Study on the printing stability of Invar 36 alloy under different process parameter conditions in gas metal arc additive manufacturing

Invar 36, a nickel–iron alloy distinguished by its low coefficient of thermal expansion, is a material of significant interest for high-precision applications in aerospace, moulds used in composite material fabrication processes and metrology. This work investigates the stability of depositing Invar 36 through gas metal arc additive manufacturing (GMA-AM), also known as wire arc additive manufacturing, with a focus on identifying process conditions, in a standard gas metal arc welding (GMAW) process, that promote consistent and defect-minimised builds. A series of experiments was conducted to assess the effects of key process parameters – including wire feed speed, welding speed and arc voltage – on deposition stability. Stability was evaluated through geometrical consistency of the deposited walls, arc behaviour and visual inspection of process-induced anomalies such as spatter and lack of fusion. This study presents a novel methodology to quantitatively assess the stability of the GMA-AM process, along with the construction of a process map specifically tailored for the Invar 36 alloy. The insights gained contribute to advancing the understanding of wire-based additive manufacturing of Invar 36, which is still understudied, and provide a foundation for further investigations into its mechanical performance and microstructural evolution under optimised process parameter conditions.