Magnetron sputtering aluminum-ion nitriding composite treatment method for 40Cr steel surface

Abstract

The invention relates to the technical field of metal surface treatment, in particular to a magnetron sputtering aluminum-ion nitriding composite treatment method for the surface of 40Cr steel. The method comprises the steps that firstly, 40Cr steel is placed in a magnetron sputtering furnace to be subjected to magnetron sputtering treatment, and a protective film layer is formed on the surface of the 40Cr steel through the magnetron sputtering treatment; and then, the 40Cr steel subjected to magnetron sputtering treatment is suspended in an ion nitriding furnace for ion nitriding treatment, the total pressure of ammonia gas in the furnace is 650 Pa, the nitriding voltage is 600-650 V, the nitriding temperature is 500-550 DEG C, continuous nitriding treatment is conducted for 6-10 h, and magnetron sputtering aluminum-ion nitriding composite treatment on the surface of the 40Cr steel is completed. According to the treatment method, the surface of the 40Cr steel is treated through a two-step method, the hardness of the treated 40Cr steel is improved, the abrasion resistance is improved, meanwhile, an MSAl-PN composite infiltrated layer is formed through Al, the self-corrosion current density of 40Cr is reduced through the composite infiltrated layer, the corrosion rate is decreased, and therefore the corrosion resistance of the 40Cr steel is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and particularly relates to a method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel. Background Art

[0002] 40Cr steel is one of the most widely used steels in the machinery manufacturing industry. After appropriate heat treatment, it has good comprehensive mechanical properties, good low-temperature impact toughness and low notch sensitivity. 40Cr steel is usually used as the material for manufacturing workpieces such as machine tool worms, spline shafts, gears, center sleeves, shafts, etc. In order to improve the wear resistance of 40Cr steel workpieces, ion nitriding is usually used to treat the surface of the workpieces.

[0003] Ion nitriding, as a chemical heat treatment method for strengthening the surface properties of metals, forms a nitrided layer on the metal surface after surface treatment of the metal, thereby improving the surface hardness of the material and endowing it with high wear resistance and fatigue strength. Although the surface hardness of 40Cr steel is improved after ion nitriding treatment, which can improve the wear resistance of the steel matrix, the improvement of the corrosion resistance of the steel matrix is not obvious, and it cannot meet the use requirements in complex environments.

[0004] By using magnetron sputtering to form an aluminum (Al) film with strong bonding force and good compactness on the surface of the steel matrix, on the one hand, after the Al film is oxidized by itself, it can effectively block the contact between the environmental medium and the surface of the steel matrix, thereby improving the corrosion resistance of the steel matrix. Generally, the thickness of the Al film obtained by magnetron sputtering is only dozens to hundreds of nanometers. The single aluminum (Al) film is relatively thin and has low hardness, and it cannot improve the wear resistance of the steel matrix. This makes the aluminum film layer easily worn and eliminated, resulting in poor durability of the corrosion resistance of 40Cr steel and being unable to adapt to complex use environments.

[0005] Therefore, based on the problems existing in the wear resistance and corrosion resistance of 40Cr steel in complex use environments, it is necessary to provide a new technical solution to effectively solve these problems so that the 40Cr steel matrix can have excellent wear resistance and long-term corrosion resistance. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel to solve the problems of low surface hardness, insufficient wear resistance and difficult adaptation of corrosion resistance to complex working environments of the current 40Cr steel. Through the treatment method of the present invention, a composite film layer structure can be formed. By using this composite film layer, a protective film with high hardness can be formed on the surface of 40Cr steel, and this composite film layer can reduce the self-corrosion current density of 40Cr steel and reduce the corrosion rate, thereby improving the corrosion resistance of the surface of 40Cr steel.

[0007] More specifically, in view of the complex service environment of 40Cr steel, the present invention obtains a composite film layer through magnetron sputtering aluminum-ion nitriding composite treatment, so that the surface of the workpiece made of 40Cr steel has a high hardness and a corrosion-resistant film layer, thereby endowing the 40Cr steel substrate with excellent wear resistance and long-term corrosion resistance.

