Method for physical vapor deposition assisted laser shock peening fatigue strengthening and application

Abstract

The application provides a method for physical vapor deposition assisted laser shock fatigue strengthening, comprising the following steps: firstly, depositing a metal film on the surface of a substrate by a physical vapor deposition method; secondly, applying a laser shock technology to the surface of the substrate coated with the metal film; and finally, removing the metal film deposited on the surface of the substrate. The metal film formed by the physical vapor deposition is weakly combined with the substrate, which can prevent the cracks in the laser shock or ablation from continuing to evolve and develop inside the material to be strengthened and from expanding to the interlayer cracks of the composite material, and effectively improve the fatigue strength of the material. In addition, the metal film can also be beneficial to the conduction of impact force, heat and other effects; as a sacrificial layer, the metal film can be closely attached to the substrate and will not peel off randomly during the impact process. The application combines the physical deposition and the laser shock technology, widens the application scenarios of the laser shock, breaks through the material limitation of the traditional laser shock, prevents the crack evolution and development, improves the fatigue strength, and has a wide popularization and application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface engineering, and particularly relates to a method for laser shock peening assisted by physical vapor deposition, and further relates to an alloy material for fatigue strengthening to inhibit crack evolution and development during laser shock peening. BACKGROUND

[0002] Laser shock peening is a material strengthening method, but cracks may be generated in the ablation layer caused by laser shock during the strengthening process, and the cracks may evolve and develop into the interior of the material to be strengthened and expand between layers of the composite material, which adversely affects the quality of the material.

[0003] In some laser shock processes, black paint or adhesive tape is placed on the surface of the substrate as a sacrificial layer to absorb laser energy, but the two sacrificial layers are usually not resistant to high temperature and cannot be applied to high-temperature laser shock processes. The sacrificial layer such as black paint is difficult to peel off from the substrate after laser shock peening of the substrate.

[0004] Therefore, it is a technical problem to be solved to provide a fatigue strengthening method that can effectively inhibit the evolution and development of cracks or cracks into the interior of the material to be strengthened during the laser shock peening process to improve the surface quality of the sample after laser shock peening. SUMMARY

[0005] One of the purposes of the present application is to provide a method for laser shock peening assisted by physical vapor deposition.

[0006] The second purpose of the present application is to provide an alloy material for fatigue strengthening to inhibit the evolution and development of cracks during laser shock peening.

[0007] The technical solution adopted by one of the purposes of the present application is to provide a method for laser shock peening assisted by physical vapor deposition, comprising the following steps:

[0008] S1, a layer of metal film is plated on the surface of the substrate by a physical vapor deposition method, and the bonding force between the metal film and the surface of the substrate is lower than the atomic bonding force of the substrate itself;

[0009] S2, laser shock technology is applied to the surface of the substrate plated with the metal film, and the thickness of the ablation layer formed by the laser shock technology is less than the thickness of the metal film;

[0010] S3, the metal film is removed from the surface of the substrate.

[0011] The general idea of the method for physical vapor deposition assisted laser shock peening fatigue strengthening provided by the application is as follows: the physical vapor deposition and the laser shock are combined, the target material (i.e. the sacrificial metal) is deposited on the surface of the substrate in the form of physical deposition to form a sacrificial layer, the metal film is beneficial to the conduction of the impact force, has good high-temperature resistance, and forms a relatively close fit with the substrate, so that the limitations of the conventional sacrificial material can be overcome. Through the selection of the metal film and the substrate material and the regulation of the plating process, a weak bond is formed between the metal film and the surface of the substrate, which will not peel off from the surface of the substrate during the laser shock process, and will make the cracks generated during the subsequent laser shock or ablation process first expand along the interface between the metal film and the substrate instead of expanding into the substrate, thereby achieving the effect of preventing the evolution and development of the cracks.

[0012] In the application, the bonding force between the metal film and the surface of the substrate needs to be lower than the atomic bonding force of the substrate itself, so as to ensure that a weak bond is formed between the metal and the substrate instead of a strong bond, so that the metal film can be removed from the surface of the substrate in the subsequent step.

[0013] In addition, the thickness of the metal film also needs to be strictly controlled, and the thickness of the metal film should be greater than the depth of the laser shock ablation, so that the plating layer formed can prevent the cracks from expanding into the substrate; in addition, the metal film cannot be too thick, otherwise the impact strengthening effect of the surface of the substrate will be weakened and the thickness of the residual compressive stress layer will be reduced.

