Abstract
The brittle Fe-Zn intermetallic compound coating layer on GA steel showed multiple cracking perpendicular to the tensile axis. The average crack spacing of the coating layer decreased with increasing applied strain. The crack spacing was dependent on the coating thickness and species of the steel substrate. The calculation of the exerted stress of the coating layer with the finite element method revealed that, when the steel substrate deforms plastically and the crack spacing is narrower than that of critical length, the maximum tensile stress of the coating layer is approximately proportional to the crack spacing and to the tensile stress of substrate, and inversely proportional to the coating thickness. From the comparison of the measured crack spacing on the IF (Interstitial Free) and SPCC (Steel Plate Cold Commercial) steels with the calculated one, the strength of the coating layer was estimated to be around 260 MPa. From these results, an empirical equation was proposed, which can be used for rough prediction of the crack spacing as a function of applied strain for any substrate steels and thickness of the coating layer.
