Microstructure Evolution and Mechanical Properties of Ferrite-Austenite Stainless Steel Bimetals Fabricated via Wire Arc Additive Manufacturing

A bimetallic structure is implemented by wire arc additive manufacturing from 316L austenitic stainless steel to 430 ferritic stainless steel. Microstructure, interface characteristics, and tensile properties of 316L-430 bimetals are investigated. In 316L/430 bimetals, defects like porosity and cracks are not present. The compositional distribution and microstructure evolution of 316L-430 bimetallic deposition are significantly impacted by the deposition sequence and heat input. As heat input increases, microstructure evolution of 430 deposited layer is single F -> F+ diffusely distributed (Cr, Fe)23C6 -> F+ grain internal (Cr, Fe)23C6 -> F + M, and 316L deposited layer presents typical austenite + skeletal delta ferrite. Microstructure of 430 deposited layers presents heterogeneous, grain coarsening, and martensite along grain boundaries, resulting in high-temperature embrittlement. The highest hardness of 316L-430 bimetals appears on 430 sides near the interface. The tensile strength of 430/316L bimetals is greater than that of 316L/430, and the tensile specimens exhibit brittle fracture. 316L/430 bimetallic free of defects is fabricated by wire arc additive manufacturing. 430 deposited layer presentes F (ferrite) + M (martensite) + (Cr, Fe)23C6. The highest hardness of 316L-430 bimetals appears on 430 side near the interface. The tensile strength of 430/316L bimetals is greater than that of 316L/430, and the tensile specimens exhibit brittle fracture.image (c) 2023 WILEY-VCH GmbH