Nanoindentation creep behavior of vacuum diffusion-bonded stainless steel and Inconel 718 joints using a Cu interlayer

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Exhaust components combining Inconel and stainless steel offer the most cost-effective hybrid design for high-performance engines. Owing to the formation of brittle compounds, the most critical zone in such components is the joint interface, which must have a suitable creep life. The present study investigated the nano creep and nanomechanical behavior of diffusion-bonded Austenitic stainless steel (AISI 304) and Inconel (IN-718) with a Cu interlayer. Maximum nano hardness of 3.25 GPa in AISI 304 and 3.12 GPa in IN-718 was achieved at the Cu/IN-718 and Cu/AISI 304 interfaces, respectively. Additionally, the least elastic modulus of 159 GPa in the Cu interlayer, and 160 GPa in the bonding interface was occurred at the Cu/IN-718 and Cu/AISI 304 interfaces, respectively. Moreover, the creep displacement of the Cu/AISI 304 interface was 327% higher than that of the Cu/IN-718 interface. Lastly, the Cu/IN-718 interface exhibited diffusional creep, while the Cu/AISI 304 interface exhibited both diffusional and dislocation creep as active mechanisms.