Local chemical surface heat treatment method for parts
Through the integrated electroless nickel plating and the local area is carved and removed by a laser marking machine, combined with nitriding treatment, the applicability limitations of local chemical surface heat treatment in the prior art are solved, and the applicability and simplicity of operation are achieved, and the dimensional accuracy and corrosion resistance of parts are improved.
Patent Information
- Application Number
- CN202510412056.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-08-08
AI Technical Summary
The prior art has limitations in applicability when treating local chemical surface heat, especially in thin-walled parts, welding areas, parts with high dimensional accuracy and stainless steel parts with high corrosion resistance requirements, resulting in increased brittleness, poor welding, dimensions exceeding standards and reduced corrosion resistance.
After using integral electroless nickel plating, the area that needs to be treated is engraved and removed by a laser marking machine, and then local nitriding treatment is carried out, including ionic nitriding or gas nitriding. It is suitable for steel parts made of stainless steel and non-stainless steel materials, and is suitable for both nitriding and nitrogen-carbon co-permethod and carbon-nitriding.
It achieves wider applicability, avoids the design complexity of special tooling, reduces operating steps, improves the dimensional accuracy and corrosion resistance of parts, reduces costs, and is thin and easy to remove.
Smart Images
Figure CN120443101A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of chemical surface heat treatment processing, and in particular relates to a local chemical surface heat treatment method for parts. Background Art
[0002] In order to meet the wear resistance requirements, some parts need to use chemical surface heat treatment technology to improve the surface hardness. However, in some special applications, some parts only allow local chemical surface heat treatment, such as:
[0003] (1) Parts with thin-walled areas; chemical surface heat treatment is also performed on the thin-walled surfaces of these parts, which will cause the thin-walled areas to be more brittle overall, thereby increasing the risk of fracture;
[0004] (2) Parts that require welding in some areas; chemical surface heat treatment of the areas where these parts require welding will result in poor welding;
[0005] (3) There are parts with some areas corresponding to the wear parts; if these parts are subjected to chemical surface heat treatment, the areas corresponding to the wear parts will become highly hard, which will cause the wear parts to wear faster;
[0006] (4) Parts with high dimensional accuracy requirements; parts that do not require chemical surface heat treatment will have dimensions exceeding standard requirements after chemical surface heat treatment;
[0007] (5) Stainless steel parts with high corrosion resistance requirements; after these parts are subjected to overall chemical surface heat treatment, the overall corrosion resistance will decrease.
[0008] Currently, when chemical surface heat treatment is performed locally on parts, the main approach is to perform anti-seepage treatment on the remaining areas. The treatment methods mainly include: anti-seepage coating, mechanical shielding, electroplating and oxidation. These four methods have certain limitations:
[0009] The anti-seepage coating is not suitable for ion chemical surface heat treatment and gas chemical surface heat treatment of stainless steel;
[0010] Mechanical shielding requires the design and manufacture of special tooling, which is complicated to operate and is not applicable to gas nitriding;
[0011] Although electroplating is suitable for gas chemical surface heat treatment and ion chemical surface heat treatment, local electroplating is not easy to achieve. In addition, the density of the electroplated layer is not high, and a relatively thick plating layer is required to effectively prevent chemical surface heat treatment. Parts with high dimensional requirements need to be stripped after chemical surface heat treatment, which is labor-intensive and costly.
[0012] Oxidation requires a dedicated heat introduction unit and a complex cover, and is not suitable for ion chemical surface heat treatment and gas chemical surface heat treatment of stainless steel. Summary of the Invention
[0013] In order to solve the above problems, the purpose of the present invention is to provide a method for local chemical surface heat treatment of parts, which is more applicable and convenient to operate.
[0014] In order to achieve the above objectives, the technical solutions of the present invention are as follows.
[0015] A method for local chemical surface heat treatment of a component, characterized by comprising:
[0016] Step 1: Chemically plate the entire component;
[0017] Step 2: Remove the chemical plating layer from the parts that need to be subjected to chemical surface heat treatment;
[0018] Step 3: Chemical surface heat treatment of parts.
[0019] Furthermore, in step 1, the entire component is subjected to chemical nickel plating.
[0020] Furthermore, in step 2, a laser marking machine is used to carve away the chemical plating layer in the area of the component that requires chemical surface heat treatment.
[0021] Furthermore, the thickness of the chemical plating layer is 3 to 20 μm.
