part and preparation method thereof

Abstract

The application discloses a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part and a preparation method thereof. The composite film layer comprises, from the surface of the stainless steel welded part outward, a pure Cr layer, a TiN / ALN composite film layer, a TiN / CrN / ALN composite film layer and a CrN film layer. In the preparation of the composite film layer, multi-arc ion plating is adopted, and wet sand blasting, hydrofluoric acid cleaning, drying, assembling and protection, ion source etching are sequentially performed before the multi-arc ion plating. Then, four-stage film plating is adopted, a pure chromium metal layer is deposited first, then the TiN / ALN composite film layer is deposited, then the TiN / CrN / ALN composite film of three components is deposited, and finally the CrN component film layer is deposited. The application solves the problem of insufficient corrosion resistance of the stainless steel welded part at the weld and the heat affected zone, and meets the requirement that the surface of the workpiece is medium gray.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of stainless steel surface treatment, and particularly relates to a method for multi-arc ion plating of a CrN / TiN / AlN composite film layer on a surface of a stainless steel welded part. BACKGROUND

[0002] Multi-arc ion plating technology is an improved method of ion plating technology, which is a surface coating technology taking arc discharge as a metal evaporation source, and has the characteristics of high plating film speed, large film compactness, and good film adhesion, etc. In the application of stainless steel, austenitic stainless steel is most widely used due to its excellent corrosion resistance, good mechanical properties, convenience for mechanical processing, stamping and welding, etc. However, the "stainless" of the austenitic stainless steel is only relative, and when it is in a specific medium or due to heat treatment, welding and other process operations, the corrosion resistance of the material will be significantly reduced, especially the existence of the heat affected zone of welding will produce an area with increased intergranular corrosion tendency.

[0003] In order to improve the appearance quality, corrosion resistance and wear resistance of the surface of the stainless steel welded part, the product needs to be treated with a composite film layer, so as to improve the corrosion resistance of the stainless steel welded part. On the other hand, in combination with the appearance requirements of high-quality engineering of domestic aircraft engines, the internal systems of the engine need to be uniformly colored, and the specific color requirement is to present a medium gray color. The present application is generated based on the above requirements. SUMMARY

[0004] The present application aims to provide a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part and a preparation method thereof, to solve the problem of insufficient corrosion resistance of the stainless steel welded part in the weld and heat affected zone, and to meet the requirement of the workpiece surface being medium gray in the technical requirement.

[0005] The present application is implemented through the following technical solutions:

[0006] The CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part comprises,

[0007] a pure Cr layer, which is located on the surface of the stainless steel welded part;

[0008] a TiN / ALN composite film layer, which is located on the surface of the pure Cr layer;

[0009] a TiN / CrN / ALN composite film layer, which is located on the surface of the TiN / ALN composite film layer;

[0010] a CrN film layer, which is located on the surface of the TiN / CrN / ALN composite film layer.

[0011] That is, the film layers are, from the surface of the stainless steel welded part outward, a pure Cr layer, a TiN / ALN composite film layer, a TiN / CrN / ALN composite film layer, and a CrN film layer.

[0012] Preferably, the CrN / TiN / AlN composite film layer is medium gray, and the colors of the film layers constituting the CrN / TiN / AlN composite film layer satisfy:

[0013] The color of the TiN / ALN composite film layer is dark gray;

[0014] The color of the TiN / CrN / ALN composite film layer is gray;

[0015] The color of the CrN film layer is silver gray.

[0016] A method for preparing a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part, comprising,

[0017] Using multi-arc ion plating, and comprising three groups of target materials:

[0018] The first group is a pure chromium target material, with a chromium content of not less than 99.99%;

[0019] The second group is an aluminum-titanium alloy target material, with a mass ratio of aluminum 67±0.1% and titanium 33±0.1%, and an aluminum-titanium content of not less than 99.99%;

[0020] The third group is a chromium-aluminum alloy target material, with a mass ratio of chromium 60±0.1% and aluminum 40±0.1%, and a chromium-aluminum content of not less than 99.99%.