[0008] Specifically, the present invention adopts the following technical solutions: A magnetron sputtering aluminum-ion nitriding composite treatment method for the surface of 40Cr steel, the composite treatment method specifically includes the following steps: Step (1), pretreatment: perform rust removal, degreasing, and dirt removal ultrasonic cleaning treatment on 40Cr steel. After the cleaning treatment, dry the 40Cr steel. Step (2), magnetron sputtering treatment: place the 40Cr steel pretreated in step (1) into a magnetron sputtering furnace for magnetron sputtering treatment to form an aluminum film on the surface of the 40Cr steel. The sputtering power in the magnetron sputtering furnace is 150 - 200 W, the target voltage is 300 - 400 V, the target-substrate distance is 70 mm, the sputtering gas pressure is 9 mT, and the sputtering duration is 80 - 100 min; a protective film layer is formed on the surface of the 40Cr steel through magnetron sputtering treatment. Step (3): Hang the 40Cr steel after magnetron sputtering treatment in step (2) in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650 Pa, the nitriding voltage is 600 - 650 V, the nitriding temperature is 500 - 550 °C, and continuous nitriding treatment is carried out for 6 - 10 h to complete the magnetron sputtering aluminum-ion nitriding composite treatment on the surface of the 40Cr steel.

[0009] The above is the basic solution of the present invention. Regarding the above solution: First of all, in this solution, a layer of Al protective film (Magnetron Sputtering Aluminum, abbreviated as MSAl) is formed on the surface of 40Cr steel through magnetron sputtering. This protective film has the advantages of strong bonding force and good compactness, and its thickness is between 80 - 300 nm; the purpose of generating this protective film is to effectively improve the corrosion resistance of the surface of 40Cr steel.

[0010] Then, through the Plasma Nitriding (PN) process in step (3), the surface of 40Cr steel is subjected to plasma nitriding treatment. During this treatment process, as N element penetrates into the surface of 40Cr steel, FeN is generated. At the same time, by virtue of the strong affinity between Al and N, AlN is generated while FeN is formed. Utilizing the generated AlN, an MSAl-PN composite nitrided layer is formed. The thickness of the MSAl-PN composite nitrided layer increases, and the hardness shows a gradient distribution, thereby improving the wear resistance of 40Cr steel. At the same time, the composite nitrided layer also reduces the self-corrosion current density on the surface of 40Cr steel, thereby reducing the corrosion rate of 40Cr steel, and finally enabling 40Cr steel to have excellent corrosion resistance.

[0011] The generated MSAl-PN composite nitrided layer, compared with the ordinary Al protective film layer, has an increased thickness and an improved hardness. Its wear resistance is also significantly improved compared with the current single Al protective film layer. Based on this, the MSAl-PN composite nitrided layer has a more durable life than the single Al protective film layer, thereby improving the surface hardness of 40Cr steel while maintaining long-term corrosion resistance.

[0012] Preferably, in step (1), the surface of 40Cr steel is subjected to sandblasting treatment.

[0013] Preferably, the target in step (2) is aluminum.

[0014] Preferably, the target in step (2) is an alloy target, and the alloy target is Al 81.6 - 85.4 wt%, Zn 8.2 - 15.6 wt%, Nd 2.4 - 4.6 wt%, Sc 0.5 - 0.8 wt%.

[0015] Preferably, the composite treatment method specifically includes the following steps: Step (1), pretreatment: The 40Cr steel is subjected to ultrasonic cleaning treatment for rust removal, degreasing, and decontamination. After the cleaning treatment, the 40Cr steel is dried. Step (2), magnetron sputtering treatment: The 40Cr steel pretreated in step (1) is placed in a magnetron sputtering furnace for magnetron sputtering treatment, and an aluminum film is formed on the surface of the 40Cr steel through the treatment. The sputtering power in the magnetron sputtering furnace is 150W, the target voltage is 300 - 400V, the target-substrate distance is 70mm, the sputtering gas pressure is 9mT, and the sputtering duration is 90min. A protective film layer is formed on the surface of the 40Cr steel through the magnetron sputtering treatment. Step (3): The 40Cr steel after the magnetron sputtering treatment in step (2) is suspended in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650Pa, the nitriding voltage is 650V, the nitriding temperature is 510°C, and continuous nitriding treatment is carried out for 6 h to complete the magnetron sputtering ion nitriding composite treatment on the surface of the 40Cr steel.

