Ferrite soft magnetic stainless steel material treated by surface composite strengthening process

Abstract

The utility model relates to a ferrite soft magnetic stainless steel material treated by a surface composite strengthening process, which comprises a base body, and the surface of the base body is sequentially coated with an ion nitriding layer, a base coat, a support layer, a transition layer and a gradient DLC layer from inside to outside. Compared with the prior art, the ferrite soft magnetic stainless steel material disclosed by the utility model is obtained by an impact-wear-resistant surface strengthening process in a pure hydrogen environment. According to the technical process and the plating layer design, the locking reliability of the electromagnetic valve of the low-pressure hydrogen ejector under the pure hydrogen environment of parts can be effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of metal surface treatment technology, and in particular to a ferritic soft magnetic stainless steel material treated by a surface composite strengthening process. Background Technology

[0002] Hydrogen internal combustion engines are a type of energy-saving and environmentally friendly green power source that can effectively solve the energy crisis and achieve sustainable development. The flammability, high combustion temperature, and short combustion time of hydrogen in the cylinder present significant technical challenges in its control, necessitating further research and understanding of hydrogen combustion and control. As a precision flow control component that regulates hydrogen supply, the hydrogen injector's stable performance and long-term reliability under the complex operating conditions of the internal combustion engine are particularly important.

[0003] Currently, mainstream automotive engine fuel injectors use solenoid valve control units, which achieve precise flow control by driving the solenoid valve to stop via current / voltage. In a high-purity hydrogen environment, due to the inherent characteristics of hydrogen, such as its dry friction properties and the ease with which small molecules can penetrate materials, the solenoid valve's stop impact surface and side motion guide surface are prone to severe impact fatigue wear and sliding adhesive wear, respectively. This causes the hydrogen injector's injection flow to drift over time, eventually leading to nozzle jamming and failure.

[0004] Analysis revealed that the solenoid valve of the hydrogen injector is made of ferritic stainless steel. This type of steel has excellent soft magnetic properties while also possessing corrosion resistance. However, to ensure its excellent soft magnetic properties, this material undergoes a special magnetic annealing heat treatment process, resulting in a very low overall hardness (below 200 HV Vickers hardness). To improve its resistance to impact fatigue wear and sliding adhesive wear in a hydrogen environment, it needs to be strengthened without compromising its corrosion resistance or sacrificing its soft magnetic properties. Utility Model Content

[0005] The purpose of this invention is to provide a ferritic soft magnetic stainless steel material treated with a surface composite strengthening process. This ferritic soft magnetic stainless steel material is obtained through a surface strengthening process resistant to impact and wear in a pure hydrogen environment.

[0006] The objective of this utility model can be achieved through the following technical solutions:

[0007] A ferritic soft magnetic stainless steel material treated with a surface composite strengthening process includes a substrate, the surface of which is sequentially coated from the inside out with an ion nitriding layer, a base layer, a support layer, a transition layer and a gradient DLC layer.

[0008] In one embodiment of this utility model, the thickness of the ion nitrided layer is greater than 20 μm and less than 40 μm.

[0009] In one embodiment of this utility model, the underlayer is a Cr layer, and the thickness of the underlayer is greater than 0.2 μm and less than 0.5 μm.

[0010] In one embodiment of this utility model, the support layer is a CrN layer, and the thickness of the support layer is 2-4 μm.

[0011] In one embodiment of this utility model, the transition layer is a Cr+WC layer, and the thickness of the transition layer is greater than 0.1 μm and less than 0.3 μm.

[0012] In one embodiment of this utility model, the gradient DLC layer consists of a W-DLC layer, a hard hydrogen-containing DLC ​​layer, and a soft hydrogen-containing DLC ​​layer, arranged vertically from the inside to the outside of the transition layer surface.

[0013] In one embodiment of this utility model, the thickness of the W-DLC layer is greater than 0.2 μm and less than 0.5 μm.

