Evaluation of laser ultrasonic testing for inspection of metal additive manufacturing

Additive Manufacturing (AM) offers a number of benefits over conventional processes. However, in order for these benefits to be realised, further development and integration of suitable monitoring and closed loop control systems are needed. Laser Ultrasonic Testing (LUT) is an inspection technology which shows potential for in-situ monitoring of metallic AM processes. Non-contact measurements can be performed on curved surfaces and in difficult to reach areas, even at elevated temperatures. Interrogation of each build layer generates defect information which can be used to highlight processing errors and allow for real-time modification of processing parameters, enabling improved component quality and yield. This study evaluates the use of laser-generated surface waves to detect artificially generated defects in titanium alloy (Ti- 6Al-4V) samples produced by laser-based Powder Bed Fusion. The trials undertaken utilise the latest LUT equipment, recently installed at Manufacturing Technology Centre which is capable of being controlled remotely. This will allow the system to optimise or adapt "on-the-fly", simplifying the eventual integration of the system within an AM machine.