[0022] Furthermore, the P content (weight percentage) in the chemical plating layer is 1% to 13%.
[0023] Furthermore, the engraving depth of the laser marking machine is greater than the thickness of the chemical plating layer by 1 to 10 μm.
[0024] Furthermore, in step 3, the component is subjected to nitriding treatment, nitrocarburizing treatment, carbonitriding treatment, or carburizing treatment.
[0025] Furthermore, in step 3, the components are subjected to gas nitriding treatment or ion nitriding treatment.
[0026] Furthermore, in step 3, the parts are first activated with a pickling activator and then subjected to a gas nitriding treatment.
[0027] Furthermore, the components are made of stainless steel or non-stainless steel.
[0028] The advantages of the present invention are:
[0029] 1. Greater applicability; this application is applicable to both gas nitriding and ion nitriding; it is applicable to both stainless steel nitriding and nitriding of non-stainless steel parts; it is applicable to both nitriding and nitrocarburizing, carbonitriding and carburizing.
[0030] 2. Compared with the local anti-seepage coating process commonly used in local nitriding, this application can be applied to ion nitriding and stainless steel gas nitriding. Moreover, because only a very thin 3-5 micron chemical nickel plating layer is required, even if it is not removed after nitriding, it can meet the size requirements of parts. In addition, because the chemical nickel plating layer is very thin, it is easy to remove by laser carving.
[0031] 3. Compared with the local mechanical shielding process commonly used in local nitriding, the present application can be applied to gas nitriding and does not require the design and manufacture of special tooling.
[0032] 4. Compared with the local electroplating process commonly used for local nitriding, the chemical nickel plating layer of this application is thinner and denser. It only needs to be 3 to 5 microns thick to effectively shield nitriding, and has little impact on the size of parts. Even if it is not removed after nitriding, it can still meet the size requirements of the parts. In addition, because the chemical nickel plating layer is very thin, it is easy to remove by laser carving.
[0033] 5. Compared with the local oxidation process used in local nitriding, the present application can be applied to ion nitriding and stainless steel gas nitriding, eliminating the need for a heat introduction unit and a complex cover. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 This is a schematic diagram of the initial state of the components.
[0035] Figure 2 This is a schematic diagram of the chemical nickel plating status of parts.
[0036] Figure 3 This is a schematic diagram of the engraving and removal of the chemical nickel plating layer on the top of the component.
[0037] Figure 4 It is a schematic diagram of the nitriding state of components.
[0038] Figure 5 This is a metallographic image of the cam position observed under an optical microscope after chemical nickel plating in Example 1.
[0039] Figure 6 This is a metallographic image of the cam position after chemical nickel plating in Example 1 observed using a scanning electron microscope.
[0040] Figure 7 This is a table of the coating composition at the cam position after chemical nickel plating in Example 1.
[0041] Figure 8 This is a metallographic image of the cam position after laser engraving in Example 1 observed under an optical microscope.
[0042] Figure 9 This is a metallographic image of the cam position after laser engraving in Example 1 observed using a scanning electron microscope.
[0043] Figure 10 This is a table of coating compositions at the cam position after laser engraving in Example 1.
[0044] Figure 11 This is a metallographic image of the cam position after nitriding in Example 1 observed with a low-magnification optical microscope.
[0045] Figure 12 This is a metallographic image of the cam position after nitriding in Example 1 observed with a high-magnification optical microscope.
[0046] Figure 13 This is a metallographic image of the cam position observed under an optical microscope in Example 2.
[0047] Figure 14 This is a metallographic image of the cam position observed under an optical microscope after chemical nickel plating in Example 2.
[0048] Figure 15 This is a metallographic image of the cam position after nitriding in Example 2 observed under an optical microscope. DETAILED DESCRIPTION
[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0050] This embodiment provides a method for local chemical surface heat treatment of a component. Figure 1 , is the initial state of component 1;
[0051] The local chemical surface heat treatment method of the component 1 includes:
[0052] Step 1: Electrolessly plate the entire component 1; for details, see Figure 2 First, component 1 is placed in an electroless plating solution for overall electroless nickel plating, thereby forming an electroless nickel layer 2 on the outer surface of component 1. The electroless nickel layer 2 has a thickness of 3 to 20 μm, preferably 3 to 5 μm. The phosphorus content (by weight) of the electroless nickel layer 2 is 1% to 13%, preferably 1 to 4%. It should be emphasized that the electroless nickel layer 2 in this embodiment is the aforementioned electroless plating layer.