[0021] As an alternative,

[0022] The number of the pure chromium target materials is 3;

[0023] The number of the aluminum-titanium alloy target materials is 3;

[0024] The number of the chromium-aluminum alloy target materials is 4;

[0025] And the target materials are divided into two columns, one of which has, from top to bottom, 3 pure chromium target materials and 2 aluminum-titanium alloy target materials, and the other of which has, from top to bottom, 4 chromium-aluminum alloy target materials and 1 aluminum-titanium alloy target material.

[0026] As an alternative, before the multi-arc ion plating starts, the following steps are sequentially performed:

[0027] A wet sandblasting step;

[0028] A hydrofluoric acid cleaning step;

[0029] A drying step;

[0030] Assembly and protection steps for welded components;

[0031] Ion source etching step.

[0032] further,

[0033] In the wet sandblasting step, 600-680 mesh alumina material is used to clean the surface of the welded parts with a pressure of 0.4-0.6 MPa to remove the welding oxide scale.

[0034] In the hydrofluoric acid cleaning step, a cleaning agent with hydrofluoric acid and corrosion inhibitor as the main components is used to clean the surface of the welded parts. After cleaning, the residual cleaning agent on the surface is rinsed off with clean water.

[0035] In the drying step, the drying temperature is 100±10℃ and the drying time is 0.5±0.1h;

[0036] In the assembly and protection steps of the welded parts, the surfaces that do not require coating are protected and shielded in accordance with the design drawings.

[0037] In the ion source etching step, the weldment is placed in a vacuum furnace, and the vacuum level of the furnace is reduced to 1×10⁻⁶. - 3 Pa, raise the temperature of the vacuum furnace to 150℃±10℃, raise the voltage to 800V, raise the power to 7KW, and maintain 800V and 7KW for 120 minutes with a pulse ratio of 40%.

[0038] further,

[0039] In the drying step, the dried welded parts need to undergo multi-arc ion plating within 4 hours;

[0040] In the ion source etching step, the vacuum level of the vacuum furnace is reduced to 1×10⁻⁶ within 1 hour. -3 Pa, within 30±5min, the temperature of the vacuum furnace is raised to 150℃±10℃, the voltage is raised from 100V to 800V, and the power is raised from 1KW to 7KW (voltage and power are increased simultaneously).

[0041] Furthermore, during the multi-arc ion plating process, the following four-stage deposition is performed sequentially in a vacuum furnace:

[0042] For the first stage of deposition, turn on the chromium target power supply, set the voltage to 60V and the current to 80A, and maintain for 60 minutes.

[0043] For the second stage of deposition, turn off the chromium target power supply and turn on the aluminum-titanium alloy target power supply. The voltage is 80V, the current is 80A, the nitrogen flow rate is 850mL / min, and the holding time is 30min.

[0044] The third segment is deposited, and the power supply of the aluminum-titanium alloy target and the aluminum-chromium alloy target is turned on, the voltage is 60V, the current is 60A, the nitrogen flow rate is 650mL / min, and the process is maintained for 50min;

[0045] The fourth segment is deposited, the power supply of the aluminum-titanium alloy target and the aluminum-chromium alloy target is turned off, the power supply of the chromium target is turned on, the voltage is 80V, the current is 70A, the nitrogen flow rate is 700mL / min, and the process is maintained for 20min.

[0046] Alternatively, after the fourth segment is deposited, the vacuum furnace is cooled to 80℃, and then the furnace is opened.

[0047] Alternatively, before the first segment is deposited, the temperature of the surface of the welded part is not higher than 300℃.

[0048] The composite film layer prepared by the application can realize the transition from silver gray to dark gray to black on the surface of the stainless steel welded part through parameter adjustment, and the modulated medium gray film layer can meet the uniform color requirement of the engine system. The part processed by the application can effectively improve the corrosion resistance and wear resistance of the welded part and the heat-affected zone of the stainless steel welded part, and also meets the requirement that the surface of the processed part is medium gray.

