Porosity Evaluation and Analysis for 316L Stainless Steel by Selective Laser Melting Using Laser Ultrasonic Technology

Selective laser melting (SLM) is a state-of-the-art technology for efficiently manufacturing individually customized complex geometric components. The parameter control is prone to induce varying microstructures that may adversely affect SLM components. Therefore, a reliable technique that enables monitoring the integrity of SLM components and return helping to optimize manufacturing parameters in critical manufacturing missions is greatly needed. This work presents a contact-free method using laser ultrasonic technique for evaluating the porosity in SLM components. A fully noncontact laser ultrasonic system is implemented to generate and detect ultrasonic waves using a pulsed laser and laser vibrometer, respectively. Firstly, the complex pore structure under different laser powers was studied by optical microscopy. The longitudinal wave velocity described as transverse isotropic correlated with the porosity analyzed by optical microscopy was subsequently measured by laser ultrasound in contrast to the pulsed-echo ultrasound method for different forming directions. The feasibility of the proposed method is eventually verified on 316L components evaluating porosity. It suggests that it is an effective method for evaluating SLM components to ensure quality control and feedback.