[0014] Further, in step S1 of the application, the physical vapor deposition can adopt methods such as magnetron sputtering, radio frequency sputtering, etc., and the metal film with the required thickness can be obtained by adjusting the process parameters such as the time and power of the physical vapor deposition. In the application, the metal film is formed by physical vapor deposition, and the thickness of the metal film is easier to control, so as to ensure that the thickness of the metal film is greater than the ablation depth; at the same time, the physical vapor deposition is carried out in a vacuum condition, which can effectively prevent the surface of the substrate from chemical reaction or corrosion, and avoid direct damage to the substrate during the formation process of the metal film.

[0015] Further, in the application, the substrate in step S1 is an alloy material, which includes one or more of iron, non-ferrous metal, alloy containing iron or non-ferrous metal, or high-entropy alloy containing iron or non-ferrous metal. Specifically, the commonly used alloys such as 45 steel, TC4 alloy or 40CrMo and other materials that need to be subjected to laser shock peening are determined according to the process requirements.

[0016] Further, in the step S1, the raw material of the metal film includes one or more of iron, non-ferrous metal, alloy of iron or non-ferrous metal, and oxide of iron or non-ferrous metal. Specifically, the target metal can be selected according to the material of the substrate, and the intermolecular binding force of the target metal is greater than the binding force between the target and the substrate, so as to prevent the crack from evolving to the inside. In the present application, Al is preferably used as the metal for depositing the metal film from the perspective of reducing cost and facilitating industrial application.

[0017] Preferably, the thickness of the metal film is 10 nm to 100 μm, and the specific thickness can be selected and adjusted according to the parameters of the laser shock, so as to ensure that the thickness of the metal film is greater than the ablation depth.

[0018] Further, in the step S2 of the present application, the parameters of the laser shock strengthening need to meet the following two conditions: one is to meet the requirements of the desired residual stress, surface hardness and the like of the shock strengthening; the other is that the shock parameters should be matched with the thickness of the plated metal film, and should not cause the substrate to be ablated. Specifically, the laser shock technology can be one of warm laser shock strengthening, droplet-enhanced laser shock strengthening or femtosecond laser shock strengthening.

[0019] Preferably, the pulse width of the laser shock technology is 100 ns or less.

[0020] Preferably, the ablation layer formed by the laser shock technology has a thickness of less than 100 μm.

[0021] Further, in the step S3, the way of removing the metal film from the surface of the substrate includes one or more of ultrasonic vibration, adhesive adhesion, mechanical polishing or chemical removal. In the present application, the metal film as the sacrificial layer can form a weak van der Waals force with the substrate, and will not peel off without external force. After the laser shock process in the step S2 is completed, the weak binding force can be overcome by using ultrasonic vibration or adhesive adhesion, so as to remove the metal film from the surface of the substrate.

[0022] The second technical means for achieving the purpose of the present application is to provide a fatigue-strengthened alloy material, which is prepared by the method according to the first technical means of the present application.

[0023] In some preferable embodiments, the alloy material is TC4 titanium alloy, and the metal of the metal film is Al.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] (1) The application provides a physical vapor deposition assisted laser shock fatigue strengthening method, a sacrificial layer is formed on the surface of a substrate by physical deposition, and a weak bond is formed between the sacrificial layer and the substrate, in the process of laser shock or ablation, cracks are first expanded along the interface between the target material and the substrate instead of expanding into the material, thereby preventing the evolution and development of the cracks, and the fatigue strength of the material is effectively improved. In addition, the metal film formed by physical vapor deposition can beneficially conduct impact force, heat and other effects; the metal film as the sacrificial layer can form a relatively tight fit with the substrate, without the need for substances such as adhesive tape that cannot withstand high temperatures, and will not peel off at will during the impact process.

[0026] (2) The application provides a physical vapor deposition assisted laser shock fatigue strengthening method, a weak bond is formed between the sacrificial layer and the substrate, and after laser shock or ablation, the sacrificial layer can be removed by mechanical removal methods such as ultrasonic vibration, adhesive tape adhesion or friction, which is convenient to operate.