[0053] Step 2: Remove the chemical nickel plating layer 2 of the component 1 in the area requiring chemical surface heat treatment; for details, see Figure 3A laser marking machine is used to laser engrave the top 3 of component 1, which has been completely electroless nickel-plated. This is done to remove the electroless nickel layer from the top 3 of component 1, exposing the substrate of component 1. Laser marking machines include, but are not limited to, one or more of fiber laser marking machines, end-pump laser marking machines, and CO2 laser marking machines. The engraving depth of the laser marking machine is 1 to 10 μm greater than the thickness of the electroless nickel layer, preferably 1 to 3 μm.
[0054] Step 3: Perform chemical surface heat treatment on the parts. Figure 4 Component 1, whose top electroless nickel layer has been removed by laser engraving, is then ion nitrided or gas nitrided to form a nitrided layer 4 on its top 3. The choice of ion nitriding or gas nitriding can be determined based on specific processing requirements. In other implementations, the chemical surface heat treatment can be replaced by nitrocarburizing, carbonitriding, or carburizing instead of nitriding.
[0055] It is worth noting that during ion nitriding, the component 1 is placed in the ion nitriding furnace, first evacuated, then glow discharged and heated. After reaching the nitriding temperature, it is kept warm and ion nitrided. This process is accompanied by glow discharge. After nitriding is completed, the glow discharge is stopped and the component is cooled to below 100°C in the furnace and then taken out of the furnace.
[0056] The main parameters of ion nitriding include: (1) the main working gas is ammonia or nitrogen; (2) other working gases include but are not limited to argon and hydrogen; (3) nitriding temperature 380-600°C; (4) holding nitriding time 2-60 hours, preferably 10-30 hours; (5) working voltage 450-1000V, preferably 550-800V; (6) working gas pressure 50-600Pa, preferably 100-400Pa.
[0057] It is worth noting that during gas nitriding, the component 1 is placed in a gas nitriding furnace and first activated with an acidic activator at a temperature of 250-600°C by resistance heating for 5-120 minutes. After activation, the component is heated to the gas nitriding temperature by resistance heating and then maintained at this temperature for gas nitriding.
[0058] The main parameters of gas nitriding include: (1) the main working gas is ammonia; (2) other working gases include but are not limited to nitrogen; (3) nitriding temperature 380-600°C; (4) nitriding holding time 2-60 hours, preferably 10-40 hours; (5) working pressure 1 bar + (20-100 mbar), that is, maintaining a positive pressure in the gas nitriding furnace. After gas nitriding, the parts are cooled in the furnace to below 100°C and then removed from the furnace.
[0059] In order to better illustrate the present application, this embodiment provides the following two specific examples.
[0060] Example 1:
[0061] The component is a maraging stainless steel component. It has a cam in some parts and needs to be nitrided and hardened for high wear resistance. In addition, there are thin-walled parts in some parts of the maraging stainless steel component with a thickness of 0.5mm. In order to prevent the thin-walled parts from increasing brittleness after nitriding and causing breakage during use, nitriding is required to be prohibited.
[0062] First, the maraging stainless steel component was electrolessly nickel-plated. The electroless nickel plating solution contains 25g / L NiSO4·6H2O, 30g / L NaH2PO2·H2O, 20g / L lactic acid, and 5g / L propionic acid; the pH is 4.5-5.0; and the temperature is 85-90°C. The maraging stainless steel component was immersed in the plating solution and removed after one hour.
[0063] The metallographic examination was carried out using an optical microscope and the coating was uniform. Figure 5 The metallographic sample was further magnified using a scanning electron microscope and the coating thickness was measured to be about 5 μm. Figure 6 . Use EDS to test the coating composition, the results are shown in Figure 7 .
[0064] A fiber laser was used to laser engrave the cam area of a chemically nickel-plated maraging stainless steel component. The laser marking machine, a Han's J20H-QD, was used. Laser engraving parameters included a marking speed of 250 mm / s, a Q frequency of 20, and a power setting of 90%. The laser engraving was repeated twice.
[0065] After laser engraving is completed, the metallographic observation cam is made, such as Figure 8 The chemical nickel plating layer has been cleaned by laser etching. The white layer remaining in some areas of the cam position is tested for composition using EDS, such as Figure 9 and Figure 10 , it was found that most of the components were from the base material maraging stainless steel, indicating that it was the heat affected zone of laser carving.
