Effect of steel substrate thickness on the structure of coating and powdering resistance of galvannealed coating: significance of texture

Abstract

We describe here the effect of steel substrate thickness on the structure and powdering behavior of galvannealed (GA) coating. The study indicated that the formability of GA coating was decreased and the powdering resistance was increased with increased substrate thickness. This was attributed to differences in microstructure and Fe-content in the coating, especially the thickness of intermetallic Γ phase. The change in the thickness of steel substrate changes the microstructure of substrate, including texture, grain boundary character, and crystallographic orientation, which had a significant impact on the powdering resistance of GA coating. With increased thickness of the substrate, the intensity of γ-fiber was decreased, the crystallographic orientation of (111)–(113)–(313)//RP (rolling plane) planes on the surface of the substrate was increased and (001)–(101)//RP decreased. Furthermore, the ratio between {113} and {111} orientations was decreased and the fraction of high energy boundaries was increased. All these factors played a vital role in the formation and growth of Fe-Zn intermetallic phase and finally led to a different phase structure and change in the powdering properties of GA coating.