CN113740319B - Nondestructive implementation method for laser-induced breakdown spectroscopy component detection and application thereof - Google Patents

Abstract

The invention relates to the technical field of material microscopic information monitoring and detection, in particular to a non-destructive realization method and application of laser-induced breakdown spectrum component detection. In order to solve the ablation damage caused by the laser-induced breakdown spectroscopy detection in the existing atmospheric environment, the laser-induced breakdown spectroscopy detection in the underwater environment is due to the ionization loss of the laser beam energy by liquid water and the impact of liquid water on the spectrum. Significant weakening of signal propagation reduces test accuracy and reliability. The present invention proposes a non-destructive implementation method and application of laser-induced breakdown spectrum component detection. A new method of constrained improvement, using pulsed laser shock strengthening effect to effectively compensate the lossy results of laser-induced breakdown spectroscopy, so as to realize "non-destructive" detection of laser-induced breakdown spectrum components.

Description

Non-destructive Realization Method and Application of Laser Induced Breakdown Spectroscopy Component Detection

technical field

The invention relates to the technical field of material microscopic information monitoring and detection, in particular to a non-destructive realization method and application of laser-induced breakdown spectrum component detection.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

Laser-induced breakdown spectroscopy (LIBS) technology focuses ultrashort pulse laser on the surface of the sample to form plasma, and then analyzes the plasma emission spectrum to determine the material composition and content of the sample. After the ultrashort pulse laser is focused, the energy density is high, and it can excite samples in any state of matter (solid, liquid, gas) to form plasma. LIBS technology (in principle) can analyze samples in any state of matter, only by the power of the laser and Sensitivity and wavelength range limitations of spectrographs & detectors.

Laser-induced breakdown spectroscopy in an atmospheric environment is a destructive means of testing material composition. Laser-induced breakdown spectroscopy technology uses the spectral signal formed by the ablation of the surface of the material to be detected caused by laser pulses, and quantitatively characterizes the information such as the type and concentration of elements on the surface of the material. Since the premise of laser-induced breakdown spectroscopy to generate spectral signals is the ablation of the area to be detected on the surface of the material, and the ablation effect has an adverse effect on the surface quality of the material, so this technology is essentially a destructive testing method.

Since the laser pulse can form a more significant plasma impact effect under the action of confined materials such as liquid water, and this physical process can make the surface of the material subject to obvious impact pressure, the laser-induced breakdown spectrum detection in the underwater environment can be It produces a strengthening effect on the surface of the material while analyzing the composition.

However, the inventors found that the laser-induced breakdown spectroscopy technology in the underwater environment has greatly reduced the precision and accuracy of spectral analysis due to the increased difficulty of spectral signal acquisition and other reasons, and its application limitations are obvious.

Contents of the invention

In order to solve the ablation damage caused by the laser-induced breakdown spectroscopy detection in the existing atmospheric environment, the laser-induced breakdown spectroscopy detection in the underwater environment is due to the ionization loss of the laser beam energy by liquid water and the impact of liquid water on the spectrum. Significant weakening of signal propagation reduces the problem of test accuracy and reliability. The present invention proposes a non-destructive implementation method and application of laser-induced breakdown spectrum component detection. Through the laser-induced breakdown spectrum test process in the atmospheric environment The new method of constrained improvement enables the laser pulse to form a spectral signal on the surface of the material while introducing strengthening effects such as residual compressive stress distribution and microstructure evolution. The invention adopts the shock strengthening effect of the pulsed laser to effectively compensate the lossy result of the laser-induced breakdown spectrum, thereby realizing "non-destructive" detection of the laser-induced breakdown spectrum components.

Specifically, the present invention is achieved through the following technical solutions:

In the first aspect of the present invention, a non-destructive implementation method of laser-induced breakdown spectral component detection is provided, including:

Step 1: Adjust the thickness of the constrained layer on the surface of the material to be detected;

Step 2: Adjust the relative distance between the focus position of the laser beam and the surface of the material;

Step 3: The focus position of the laser beam is above the confinement layer on the surface of the material;

Step 4: Use laser detection technology to detect the composition of the material to be tested.

The second aspect of the present invention provides a material prepared by a non-destructive method for detecting laser-induced breakdown spectral components.

The third aspect of the present invention provides an application of a non-destructive implementation method of laser-induced breakdown spectrum component detection in the field of material surface component analysis and/or material testing methods.

