热浸镀铝球墨铸铁的耐蚀性能和冲击韧性

Corrosion resistance and impact toughness of hot-dip aluminized ductile iron

研究了热浸镀铝球墨铸铁在3.5%NaCl溶液中的耐腐蚀性能和不同温度下的冲击韧性。极化曲线和阻抗谱测试结果表明,热浸镀铝球墨铸铁在3.5%NaCl溶液中耐蚀性能得到了显著提高,主要原因为表面铝层易形成Al2O3钝化膜,降低了腐蚀电流密度。纯铝热浸镀形成的不规则舌状Fe2Al5硬脆相/铁素体基体界面处可能产生应力集中,承受冲击载荷时呈现为解理断裂。采用Al-3.6%Si浸镀液可改善Fe2Al5硬脆相/基体界面形貌,降低Fe2Al5合金层厚度,在良好低温冲击韧性的前提下,显著提高了球墨铸铁在3.5%NaCl溶液中的耐蚀性能。

The corrosion resistance of hot-dip aluminized ductile iron in 3.5% NaCI aqueous solution and its impact toughness at different temperatures were investigated. The polarization curves and electrochemical impedance spectroscopy indicate that the hot-dip aluminized ductile iron performs much better corrosion resistance in 3.5% NaC1 aqueous solution due to the formation of AI203 passivation layer and reduction of the corrosion current density. Under impact load, the cleavage fracture of hot-dip aluminized iron can be observed near brittle phase of Fe2A15 layer, where the irregular interface between the ferrite substrate and the tongue-like Fe2A15 layer may lead to stress concentration. When hot-dip aluminum added 3.6% Si, the morphology of interface becomes fiat and the thickness of Fe2A15 layer decreases, and the corrosion resistance of this ductile iron in 3.5% NaC1 aqueous solution is greatly improved, combined with better impact toughness at low temperatures.