A metal part

Abstract

The application relates to the technical field of metal surface treatment, and discloses a metal part, which comprises a metal base, the metal base is low-carbon stainless steel, and has a contact surface, and the contact surface is formed with a nitriding layer. Nitriding of the contact surface can improve the anti-cavitation performance of the contact surface of the metal base, in particular the anti-cavitation performance of the inner surface of micropores, can improve the hardness of the contact surface of the low-carbon stainless steel metal base, and can have good hardness while being resistant to high-temperature methanol and formic acid corrosion. The surface of the nitriding layer is formed with a silicon coating layer, the silicon coating layer has the characteristics of acid corrosion resistance, can further reduce the risk of trace carbon in the contact surface of the low-carbon stainless steel being precipitated in the form of a carbide compound, and can form secondary strengthening on the corrosion resistance of the contact surface of the metal base.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a metal component. Background Technology

[0002] This invention primarily addresses the corrosion and wear problems of methanol direct injection injector valve seats under high-temperature methanol environments and surface cavitation issues in high-pressure gradient methanol fluid environments. It proposes an anti-cavitation solution for ion sputtering processes applied to microporous components. During direct injection injector verification tests, multiple cases of injector valve seat wear were observed. Failure mode analysis revealed that carbon elements on the valve seat surface precipitated under high-temperature methanol conditions, causing accelerated surface wear, leading to valve seat sealing failure and methanol leakage from the injector. Therefore, methanol direct injection injectors require the use of low-carbon stainless steel and coating technology to improve surface wear resistance and corrosion resistance.

[0003] Currently disclosed valve seat coating patents, such as valve seat DLC coatings, utilize metastable amorphous materials formed by sp3 and sp2 bonds. Because the low-carbon, acid-resistant stainless steel valve seat substrate is relatively soft, the sealing surface of the substrate undergoes slight deformation during injector operation. This deformation increases the internal stress of the DLC coating, ultimately leading to the breakage and failure of the sp3 and sp2 bonds. Therefore, valve seats made of conventional materials and using the DLC process are currently unsuitable for methanol direct injection injector valve seats.

[0004] Valve seat materials require high hardness and wear resistance, so stainless steel with a carbon content of 0.2% or higher is necessary to achieve this high hardness. Simultaneously, valve seat materials also need strong corrosion resistance, including resistance to high-temperature methanol and the formic acid and its derivatives generated in high-temperature methanol environments. Stainless steel with good resistance to high-temperature methanol and formic acid corrosion is generally a low-carbon alloy stainless steel with a carbon content of less than 0.1%. However, corrosion-resistant stainless steel with a carbon content of less than 0.1% has low hardness and cannot meet the wear resistance requirements of valve seats. These two performance requirements create a technical contradiction regarding the carbon content. Summary of the Invention

[0005] This invention discloses a metal component designed to balance the requirements of low-carbon steel's good resistance to high-temperature methanol and formic acid corrosion with high hardness, thereby alleviating the technical contradiction regarding carbon content requirements.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A metal component includes: a metal substrate, wherein the metal substrate is low-carbon stainless steel, and has a contact surface on which a nitrided layer is formed. Nitriding the contact surface improves the cavitation resistance of the metal substrate's contact surface, particularly the cavitation resistance of the microporous inner surface, and also increases the hardness of the low-carbon stainless steel contact surface. This allows the low-carbon stainless steel to withstand high-temperature methanol and formic acid corrosion while maintaining good hardness. A silicon coating is formed on the surface of the nitrided layer. Utilizing the acid corrosion resistance of the silicon coating, the risk of trace amounts of carbon on the low-carbon stainless steel contact surface precipitating as carbides is further reduced, thus providing a secondary strengthening of the corrosion resistance of the metal substrate's contact surface.

[0008] Optionally, the thickness of the nitrided layer is between 2 μm and 20 μm.

[0009] Optionally, the metal matrix is ​​low-carbon stainless steel with a carbon content of less than 0.1%.

[0010] Optionally, a silicon coating is formed on the surface of the nitrided layer.

[0011] Optionally, the thickness of the silicon coating is between 0.1 μm and 0.5 μm.

[0012] Optionally, a chromium nitride coating is formed on the surface of the silicon coating opposite to the nitriding layer.

