Microstructure and tensile properties of AISI 321 stainless steel with aluminizing and annealing treatment

In the present work, the tensile properties and microstructure of pack cementation preparing aluminized AISI 321 stainless steel with subsequent annealing treatment was investigated. The results reveal that the coatings of aluminized AISI 321 stainless steel are mainly composed of outermost Al2O3 layer, Fe-Al com-pound intermediate layer and Fe(Al,Cr) solid solution diffusion layer. The cross shape precipitate (NiAl) and strip precipitate (Ni3Al) are observed in Fe(Al,Cr) layer. After annealing, no new phase in aluminized coating is detected, meanwhile, the thickness of the aluminized coatings is increased and the porosity of Fe-Al layer is increased as well. In addition, the size of NiAl precipitates is decreased. The strength and plasticity of stainless steel are degraded by aluminizing treatment. However, after annealing, the alu-minized steel exhibits a lower strength but a higher ductility. The crack initiation region of both alu-minized steel with or without annealing treatment comprise coarse columnar grains and cleavage planes with river patterns. The fracture model of aluminized steel is cleavage fracture, while a mixed of intergranular and transgranular fracture is observed in aluminized annealed steel. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

The study investigated the tensile properties and microstructure of aluminized AISI 321 stainless steel prepared by pack cementation with subsequent annealing. The results showed that the coatings were mainly composed of Al2O3 layer, Fe-Al compound intermediate layer, and Fe(Al,Cr) solid solution diffusion layer. Annealing increased coating thickness, reduced NiAl precipitate size, and affected the strength and plasticity of the stainless steel.