[0016] A 40Cr steel with a surface subjected to composite treatment to form a composite penetration layer on the surface, prepared by the above method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The basic solution of the present invention uses a two-step method to treat the surface of 40Cr steel. After treatment, the hardness performance of the 40Cr steel is improved. At the same time, an MSAl-PN composite penetration layer is formed by using an Al film. This composite penetration layer reduces the corrosion rate by reducing the self-corrosion current density of the 40Cr steel, thereby improving the corrosion resistance of the 40Cr steel. For the improved solution of the present invention, by improving the target material, an Al-Zn-Nd-Sc composite layer is first formed on the surface of the 40Cr steel. This composite layer is mainly composed of an Al layer, forming a composite protective film layer on the 40Cr steel, which improves the density. Subsequently, during the ion nitriding treatment process, the composite protective film layer is beneficial to the nitriding process, increasing the thickness of the composite penetration layer, thereby assisting in improving the hardness of the 40Cr steel. Description of the Drawings

[0018] Figure 1 It is the X-ray diffraction pattern of the composite penetration layer on the surface of 40Cr steel in Example 1 of the present invention.

[0019] Figure 2 It is the field emission scanning electron micrograph of the composite penetration layer on the surface of 40Cr steel in Example 1 of the present invention.

[0020] Figure 3 It is the field emission scanning electron micrograph of the composite penetration layer on the surface of 40Cr steel in Example 1 of the present invention.

[0021] Figure 4 It is the electrochemical corrosion polarization curve graph of 40Cr steel in Example 1 of the present invention, 40Cr steel in Comparative Example 1, and 40Cr steel without any treatment.

[0022] Figure 5 It is the corrosion morphology of the surface of 40Cr steel in Example 1 of the present invention, 40Cr steel in Comparative Example 1, and 40Cr steel without any treatment after 2 h of salt spray corrosion.

[0023] Figure 6 It is the comparison graph of the hardness distribution curves of the composite penetration layers on the surfaces of 40Cr steels prepared in Example 1, Example 2, and Comparative Example of the present invention. Detailed Embodiments

[0024] The representative embodiments shown in the accompanying drawings will now be further refined. It should be understood that the following description is not intended to limit the embodiments to a preferred embodiment. On the contrary, it is intended to cover alternative forms, modifications, and equivalent forms that may be included within the spirit and scope of the described embodiments defined by the appended claims.

[0025] Example 1: The applicant used a composite treatment method to prepare a composite layer on 40Cr steel, thereby improving the wear resistance and corrosion resistance of 40Cr steel. Specifically, this is a magnetron sputtering aluminum-ion nitriding composite treatment method on the surface of 40Cr steel. This composite treatment method specifically includes the following steps: Step (1), pretreatment: The 40Cr steel is subjected to rust removal, degreasing, and decontamination ultrasonic cleaning treatment. After the cleaning treatment, the 40Cr steel is dried. Step (2), magnetron sputtering treatment: The 40Cr steel pretreated in step (1) is placed in a magnetron sputtering furnace for magnetron sputtering treatment, and an aluminum film is formed on the surface of the 40Cr steel through the treatment. The sputtering power in the magnetron sputtering furnace is 150W, the target voltage is 300 - 400V, the target-substrate distance is 70mm, the sputtering gas pressure is 9mT, and the sputtering duration is 90min. A protective film layer is formed on the surface of the 40Cr steel through the magnetron sputtering treatment; the target material is aluminum. Step (3): The 40Cr steel after the magnetron sputtering treatment in step (2) is suspended in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650Pa, the nitriding voltage is 650V, the nitriding temperature is 510°C, and continuous nitriding treatment is carried out for 6 h to complete the magnetron sputtering ion nitriding composite treatment on the surface of the 40Cr steel.

[0026] Example 2: Based on Example 1, the target material is improved, which is also used to improve the hardness and corrosion resistance of 40Cr steel; this composite treatment method specifically includes the following steps: Step (1), pretreatment: The 40Cr steel is subjected to rust removal, degreasing, and decontamination ultrasonic cleaning treatment. After the cleaning treatment, the 40Cr steel is dried. Step (2), magnetron sputtering treatment: The 40Cr steel pretreated in step (1) is placed in a magnetron sputtering furnace for magnetron sputtering treatment, and an aluminum film is formed on the surface of the 40Cr steel through the treatment. The sputtering power in the magnetron sputtering furnace is 150W, the target voltage is 300 - 400V, the target-substrate distance is 70mm, the sputtering gas pressure is 9mT, and the sputtering duration is 90min. A protective film layer is formed on the surface of the 40Cr steel through the magnetron sputtering treatment; the target material is an alloy target material with a content of Al 84.5wt%, Zn 12.3 wt%, Nd 2.6wt%, and Sc 0.6 wt%. Step (3): Suspend the 40Cr steel after magnetron sputtering treatment in step (2) in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650 Pa, the nitriding voltage is 650 V, the nitriding temperature is 510 °C, and continuous nitriding treatment is carried out for 6 h to complete the magnetron sputtering aluminum-ion nitriding composite treatment on the surface of the 40Cr steel.