The above one or more technical solutions have the following beneficial effects:

1) Reasonably adjust the thickness of the confinement layer on the surface of the material to be detected to restrain the plasma expansion, and set the defocus state of the laser pulse irradiating the material surface, so that the material surface can simultaneously form a spectrum representing chemical element information The signal and the modification effect of strengthening the mechanical properties of a certain layer depth on the surface of the material.

2) Before implementing the composition detection work, apply a water constrained layer on the surface of the material, and the thickness of the constrained layer is 0.5mm to 1mm. The constrained layer of this thickness can produce a confinement effect on the high temperature and high pressure plasma on the surface of the material, and can avoid the confinement layer Excessive loss of laser energy during beam propagation.

3) Before implementing the component detection work, adjust the relative distance between the focus position of the laser beam and the surface of the material, so that the focus position of the laser beam is above the coated water layer on the surface of the material, that is, the pulsed laser beam is at a positive distance from the surface of the material to be tested. focus state, and the defocus amount is greater than the thickness of the water layer. The positive defocus state can reduce material surface ablation, and the positive defocus amount is greater than the thickness of the water layer, which can also avoid the occurrence of cavitation effect in the water environment and reduce the loss of laser energy in the propagation path.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. Below, describe embodiment of the present invention in detail in conjunction with accompanying drawing, wherein:

Fig. 1 is the schematic diagram of laser-induced breakdown spectrum detection under the atmospheric environment of Experimental Example 1 of the present invention;

Fig. 2 is a schematic diagram of laser-induced breakdown spectrum detection under the underwater environment of Experimental Example 2 of the present invention;

Fig. 3 is a schematic diagram of the material composition test of "non-destructive" laser-induced breakdown spectroscopy in Example 1 of the present invention;

Among them: 1. Laser, 2. Mirror, 3. Focusing mirror, 4. Spectrometer, 5. Optical fiber, 6. Receiving head, 7. Material to be tested, 8. Focus position of laser beam, 9. Underwater environment, 10. Water-restricting layer.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. For the experimental methods without specific conditions indicated in the following examples, usually follow the conventional conditions or the conditions suggested by the manufacturer.

It should be noted that the terminology used herein is only for describing specific embodiments, and is not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

It should be understood that the orientation or positional relationship indicated by the terms "upper", "lower" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying Any device or element must have a specific orientation, be constructed and operate in a specific orientation and therefore should not be construed as limiting the invention.

In the existing detection method of using the physical principle of laser-induced breakdown spectroscopy to analyze the chemical element composition of the material surface, the detection of laser-induced breakdown spectroscopy in the atmospheric environment will inevitably cause ablation damage to the surface of the material, while the underwater environment In the laser-induced breakdown spectroscopy detection, the test accuracy and reliability are reduced due to the ionization loss of the laser beam energy by liquid water and the significant weakening of the spectral signal propagation by liquid water.

Therefore, the present invention proposes a non-destructive realization method and its application of laser-induced breakdown spectrum component detection. By constraining the new method of improving the laser-induced breakdown spectrum test process in the atmospheric environment, the laser pulse is formed on the surface of the material. At the same time as spectral signals, enhancement effects such as residual compressive stress distribution and microstructure evolution are introduced. The invention adopts the shock strengthening effect of the pulsed laser to effectively compensate the lossy result of the laser-induced breakdown spectrum, thereby realizing "non-destructive" detection of the laser-induced breakdown spectrum components.

Specifically, the present invention is achieved through the following technical solutions:

In the first aspect of the present invention, a non-destructive implementation method of laser-induced breakdown spectral component detection is provided, including:

Step 1: Adjust the thickness of the constrained layer on the surface of the material to be detected;

Step 2: Adjust the relative distance between the focus position of the laser beam and the surface of the material;

Step 3: The focus position of the laser beam is above the confinement layer on the surface of the material;

Step 4: Use laser detection technology to detect the composition of the material to be tested.