[0027] (3) The application combines physical deposition and laser shock processes, broadens the application scenarios of laser shock, breaks through the material limitations of traditional laser shock, and can effectively prevent the evolution and development of cracks in the material, and has broad popularization prospect and application value. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic diagram of the physical vapor deposition assisted laser shock fatigue strengthening method provided by the embodiments of the application is shown in the figure.

[0029] Wherein, 101-metal plated by physical vapor deposition; 102-substrate; 103-pulse laser; 104-residual metal; 105-hardened layer; 106-ultrasonic vibration. DETAILED DESCRIPTION

[0030] The technical solutions of the application will be described clearly and completely in combination with the embodiments. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0031] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0032] The application will be further described in combination with specific embodiments, but is not limited by the application.

[0033] The main materials and process parameters involved in embodiments 1-5 of the present application are shown in Table 1, and the sample size is uniformly 120mmx8mmx4mm. The bending fatigue test is carried out by impacting the middle part of the sample, and the size is 8mmx8mm.

[0034] Table 1

[0035]

[0036] Embodiment 1

[0037] The present embodiment provides a method for fatigue strengthening of TC4 titanium alloy by physical vapor deposition assisted laser impact, comprising the following steps:

[0038] Step 1: After the TC4 titanium alloy is cleaned with anhydrous ethanol and dried, Al is plated on the surface of the TC4 titanium alloy by a magnetron sputtering method to form a metal film with a thickness of 0.8μm; the power of the magnetron sputtering is 60W, and the sputtering time is 720s;

[0039] Step 2: After the TC4 titanium alloy with the Al metal film is heated to 400℃, the surface of the TC4 titanium alloy with the metal film is fatigue strengthened by pulse laser strengthening, and the pulse width of the pulse laser is 7ns;

[0040] Step 3: The residual Al metal film on the surface of the TC4 titanium alloy is removed by mechanical removal to obtain the fatigue strengthened TC4 titanium alloy.

[0041] Figure 1 The present embodiment provides a process schematic diagram of the method for fatigue strengthening based on physical vapor deposition assisted laser impact. Among them, 101 is the metal plated by physical vapor deposition; 102 is the substrate; 103 is the pulse laser; 104 is the residual metal; 105 is the hardening layer (i.e. compressive stress layer) formed by laser impact; 106 is the metal film removed by ultrasonic vibration.

[0042] Embodiment 2

[0043] The present embodiment provides a method for fatigue strengthening of TC4 titanium alloy by physical vapor deposition assisted laser impact, comprising the following steps:

[0044] Step 1: After the TC4 titanium alloy is cleaned with anhydrous ethanol and dried, Ni is plated on the surface of the TC4 titanium alloy by a magnetron sputtering method to form a metal film with a thickness of 1.5μm; the power of the magnetron sputtering is 60W, and the sputtering time is 1350s;

[0045] Step 2: After the TC4 titanium alloy with the Ni metal film is heated to 400℃, the surface of the TC4 titanium alloy with the metal film is fatigue strengthened by pulse laser strengthening, and the pulse width of the pulse laser is 7ns;

[0046] Step 3: Remove the residual Ni metal film on the surface of the TC4 titanium alloy by mechanical removal to obtain the fatigue-strengthened TC4 titanium alloy.

[0047] Example 3

[0048] The present embodiment provides a method for fatigue strengthening of 40CrMo alloy assisted by physical vapor deposition and laser shock, comprising the following steps:

[0049] Step 1: After the 40CrMo alloy is cleaned with anhydrous ethanol and dried, Cu is plated on the surface of the 40CrMo alloy by magnetron sputtering to form a metal film with a thickness of 2 μm; the parameters of magnetron sputtering are a power of 60 W and a sputtering time of 1800 s;

[0050] Step 2: The 40CrMo titanium alloy with a Cu metal film is fatigue-strengthened on the surface of the 40CrMo titanium alloy with a metal film by pulse laser strengthening, and the pulse width of the pulse laser is 7 ns;

[0051] Step 3: Remove the residual Cu metal film on the surface of the 40CrMo alloy by mechanical removal to obtain the fatigue-strengthened 40CrMo alloy.