[0013] Optionally, the chromium nitride coating contains more than 80% chromium nitride, and the thickness of the chromium nitride coating is between 0.6 μm and 1 μm.

[0014] Optionally, a sealing layer is formed on the surface of the chromium nitride coating away from the silicon coating. The hardness of the sealing layer is lower than that of the chromium nitride coating, and the corrosion resistance of the sealing layer is higher than that of the chromium nitride coating.

[0015] Optionally, the sealing functional layer is a chromium coating.

[0016] Optionally, the thickness of the chromium coating is between 0.3 μm and 0.7 μm.

[0017] Optionally, a gradient transition layer is provided between the chromium coating and the chromium nitride coating; in the gradient transition layer, the content of chromium nitride gradually decreases and the content of chromium gradually increases along the direction from the chromium nitride coating to the chromium coating.

[0018] Optionally, the metal substrate is the valve seat of a methanol direct injection injector, and the contact surface is the contact sealing surface between the valve seat and the valve core. Attached Figure Description

[0019] Figure 1A partial structural schematic diagram of the metal component provided in an embodiment of this application;

[0020] Figure 2 This is a schematic diagram of the methanol direct injection injector in the embodiments of this application;

[0021] Figure 3 for Figure 2 Schematic diagram of the middle valve core;

[0022] Figure 4 for Figure 2 A schematic diagram of the structure of the middle valve seat. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] refer to Figure 1 The metal component provided in this application embodiment can adapt to high-temperature methanol corrosion environments and can be a moving part in contact with high-temperature methanol for various applications. The metal component includes: a metal substrate 1, which is low-carbon stainless steel, for example, low-carbon stainless steel with a carbon content of less than 0.1%. This type of stainless steel has good resistance to high-temperature methanol and formic acid corrosion and has a contact surface S, on which a nitrided layer 2 is formed. Nitriding the contact surface S can improve the cavitation resistance of the contact surface S of the metal substrate 1, especially the cavitation resistance of the microporous inner surface, and can improve the hardness of the contact surface S of the low-carbon stainless steel metal substrate. While using low-carbon stainless steel to resist high-temperature methanol and formic acid corrosion, it can also have good hardness. A silicon coating 3 is formed on the surface of the nitrided layer 2. Utilizing the acid corrosion resistance of the silicon coating 3, the risk of trace amounts of carbon on the contact surface S of the low-carbon stainless steel precipitating in the form of carbon compounds is further reduced, thus providing secondary reinforcement to the corrosion resistance of the contact surface S of the metal substrate 1. The silicon coating 3 can be a silicon-infiltrated layer formed by a silicon infiltration process, serving as a high-temperature methanol corrosion-resistant layer to prevent high-temperature methanol from corroding the metal substrate 1. Specifically, the silicon coating 3 can be formed using an ion sputtering process.

[0025] The aforementioned contact surface S represents a surface that comes into contact with methanol or a high-temperature methanol environment and bears impact loads or friction loads. This surface can be the sealing contact surface between the valve seat and the valve core / ball.

[0026] In one specific embodiment, the thickness of the nitriding layer 2 is between 2μm and 20μm, specifically 2μm, 4μm, 6μm, 7μm, 9μm, 12μm, 14μm, 15μm, 17μm, 19μm and 20μm, etc. Within this thickness range, the anti-cavitation performance of the inner surface of the micropores can be sufficiently improved, while the surface hardness of the metal substrate 1 can be increased, and the cost of nitriding can be limited to a reasonable range.

[0027] In one specific embodiment, the thickness of the silicon coating 3 is between 0.1 μm and 0.5 μm, specifically 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm. When the thickness of the silicon coating 3 is within this range, the precipitation of carbon in the form of carbides can be significantly reduced, achieving sufficient corrosion resistance while maintaining a reasonable cost.

[0028] In one specific embodiment, a chromium nitride coating 4 is formed on the surface of the silicon coating 3 facing away from the nitriding layer 2. The chromium nitride coating 4 can simultaneously improve the wear resistance and corrosion resistance of the contact surface S of the metal substrate 1 subjected to impact loads. The chromium nitride coating 4 can be a chromium nitriding layer formed by a chromium nitriding process, which has higher hardness and better impact resistance than the silicon coating 3.

