On the Microstructure and Corrosion Behavior of Wire Arc Additively Manufactured AISI 420 Stainless Steel

Abstract

In this study, a robotic wire arc additive manufacturing (WAAM) technology utilizing advanced surface tension transfer mode was adopted to fabricate a thin wall of AISI 420 stainless steel containing 25 layers. The microstructure and corrosion properties of the as-printed wall were studied. Optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were used to determine the microstructure of the wall. The dominant microstructure of the wall comprised of austenite and delta ferrite phases as micro-constituents embedded in a martensitic matrix, revealing a gradual increase in the amount of retained austenite from the bottom of the wall towards its top. The corrosion behavior of the wall was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) testing. As a general trend, the upper portion of the fabricated wall revealed an improved corrosion resistance and reduced pitting susceptibility than the bottom layers.