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

Abstract

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 δ 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.