阅读说明：本技术 基于电磁感应原理的涂层结合强度评估方法 (Coating bonding strength evaluation method based on electromagnetic induction principle ) 是由 崔崇 肖德铭 郑相锋 陶业成 于 2020-06-19 设计创作，主要内容包括：本发明公开了一种基于电磁感应原理的涂层结合强度评估方法,该方法包括以下步骤：测定带涂层样品的饱和磁滞回线；提取其特征参数,其中,特征参数包括Mr、Hc、μ、不可逆磁导率；检测、评估涂层的结合强度。通过该方法,采用无损检测的方法评估涂层与基材结合强度；采用了基于电磁感应原理的方法,实现了涂层结合强度评估；本发明方法不需要耦合剂,对样品表面状态不敏感,样品有油污、灰渣等均不影响检测,并且仪器测头可以提离表面3-5mm左右。(The invention discloses a coating bonding strength evaluation method based on an electromagnetic induction principle, which comprises the following steps of: determining the saturation hysteresis loop of the coated sample; extracting characteristic parameters of the magnetic resonance imaging device, wherein the characteristic parameters comprise Mr, Hc, mu and irreversible permeability; and detecting and evaluating the bonding strength of the coating. By the method, the bonding strength of the coating and the base material is evaluated by adopting a nondestructive testing method; the method based on the electromagnetic induction principle is adopted, so that the coating bonding strength is evaluated; the method of the invention does not need a coupling agent, is not sensitive to the surface state of the sample, the sample has oil stain, ash residue and the like, which do not affect the detection, and the measuring head of the instrument can be lifted to about 3-5mm away from the surface.)

1. The method for evaluating the bonding strength of the coating based on the electromagnetic induction principle is characterized by comprising the following steps of:

s1: determining the saturation hysteresis loop of the coated sample;

s2: extracting characteristic parameters of the magnetic resonance imaging device, wherein the characteristic parameters comprise Mr, Hc, mu and irreversible permeability;

s3: and detecting and evaluating the bonding strength of the coating.

2. The method for evaluating the bonding strength of a coating according to claim 1, wherein Mr is a residual magnetism in step S2.

3. The method for evaluating the bonding strength of a coating based on the electromagnetic induction principle as claimed in claim 1, wherein Hc is a coercive force in step S2.

4. The method for evaluating the bonding strength of a coating based on the electromagnetic induction principle as claimed in claim 1, wherein μ reversible magnetic permeability in said step S2.

5. The method for evaluating the bonding strength of a coating based on the electromagnetic induction principle as claimed in claim 1, wherein said step S3 further comprises: substituting the parameters extracted in the step S2 into a combined function expression.

6. The method for evaluating the bonding strength of a coating based on the electromagnetic induction principle as claimed in claim 5, wherein the combinatorial function expression is Q = f (μ, Hc).

7. The method of claim 5, wherein the parameters substituted into the combinatorial function expression are μ and Hc.

8. The method for evaluating the bonding strength of a coating based on the electromagnetic induction principle as claimed in claim 5, wherein the step of creating the combined functional expression comprises the steps of:

preparing a series of coating samples with different bonding strengths by adopting regularly-changed thermal spraying process parameters;

accurately measuring the tensile strength of each sample through experiments, and obtaining the bonding strength value of each sample;

measuring the saturated magnetic hysteresis loop of each coating sample by adopting an instrument manufactured based on the electromagnetic induction principle, and extracting characteristic parameters of reversible magnetic permeability mu and magnetic coercive force Hc;

the combined function f (mu, Hc) of mu and Hc is constructed by multivariate statistical regression analysis to make the function value equal to the measured binding strength value Q.

9. The method of claim 6, wherein Q is a bonding strength value.

10. The method for evaluating the bonding strength of a coating based on the electromagnetic induction principle as claimed in claim 8, wherein the experiment is a mechanical tensile experiment.

Technical Field

The invention relates to the technical field of coating evaluation, in particular to a coating bonding strength evaluation method based on an electromagnetic induction principle.

Background

The thermal spraying technique is a surface strengthening technique, which is a technique of heating a metallic or non-metallic material in a powder or wire form to a molten or semi-molten state by using a certain heat source (such as an electric arc, plasma spraying or combustion flame, etc.), and then spraying the heated material onto a surface of a substrate to be pretreated at a certain speed by means of flame itself or compressed air, thereby depositing the heated material to form a surface coating having various functions.

