Microstructure and tribological characterization of thin wall of bimetallic austenitic steel fabricated through wire arc additive manufacturing (WAAM)

Austenitic stainless steels, such as SS316L, are widely employed in thin rotary components like blades and impellers due to their exceptional thermal resistance, wear resistance, and corrosion properties. This study examines the dry sliding wear behaviour of wire arc additive manufactured (WAAM) austenitic bimetallic structures (BMS) comprising SS316L and SS309. Wear tests were conducted using a pin-on-disc tribometer with a flat-on-flat configuration, utilizing 3 mm square pins extracted from distinct regions of the base metals and their interface, tested against an EN31 steel disc (61 HRC). The initial average coefficient of friction (CoF) for SS316L ranged between 0.41 and 0.64, whereas the SS316L-SS309 interface demonstrated a lower CoF of 0.42 to 0.58, attributed to increased ferrite content and hardness during the initial running-in phase. X-ray diffraction results revealed the formation of iron oxides and chromium oxide on the worn surface of the plate. Microstructural and energy dispersive spectroscopy (EDS) analyses indicated that the higher ferrite content in SS309 and interface regions significantly enhanced wear resistance compared to SS316L. The wear mechanism transitioned from combined abrasive-adhesive wear to adhesive wear with plastic deformation and severe material loss. Analysis of wear debris confirmed progressive oxide layer removal during sliding, leading to increased wear. The superior hardness and ferritic phase in SS309 and interface regions contributed to improved wear resistance, underscoring the potential of austenitic BMS for applications requiring high wear performance. This study emphasizes the critical role of microstructural tailoring in optimizing wear characteristics in WAAM-fabricated austenitic BMS components.