Analysis of buckling and interfacial debonding of galvannealed coating layer on steel substrates under applied tensile strain

Abstract

As the hot-dipped galvannealed steels are composed of brittle coating layer with low failure strain and ductile substrate with far higher failure strain. When tensile stress is applied externally on the coated steels, the coating layer exhibits multiple cracking perpendicular to the tensile direction, and then interfacial debonding occurs, following the buckling of the coating layer in the sample width direction. In the present work, the interfacial debonding behavior was observed with the scanning electron microscope and analyzed with 3-dimentional finite element models, to reveal the influence of the crack spacing on the buckling-induced interfacial debonding. In the analysis, three cases with different crack spacing in the coating layer were used. The results of analysis could account well for the experimentally observed buckllng-induced spalling process of the coating layer. Furthermore it was revealed that, the shorter the crack spacing of the coating layer in the tensile direction, the less the interfacial debonding takes place. © 2007 ISIJ.