Good bonding (high bond strength) between the thermal spray coating and the substrate material is the most important prerequisite for the coating to function. The bonding strength of the thermal spray coating and the substrate is mainly based on the mechanical embedding effect between the thermal spray coating and the substrate. The main factors influencing the bonding strength include the degree of closeness of the fit of the coating to the substrate surface and the residual stress in the coating. The tighter the mechanical engagement between the coating and the substrate, the smaller the residual stress in the coating is tensile stress or the larger the residual stress is compressive stress, the higher the bonding strength between the coating and the substrate.

The tensile strength between the coating and the substrate is generally measured as a value of the bonding strength by a mechanical stretching method. For samples which cannot be damaged or finished products with coatings, a good mode for evaluating the bonding strength does not exist at present, a good mode for evaluating a base material and a coating material with magnetic conductivity does not exist, or a coupling agent is needed, and when the samples have oil stains, ash residues and the like, the detection results are influenced.

Disclosure of Invention

In view of the above technical problems in the related art, the present invention provides a method for evaluating the bonding strength of a coating based on the electromagnetic induction principle, which can overcome the above disadvantages in the prior art.

In order to achieve the technical purpose, the technical scheme of the invention is realized as follows:

a method for evaluating the bonding strength of a coating based on the principle of electromagnetic induction, which comprises the following steps:

s1: determining the saturation hysteresis loop of the coated sample;

s2: extracting characteristic parameters of the magnetic resonance imaging device, wherein the characteristic parameters comprise Mr, Hc, mu and irreversible permeability;

s3: and detecting and evaluating the bonding strength of the coating.

Further, in step S2, Mr is remanence.

Further, in step S2, Hc is a coercive force.

Further, in step S2, μ has a reversible magnetic permeability.

Further, the step S3 further includes: substituting the parameters extracted in the step S2 into a combined function expression.

Further, the combinatorial function expression is Q = f (μ, Hc).

Further, the parameters substituted into the combinatorial function expression are μ and Hc.

Further, the step of creating a combined functional expression comprises the steps of:

preparing a series of coating samples with different bonding strengths by adopting regularly-changed thermal spraying process parameters;

accurately measuring the tensile strength of each sample through experiments, and obtaining the bonding strength value of each sample;

measuring the saturated magnetic hysteresis loop of each coating sample by adopting an instrument manufactured based on the electromagnetic induction principle, and extracting characteristic parameters of reversible magnetic permeability mu and magnetic coercive force Hc;

the combined function f (mu, Hc) of mu and Hc is constructed by multivariate statistical regression analysis to make the function value equal to the measured binding strength value Q.

Further, Q is a bonding strength value.

Further, the experiment is a mechanical tensile experiment.

The invention has the beneficial effects that: by the method, the following effects are achieved:

(1) the bonding strength of the coating and the base material can be evaluated by adopting a nondestructive testing method without a destructive tensile test;

(2) the coating is suitable for base materials and coating materials with magnetic conductivity;

(3) the method based on the electromagnetic induction principle is adopted to realize the evaluation of the bonding strength of the coating, and specifically, the saturated magnetic hysteresis loop of a sample is measured and characteristic parameters of magnetic coercive force and magnetic permeability are extracted;

(4) the method of the invention does not need a coupling agent, is not sensitive to the surface state of the sample, the sample has oil stain, ash residue and the like, which do not affect the detection, and the measuring head of the instrument can be lifted to about 3-5mm away from the surface.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a block flow diagram of a method for evaluating bonding strength of a coating based on electromagnetic induction principle according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

As shown in fig. 1, the method for evaluating the bonding strength of a coating based on the electromagnetic induction principle according to an embodiment of the present invention includes the following steps:

s1: determining the saturation hysteresis loop of the coated sample;

s2: extracting characteristic parameters of the magnetic resonance imaging device, wherein the characteristic parameters comprise Mr, Hc, mu and irreversible permeability;

s3: and detecting and evaluating the bonding strength of the coating.

In a specific embodiment of the present invention, in the step S2, Mr is remanence.

In a specific embodiment of the present invention, in step S2, Hc is a coercivity.

In one embodiment of the present invention, in step S2, μ has reversible magnetic permeability.

Step S3 further includes: substituting the parameters extracted in the step S2 into a combined function expression.

In a specific embodiment of the present invention, the combinatorial function expression is Q = f (μ, Hc).

In one embodiment of the invention, the parameters substituted into the combinatorial function expression are μ and Hc.

The step of creating a combined functional expression comprises the steps of:

preparing a series of coating samples with different bonding strengths by adopting regularly-changed thermal spraying process parameters;

accurately measuring the tensile strength of each sample through experiments, and obtaining the bonding strength value of each sample;

measuring the saturated magnetic hysteresis loop of each coating sample by adopting an instrument manufactured based on the electromagnetic induction principle, and extracting characteristic parameters of reversible magnetic permeability mu and magnetic coercive force Hc;

the combined function f (mu, Hc) of mu and Hc is constructed by multivariate statistical regression analysis to make the function value equal to the measured binding strength value Q.

