Evaluation Methods of Cohesive Strength of Coatings

Abstract

Based on the test results of the coatings applied by gas-dynamic deposition, the paper evaluates the possibility of using the “pin” and “ring separation” methods to examine the cohesive strength of coatings on tensile test. There is a limitation of the “pin” method application for coatings with porosity due to a significant scatter in results (≤50%). Using the method of the “ring separation” with a high reliability of the results (scatter ≤5%) makes it possible to evaluate the effect of technological parameters of deposition, as well as changes in the phase composition of the coating on cohesion. For example, the cohesive strength of the aluminum coating decreases from ≈180 MPa to ≈50 MPa with rising deposition temperature from 180°C to 540°C; a sharp drop in cohesion of the applied metal layer from 78 MPa to 44 MPa is observed for the coating based on copper and zinc particles on formation of βʹ - and γ phases.