[0027] Comparative Example 1: Perform rust removal, degreasing, and decontamination ultrasonic cleaning treatment on the 40Cr steel. After the cleaning treatment, dry the 40Cr steel. Then suspend the treated 40Cr steel in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650 Pa, the nitriding voltage is 650 V, the nitriding temperature is 510 °C, and continuous nitriding treatment is carried out for 6 h to complete the magnetron sputtering aluminum-ion nitriding composite treatment on the surface of the 40Cr steel.

[0028] Perform performance testing on the products obtained by the treatment method of the present invention.

[0029] Regarding the 40Cr steel product prepared in Example 1, as Figure 1 shown, the XRD pattern shows that the obtained nitrided layer is composed of a duplex phase of AlN and Fe4N, indicating that the nitrided layer of the composite treatment is neither the Fe-N compound of the nitrided layer nor the Fe-Al compound after aluminizing treatment.

[0030] As Figure 2 shown, it can be seen that the composite nitrided layer on the surface of the obtained 40Cr steel is dense and no obvious cracks are found.

[0031] As Figure 3 shown, it can be seen that the composite nitrided layer on the surface of the prepared 40Cr steel is continuous, with uniform thickness, about 30 µm.

[0032] Adopt a three-electrode system, add 3.5% NaCl, install 40Cr specimens treated differently as the working electrode, use a Pt electrode as the reference electrode, a saturated calomel electrode as the auxiliary electrode, and connect the corrosion tester to the three-electrode system. With a scanning rate of 0.5 mv / s and a scanning frequency of 2 Hz, repeat the above steps to test the polarization curves of different specimens. The results are as Figure 4 shown, Figure 4 in the polarization curve diagram in, it can be seen that the self-corrosion current density of the composite nitrided layer 40Cr prepared in Example 1 is reduced by 19.07% compared with the single PN layer 40Cr in Comparative Example 1 and is reduced by 30.41% compared with the 40Cr without nitrided layer treatment, indicating that the prepared MSAl-PN composite nitrided layer has excellent corrosion resistance.

[0033] As Figure 5As shown, by observing the morphology after the retest, it can be concluded that under the same corrosion conditions, there are obvious corrosion products and corrosion cracks on the surface of 40Cr without diffusion layer treatment; the corrosion products on the surface of the single PN layer 40Cr of comparative example 1 are less, but there are obvious corrosion cracks; the surface of the composite diffusion layer 40Cr of embodiment 1 is smooth, and no obvious corrosion products and corrosion cracks are found, indicating that the prepared MSAl-PN composite diffusion layer has excellent corrosion resistance.

[0034] The surface hardness of the 40Cr steel in Example 1 and Example 2 was tested. Figure 6 As shown,.

[0035] pass Figure 6 It can be seen that by changing the target material, the alloy target can be used to improve the surface hardness distribution of the prepared 40Cr steel. At the same time, the depth of the nitriding layer can be increased. The hardness of the 40Cr steel surface is an important parameter for directly evaluating the nitriding effect. Regarding the hardness of the formed nitriding layer, Figure 6 It can be seen that in Example 1, after the aluminum film is first sputtered, there is no positive effect on the depth of ion nitriding, but after changing the composition of the target material, the depth of ion nitriding is improved to a certain extent.

[0036] 40Cr steel is a quenched and tempered steel with low hardenability. Ion nitriding treatment can improve its hardness and wear resistance. However, after the Al film is pre-sputtered, the ion nitriding is affected, which will affect the depth of the ion nitriding layer. Therefore, it is necessary to improve the process of magnetron sputtering. The conventional single Al film, such as that in Example 1, affects the depth of the ion nitriding layer. After the alloy target material is used, the depth of the ion nitriding layer is improved, so that the hardness is guaranteed.

