Smart WAAM: Microstructural Engineering and Integrated Non-Destructive Testing

Wire and Arc Additive Manufacturing (WAAM) presents unique opportunities for production, repair, refurbishment and life extension of large industrial equipment by melting and solidification of any given wire(s) using an electrical arc as heat source. Two challenges exist:
1) due to process thermal cycles, certain alloy families can be susceptible to the formation of large grain size microstructures which are typically associated with poor mechanical properties;
2) the process can lead to the formation of defects, such as pores and lack of fusion, that may be detrimental to the part’s in-service performance. Solving the poor mechanical properties of the as-built parts is performed by thermomechanical treatments aiming at homogenising the microstructure, i.e., decrease grain size and, eventually, dissolve any detrimental phases that have formed. However, this is a time- and energy-consuming effort, which leads to an increase in production time and costs. Assessing the presence of defects is usually performed after the parts are built. If upon NDT inspection, defects are found, depending on their volumetric fraction, morphology and type, the material can be considered as waste. Hence, the need for inline and offline reliable detection methods is fundamental.

We propose to tackle these challenges in a comprehensive way by performing direct microstructural engineering of the deposited material via newly developed and validated WAAM process variants. These will encompass the introduction of inoculating agents to promote grain refinement but also the of use in-situ hot forging to promote material hardening, as well as, decrease its waviness, roughness and, more importantly, the likelihood for pore formation. An optimization of the thermal cycles, which influences the solid-state transformations of the deposited materials will also be implemented. Furthermore, a multiparametric non-destructive system for inline monitoring will be developed to identify defects that may occur during parts production. These ambitious goals aim at decreasing production time, material waste while increasing process efficiency during WAAM. Moreover, two case studies will be conducted: one will focus on the repair of damaged or obsolete industrial equipment (C-steel), while the other will concentrate on reducing lead-times by replacing forged components (Inconel). It is expected that the implementation of these new WAAM variants in conjunction with the use of the NDT multiparametric system can lead to an extension of the lifetime of repaired equipment by 20% or to a substantial lead time reduction (factor 5-10) which reduces or completely eliminates the need for stock-keeping, thus significantly decreasing the industry associated carbon footprint.

This work will be supported by numerical simulation tools which will be experimentally validated via advanced materials characterization. On top of these process innovations and their industrial implementation a life cycle assessment platform for companies already using or interested in adopting WAAM will be developed and made available. Moreover, lifelong learning initiatives will be implemented within the framework of this project.

Visit the project page here.