Test method for testing residual stress of coating

Abstract

The invention provides a test method for testing the residual stress of a coating, aiming at the particularity of the coating and the problems existing in actual detection, the composition and phase analysis of the coating are researched, and the test method for testing the residual stress of the coating by applying different X-ray diffraction emission sources is established. Therefore, in the residual stress test of the coating, in addition to basic preparatory work including component analysis and phase analysis, 2 theta angle conversion between different ray sources, namely diffraction characteristics of the different ray sources, is carried out according to the Bragg law, then an X-ray stress constant is further calculated, a residual stress calculation formula is imported, and the residual stress of the coating is calculated. And establishing a residual stress database. The method has the advantages that the residual stress value is calculated by applying physical characteristics of different emission ray sources according to component composition and phase analysis of the coating, the test requirement of the X-ray diffractometer can be flexibly met, the residual stress test of the coating with different components can be met, and the practical value is very high.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, and in particular to a test method for testing residual stress of a coating. Background Art

[0002] Coatings are very different from metal materials in composition, organization, and performance. They have special intrinsic structural characteristics such as special holes, oxides, unmelted particles, microcracks, and layered anisotropy. The surface is rough, and its chemical composition is complex. There are non-metallic chemical elements in the composition. Therefore, the test method for residual stress testing of coatings is relatively complicated. The residual stress of metal materials can be obtained by X-ray diffraction detection using standard methods, while the residual stress of coatings must first know its composition and phase analysis, and then combine the characteristics of the emitting ray source to select the best test method, or solve the calculation through ray source conversion to obtain the measured value. Summary of the invention

[0003] The purpose of the present invention is to solve the detection problem of coating residual stress test, establish a new test method, fill the detection gap in this aspect, meet the detection needs of scientific research and production, and provide a test method for coating residual stress test.

[0004] The present invention provides a test method for residual stress testing of coatings. In view of the particularity of coatings and the problems existing in actual testing, the composition and phase analysis of coatings are studied with reference to the GJB10056 standard, and a test method for testing residual stress of coatings using different X-ray diffraction emission sources is established. Therefore, in the residual stress test of coatings, in addition to basic preparation work, including component analysis and phase analysis, the 2θ angle conversion between different ray sources, i.e., the diffraction characteristics of different ray sources, is also performed according to the Bragg law, and the X-ray stress constant is further calculated, the residual stress calculation formula is introduced, and a residual stress database is established, which is a key technology for testing residual stress of coatings.

[0005] Detailed description of technical solution:

[0006] a. Determination of coating composition

[0007] The coating composition is determined by energy spectrum analysis to determine the proportion of each element in the composition.

[0008] b. Coating phase analysis

[0009] X-ray diffractometer is used for phase analysis of coating to determine the phase components present in the coating and their proportions, and the phase with the strongest diffraction signal is selected as the preferred phase analysis.

[0010] c. Determination of coating residual stress

[0011] The X-ray diffraction method is used, based on Bragg's law: 2d Sinθ=nλ, to convert the diffraction angle 2θ of different target sources into a relationship with the microscopic crystal plane spacing d. Then, based on Bragg's law and elasticity theory, it can be derived that the stress value σ is proportional to the slope M of 2θ changing with Sin2ψ. The macroscopic stress, i.e., residual stress, can be inferred from the lattice strain measured by the X-ray method.

[0012] Where: σ = K·M;

[0013]

[0014] d. Use Mn, Cr, and Ti emission targets to convert residual stress values

[0015] According to Bragg's law: 2d Sinθ=nλ, the Sinθ values ​​of different target sources, including Mn target, Cr target, and Ti target, are converted according to d and λ obtained from phase analysis, and then the corresponding 2θ is obtained. Then the X-ray stress constant is calculated, the residual stress formula is imported, a database is established, and the residual stress value of the test is obtained.

[0016] Coating residual stress test process:

[0017] Prepare substrate test pieces (GH4169 material) with specifications of 15*1.5*70mm, sandblast the substrate test pieces, perform atmospheric plasma spraying coating on the substrate test pieces with a thickness of 1.5mm, cut and prepare coating test pieces, determine the coating composition, analyze the coating phase, calculate the K value, calculate the M value, calculate the Sinθ value and 2θ of different emission sources, and calculate the stress value σ using Bragg's law and elasticity theory.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The test method for residual stress testing of coatings described in the present invention calculates the residual stress value based on the component composition and phase analysis of the coating, and utilizes the physical characteristics of different emitting radiation sources to flexibly meet the testing requirements of an X-ray diffractometer and the residual stress testing of coatings with different components, and has great practical value. DETAILED DESCRIPTION

[0020] The present invention will be further explained below in conjunction with specific implementation schemes, but the present invention is not limited thereto.