[0029] In one specific embodiment, the chromium nitride coating 4 contains more than 80% chromium nitride, and the thickness of the chromium nitride coating 4 is between 0.6 μm and 1 μm, specifically 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, and 1 μm. When the thickness of the chromium nitride coating 4 is within this range, the wear resistance and corrosion resistance of the contact surface S can be maintained while also considering a reasonable cost.

[0030] In one specific embodiment, a sealing functional layer 5 is formed on the surface of the chromium nitride coating 4 away from the silicon coating 3. The hardness of the sealing functional layer 5 is lower than that of the chromium nitride coating 4, which can accelerate the running-in speed between the contact surface S and the mating surface, such as improving the running-in speed between the valve seat and the valve core and valve ball, and quickly forming a sealing surface in the early stage of the injector operation. Moreover, the corrosion resistance of the sealing functional layer 5 is higher than that of the chromium nitride coating 4, so as to further improve the corrosion resistance.

[0031] In one specific embodiment, the sealing functional layer 5 is a chromium coating. The hardness of the chromium coating is lower than that of the chromium nitride coating 4, and its corrosion resistance is higher than that of the chromium nitride coating 4, making it an ideal material for the sealing functional layer 5. The thickness of the chromium coating can be between 0.3 μm and 0.7 μm, specifically 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, and 0.7 μm. This thickness range can simultaneously balance hardness, corrosion resistance, and reasonable cost.

[0032] In one specific embodiment, there is a gradient transition layer between the chromium coating and the chromium nitride coating 4; in the gradient transition layer, along the direction from the chromium nitride coating 4 to the chromium coating, the content of chromium nitride gradually decreases and the content of chromium gradually increases, so as to gradually evolve towards the composition of the chromium coating and avoid poor bonding due to the large difference in composition between the two.

[0033] Combination Figures 2 to 4 A conical surface on the injector valve seat a contacts the ball head of the valve core b to form a sealing surface. The ball head of the valve core b and the conical sealing surface of the valve seat a form a kinematic pair subjected to impact loads. In a specific embodiment, the metal substrate 1 is the valve seat a of the methanol direct injection injector, and the contact surface S is the sealing surface between the valve seat a and the valve core b. The valve seat a is located at the oil outlet end of the valve body c, and the valve core b is located within the space of the valve body c, and is sealed to the contact sealing surface of the valve seat a through the valve ball at its end. By surface treating the contact surface S of the valve seat a, the hardness of the sealing surface between the valve seat a and the valve core b can be improved, and the use of low-carbon stainless steel can prevent carbon precipitation from the valve seat a.

[0034] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A metal component, characterized in that, include: The metal substrate is a valve seat of a methanol direct injection injector and has a contact surface. A nitriding layer is formed on the contact surface, and a silicon coating is formed on the surface of the nitriding layer. The carbon content of the metal substrate is less than 0.1%. A chromium nitride coating is formed on the surface of the silicon coating away from the nitriding layer; A sealing layer is formed on the surface of the chromium nitride coating away from the silicon coating. The hardness of the sealing layer is lower than that of the chromium nitride coating, and the corrosion resistance of the sealing layer is higher than that of the chromium nitride coating. The contact surface is the contact sealing surface between the valve seat and the valve core, and the contact sealing surface and the valve core form a kinematic pair subjected to impact loads.

2. The metal component according to claim 1, characterized in that, The thickness of the nitrided layer is between 2 μm and 20 μm.

3. The metal component according to claim 1, characterized in that, The metal matrix is ​​low-carbon stainless steel with a carbon content of less than 0.1%.

4. The metal component according to claim 3, characterized in that, The thickness of the silicon coating is between 0.1 μm and 0.5 μm.

5. The metal component according to claim 1, characterized in that, The chromium nitride coating contains more than 80% chromium nitride, and the thickness of the chromium nitride coating is between 0.6 μm and 1 μm.

6. The metal component according to claim 1, characterized in that, The sealing functional layer is a chromium coating.

7. The metal component according to claim 1, characterized in that, The thickness of the chromium coating is between 0.3 μm and 0.7 μm.

8. The metal component according to claim 6, characterized in that, A gradient transition layer exists between the chromium coating and the chromium nitride coating; In the gradient transition layer, along the direction from the chromium nitride coating to the chromium coating, the content of chromium nitride gradually decreases and the content of chromium gradually increases.

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