[0066] Place the laser-engraved maraging stainless steel parts in a nitriding furnace for nitriding. First, vacuum the parts, then activate them. Activation parameters: acidic activator, temperature 250-600°C, time 40 minutes. After activation, nitriding is performed. Nitriding parameters: nitriding gas 1.3 L / min, temperature 500-600°C, time 20 hours. After nitriding, cool the maraging stainless steel parts to below 80°C in the furnace before removing them from the furnace.
[0067] After being fired, the surface hardness of the cam was tested with a microhardness tester, and the result was 940~992HV0.05. Metallographic observation was made to observe the shielding effect of the nitrided and non-nitrided areas of the cam, such as Figure 11 and Figure 12 The nitriding thickness of the cam surface is 106 to 124 μm, there is no nitriding layer in the non-nitriding area, and the chemical nickel plating layer is complete with a thickness of about 7.2 μm, indicating that the shielding effect is very good.
[0068] Example 2:
[0069] like Figure 13 The component shown is made of SKD11 alloy steel. There is a cam on the top of the component, which needs to be nitrided and hardened for high wear resistance. Other parts of the component have toughness requirements. In order to prevent the toughness from being reduced after nitriding, nitriding is required.
[0070] First, the parts are electrolessly plated with nickel. The main components of the electroless nickel plating solution are: NiSO4·6H2O25g / L, NaH2PO2·H2O 30g / L, lactic acid 20g / L, propionic acid 5g / L; pH value: 4.5-5.0; temperature: 85-90℃. Immerse the parts in the plating solution and remove them after 45 minutes. Figure 14 , the thickness of the chemical nickel plating layer is 4 to 5 μm.
[0071] The cam area of the chemically nickel-plated parts was laser engraved using a fiber laser marking machine. The model of the fiber laser marking machine was a Han's J20H-QD. The laser engraving parameters were: a marking speed of 500 mm / s, a Q frequency of 20, a power setting of 20-30%, and four repetitions.
[0072] Place the laser-engraved parts into the nitriding furnace for nitriding. First, vacuum the parts, then proceed with nitriding. Nitriding parameters: nitriding gas (composition confidential) at 4 L / min, temperature 500-550°C, time 4 hours. After nitriding, cool the parts to below 80°C before removing them from the furnace.
[0073] After being fired, the surface hardness of the cam was tested with a microhardness tester, and the result was 1081~1277HV0.05. Metallographic observation was made to observe the shielding effect of the nitrided and non-nitrided areas of the cam, such as Figure 15 The nitriding thickness of the cam surface is 48.6~50.7μm, there is no nitriding layer in the non-nitriding area, and the chemical nickel plating layer is complete, indicating that the shielding effect is very good.
[0074] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for local chemical surface heat treatment of parts, characterized in that: include: Step 1: Chemically plate the entire component; Step 2: Remove the chemical plating layer from the parts that need to be subjected to chemical surface heat treatment; Step 3: Chemical surface heat treatment of parts.
2. The method for local chemical surface heat treatment of a component according to claim 1, characterized in that: In step 1, the entire component is electrolessly nickel plated.
3. The method for local chemical surface heat treatment of a component according to claim 2, characterized in that: In step 2, a laser marking machine is used to carve away the chemical plating layer in the area of the component that requires chemical surface heat treatment.
4. The method for local chemical surface heat treatment of a component according to claim 2, characterized in that: The thickness of the chemical plating layer is 3 to 20 μm.
5. The method for local chemical surface heat treatment of a component according to claim 2, characterized in that: The P content (weight percentage) in the chemical plating layer is 1% to 13%.
6. The method for local chemical surface heat treatment of a component according to claim 3, characterized in that: The engraving depth of the laser marking machine is 1 to 10 μm greater than the thickness of the chemical plating layer.
7. The method for local chemical surface heat treatment of a component according to claim 1, characterized in that: In step 3, the component is nitrided or nitrocarburized or carbonitrided or carburized.
8. The method for local chemical surface heat treatment of a component according to claim 1, characterized in that: In step 3, the component is gas nitrided or ion nitrided.
9. The method for local chemical surface heat treatment of a component according to claim 1, characterized in that: In step 3, the parts are activated with a pickling activator before being gas nitrided.
10. The method for local chemical surface heat treatment of a component according to claim 1, characterized in that: Components are made of stainless steel or non-stainless steel.