In one embodiment of the invention, Q is the bond strength value.

In a specific embodiment of the present invention, the experiment is a mechanical tensile experiment.

In a specific embodiment of the present invention, for a certain combination of a certain coating material a + a base material B, the specific technical implementation for implementing nondestructive testing for evaluating the bonding strength of the coating by using the technical solution mainly includes the following steps:

firstly, a characteristic function expression of the A + B material combination is created:

1) preparing A + B coating samples with different bonding strengths by adopting regularly-changed thermal spraying process parameters;

2) accurately measuring the tensile strength of each sample through a mechanical tensile experiment to obtain a bonding strength value of each sample;

3) measuring the saturated magnetic hysteresis loop of each coating sample by adopting an instrument manufactured based on the electromagnetic induction principle, and extracting characteristic parameters of magnetic permeability mu and magnetic coercive force Hc;

4) the combined function f (mu, Hc) of mu and Hc is constructed by multivariate statistical regression analysis to have a function value equal to the measured binding strength value.

And secondly, extracting characteristic parameters mu and Hc from a magnetic hysteresis loop actually measured on a certain coating sample to be evaluated, and substituting Q = f (mu, Hc) to obtain the coating bonding strength of the sample to be evaluated.

In order to facilitate understanding of the above-described aspects of the present invention, the above-described aspects of the present invention will be described in detail below.

The technical scheme of the invention is as follows: the saturation hysteresis loop of the coated sample is measured, and characteristic parameters (such as remanence Mr, coercive force Hc, reversible permeability, irreversible permeability and the like) of the sample are extracted to evaluate the bonding strength of the coating. The technical principle is expressed as follows:

when the mechanical interlocking of the coating is poor, a gap is generated between the coating material and the base material, and the magnetic permeability inside the gap is different from that of the coating and the base material. Thus, the coating is mechanically engaged with the substrate to a different degree, resulting in a change in the permeability of the material near the faying surface. The permeability is defined by formula (1):

μ = B / H (1)

in the formula: μ -permeability;

b-magnetic induction of the material;

h-the intensity of the externally applied magnetic field.

The process of measuring the hysteresis loop of the sample is that a magnetic field (represented by magnetic field strength H) with known magnitude is applied to the sample, after the sample passes through the sample (having the effect of preventing the conduction of the magnetic field and represented by magnetic permeability mu), the magnitude of the measured magnetic induction B is plotted, and the plotted B-H curve is the hysteresis loop. The tangential slopes (i.e., the reversible and irreversible permeability) of the hysteresis loop reflect the change in the permeability μ of the material.

When the residual stress inside the coating changes, the magnetic property parameters of the ferromagnet also change, and conversely, the ferromagnet also deforms under the action of a magnetic field, and the phenomenon (effect) that the magnetic forces are closely related to each other is generally called magnetostriction effect. Studies have shown that the presence of residual stress increases the value of coercivity Hc, the greater the residual stress, the greater the value of Hc.

From the above analysis, it can be known that the magnetic permeability (tangent slope) of one of the characteristic parameters of the hysteresis loop of the material is positively correlated with the tightness of the mechanical embedding between the coating and the substrate, and the two magnetic coercive forces of the characteristic parameter are positively correlated with the participating stress magnitude in the coating. Therefore, the evaluation of the bonding strength Q of the coating can be realized by measuring the hysteresis loop of the coating sample, extracting the characteristic parameters of the curve, namely the magnetic permeability mu and the magnetic coercive force Hc, and establishing the mathematical combination of the two parameters by a mathematical method, see formula (2).

Q = f (μ, Hc) (2)

In summary, with the above technical solution of the present invention, the following effects are achieved by the method: the bonding strength of the coating and the base material can be evaluated by adopting a nondestructive testing method without a destructive tensile test; the coating is suitable for base materials and coating materials with magnetic conductivity; the method based on the electromagnetic induction principle is adopted to realize the evaluation of the bonding strength of the coating, and specifically, the saturated magnetic hysteresis loop of a sample is measured and characteristic parameters of magnetic coercive force and magnetic permeability are extracted; the method of the invention does not need a coupling agent, is not sensitive to the surface state of the sample, the sample has oil stain, ash residue and the like, which do not affect the detection, and the measuring head of the instrument can be lifted to about 3-5mm away from the surface.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.