WO2019200677A1 - Surface strengthening method for metal component by vibration-assisted laser shock processing - Google Patents

Abstract

A surface strengthening method for a metal component by vibration-assisted laser shock processing. Laser shock peening technology is combined with vibratory stress relief; a vibration exciter (3) is used for excitation and a sensor (5) is used for vibration pick-up; the vibration frequency is controlled to keep an amplitude value within a specified range; laser lap-based shock peening is carried out with the aid of vibratory stress relief processing, so that more serious plastic deformation occurs on the surface of a metal component, and high-amplitude residual compressive stress is induced in a shock area; meanwhile, under the condition that a laser beam irradiates the metal surface, the vibration further refines or even nanocrystallizes surface grains, and under the effect of a temperature field, the vibration reduces the thermal stress field gradient, and thus the residual stress inside the material is uniformized; the mechanical properties of the metal component are remarkably improved, and the metal surface is strengthened, thereby effectively prolonging the fatigue life of the metal component, and preventing initiation and extension of fatigue cracks.

Description

Surface strengthening method for vibration-assisted laser shock treatment of metal members Technical field

The invention relates to the field of new processes of laser processing and vibration aging, in particular to a laser impact strengthening of a metal surface to be strengthened under an auxiliary field of vibration aging, and obtaining a surface strengthening layer resistant to fatigue. This method is suitable for the strengthening treatment of metal surfaces.

Background technique

Most of the industrial parts are made of metal materials. During the work, the metal alloy parts are prone to cracks due to wear, impact, fatigue, etc., causing the materials to be scrapped. With the rapid development of China's industry, higher requirements are placed on the workpiece industry. How to improve the processing quality and service life of the workpiece has been a subject that people are constantly exploring. At present, surface strengthening technology is gradually becoming an important way to improve the quality and service life of workpieces. Commonly used are two methods of shot peening and rolling. Although shot peening can induce large residual compressive stress on the surface of the material, it has a great influence on the surface roughness of the material, and the residual compressive stress layer produced by rolling is shallow, which can not achieve a good strengthening effect.

Laser shock peening (also known as laser peening) is a new type of material surface strengthening technology that uses high-laser-induced shock wave mechanical effects to process materials with high pressure, high energy, ultra-fast and ultra-high strain rate. The residual compressive stress layer can effectively eliminate the stress concentration inside the material and inhibit the initiation and expansion of cracks, and can significantly improve the fatigue life and corrosion resistance and wear resistance of metal parts. A large number of studies have proved that laser shock strengthening technology is prolonged crack initiation. Time, an effective means of reducing the crack growth rate and increasing the life of the material.

The essence of vibration aging is to apply a dynamic stress to the workpiece in the form of vibration. When the dynamic stress is superimposed with the residual stress of the workpiece itself, when the microscopic yield limit of the material is reached or exceeded, the workpiece will have a microscopic or macroscopic local and overall Elastic and plastic deformation, at the same time reduce and homogenize the residual stress inside the workpiece, and finally achieve the purpose of preventing deformation and cracking of the workpiece and stabilizing the workpiece size and geometric accuracy.

Summary of the invention

An object of the present invention is to provide a surface strengthening method for vibration-assisted laser shock treatment of a metal member, which is characterized in that: laser shock tensification technology is combined with vibration aging treatment, vibration is excited by an exciter, and the sensor is vibrated by controlling vibration. The frequency is such that the amplitude value is kept within the specified range, the grain of the metal member is refined, the material undergoes a slight plastic deformation, the internal stress inside the material is relaxed and reduced, and the surface of the metal member is assisted by the vibration aging treatment. Laser lap impact strengthening treatment causes more severe plastic deformation on the surface and induces high residual compressive stress in the impact region. At the same time, the laser beam irradiates the surface of the metal, and the vibration causes the surface grains to be further refined or even nanometer. In the presence of a temperature field, the vibration reduces the thermal stress field gradient, so that the internal residual stress of the material is uniformized, the mechanical properties of the metal member are significantly improved, and the metal surface is strengthened, thereby effectively improving the fatigue life of the metal member. To prevent the initiation and expansion of fatigue cracks.

