Method for measuring residual stress of pyrolytic carbon coating by virtue of X ray diffraction

Abstract

The invention relates to a method for measuring the residual stress of a pyrolytic carbon coating by virtue of X ray diffraction and solves the problem that no complete technique for measuring the residual stress of the pyrolytic carbon coating by virtue of an X ray diffraction method is issued currently. The method comprises the following specific steps: carrying out conventional X-ray detection on an experimental sample to obtain a full diffraction spectrum, and determining a maximal diffraction angle 2theta of a diffraction peak; setting a scanning starting angle, a scanning end angle, a scanning step, a scanning speed and a counting time, selecting six azimuth angles psi, measuring a crystal face diffraction angle 2thetapsi, corresponding to each azimuth angle psi, of the experimental sample, counting sin<2>psi corresponding to each azimuth angle psi, drawing a 2thetapsi-sin<2>psi dispersing graph, and fitting according to each discrete point so as to obtain a straight slope formula (described in specification); calculating a residual stress value formula (described in specification), wherein E represents elasticity modulus of the experimental sample, v represents Poisson's ratio of the experimental sample, and theta0 is a half-crystal face diffraction angle when the experimental sample is not stressed. According to the method, the residual stress value of the pyrolytic carbon coating can be simply, conveniently and accurately obtained on the premise that the coating is not damaged.

Description

technical field

[0001] The invention belongs to the technical field of testing and relates to an X-ray diffraction method, in particular to a method for measuring the residual stress of a pyrolytic carbon coating by X-ray diffraction. Background technique

[0002] Pyrolytic carbon coatings prepared by fluidized bed chemical vapor deposition (CVD) process will have residual stress during the deposition process. The residual stress is related to the deposition process and deposition conditions, and also affects the structure and performance of the pyrolytic carbon coating. The strength of the coating can be improved by preparing the pyrolytic carbon coating with an appropriate residual stress. For the pyrolytic carbon coating of the artificial heart valve, it is required to have an appropriate compressive stress in the coating, so as to prevent the valve from cracking under the impact of blood. Therefore, it is of far-reaching significance to quantitatively measure the resid...

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