[0052] Example 4

[0053] The present embodiment provides a method for fatigue strengthening of TC4 titanium alloy assisted by physical vapor deposition and laser shock, comprising the following steps:

[0054] Step 1: After the TC4 titanium alloy is cleaned with anhydrous ethanol and dried, Au is plated on the surface of the TC4 titanium alloy by radio frequency sputtering to form a metal film with a thickness of 0.8 μm; the parameters of magnetron sputtering are a power of 60 W and a sputtering time of 720 s;

[0055] Step 2: The TC4 titanium alloy with an Au metal film is fatigue-strengthened on the surface of the TC4 titanium alloy with a metal film by pulse laser strengthening, and the pulse width of the pulse laser is 7 ns;

[0056] Step 3: Remove the residual Au metal film on the surface of the TC4 titanium alloy by mechanical removal, and clean it at a frequency of 40000 Hz until there is no metal film left on the surface under the ultrasonic electric power of 100 W. Obtain the fatigue-strengthened TC4 titanium alloy.

[0057] Example 5

[0058] The present embodiment provides a method for fatigue strengthening of 45 steel assisted by physical vapor deposition and laser shock, comprising the following steps:

[0059] Step 1: after the 45# steel is cleaned with anhydrous ethanol and dried, Ti is plated on the surface of the 45# steel by a magnetron method to form a metal film with a thickness of 1 μm; the parameters of the magnetron sputtering are that the power is 60 W and the sputtering time is 720 s;

[0060] Step 2: the 45# steel with the Ti metal film is subjected to pulse laser strengthening to fatigue strengthen the surface of the 45# steel with the metal film; the pulse laser pulse width is 7 ns;

[0061] Step 3: the Ti metal film remaining on the surface of the 45# steel substrate is removed by a mechanical removal method to obtain the fatigue strengthened 45# steel.

[0062] Comparative Example 1

[0063] The TC4 titanium alloy substrate is not subjected to film plating treatment, is heated to 400 ℃, and is subjected to laser shock peening to fatigue strengthen the surface of the TC4 titanium alloy substrate; the pulse laser energy is 0.7 J and the pulse width is 7 ns; and the fatigue strengthened TC4 titanium alloy is obtained.

[0064] Performance Test

[0065] The samples prepared in Example 1 and Comparative Example 1 are subjected to a bending fatigue test; the sample in Example 1 and the sample in Comparative Example 1 are placed on a three-point bending test machine; the maximum pressure is kept at 300 Mpa until the sample is broken; and the test results are shown in Table 2 below:

[0066] Table 2

[0067]

[0068] From the above table, it can be seen that,

[0069] The fatigue life of the alloy material treated by the physical vapor deposition assisted laser shock fatigue strengthening method provided by the present application is significantly improved. It fully illustrates that the present application uses the physical vapor deposition and laser shock to fatigue strengthen the material substrate, which can effectively prevent the crack evolution caused by laser shock to the material substrate, and further improve the fatigue strength of the material.

[0070] The above is only a preferred embodiment of the present application, and does not limit the implementation and protection scope of the present application. For those skilled in the art, it should be realized that any equivalent replacement and obvious changes made by using the content of the present application should be included in the protection scope of the present application.

Claims

1. A method for physical vapor deposition-assisted laser shock fatigue strengthening, characterized in that, Includes the following steps: S1. A metal film is deposited on the surface of a substrate by physical vapor deposition, wherein the bonding force between the metal film and the substrate surface is lower than the atomic bonding force of the substrate itself. S2. Applying laser shock technology to the surface of a substrate coated with a metal film, wherein the thickness of the ablation layer formed by the laser shock technology is less than the thickness of the metal film; S3. Remove the metal film from the substrate surface.

2. The method according to claim 1, characterized in that, In step S1, the substrate includes one or more of iron, non-ferrous metals, and alloys containing iron or non-ferrous metals.

3. The method according to claim 2, characterized in that, The raw materials for metal films include one or more of iron, non-ferrous metals, and alloys containing iron or non-ferrous metals.

4. The method according to claim 3, characterized in that, The thickness of the metal film is 10 nm to 100 μm.

5. The method according to claim 1, wherein in step S2, the laser shock technology includes one of warm laser shock enhancement, droplet-enhanced laser shock enhancement, or femtosecond laser shock enhancement.

6. The method according to claim 5, characterized in that, The pulse width of the laser shock technology is less than 100 ns.

7. The method according to claim 6, characterized in that, The ablation layer formed by the laser shock blasting technique has a thickness of less than 100 μm.

8. The method according to claim 1, characterized in that, In step S3, the method of removing the metal film from the substrate surface includes one or more of ultrasonic vibration, tape adhesion, mechanical polishing, or chemical removal.

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