Improved corrosion resistance of AISI 321 steel to molten Al-Si alloy by aluminizing and laser shock peening

Abstract

The service life of AISI 321 steel for solar thermal power generation system is strongly dependent on its corrosion resistance. In the present work, therefore, the influence of aluminizing and subsequent laser shock peening (LSP) treatment on corrosion resistance of AISI 321 steel against molten Al-Si alloy was investigated. These two treatments are found to lower the corrosion rate of AISI 321 steel. Concretely, microstructural characterizations showed that the aluminized layers were oxidized during heating process of corrosion test after aluminizing. Such oxide layer could remarkably decrease the diffusion rate of Al and Si elements. On the other hand, high density dislocation was introduced on the surface layer of AISI 321 steel after aluminizing and subsequent LSP treatment, enabling the rapid growth of thicker and denser oxide film at the early stage of corrosion. And the residual stress introduced by LSP treatment could inhibit the formation of cracks and favor the formation of stronger bonds between the corrosion products. As a result, clear improvement was observed in the corrosion resistance of the AISI 321 steel treated by aluminizing and LSP.