Growth of Fe_3Si layer deposited from the molten salt

摘要

The corrosion-resistive intermetallic compound Fe_3Si can non-electrolytically coat the iron substrate at 973-1173K in the molten salt composed of NaCl-KCl-NaF-Na_2SiF_6-SiO_2. However, the adhesion of Fe_3Si layer was weak because of the crack formation in the Fe_3Si layer.The mechanism of the layer growth and defect formation was studied experimentally. The marker experiments showed that the salt was caught up on the initial surface and left large voids in the layer. The fast deposition of silicon on pure iron surface and the quick growth Fe_3Si wrapped the salt in the layer at the first stage of deposition. The Si penetration from the Fe_3Si layer into the #alpha#-Fe substrate small due to the slow diffusion of Si in #alpha#-Fe. The fast Fe diffusion in the Fe_3Si layer left the Kirkendall holes. The formation of thes fects could be suppressed in the high Si concentration-iron alloys.