[0014] In one embodiment of this utility model, the thickness of the hard hydrogen-containing DLC ​​layer is greater than 2μm and less than 3μm, and the hardness of the hard hydrogen-containing DLC ​​layer is less than 2800HV.

[0015] In one embodiment of this utility model, the thickness of the soft hydrogen-containing DLC ​​layer is greater than 1 μm and less than 2 μm, and the hardness of the soft hydrogen-containing DLC ​​layer is less than 1400 HV.

[0016] In one embodiment of this utility model, the substrate is made of ferritic stainless steel.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This utility model improves the hardness of the original stainless steel near the surface layer (within 1300HV0.1) by controlling the nitrogen concentration gradient and the thickness of the ion nitriding layer (the total thickness of the ion nitriding layer is controlled within 40 micrometers) without causing the ion nitriding layer to become too brittle or have excessive internal stress, thus preventing self-cracking.

[0019] 2. This utility model improves the surface roughness of the substrate parts by grinding and polishing the ion nitriding layer, removing impurities and micro-defects from the surface of the ion nitriding layer, and thus improving the quality of the outermost surface of the substrate parts.

[0020] 3. This utility model improves the adhesion between the subsequent coating and the substrate ion nitriding layer by setting an underlayer (Cr layer).

[0021] 4. The process flow and coating design provided by this utility model can effectively improve the reliability of the solenoid valve of the low-pressure hydrogen injector in a pure hydrogen environment. Attached Figure Description

[0022] Figure 1 This is a structural schematic diagram of the ferritic soft magnetic stainless steel material in this utility model;

[0023] Figure 2 The measured image of the ion nitride layer (chemical etching method after metallographic sectioning);

[0024] Figure 3 This is a measured cross-sectional view of ferritic stainless steel after surface hardening using the process in Example 2.

[0025] Explanation of the attached figures: 1. Ion nitrided layer, 2. Underlayer, 3. Support layer, 4. Transition layer, 5. Gradient DLC layer, 6. Substrate, 7. W-DLC layer, 8. Hard hydrogen-containing DLC ​​layer, 9. Soft hydrogen-containing DLC ​​layer. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. This embodiment is based on the technical solution of the present invention and provides detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] In the description of this utility model, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this utility model. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0030] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0031] Example 1

[0032] See Figure 1 This embodiment provides a ferritic soft magnetic stainless steel material treated with a surface composite strengthening process, including a substrate 6. The surface of the substrate 6 is sequentially coated from the inside out with an ion nitriding layer 1, a base layer 2, a support layer 3, a transition layer 4, and a gradient DLC layer 5.

[0033] In this embodiment, the thickness of the ion nitrided layer 1 is greater than 20 μm and less than 40 μm.

[0034] In this embodiment, the base layer 2 is a Cr layer, and the thickness of the base layer 2 is greater than 0.2 μm and less than 0.5 μm.

[0035] In this embodiment, the support layer 3 is a CrN layer, and the thickness of the support layer 3 is 2 to 4 μm.

[0036] In this embodiment, the transition layer 4 is a Cr+WC layer, and the thickness of the transition layer 4 is greater than 0.1 μm and less than 0.3 μm.

[0037] In this embodiment, the gradient DLC layer 5 consists of a W-DLC layer 7, a hard hydrogen-containing DLC ​​layer 8, and a soft hydrogen-containing DLC ​​layer 9, arranged vertically from the inside to the outside of the transition layer 4 surface.

[0038] In this embodiment, the thickness of the W-DLC layer 7 is greater than 0.2 μm and less than 0.5 μm.

[0039] In this embodiment, the thickness of the hard hydrogen-containing DLC ​​layer 8 is greater than 2 μm and less than 3 μm, and the hardness of the hard hydrogen-containing DLC ​​layer 8 is less than 2800 HV.

[0040] In this embodiment, the thickness of the soft hydrogen-containing DLC ​​layer 9 is greater than 1 μm and less than 2 μm, and the hardness of the soft hydrogen-containing DLC ​​layer 9 is less than 1400 HV.

