Manufatura aditiva baseada em GMA pulsado de aço inoxidável 308 L: um estudo sobre a influência dos modos de destacamento de gotas nas propriedades mecânicas e na geometria do material depositado

Abstract

Recent studies point to promising prospects for pulsed gas metal arc (GMA)-based wire arc additive manufacturing (WAAM) process, due to its high deposition rate, energy efficiency, and low operational cost, when compared to other processes such as LASER and electron-beam. Furthermore, the projected spray metal transfer is considered ideal, as it ensures a regular detachment of droplets with uniform size and minimal spatter. However, in the conventional GMA process, the high current intensity required to achieve spray metal transfer generates significant heat input. In this regard, the pulsed GMA process can be employed with reduced heat input. Thus, this study aimed to present the results obtained in pulsed GMA-based WAAM for the deposition of 308 L stainless steel, based on the analysis of the influence of different droplet detachment modes on the geometric characteristics and mechanical properties of the deposited metal. The detachment modes of one drop per multiple pulses (ODMP), one drop per pulse (ODPP), and multiple drops per pulse (MDPP) were analyzed. The experiments were performed by depositing preforms using 308 L stainless steel wire with a diameter of 1.0 mm on a 316 L stainless steel substrate. Characterization of the droplet detachment modes was performed during deposition, using a high-speed camera and data acquisition system. After characterization, the pulse parameters were selected for the deposition of three identical preforms for each droplet detachment mode. Geometric analysis of the preforms was performed by photogrammetry. The mechanical properties were analyzed through tensile and hardness tests. A greater heat input was observed in the ODMP mode. The MDPP and ODPP modes produced thinner preforms with a better surface finish. In addition, the MDPP mode generated better results in the manufactured preforms, with lower hardness and higher tensile strength. The ODMP mode led to relatively poorer results, with wider walls, greater surface waviness, and lower tensile strength. Nevertheless, the statistical modeling and analysis yielded inconsistent and inconclusive predictions, mainly because of limited sample sizes. The results of this research are expected to provide technical and scientific support for the development of the manufacturing process by pulsed GMA-based WAAM, especially for stainless steel applications.