The physical method and principle adopted in the present invention are as follows: rationally adjust the thickness of the confinement layer on the surface of the material to be detected to restrain the expansion of the plasma, and set the defocus state of the laser pulse irradiating the surface of the material, so that the surface of the material It can simultaneously form the spectral signal representing the information of chemical elements and the modification effect of strengthening the mechanical properties of a certain layer depth on the surface of the material. One or more embodiments of the present invention require technicians to coat the surface of the material with a confinement layer before implementing composition detection. The confinement layer can produce a confinement effect on the high-temperature and high-pressure plasma on the surface of the material, and can avoid the confinement layer from affecting the beam propagation process. Excessive loss of laser energy in the medium; one or more embodiments of the present invention adjust the relative distance between the laser beam focus position and the material surface before implementing the composition detection work, so that the laser beam focus position is above the coated constrained layer on the material surface , that is, the pulsed laser beam is in a positive defocus state relative to the surface of the material to be detected, and the defocus amount is greater than the thickness of the constrained layer. Experiments have found that the positive defocus state can not only reduce the ablation of the material surface, but the positive defocus amount is greater than the thickness of the constrained layer, which can also avoid the cavitation effect in the water environment and reduce the loss of laser energy in the propagation path.

In the process of atmospheric environment detection, the surface of the material must be directly irradiated by laser light, and surface ablation must exist. Therefore, it is necessary to propose a new method to compensate for this damage. In the laser spectral composition testing process of the principle of laser thermal induction, the laser force effect is introduced, which is mainly aimed at the optimization and improvement of the material testing method. The parameters such as the thickness of the constrained layer in the present invention are specially adjusted. It is only proposed for the damage problem in the process of laser spectral composition testing.

In one or more embodiments of the present invention, the thickness of the constrained layer is 0.5 mm to 1 mm. Experiments have found that a constrained layer of this thickness can confine the high-temperature and high-pressure plasma on the surface of the material, and can prevent the water layer from propagating the beam. Excessive loss of laser energy during the process.

In one or more embodiments of the present invention, the constrained layer includes a water layer flowing on the surface of the material to be detected and/or a transparent container is arranged on the surface of the material to be detected, and the transparent container is filled with deionized water.

In one or more embodiments of the present invention, the order of the first step and the second step can be adjusted or performed simultaneously.

In one or more embodiments of the present invention, the method for adjusting the relative distance between the focus position of the laser beam and the material surface includes but is not limited to adjusting the relative distance between the laser emitting device and the surface of the sample to be tested, or adjusting the parameters of the external optical path system to Change the focus position of the laser beam to meet the requirements of the test conditions for changing the focus position of the laser beam.

In one or more embodiments of the present invention, the laser beam is in a positive defocus state relative to the surface of the material to be detected, and the defocus amount is greater than the thickness of the constrained layer.

Preferably, the constrained layer has a thickness of 0.7 mm to 0.8 mm, and the positive defocus of the laser beam relative to the material surface is 0.9 mm. Under the condition of this parameter, the ablation area of the material after the laser detection detection process is introduced into the surface residual compressive stress of -260MPa. The introduction of residual compressive stress is an important factor to improve the service performance of materials.

In one or more embodiments of the present invention, the laser detection process parameters are: the laser pulse wavelength is 1064 nm, the energy is 50 mJ, and the pulse width is 9 ns.

In one or more embodiments of the present invention, the method for setting the thickness of the constrained layer includes, but is not limited to: selecting a plastic hose for fixed-point spraying at the location to be detected, and adjusting the thickness of the constrained layer.

In one or more embodiments of the present invention, the material to be detected is selected from metals and/or non-metals.

In some embodiments, the material to be detected is a stainless steel material, and after the component detection result of the material to be detected is obtained, residual stress detection is performed on the ablation position of the laser detection area. The results show that the surface residual compressive stress is introduced into the ablation area of the material after detection using the method described in the embodiment of the present invention. The introduction of residual compressive stress is an important factor to improve the service performance of materials.

The main application object of the method of the present invention refers to that the existing laser-induced breakdown spectroscopy method can detect its composition, but the higher surface quality and mechanical performance requirements conflict with the surface ablation generated during the detection process. Therefore, there is an urgent need to seek materials to be tested that can lead to "low surface ablation degree" and enhance "surface mechanical properties". In some more specific implementations:

1. Build the existing conventional laser-induced breakdown spectroscopy material composition detection device.

This step requires technicians to determine the laser-induced breakdown spectroscopy detection process of the material to be tested, and to build a corresponding device.

By default, the detection device is based on the existing relevant detection work and data. The laser component detection equipment for the material to be detected is already available, but the existing detection means can cause obvious ablation of the material surface. The detection principle of the laser component detection equipment is the laser-induced breakdown spectroscopy method. The determined process parameters of the detection process include the pulse laser wavelength, energy, pulse width, etc. of the emitted laser pulse signal, and also include the spectrometer receiving the spectral signal Related instrument setting parameters, etc.

