Influence of Layer Thickness and Disc Orientation on Additively Manufactured Disc-Shaped Reflectors for Ultrasonic Testing

Abstract

This research investigates the impact of additive manufacturing (AM) parameters on the quality of disc-shaped reflectors (DSRs) embedded within test specimens for ultrasonic testing (UT). Using Direct Metal Laser Sintering (DMLS) technology on MS1 Maraging Steel, the study focuses on two critical AM parameters influencing the staircase effect: layer thickness and disc orientation. These factors affect the dimensional accuracy, shape, and surface quality of the additively manufactured discs. Discs of 1 mm and 2 mm diameter were produced and evaluated for their suitability as reference reflectors for setting the sensitivity of UT systems. A factorial design of experiments (DOE) was applied to quantify the effects of these parameters on the equivalent reflector size (ERS) of discs using the Distance-Gain-Size (DGS) technique. Results show that disc orientation is the dominant factor affecting ultrasonic response, and consequently, ERS value, with optimal results achieved when discs are embedded in the layer direction (0°). The influence of layer thickness is more pronounced for 1 mm discs, where reducing layer thickness to 20 μm enhances reproducibility. For 2 mm discs, the effect of layer thickness is minimal, allowing for cost-effective production with 50 μm layer thickness. These findings provide guidance for optimising AM process parameters to produce high-quality additively manufactured DSRs, contributing to setting the sensitivity of the UT system.