MONITORING QUALITY IN LASER POWDER-BED FUSION PARTS THROUGH COMPARISON OF POROSITY, MECHANICAL PROPERTIES, AND NONLINEAR ACOUSTIC RESPONSE

Abstract

Ultrasonic nondestructive evaluation methods are well established for detecting and measuring defects within engineering parts and components. Sideband peak counting (SPC) is a recently developed nonlinear ultrasonic technique used for evaluation of defects down to 10 μm. In this work, 316L stainless steel tensile test specimens were manufactured using laser powder-bed fusion (LPBF) with four levels of energy density which was controlled by scan speed. The ensuing porosity and its interplay with other processing defects in the different samples were evaluated using the SPC technique. In parallel, metallographic analysis in conjunction with wave propagation simulations, and mechanical testing were also carried out to complement the SPC characterization. Using machine learning methods, correlations between the SPC index of samples and the underlying porosity, defects, mechanical properties, and LPBF process parameters were obtained, thereby providing the pathway for a fully non-destructive evaluation of additively manufactured 316L stainless steel parts and components.