Wire and Arc Additive Manufacturing: Developments and Parts Characterization

• Autor(a) principal: Ó, Stefan Pereira do
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/92301
• topic: Additive Manufacturing; WAAM; arc welding; 316L stainless steel; Inconel 625 superalloy; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Mecânica

Wire and arc additive manufacturing (WAAM) is a low capital investment technology that allows a reduction in material usage and production times while enabling the production of complex components. But despite its advantages, components produced in WAAM are prone to defects depending on the materials used and have overall inferior mechanical properties when compared to conventional processes. This study focused on building and testing a system capable controlling the thermal cycles to manipulate the cooling rates and consequently the microstructure of produced parts in order to control the resulting hardness. Two heat exchangers were built, one to heat and the other to cool the shielding gases. The exchangers were tested through the manufacturing of thin walls of 316L stainless steel and Inconel 625 superalloy using hot, ambient and cold argon gas. Obtained parts where characterized for their geometry, hardness and microstructure. It was shown that varying the temperature of the shielding gas by itself is not enough to significantly influence the microstructure and mechanical properties of WAAM components. Using the cooling heat exchanger with cooling turned on caused an increase in hardness up to 30 HV and a decrease in primary dendrite arm spacing (PDAS) of 13.2 % for Inconel 625 while using the same heat exchanger without cooling caused an increase of 16.8 % in effective wall width (EWW) and a decrease of 15.8 % in height for 316L stainless steel. These differences were due to the cooling exchanger acting as a heat sink or as a heat accumulator depending on whether the cooling was turned on or off.