[0041] In this embodiment, the substrate 6 is made of ferritic stainless steel.

[0042] Example 2

[0043] This embodiment provides a surface composite strengthening process for ferritic soft magnetic stainless steel materials, the specific steps of which are as follows:

[0044] S1. After machining and turning, the ferritic stainless steel substrate 6 parts are ultrasonically cleaned with anhydrous ethanol to remove contaminants and solid impurity particles from the surface of the substrate 6 parts; at the same time, it prepares for the next step of ion nitriding.

[0045] S2. Ion Nitriding: The cleaned substrate 6 parts obtained in step S1 are processed in a dedicated ion nitriding furnace. The nitriding temperature of the dedicated ion nitriding furnace is controlled at 520-560 degrees Celsius, and the vacuum degree of the dedicated ion nitriding furnace is controlled at 300-450 Pa. The flow rates of different nitriding gases are controlled at different heating stages and times: hydrogen flow rate 800-1600 ml / min, nitrogen flow rate 200-500 ml / min, argon flow rate 100-400 ml / min, and methane flow rate 20-100 ml / min. The ion nitriding time is 8 hours. After the ion nitriding is completed, the parts are cooled to about 80 degrees Celsius with the furnace under gas protection, and then the furnace is opened and the substrate 6 parts are taken out.

[0046] S3. Mechanical grinding and polishing of ion nitrided layer 1: Fix the substrate 6 part obtained in step S2 after ion nitriding in the fixture, fix the fixture on the rotatable rotating table, and use SiC brush to polish the surface of the substrate 6 part after ion nitriding at a set pressure height. The brush rotation speed is set to 990-1100 rpm, and the polishing time is set to 200 seconds.

[0047] S4, DLC Coating: A dedicated PVD / CVD coating process is used. The substrate 6, after mechanical grinding and polishing in step S3, is sequentially coated with the following gradient layers: Underlayer 2 (Cr layer), CrN support layer 3 (CrN layer), transition layer 4 (Cr+WC layer), and gradient DLC layer 5 (W-DLC layer 7 + hard hydrogen-containing DLC ​​layer 8 + soft hydrogen-containing DLC ​​layer 9). The implementation process is as follows:

[0048] S4-1. The substrate 6 parts obtained in step S3 after mechanical grinding and polishing are ultrasonically cleaned with acetone, alcohol and deionized water for 20 minutes in sequence and then dried.

[0049] S4-2. After fixing the dried substrate 6 part obtained in step S4-1 onto the rotating workpiece rack, push it into the multi-functional ion plating machine to perform gradient plating according to the set program.

[0050] S4-2-1. Before deposition, the furnace should be evacuated to 110°C. -3 Pa uses ionized argon ions from an ion source to bombard the surface of the part, removing the oxide film on the part surface and exposing the fresh metal surface;

[0051] S4-2-2, During the deposition process, a substrate bias is set, and a Cr target is used to deposit the bottom layer 2 (Cr layer), the thickness of which is controlled within 0.5 micrometers;

[0052] S4-2-3, After nitrogen ionization, CrN support layer 3 (CrN layer) (2-4 micrometers thick) and transition layer 4 (Cr+WC layer) (within 0.1 micrometers thick) are deposited by combining Cr target and WC target.

[0053] S4-2-4, Then, ionization of high-purity C2H2 is used as the carbon source, and W element is doped into the W target film by non-equilibrium magnetron sputtering. The W-DLC layer 7 (within 0.5 micrometers in thickness) is deposited by controlling the target voltage. The W-DLC layer 7 is a W-doped DLC layer.

[0054] S4-2-5. Finally, after shutting off the W target, ionized high-purity C2H2 is used to complete the deposition of hydrogen-containing DLC ​​gradient functional layers: the hard hydrogen-containing DLC ​​layer 8 is controlled within 3 micrometers and the hardness is controlled within 2800 HV; the soft hydrogen-containing DLC ​​layer 9 is controlled within 2 micrometers and the hardness is controlled within 1400 HV. The part temperature is controlled within 220 degrees Celsius throughout the deposition process to obtain ferritic soft magnetic stainless steel material.