Specific steps are as follows:

(1) After the sample to be processed is subjected to stepwise grinding treatment using metallographic sandpaper, the dust and oil stains on the surface are removed by an ultrasonic cleaning machine in an alcohol solution;

(2) Fixing the vibration exciter on the sample to be treated, and the exciter is connected to the controller through the motor cable;

(3) placing the sensor on the surface of the metal substrate sample, fixed to the sample through a magnet at the bottom thereof, and the sensor is connected to the controller through a shielded cable;

(4) mounting the metal matrix sample on the loading platform of the combined process device, and supporting the sample with a rubber pad, and then superimposing the center of the laser beam spot on the upper left corner of the surface to be impacted as the starting position of the impact strengthening treatment;

(5) A special aluminum foil with a thickness of 0.10-0.12mm is used as the absorption layer, which is attached to the surface to be impacted on the surface of the sample, and then sprayed water onto the surface of the metal substrate by a water spray device to form a liquid constraint with a thickness of 1 to 2 mm. Floor;

(6) The controller transmits and displays the signal transmitted from the sensor, monitors the amplitude value of the sample, and adjusts the vibration frequency to control the amplitude value between 10 μm and 50 μm, and remains unchanged;

(7) Setting the output power and spot parameters of the laser through the laser control device, turning on the laser, controlling the movement of the sample loading platform by the robot control system by the method of progressive processing, and performing large-area laser bonding on the impact region of the metal sample. Impact strengthening treatment;

In the step (1), the metal surface is ground to clean the dust and oil on the surface to ensure the smoothness of the surface of the base sample and improve the laser lap impact strengthening efficiency.

In the step (2), the vibration exciter is composed of a DC motor driving an eccentric rotating mechanism with adjustable eccentricity, and is an excitation source of the vibration aging process, and its function is to cause vibration of the workpiece and apply dynamic stress to the workpiece. .

In the step (4), the sample supported by the rubber pad mainly acts as a vibration isolation to reduce the energy loss of the vibration system.

In the step (6), the vibration frequency control range is 20 Hz to 120 Hz.

In the step (7), the single-pulse Nd:YAG laser used by the laser has the following operating parameters: a wavelength of 1064 nm, a pulse width of 5-10 ns, a single pulse energy of 1.5-10 J, a spot radius of 1-3 mm, and a spot lap rate. It is 50%.

The technical effect of the invention: the invention performs large-area laser lap impact strengthening treatment on the surface of the metal component with the aid of the vibration aging treatment, and the vibration causes the surface layer crystal grains to be refined or even nano-sized under the irradiation of the metal surface of the laser beam, Under the action of temperature field, the vibration reduces the thermal stress field gradient, so the residual stress inside the material is uniformized, the laser impact causes severe plastic deformation on the metal surface, and high residual compressive stress is induced in the impact region, which is significantly improved. The mechanical properties of the metal members strengthen the metal surface, thereby effectively improving the fatigue life of the metal members and preventing the initiation and expansion of fatigue cracks.

DRAWINGS

Figure 1 is a schematic view of a vibration aging treatment apparatus of the present invention.

In the figure: 1. Sample, 2. Rubber pad, 3. Exciter, 4. Motor cable, 5. Sensor, 6. Shielded cable, 7. Controller.

detailed description

The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

The sample base material used in this embodiment is 304 stainless steel, and its geometrical dimension is 60 mm × 30 mm × 10 mm.

An example of processing a sample using the above-described strengthening method, the steps of which are:

(1) After the sample to be processed is subjected to stepwise grinding treatment using metallographic sandpaper, the dust and oil stains on the surface are removed by an ultrasonic cleaning machine in an alcohol solution;

(2) Fixing the exciter 3 on the 304 stainless steel sample 1 to be processed, and the exciter 3 is connected to the controller 7 through the motor cable 4;

(3) The sensor 5 is placed on the surface of the 304 stainless steel sample, fixed to the sample by a magnet at the bottom thereof, and the sensor 5 is connected to the controller 7 through the shielded cable 6;

(4) The 304 stainless steel base sample 1 is mounted on the loading platform of the combined process device, and the sample is supported by the rubber pad 2, and then the center of the laser beam spot is coincident with the upper left corner of the impact surface of the base sample 1 as impact strengthening. Processing start position;

(5) Using a special aluminum foil with a thickness of 0.10 mm as an absorbing layer, attached to the surface to be impacted on the surface of the sample, and then spraying water onto the surface of the 304 stainless steel substrate by a water spray device to form a liquid constraining layer having a thickness of 1 mm;

(6) The signal transmitted from the sensor 5 is processed and displayed by the controller 7, the amplitude value of the sample is monitored, the vibration frequency is adjusted to 60 Hz, and the amplitude of the sample is controlled to 25 μm, and remains unchanged;

(7) Set the laser output power and spot parameters through the laser control device: wavelength 1064nm, pulse width 10ns, single pulse energy 5J, spot radius 2mm, spot overlap rate 50%, turn on the laser, use progressive processing method Control the movement of the sample loading platform by the robot control system, and perform large-area laser lap impact strengthening treatment on the area to be impacted of the 304 stainless steel base sample 1;

In this example, the surface mechanical properties of the 304 stainless steel sample were tested and compared with those before the treatment. The results show that a good residual compressive stress distribution is formed on the surface of the sample, the maximum residual compressive stress reaches -758 MPa, the residual compressive stress layer depth is about 0.6 mm, the surface hardness is increased by 43%, and the service life ratio of the workpiece treated by the process is Increased by more than 35% before strengthening.

