Effect of protecting coatings on mechanical properties of metal surfaces

Abstract

The effects of epoxy-polyester based powder coatings on the mechanical properties of plates made of rolled steel sheets were investigated in this work. The effect of coatings of the order of 100 µm thickness on the mechanical properties of specimens of 0.7-1.5 mm thick was considered. Tests carried out at room and elevated temperatures showed that thin coatings had an insignificant effect on the mechanical properties of the plates in bend and tensile tests. In particular, the tensile and bending stiffness of the plates is virtually unchanged in the presence of coatings, despite the fact that the modulus of elasticity determined in tests of steel plates with coatings is always somewhat lower than the Young's modulus of steel, due to the increased thickness of specimens determined in the presence of coatings. In compression strength tests, on the contrary, the influence of coatings is significant. In the overcritical mode of deformation, the load carrying capacity of coated plates is significantly reduced and their critical load of stability loss becomes 1.2-2.3 times lower (depending on substrate thickness) compared to uncoated samples. This effect can be explained by the influence of residual temperature stresses that arise in the samples after coating.