Enhanced oxidation resistance of an AlSi alloy coating via Cr barrier layer insertion.

A novel Cr barrier layer was designed for suppressing the interdiffusion of an AlSi alloy coating on stainless steel. Without a Cr barrier layer, the same coating experienced a severe element interdiffusion upon exposure to high-temperature air. The rapid upward movement of the Fe atoms induced the formation of the (FeAl + Fe 2 Al 5) alloy compounds and eventually led to severe volume shrinkage and the ultimate fracture of coating. The significant downward diffusion of the (Al + Si) atoms not only triggered numerous pores but also induced the accumulation of the FeAl alloy compound in the substrate resulting in extreme interfacial cracking. In contrast, a diffusion barrier layer comprising (Cr 2 O 3 + SiO 2) and Al 2 O 3 was formed in the coating with a Cr layer during high-temperature exposure, effectively preventing the rapid elemental interdiffusion. Moreover, it inhibited the formation of the (FeAl + Fe 2 Al 5) alloy compounds in the coating as well as prevented the accumulation of the FeAl in the substrate. The obvious upward diffusion of Cr atoms further healed these pores induced by the downward diffusion of (Al + Si) atoms. The strong barrier capability of this composite oxide layer and the healing effect of Cr diffusion eventually led to an improved oxidation resistance of the Cr-coated layer. • Effect of Cr layer on the oxidation resistance of AlSi alloy coating was investigated. • The Cr diffusion triggered the growth of the (Al 2 O 3 + SiO 2) and Al 2 O 3 barrier layer. • This oxide barrier layer effectively suppressed severe inerdiffusion of Fe and Al. • The sufficient upward diffusion of Cr induced a significant self-healing effect. • The AlSi alloy coating with a Cr layer showed an improved oxidation resistance. [ABSTRACT FROM AUTHOR]