Study of In-Process Monitoring for PBF (powder bed fusion) Using Laser Ultrasonics

Abstract

Metal additive manufacturing (AM) is being employed in industries because it creates metal objects of any shape. The applicability of metal AM in industries will improve if related costs and reliability issues are addressed. Powder bed fusion (PBF), a metal AM technique, is slower than other metal AM methods but offers several advantages. It excels at fine modeling, generates shapes that cannot be generated using conventional methods, and reduces post-processing workload. PBF is currently being vigorously researched. In-process inspection is necessary to reduce PBF-related costs, resources, and time and enhance the reliability of formed products. Laser ultrasonics (LU) generates acoustic waves without contact and is a promising technique adaptable to PBF. This article introduces the concept of PBF with an in-process inspection system and summarizes elemental inspection techniques, such as LU-based subsurface-defect detection in AM products and evaluation of the acoustic characteristics of solid-liquid phase transition in lead-free solder.