Effect of chemical and structural defects on the tribological performance of additively manufactured 316L stainless steel: Micro-to-macroscale characterization

As a transformative engineering discipline, additive manufacturing has greatly improved rapid prototyping by dramatically reducing lead times, enabling mass production of complex material types and shapes, and offering unparalleled functionalities in intended applications. In this study, the material and tribological properties of 316L austenitic stainless steel produced through the laser-directed energy deposition (LDED) method are examined at multiple length scales. These analyses include material and tribological characterization, particularly on LDED-induced defects such as cavities containing unfused powders, porosities at micro-to-macro scales, and oxide-rich inclusions. Extensive wear tests using a linear reciprocating wear machine were carried out to evaluate how these defects influence the wear behavior of LDED-printed 316L against hardened 52100 steel balls under dry sliding conditions, specifically targeting the defective regions. The results revealed that oxide-rich inclusions, with a high average Vickers hardness of 855 HV, substantially impair the wear performance of steel balls used, increasing the volumetric wear loss of balls by approximately 130 %. This emphasizes the need to minimize such defects during LDED for superior tribological performance. • Explored the chemical, structural, and mechanical nature of defects in DED printed 316L. • These defects had significant adverse effects on the microstructure and mechanical properties. • The oxide-based inclusions were found to cause severe abrasive wear. • Underlying wear mechanisms elucidated using surface analytical and microscopic techniques.