[0037] Alloy targets have an impact on the phase structures of the ion nitriding layer. Magnetron sputtering of the 40Cr steel surface by alloy targets increases the amount of α phase and reduces the ε phase in the surface compound layer during nitriding, forming a compound layer dominated by γ´ phase and interspersed with α phase. Such changes are conducive to the diffusion of subsurface nitrogen, accelerate the formation of the diffusion layer, and thus increase the depth of the nitriding layer. The increase in depth further improves the hardness of the nitriding layer. At the same time, other elements in the alloy target are conducive to improving the toughness of the nitriding layer, thereby reducing the brittleness of the nitriding layer and thus increasing the life of the nitriding layer.

[0038] At the same time, the use of alloy targets is conducive to the formation of dense ferroferric oxide crystals on the surface of 40Cr steel; the effect of ion nitriding, that is, the quality of ion nitriding, is usually determined by the compound layer and the diffusion layer. The alloy target of the present application can effectively change the structure of the compound layer and expand the depth range of the diffusion layer.

[0039] In summary, in the solution of the present invention, a protective film is first sputtered by a magnetron sputtering process, and then a composite layer is obtained by an ion nitriding process, which can form a composite layer on the surface of 40Cr steel to improve the surface hardness and corrosion resistance of 40Cr steel to a certain extent. Moreover, by adjusting the target composition, the depth of ion nitriding can be further increased, thereby improving the quality of ion nitriding.

[0040] It is obvious to those skilled in the art that, based on the above teaching content, certain modifications, combinations, and variations can also be made.

Claims

1. A method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel, characterized in that: The composite treatment method specifically includes the following steps: Step (1), pre-treatment: subject the 40Cr steel to rust removal, degreasing, and dirt removal by ultrasonic cleaning. After the cleaning treatment, dry the 40Cr steel. Step (2), magnetron sputtering treatment: place the 40Cr steel pre-treated in step (1) into a magnetron sputtering furnace for magnetron sputtering treatment to form an aluminum film on the surface of the 40Cr steel through the treatment. The sputtering power in the magnetron sputtering furnace is 150 - 200 W, the target voltage is 300 - 400 V, the target-substrate distance is 70 mm, the sputtering gas pressure is 9 mT, and the sputtering duration is 80 - 100 min. A protective film layer is formed on the surface of the 40Cr steel through the magnetron sputtering treatment. Step (3): Hang the 40Cr steel after the magnetron sputtering treatment in step (2) in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650 Pa, the nitriding voltage is 600 - 650 V, the nitriding temperature is 500 - 550 °C, and continuous nitriding treatment is carried out for 6 - 10 h to complete the magnetron sputtering aluminum - ion nitriding composite treatment on the surface of the 40Cr steel.

2. A method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel according to claim 1, characterized in that: In step (1), sandblasting treatment is performed on the surface of the 40Cr steel.

3. A method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel according to claim 1, characterized in that: The target material in step (2) is aluminum.

4. A method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel according to claim 1, characterized in that: The target material in step (2) is an alloy target material, and the alloy target material is Al 81.6 - 85.4 wt%, Zn 8.2 - 15.6 wt%, Nd 2.4 - 4.6 wt%, Sc 0.5 - 0.8 wt%.

5. A method for magnetron sputtering aluminum-ion nitriding composite treatment on the surface of 40Cr steel according to claim 1, characterized in that: The composite treatment method specifically includes the following steps: Step (1), pre-treatment: subject the 40Cr steel to rust removal, degreasing, and dirt removal by ultrasonic cleaning. After the cleaning treatment, dry the 40Cr steel. Step (2), magnetron sputtering treatment: place the 40Cr steel pre-treated in step (1) into a magnetron sputtering furnace for magnetron sputtering treatment to form an aluminum film on the surface of the 40Cr steel through the treatment. The sputtering power in the magnetron sputtering furnace is 150 W, the target voltage is 300 - 400 V, the target-substrate distance is 70 mm, the sputtering gas pressure is 9 mT, and the sputtering duration is 90 min. A protective film layer is formed on the surface of the 40Cr steel through the magnetron sputtering treatment. Step (3): Hang the 40Cr steel after the magnetron sputtering treatment in step (2) in an ion nitriding furnace for ion nitriding treatment. The total pressure of ammonia gas in the furnace is 650 Pa, the nitriding voltage is 650 V, the nitriding temperature is 510 °C, and continuous nitriding treatment is carried out for 6 h to complete the magnetron sputtering aluminum - ion nitriding composite treatment on the surface of the 40Cr steel.

6. A 40Cr steel with a surface composite treatment, characterized in that: Prepared by the method described in any one of claims 1 - 8.

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