2. Adjust the linear distance between the laser beam emitting device of the existing device determined in step 1 and the position to be detected on the surface of the material.

This step requires technicians to determine in advance the process plan that the laser beam is in a positive defocus state relative to the surface of the material to be inspected, and the relevant operations are based on the fact that the technician has determined that the laser beam and the surface of the material to be inspected need to maintain a positive defocus based on quantitative values. Technicians are required to adjust the non-defocused state of the laser beam in the existing laser detection method to a positive defocused state. The specific method is to increase the linear distance between the laser beam emitting device of the existing device and the position to be detected on the surface of the material.

In the actual operation process, technicians can adjust the position of the material to be detected to carry out the corresponding test work, so that the material to be detected is far away from the laser beam emitting device, and the set distance is the positive defocus amount of the laser beam to be set.

3. Coating the water confinement layer on the area to be tested of the material to be tested.

This step requires technicians to pre-set a flowing water confinement layer with a fixed thickness on the surface of the material to be detected before the laser detection work starts.

It should be pointed out that this step is based on the technical personnel having determined the specific thickness of the water-constrained layer to be used. The thickness of the water-constrained layer needs to be set at the same time as the specific value of the positive defocus of the laser beam relative to the surface of the material described in step 2. The specific value needs to be greater than the thickness of the water-constrained layer.

The second aspect of the present invention provides a material prepared by a non-destructive method for detecting laser-induced breakdown spectral components.

The third aspect of the present invention provides an application of a non-destructive implementation method of laser-induced breakdown spectrum component detection in the field of material surface component analysis and/or material testing methods.

The present invention will be described in further detail below in conjunction with specific examples. It should be pointed out that the specific examples are to explain rather than limit the present invention.

Experimental example 1

As shown in Figure 1, it is a schematic diagram of a laser-induced breakdown spectroscopy detection device in an atmospheric environment disclosed in this experimental example. In this method, 1 is a laser, 2 is a reflector, 3 is a focusing mirror, and 4 is a spectrometer. 5 is the optical fiber, 6 is the receiving head, 7 is the material to be tested, and 8 is the focusing position of the laser beam. The laser beam generated by the laser 1 is reflected by the mirror 2 and focused by the focusing mirror 3, and directly irradiates the surface of the material to be tested. In the process of forming ablation and material excitation effects, the other end of the laser 1 is connected to a spectrometer 4, and the spectrometer 4 collects spectral signals through the optical fiber 5 and the receiving head 6, and then analyzes information such as element types and composition content on the surface of the material. In the process, the laser beam focusing position 8 is on the material surface, that is, the laser beam is in a defocused state relative to the material surface.

In this experimental example, the laser-induced breakdown spectroscopy technology uses the spectral signal formed by the ablation of the surface of the material to be detected caused by the laser pulse, and quantitatively characterizes the element type and concentration on the surface of the material. Since the premise of laser-induced breakdown spectroscopy to generate spectral signals is the ablation of the area to be detected on the surface of the material, and the ablation effect has an adverse effect on the surface quality of the material, it is essentially a destructive testing method.

Take the detection of Ni element content in the Ni35+TiC laser cladding layer on the surface of a stainless steel material as an example. In this experimental example, the conventional test equipment and process conditions of laser-induced breakdown spectroscopy are used to detect the composition of the material to be tested. After obtaining the composition detection result of the material to be detected, the residual stress detection is performed on the ablation position of the laser detection area. The results show that the surface residual stress value of the ablation area of the material after detection and treatment by this method is 20MPa. The existence of residual tensile stress is one of the most likely causes of material failure during service.

Experimental example 2

As shown in Figure 2, it is a schematic diagram of a laser-induced breakdown spectroscopy detection device in an atmospheric environment disclosed in this experimental example. The difference from Experimental Example 1 is that the material 7 to be detected is completely located in the underwater environment 9, and the rest of the settings are similar to those of the experimental example. Example 1 is the same.

In this method, the laser beam passes through the underwater environment 9 to irradiate the surface of the material 7 to be detected, and in the process of forming ablation and material excitation effects, the spectrometer 4 collects spectral signals through the receiving head 6, and then analyzes the element types on the surface of the material and content of ingredients. In this process, the laser beam focus position 8 is on the material surface, that is, the laser beam is in a state of no defocus relative to the material surface; in addition, the propagation of the laser beam in water can cause laser energy loss, and the spectral signal is received through the water layer The weakening effect of the signal also occurs during the receiving process of the head, so the precision and accuracy of spectral analysis are greatly reduced.