[0049] Compared with the prior art, the application has the following characteristics:

[0050] (1) Wet sand blasting is used for pretreatment of the stainless steel welded part to improve the surface consistency of the stainless steel welded part;

[0051] (2) A cleaning agent mainly composed of hydrofluoric acid and a surfactant is used to clean the surface of the stainless steel welded part to further improve the surface activity;

[0052] (3) The surface of the stainless steel welded part is bombarded and cleaned at a voltage of 800V and a pulse ratio of 40%, to further clean the surface of the stainless steel welded part;

[0053] (4) A four-segment film layer deposition scheme is used to improve the adhesion of the film layer to the substrate;

[0054] (5) On the one hand, the CrN / TiN / AlN composition in the film layer is adjusted to achieve the effect that the film layer is medium gray. On the other hand, through the adjustment of different film layers, the corrosion resistance of the system is excellent, and it passes the 240h CASS test (ordinary welded parts generally start to corrode after 48h), and the corrosion resistance of the stainless steel welded part is improved by more than 5 times. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 It is a diagram of the distribution of target materials on the equipment in multi-arc ion plating;

[0056] Figure 2CASS salt spray test of the stainless steel welded piece after film plating. DETAILED DESCRIPTION

[0057] The application will be further described below in connection with the drawings and specific embodiments, but it should not be understood that the scope of the subject matter described herein is limited to the following examples, and any modifications, replacements and changes made according to ordinary technical knowledge and conventional means in the art without departing from the technical ideas of the application are included in the scope of the application.

[0058] In order to achieve the high corrosion resistance and color requirements of the weld and heat-affected zone on the surface of the stainless steel welded piece, the application adopts a multi-arc ion plating scheme to deposit a CrN / TiN / AlN composite film layer on the surface of the stainless steel welded piece.

[0059] The vacuum plating machine used in the embodiment is equipped with three different target materials, one group of which is pure chromium target material with chromium content not less than 99.99%. The second group is aluminum-titanium alloy target material with mass ratio of aluminum 67±0.1% and titanium 33±0.1%, and the aluminum and titanium content is not less than 99.99%. The third group is chromium-aluminum alloy target material with mass ratio of chromium 60±0.1% and aluminum 40±0.1%, and the chromium and aluminum content is not less than 99.99%. Wet sand blasting is used for pretreatment of the workpiece to improve the consistency of the workpiece surface, and hydrofluoric acid is used to clean the surface of the workpiece to improve the surface activity. A four-stage deposition scheme is used for plating to ensure the adhesion, corrosion resistance and appearance requirements of the film layer. Figure 2 As shown in the figure, Figure 2 The left figure is the actual picture after plating, and the right figure is the actual picture of the test piece after 240h CASS salt spray test, and the test piece does not produce rust.

[0060] The specific preparation process of the CrN / TiN / AlN composite film layer on the surface of the stainless steel welded piece is as follows:

[0061] 1. Wet sand blasting: 600-680 mesh alumina material is used to clean the surface of the stainless steel welded piece to be plated at a pressure of 0.4-0.6 MPa to remove the welding scale on the surface of the stainless steel welded piece and improve the consistency of the surface state of the stainless steel welded piece;

[0062] 2. Cleaning: After sand blasting of the stainless steel welded piece, a cleaning agent mainly composed of hydrofluoric acid and corrosion inhibitor is used to clean the surface of the stainless steel welded piece for 1-3 min; after cleaning, the remaining cleaning agent on the surface of the stainless steel welded piece is rinsed clean with water;

[0063] 3. Drying: After cleaning, the water on the surface of the stainless steel welded piece is dried at a temperature of 100±10℃ for 0.5±0.1h, and the plating processing in the furnace is completed within 4h;

[0064] 4. Assembly: After cleaning and drying, the stainless steel welded parts are protected and assembled according to the drawings; 5. Ion source etching: After the stainless steel welded parts are placed in the furnace, the vacuum degree of the vacuum furnace is reduced to 1×10⁻⁶ within 1 hour. -3 Pa;

[0065] The vacuum furnace temperature was raised to 150℃±10℃ within 30±5 minutes; the voltage was increased from 100V to 800V within 10 minutes; the power was increased from 1KW to 7KW; and the voltage was maintained at 800V (40% pulse ratio) and 7KW for 120 minutes.

