Interpass temperature control for enhancing tribological and microstructural properties of multi-pass GTAW aluminum-clad SCM440 steel

• Interpass temperature in GTAW governs IMC formation, microstructure, and wear resistance. • Optimum 100 °C interpass temperature refines dendrites and limits Fe–Al diffusion. • Highest hardness (380 HV) and lowest wear loss occur at 100 °C condition. • Excess heat (>200 °C) promotes Fe-rich IMCs and deteriorates weld quality. • Feedback-controlled heating/cooling ensures stable weld properties in practice. This study addresses a critical challenge in multi-pass gas tungsten arc welding (GTAW) of aluminum onto SCM440 steel, where uncontrolled interpass temperatures often lead to coarse dendritic microstructures, increased formation of Fe-Al intermetallic compounds (IMCs), and reduced wear resistance. The five-pass GTAW process was conducted using ER1100 filler metal, with precise interpass temperature regulation (room temperature to 250 °C) achieved through a feedback-controlled thermal system that combined hot air heating and forced air cooling. Mechanical and tribological performance were assessed by Vickers microhardness and ASTM G77 wear testing. Microstructural evolution was investigated using optical and scanning electron microscopy (SEM). The optimum interpass temperature (100 °C) refined dendritic structures, inhibited Fe diffusion, and favored the formation of Al-rich IMCs, resulting in increased hardness, low friction, and reduced wear rate. Interpass temperatures exceeding 200 °C led to aluminum depletion, dendritic coarsening, the formation of Fe-rich IMC combinations, and a decline in mechanical performance. Controlled interpass temperatures enhanced the microstructural stability and wear resistance of aluminum-clad steel. Industrial applications could benefit from automated thermal control systems equipped with infrared (IR) sensors and integrated heating or cooling units to monitor and adjust temperature in real time. The automotive, petrochemical, and maritime industries may leverage this technology to improve weld quality and service life.