Example 1

As shown in Figure 3, it is a schematic diagram of a laser-induced breakdown spectrum detection device in an atmospheric environment disclosed in this embodiment. The laser beam generated by the laser 1 is reflected by the reflector 2 and focused by the focusing mirror 3, and then passes through the water-confined layer. 10. During the process of irradiating the surface of the material to be tested and irradiating the surface of the material to be tested to form ablation and material excitation effects, the other end of the laser 1 is connected to a spectrometer 4, and the spectrometer 4 collects spectral signals through the optical fiber 5 and the receiving head 6. Then analyze the information such as the element type and composition content on the surface of the material. In the process, the laser beam focusing position 8 is above the water confinement layer 10 on the material surface, that is, the laser beam is in a positive defocus state relative to the material surface.

Using the method of this embodiment to carry out the laser-induced breakdown spectroscopy experiment:

Take the detection of Ni element content in the Ni35+TiC laser cladding layer on the surface of a stainless steel material as an example. The spectral line intensity of the laser-induced breakdown spectrum directly reflects the concentration of the elemental components of the material. In this embodiment, the content of the Ni element is reflected by detecting the spectral line intensity on the surface of the material. The test is carried out based on the conventional test equipment and process conditions of laser-induced breakdown spectroscopy. The laser pulse wavelength used is 1064nm, the energy is 50mJ, and the pulse width is 9ns. It is pre-set that the surface of the material to be tested needs to be coated with a water-constrained layer with a thickness of 0.7mm to 0.8mm, and the positive defocus of the laser beam relative to the material surface is 0.9mm; adjust the position of the material to be tested so that it is 0.9 away from the focus position of the laser beam mm; set a flowing deionized water layer at the location to be tested by spraying with a plastic hose, and keep the thickness of the water layer at 0.7mm to 0.8mm; use the above process conditions to perform component detection in the area to be tested.

After obtaining the composition detection result of the material to be detected, the residual stress detection is performed on the ablation position of the laser detection area. The results show that the surface residual compressive stress of -260MPa is introduced into the material ablation area after detection by this method. The introduction of residual compressive stress is an important factor to improve the service performance of materials.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still understand the foregoing embodiments The recorded technical solutions are modified, or some of the technical features are equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A non-destructive implementation method for laser-induced breakdown spectral component detection, characterized in that it comprises: Step 1: Adjust the thickness of the constrained layer on the surface of the material to be detected; Step 2: Adjust the relative distance between the focus position of the laser beam and the surface of the material; Step 3: The focus position of the laser beam is above the confinement layer on the surface of the material; Step 4: Use laser detection technology to detect the composition of the material to be tested; The thickness of the constrained layer is 0.7 mm to 0.8 mm; The positive defocus of the laser beam relative to the surface of the material is 0.9mm; The laser detection process parameters are: the laser pulse wavelength is 1064nm, the energy is 50mJ, and the pulse width is 9ns; The laser beam is in a positive defocus state relative to the surface of the material to be detected, and the defocus amount is greater than the thickness of the constrained layer. 2. The non-destructive realization method of laser-induced breakdown spectrum component detection according to claim 1, wherein the constrained layer includes a water layer flowing on the surface of the material to be detected and/or a transparent vessel is arranged on the surface of the material to be detected , the inside of the transparent container is filled with deionized water. 3. The non-destructive implementation method of laser-induced breakdown spectrum component detection according to claim 1, characterized in that the sequence of the first step and the second step can be adjusted or performed simultaneously. 4. The non-destructive implementation method of laser-induced breakdown spectral component detection according to claim 1, wherein the method for setting the thickness of the constrained layer comprises: selecting a plastic hose to spray at a fixed point at the position to be detected, and adjusting the thickness of the constrained layer. 5. The non-destructive implementation method of laser-induced breakdown spectrum component detection according to claim 1, wherein the material to be detected is selected from metals and/or non-metals. 6. The material prepared by the non-destructive realization method of laser-induced breakdown spectroscopy component detection according to any one of claims 1 to 5. 7. The application of the non-destructive realization method of laser-induced breakdown spectrum component detection according to any one of claims 1 to 5 in the field of material surface component analysis and/or material testing methods.

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