[0066] 6. Coating 1: Turn on the chromium target power supply, voltage 60V, current 80A, and maintain for 60 minutes;

[0067] 7. Coating 2: Turn off the power supply to the chromium target and turn on the power supply to the aluminum-titanium alloy target. Voltage: 80V; Current: 80A; Nitrogen flow rate: 850mL / min; Hold for 30min.

[0068] 8. Coating 3: Simultaneously turn on the power supply for both the aluminum-titanium alloy target and the chromium-aluminum alloy target, voltage 60V; current 60A;

[0069] Nitrogen flow rate: 650 mL / min; hold for 50 min;

[0070] 9. Coating 4: Turn off the power supply to the aluminum-titanium alloy target and the chromium-aluminum alloy target, and turn on the power supply to the chromium target at 80V;

[0071] Current: 70A; Nitrogen flow rate: 700mL / min; Hold for 20min;

[0072] 10. Removal from the furnace: After the coating is completed, the furnace should be cooled to below 80°C before removing the coating.

[0073] like Figure 1 As shown, three sets of targets are used for processing. The vacuum coating machine is equipped with three different sets of targets, and the three sets of targets adopt different distribution methods. Specifically, the targets are divided into two columns. One column consists of three pure chromium targets and two aluminum-titanium alloy targets from top to bottom, and the other column consists of four chromium-aluminum alloy targets and one aluminum-titanium alloy target from top to bottom. The above distribution method can effectively control the uniform distribution of the coating atmosphere in the furnace.

[0074] Considering that the bombardment process (ion source etching step) before coating will generate high temperature on the surface of stainless steel welded parts, resulting in a large temperature difference between the outside and inside of the stainless steel welded parts, the surface temperature of the stainless steel welded parts can be controlled by adjusting the bombardment power, voltage and pulse ratio, keeping the surface temperature of the stainless steel welded parts below 300℃, and preventing the stainless steel welded parts from deforming due to overheating.

[0075] In the above multi-arc ion plating process, a four-segment coating scheme is adopted, wherein:

[0076] The first paragraph uses deposition of pure chromium metal to ensure the adhesion of the substrate and the subsequent film layer;

[0077] The second paragraph is plated with TiN / ALN composite film layer, the color is dark gray, which is a base layer for manufacturing medium gray, and also has good corrosion resistance;

[0078] The third paragraph is plated with TiN / CrN / ALN three-component composite film, the color is gray, which reduces the color of the film layer and has excellent corrosion resistance;

[0079] The fourth paragraph is plated with CrN component film layer, the color is silver gray, and the transparency is high. Through the above several film layer adjustments, the requirements of the medium gray film layer are met while ensuring the corrosion resistance and wear resistance of the film layer.

[0080] The above examples are not intended to limit the scope of protection of the present application, and any deformation, modification or equivalent replacement made on the basis of the technical solutions of the present application shall fall within the scope of protection of the present application.

