EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Laser powder bed fusion (L-PBF) is a versatile additive manufacturing process that can print geometrically complex metal parts for a variety of applications. However, poor control of the formation of defects such as pores and cracks during processing remains an obstacle to its widespread industrial adoption. In particular, many materials suffer from a high crack susceptibility during L-PBF, which results in degraded mechanical properties, and hampers the certification of critical parts. In order to unveil the mechanisms of crack formation in a prone-to-cracking metallic alloy, we employ high-speed synchrotron X-ray imaging in combination with a miniaturized L-PBF set-up that reproduces close-to-reality processing conditions. This set-up provides operando imaging of crack formation during L-PBF, which is complemented by post-mortem microscopy analysis of the cracks. Further thermal simulations supported by operando X-ray diffraction-based measurements of the temperature evolution allow to identify the cracking mechanism and to differentiate hot cracking from liquation. Additionally, these operando experiments demonstrate the ability to monitor with a high temporal resolution and in realistic processing conditions a variety of critical transient phenomena taking place during L-PBF, such as formation of keyhole pores, healing of cracks and pores, or spatter formation.