Influence of interpass cooling conditions on microstructure and tensile properties of Ti-6Al-4V parts manufactured by WAAM

Wire and arc additive manufacturing (WAAM) technology is growing in interest in the last years. The technology enables the manufacturing of real geometries by overlapping weld beads and is well suited for metallic parts with high buy-to-fly ratio. Manufacturing costs and time are critical issues which determine the business case. Therefore, it is necessary to develop strategies that minimise the production time while meeting quality requirements. In this regard, cooling conditions are a key factor to reduce time and determine mechanical properties and resulting microstructure. This study aims at investigating the effect of interpass cooling conditions on resulting mechanical properties and microstructure of Ti-6Al-4V alloy. The influence of dwell time between successive deposition of layers is investigated both for air and forced interpass cooling. Forced cooling is done by using water-cooled anvil under base plate. The goal is to find a minimum dwell time to maximise arc-on time and deposition rate while avoiding wall collapse, widening, oxidation and the need to apply post building heat treatment. Obtained mechanical properties are compared with standards for products manufactured by conventional manufacturing. Additionally, microstructure, surface finishing and part accuracy of WAAM samples are characterised.