Evaluation of the influence geometric parameters of a cylindrical specimen for tensile adhesion testing of thermally sprayed coating

Abstract

The problem of calculating the required adhesion strength and the accuracy of measuring the adhesive/cohesive strength of thermally sprayed coatings (thermal barrier, electrically insulating, irradiation) on a cylindrical test specimen is of practical interest from the point of view of improving the reliability of highly loaded parts of internal combustion engines of agricultural machines, various parts of the aerospace and nuclear industries. There have been carried out a set of studies on the application in practice of standard test method for assessing adhesion or cohesion strength of electrically insulation plasma sprayed coating Al2O3 on standard and elongated specimens with a diameter of 25 mm in accordance with standards ASTM C633-13, GOST 9.304-87. In order to assess the influence of witness specimen’s geometry at common coating adhesion, there were selected 6 types of cylindrical specimens. A finite-element stress analysis was used to evaluate stress-strain state of the two bonded cylindrical specimens of the same geometry with coating by tensile testing. The uniformity of stress distribution at the interface coating/substrate was found for three elongated specimens. Compared to standard tensile testing of a cylindrical specimen, the applied significance of the conducted studies that it is possibility to obtain more accurate experimental data of bond strength. There is also needed further research in the field of determining the most optimal geometry of the witness specimen for evaluating the tensile adhesion strength of thermal spray coating.