Comparison of microstructural characteristics and mechanical properties of shipbuilding steel plates fabricated by conventional rolling versus wire arc additive manufacturing

Abstract

This study aims to investigate the fabrication feasibility of a conventionally rolled low-carbon low-alloy shipbuilding steel plate (EH36) by emerging wire arc additive manufacturing (WAAM) technology using ER70S feedstock wire. Following the fabrication process, different heat treatment cycles, including air-cooling and water-quenching from the intercritical austenitizing temperature of 800 °C, were applied to both conventionally rolled and WAAM samples. Microstructural features and mechanical properties of both rolled and WAAM fabricated ship plates were comprehensively characterized and compared before and after different heat treatment cycles. Both air-cooling and water-quenching heat treatments resulted in the formation of hard martensite-austenite (MA) constituents in the microstructure of the rolled ship plate, leading to the increased hardness and tensile strength and reduced ductility of the component. On the other hand, air-cooling heat treatment was found to homogenize the microstructure of the WAAM ship plate, causing a slight decrease in the hardness and tensile strength, while the water-quenching cycle led to the formation of acicular ferrite and intergranular pearlite, contributing to the improved mechanical properties of the part. Therefore, the enhanced mechanical integrity of the water-quenched WAAM component as compared to its rolled counterpart verified the fabrication feasibility of the ship plates by the WAAM.