[0021] This embodiment provides a test method for residual stress testing of coatings. In view of the particularity of coatings and the problems existing in actual testing, the composition and phase analysis of coatings are studied with reference to the GJB10056 standard, and a test method for testing residual stress of coatings using different X-ray diffraction emission sources is established. Therefore, in the residual stress test of coatings, in addition to basic preparations, including component analysis and phase analysis, the 2θ angle conversion between different ray sources, i.e., the diffraction characteristics of different ray sources, is also performed according to the Bragg law. Further calculation of X-ray stress constants, introduction of residual stress calculation formulas, and establishment of a residual stress database are key technologies for testing residual stress of coatings.

[0022] Detailed description of the technical solution:

[0023] a. Determination of coating composition

[0024] The coating composition is determined by energy spectrum analysis to determine the proportion of each element in the composition.

[0025] b. Coating phase analysis

[0026] X-ray diffractometer is used for phase analysis of coating to determine the phase components present in the coating and their proportions, and the phase with the strongest diffraction signal is selected as the preferred phase analysis.

[0027] c. Determination of coating residual stress

[0028] The X-ray diffraction method is used, based on Bragg's law: 2d Sinθ=nλ, to convert the diffraction angle 2θ of different target sources into a relationship with the microscopic crystal plane spacing d. Then, based on Bragg's law and elasticity theory, it can be derived that the stress value σ is proportional to the slope M of 2θ changing with Sin2ψ. The macroscopic stress, i.e., residual stress, can be inferred from the lattice strain measured by the X-ray method.

[0029] Where: σ = K·M;

[0030]

[0031] d. Use Mn, Cr, and Ti emission targets to convert residual stress values

[0032] According to Bragg's law: 2d Sinθ=nλ, the Sinθ values ​​of different target sources, including Mn target, Cr target, and Ti target, are converted according to d and λ obtained from phase analysis, and then the corresponding 2θ is obtained. Then the X-ray stress constant is calculated, the residual stress formula is imported, a database is established, and the residual stress value of the test is obtained.

[0033] Coating residual stress test process:

[0034] Prepare substrate test pieces (GH4169 material) with specifications of 15*1.5*70mm, sandblast the substrate test pieces, perform atmospheric plasma spraying coating on the substrate test pieces with a thickness of 1.5mm, cut and prepare coating test pieces, determine the coating composition, analyze the coating phase, calculate the K value, calculate the M value, calculate the Sinθ value and 2θ of different emission sources, and calculate the stress value σ using Bragg's law and elasticity theory.

[0035] Matters not covered by the present invention are known technologies.

[0036] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A test method for residual stress testing of coatings, characterized in that: The process is as follows: a. Determination of coating composition; The coating composition is determined by energy spectrum method to determine the proportion of each element in the composition; b. Phase analysis of coating; For the phase analysis of the coating, an X-ray diffractometer is used to determine the phase components in the coating and their proportions. The phase with the strongest diffraction signal is selected as the preferred phase analysis. c. Determination of residual stress of coating; Using X-ray diffraction method, based on Bragg's law: 2d Sinθ=nλ, the relationship between the diffraction angle 2θ of different target sources and the microscopic crystal plane spacing d is established. Then, according to Bragg's law and elastic theory, it can be derived that the stress value σ is proportional to the slope M of 2θ changing with Sin2ψ. The macroscopic stress, i.e. residual stress, can be deduced from the lattice strain measured by X-ray method. Where: σ = K·M; d. Use Mn, Cr, and Ti emission target sources to convert residual stress values; According to Bragg's law: 2d Sinθ=nλ, the Sinθ values ​​of different target sources, including Mn target, Cr target, and Ti target, are converted according to d and λ obtained from phase analysis, and then the corresponding 2θ is obtained. Then the X-ray stress constant is calculated, the residual stress formula is imported, a database is established, and the residual stress value of the test is obtained.

2. The test method for coating residual stress testing according to claim 1, characterized in that: The testing process of the residual stress value is as follows: preparing a substrate test piece, the material is GH4169, the specification is 15*1.5*70mm, the substrate test piece is sandblasted, the atmospheric plasma spraying coating is performed on the substrate test piece, the thickness is 1.5mm, the coating test piece is cut to prepare, the coating composition is determined, the coating phase is analyzed, the K value is calculated, the M value is calculated, the Sinθ value of different emission sources, the 2θ calculation, and the stress value σ is calculated using the Bragg law and the elastic theory.

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