[0055] The thickness of the ion nitrided layer 1 was measured after the ferritic stainless steel surface was hardened by metallographic sectioning, grinding and polishing sample preparation process and chemical etching with 5% nitric acid alcohol; the coating was observed and its thickness was measured after ion cutting by focused ion beam scanning electron microscopy.

[0056] The results of observation and measurement of the cross-sectional thickness of the ion nitrided layer 1 after hardening of ferritic stainless steel are as follows: Figure 2 As shown, the thickness of the ion nitride layer 1 is 34 micrometers.

[0057] The measured cross-sectional view of the hardened coating deposited on the surface of ferritic stainless steel is shown below. Figure 3 As shown, the test results are as follows: the thickness of the 2Cr base layer is 0.22 micrometers; the thickness of the 3CrN support layer is 2.34 micrometers; the thickness of the 4Cr+WC transition layer is 0.21 micrometers; the thickness of the W-DLC layer 7 is 0.32 micrometers; the thickness of the hard hydrogen-containing DLC ​​layer 8 is 2.4 micrometers; and the thickness of the soft hydrogen-containing DLC ​​layer 9 is 1.5 micrometers.

[0058] Figure 3 Only a portion of the ion nitrided layer is shown in the figure; during sample analysis and testing, an additional protective layer 10 is applied to protect the outermost soft hydrogen-containing DLC ​​layer 9. The protective layer 10 is not an innovative feature of this utility model.

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present utility model is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present utility model without departing from its scope should be within the protection scope of the present utility model.

Claims

1. A ferritic soft magnetic stainless steel material, comprising a matrix (6), characterized in that, The surface of the substrate (6) is covered from the inside out with an ion nitriding layer (1), a base layer (2), a support layer (3), a transition layer (4) and a gradient DLC layer (5); The thickness of the ion nitriding layer (1) is greater than 20 μm and less than 40 μm, and the ion nitriding layer (1) is used to improve the hardness of the near-surface layer of stainless steel. The base layer (2) is a Cr layer.

2. The ferritic soft magnetic stainless steel material according to claim 1, characterized in that, The thickness of the base layer (2) is greater than 0.2 μm and less than 0.5 μm.

3. The ferritic soft magnetic stainless steel material according to claim 1, characterized in that, The support layer (3) is a CrN layer, and the thickness of the support layer (3) is 2~4 μm.

4. The ferritic soft magnetic stainless steel material according to claim 1, characterized in that, The transition layer (4) is a Cr+WC layer, and the thickness of the transition layer (4) is greater than 0.1 μm and less than 0.3 μm.

5. The ferritic soft magnetic stainless steel material according to claim 1, characterized in that, The gradient DLC layer (5) consists of a W-DLC layer (7), a hard hydrogen-containing DLC ​​layer (8), and a soft hydrogen-containing DLC ​​layer (9) in the vertical direction from the surface of the transition layer (4).

6. The ferritic soft magnetic stainless steel material according to claim 5, characterized in that, The thickness of the W-DLC layer (7) is greater than 0.2 μm and less than 0.5 μm.

7. The ferritic soft magnetic stainless steel material according to claim 5, characterized in that, The thickness of the hard hydrogen-containing DLC ​​layer (8) is greater than 2 μm and less than 3 μm, and the hardness of the hard hydrogen-containing DLC ​​layer (8) is less than 2800 HV.

8. The ferritic soft magnetic stainless steel material according to claim 5, characterized in that, The thickness of the soft hydrogen-containing DLC ​​layer (9) is greater than 1 μm and less than 2 μm, and the hardness of the soft hydrogen-containing DLC ​​layer (9) is less than 1400 HV.

9. The ferritic soft magnetic stainless steel material according to claim 1, characterized in that, The substrate (6) is made of ferritic stainless steel.

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