Nondestructive Inspection of Cylindrical Components Repaired Via Directed Energy Deposition Using Scanning Acoustic Microscopy with Metal Lubricants

During the repair process via directed energy deposition (DED) additive manufacturing, porosity can be introduced owing to the lack of fusion or overmelting of metal powders. Although conventional scanning acoustic microscopy (SAM) operated under water immersion has been extensively used for porosity evaluation, it cannot be employed in situ during DED repair because water can lead to damage such as corrosion. In this study, an in situ porosity inspection system using scanning acoustic microscopy (SAM) with a metal lubricant is developed for cylindrical components repaired via DED. Contrary to conventional SAM operated under water immersion, the proposed technique evaluates porosity using a metal lubricant as a coupling medium that prevents DED from several types of damage, such as corrosion. The modified beam path for ultrasonic waves is analytically calculated considering the metal lubricant and cylindrical surface. The developed technique exhibits the potential for online inspection during DED because of its anti-corrosion, noncontact, nondestructive nature, and scanning capability. The performance of the proposed technique is validated using various metal lubricants and cylindrical components repaired using DED. The applicability of the developed technique is highlighted via the experimental results. Graphical Abstract: [Figure not available: see fulltext.]