Claims

1. A method for preparing a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part, characterized in that: the CrN / TiN / AlN composite film layer comprises: a pure Cr layer on the surface of the stainless steel welded part; a TiN / AlN composite film layer on the surface of the pure Cr layer; a TiN / CrN / AlN composite film layer on the surface of the TiN / AlN composite film layer; and a CrN film layer on the surface of the TiN / CrN / AlN composite film layer; the CrN / TiN / AlN composite film layer is mid-gray, and the colors of the film layers constituting the CrN / TiN / AlN composite film layer satisfy: the color of the TiN / AlN composite film layer is dark gray; the color of the TiN / CrN / AlN composite film layer is gray; and the color of the CrN film layer is silver gray; and the method comprises: using multi-arc ion plating, and comprising three groups of target materials: the first group is a pure chromium target material with a chromium content of not less than 99.99%; the second group is an aluminum-titanium alloy target material with a mass ratio of aluminum 67±0.1% and titanium 33±0.1%, and an aluminum-titanium content of not less than 99.99%; and the third group is a chromium-aluminum alloy target material with a mass ratio of chromium 60±0.1% and aluminum 40±0.1%, and a chromium-aluminum content of not less than 99.99%; and during the multi-arc ion plating, the following four-stage deposition is sequentially performed in a vacuum furnace: first-stage deposition, turning on the chromium target material power supply, voltage 60 V, current 80 A, and maintaining for 60 min; second-stage deposition, turning off the chromium target material power supply, turning on the aluminum-titanium alloy target material power supply, voltage 80 V, current 80 A, nitrogen flow rate 850 mL / min, and maintaining for 30 min; third-stage deposition, simultaneously turning on the aluminum-titanium alloy target material and the chromium-aluminum alloy target material power supplies, voltage 60 V, current 60 A, nitrogen flow rate 650 mL / min, and maintaining for 50 min; and fourth-stage deposition, turning off the aluminum-titanium alloy target material and the chromium-aluminum alloy target material power supplies, turning on the chromium target material power supply, voltage 80 V, current 70 A, nitrogen flow rate 700 mL / min, and maintaining for 20 min.

2. The method for preparing a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part according to claim 1, characterized in that: the number of the pure chromium target materials is three; the number of the aluminum-titanium alloy target materials is three; and the number of the chromium-aluminum alloy target materials is four; and the target materials are divided into two columns, one column comprising three pure chromium target materials and two aluminum-titanium alloy target materials from top to bottom, and the other column comprising four chromium-aluminum alloy target materials and one aluminum-titanium alloy target material from top to bottom.

3. The method for preparing a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part according to claim 2, characterized in that: before the multi-arc ion plating starts, the following steps are sequentially performed: a wet sandblasting step; a hydrofluoric acid cleaning step; a drying step; a welded part assembly and protection step; and an ion source etching step.

4. The method for preparing a CrN / TiN / AlN composite film layer on the surface of a stainless steel welded part according to claim 3, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 3. The method of claim 1, wherein the method is characterized by: ​ ​ ​ ​ ​ ​ ​ In the wet sand blasting step, the surface of the welded piece is cleaned by using 600-680 mesh alumina material and 0.4-0.6 MPa pressure to remove the welding oxide skin on the surface of the welded piece; In the hydrofluoric acid cleaning step, the surface of the welded piece is cleaned by using a cleaning agent mainly composed of hydrofluoric acid and corrosion inhibitor, and after the cleaning, the residual cleaning agent on the surface is rinsed clean with clean water; In the drying step, the drying temperature is 100±10℃, and the drying time is 0.5±0.1 h; In the welded piece assembling and protecting step, the surface not requiring film plating is protected and shielded according to the design drawing requirements; The ion source etching step, the welding piece is loaded into the vacuum furnace, the vacuum degree of the vacuum furnace is reduced to 1×10 -3 Pa, the temperature of the vacuum furnace is raised to 150℃±10℃, the voltage is raised to 800V, the power is raised to 7kW, and under the premise of 40% pulse duty ratio, 800V, 7kW is maintained for 120min.

5. The preparation method of the CrN / TiN / AlN composite film layer on the surface of a stainless steel welded piece according to claim 3, characterized in that: In the drying step, the dried welded piece needs to be subjected to multi-arc ion plating within 4 h. The vacuum degree of the vacuum furnace is reduced to 1 x 10 -3 Pa, the temperature of the vacuum furnace is increased to 150°C ± 10°C within 30 ± 5 min, the voltage is increased from 100 V to 800 V within 10 min, and the power is increased from 1 kW to 7 kW.

6. The method of claim 1, wherein the method is characterized by: After the deposition of the fourth segment is completed, the vacuum furnace is cooled to 80℃ and then taken out.

7. The method of claim 1, wherein the method is characterized by: Before the first segment deposition, the temperature of the surface of the welded piece is not higher than 300℃.

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