Influence of Deposition Sequence and Thermal Cycles on the Microstructure and Wear Behavior of WAAM-Fabricated SS309L and Inconel 625 Bimetallic Structures

This study investigates the influence of deposition sequence and cooling rate on the microstructure and wear performance of bimetallic SS309L–Inconel 625 structures fabricated via wire and arc additive manufacturing (WAAM). Higher cooling rates (~ 11.6 °C/s) refined dendritic structures in Inconel 625, increasing hardness by ~ 15% (from 280 Vicker Hardness (HV) to 322 HV) and improving wear resistance by ~ 18%. Conversely, slower cooling (~ 5.14 °C/s) in SS309L led to coarser skeletal ferrite, reducing wear resistance by ~ 12%. Deposition sequence also played a critical role: Depositing Inconel 625 over SS309L resulted in a 22% increase in wear resistance compared to the reverse order due to reduced thermal exposure and refined interfacial microstructure. The interface region exhibited mixed adhesive and abrasive wear mechanisms, with microhardness varying from 285 HV in SS309L to 340 HV in Inconel 625, influenced by residual stress and interfacial diffusion. These findings provide a framework for optimizing WAAM deposition strategies to enhance the mechanical performance and durability of bimetallic components in high-performance applications.