Abstract
Cracking behavior of Al-Si coating on hot stamping boron steel was investigated under different hot deformation conditions. The Al-Si coated steel specimens were isothermally deformed under applied tensile strain by Gleeble 3500, at 700, 750, and 800 oC with a strain rate of 0.1/s. Morphology of the coating was observed through scanning electron microscopy and optical microscopy. The results indicate that microcracks appear during the austenitizing treatment, because of thermal expansion mismatch of the Fe-Al-Si intermetallics. Under applied tensile strain, the cracks propagate along the direction perpendicular to the coating/substrate interface. When these cracks reach the interface, the surface coating layer is divided into segments by through-thickness cracks. With increasing deformation temperature, the crack density tends to be smaller, while the cracks are wider. It is suggested that with a higher deformation temperature, the Al-Si coated boron steel could withstand more deformation before the steel substrate is exposed.
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