Tensile Adhesion Strength of Atmospheric Plasma Sprayed MgAl2O4, Al2O3 Coatings

Abstract

This study analyses the distribution of stress during the testing of glued cylindrical specimens with thermally sprayed MgAl2O4, Al2O3 oxide coatings in order to evaluate the tensile adhesion strength. The set of studies that make up this work were conducted in order to evaluate the influence of the geometric parameters of cylindrical test specimens, 25 mm in diameter by 16–38.1 mm in height, on the measured tensile adhesion strength of the specimens. The stress and strain states inside the coating and at the coating-substrate interface were determined using the finite element modelling method. The debonding mechanisms, failure mode and influence of the coating microstructure on bond strength are also discussed. The finite element stress analysis shows a significant level of non-uniform stress distribution in the test specimens. The analysis of the results of the modelling stresses and strains using the finite element method for six types of cylindrical specimens, as well as the values obtained for the adhesion testing of MgAl2O4, Al2O3 coatings, show a need to increase the height of the standard cylindrical specimen (according to ASTM C633-13 (2021), GOST 9.304-87). The height should be increased by no less than 1.5–2.0 times to reduce the level of a non-uniform stress distribution in the separation area.

Application of the spherical indenter for determination of the elastic modulus of coatings

“…Thus, knowing the value ofreduced modulus, which the instrument determines from relation (5) during the processing of experimental data, by equation ( 1) we can calculate the modulus of elasticity of the sample or the film on the surface of the sample [1][2][3]. For the calculations, we need to know the Poisson's ratio of the coating which we take to be 0.33.…”

“…In recent years, the continuous indentation method, formerly known as the kinetic rigidity method, has been increasingly used to determine the rigidity of materials [1][2][3][4][5][6]. The essence of the kinetic rigidity method is that an indenter is introduced into the material under study and two parameters are recorded: the load and the depth of introduction of the indenter.…”

“…, (1) here is the sample Poisson's ratio, is the Poisson's ratio of the indenter, is a modulus of elasticity of the sample, is an indenter elastic modulus, is a resulted module. the contact can be modelled according to an analytical model describing the contact between a rigid indenter of a certain shape and a homogeneous isotropic elastic surface: ,…”

Effect of protecting coatings on mechanical properties of metal surfaces

“…Polymer protective coatings are widely used in various fields of technology to protect structural elements against corrosion, provide electrical insulation, control the friction characteristics of surfaces, and for decorative purposes, etc. [1][2][3][4][5][6][7][8][9][10][11][12]. The study of the mechanical properties of coatings is an important task in terms of ensuring their strength and wear resistance during operation [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”