Claims (8)

1. A surface enhancement method for vibration-assisted laser shock treatment of a metal member, characterized in that: excitation by a vibration exciter is used, and the sensor picks up vibration, and by controlling the vibration frequency, the amplitude value is kept within a prescribed range, so that the metal member itself is finely grained. The material undergoes a slight plastic deformation, and the internal stress inside the material is relaxed and reduced. Under the aid of vibration aging treatment, the surface of the metal member is subjected to large-area laser lap impact strengthening treatment to cause more serious plastic deformation on the surface, and the surface layer is formed. The grains are further refined or even nano-sized, and high residual compressive stress is induced in the impact region, which significantly improves the mechanical properties of the metal members and strengthens the metal surface, thereby effectively improving the fatigue life of the metal members and preventing fatigue cracks. Start and expand.
2. A surface strengthening method for vibration-assisted laser shock treatment of a metal member according to claim 1, wherein the specific steps are as follows:

   (1) After the sample to be processed is subjected to stepwise grinding treatment using metallographic sandpaper, the dust and oil stains on the surface are removed by an ultrasonic cleaning machine in an alcohol solution;

   (2) Fixing the vibration exciter on the sample to be treated, and the exciter is connected to the controller through the motor cable;

   (3) placing the sensor on the surface of the metal substrate sample, fixed to the sample through a magnet at the bottom thereof, and the sensor is connected to the controller through a shielded cable;

   (4) mounting the metal matrix sample on the loading platform of the combined process device, and supporting the sample with a rubber pad, and then superimposing the center of the laser beam spot on the upper left corner of the surface to be impacted as the starting position of the impact strengthening treatment;

   (5) using aluminum foil as an absorbing layer, attached to the surface to be impacted on the surface of the sample, and then spraying water onto the surface of the metal substrate through a water spray device to form a liquid constraining layer;

   (6) The controller transmits and displays the signal transmitted from the sensor, monitors the amplitude value of the sample, and adjusts the vibration frequency to control the amplitude value between 10 μm and 50 μm, and remains unchanged;

   (7) Setting the output power and spot parameters of the laser through the laser control device, turning on the laser, controlling the movement of the sample loading platform by the robot control system by the method of progressive processing, and performing large-area laser bonding on the impact region of the metal sample. Impact strengthening treatment;

   (8) During the laser shock strengthening process, the stable low amplitude vibration is always maintained.
3. The surface strengthening method for vibration-assisted laser shock treatment of a metal member according to claim 2, wherein in the step (1), the metal surface is ground, and the dust and oil on the surface are cleaned to ensure the substrate. The flatness of the surface of the sample improves the laser lap impact strengthening efficiency.
4. The surface strengthening method for a vibration-assisted laser shock-treated metal member according to claim 2, wherein in the step (2), the exciter is driven by a DC motor to rotate an eccentricity of an adjustable eccentricity The mechanism composition is the excitation source of the vibration aging process. Its function is to cause the workpiece to vibrate and apply dynamic stress to the workpiece.
5. The surface strengthening method for a vibration-assisted laser shock-treated metal member according to claim 2, wherein the step of supporting the sample with the rubber pad in the step (4) mainly acts as a vibration isolation mechanism to reduce the energy of the vibration system. loss.
6. The surface strengthening method for a vibration-assisted laser shock-treated metal member according to claim 2, wherein the laser shock-strengthening absorption layer in the step (5) is a special aluminum foil having a thickness of 0.10-0.12 mm; The thickness of the constraining layer is 1 to 2 mm.
7. The surface strengthening method for a vibration-assisted laser shock-treated metal member according to claim 2, wherein the vibration frequency control range in the step (6) is 20 Hz to 120 Hz.
8. The surface strengthening method for a vibration-assisted laser shock-treated metal member according to claim 2, wherein the single-pulse Nd:YAG laser used in the step (7) has an operating parameter of: a wavelength of 1064 nm, a pulse The width is 5-10ns, the single pulse energy is 1.5-10J, the spot radius is 1-3mm, and the spot overlap rate is 50%.

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