Nanoindentation and indentation creep analysis of diffusion bonded of inconel 718 and AISI 304L stainless steel joint interface

Diffusion bonding of Inconel 718 (IN718) and Austenitic Stainless Steel (AISI 304L) was performed at 950 °C for 90 minutes of holding times under 5 MPa of bonding pressure. The resultant joint interface was investigated for its microstructural and compositional analysis, nano hardness, elastic modulus, and indentation creep. The result reveals that the joint interface was comprised of NbC, Cr₂₃C₆, and δ-Ni₃Nb along with the austenitic matrix of Ni and Fe. Similarly, a nanohardness of 3.5 GPa occurred at the bonding interface, which was 10% and 33% higher as compared to the base metals (BM) of IN718 and AISI 304L, respectively. Additionally, a minimum elastic modulus of 190 GPa was achieved at the AISI 304L BM as compared to other bonding zones (BZ). Moreover, a creep deformation of 73 nm occurred at the bonding interface and the stress exponent of bonding interface was 17% and 57% lower as compared to AISI 304L and IN718 BM respectively. Lastly, the bonding interface has higher creep resistance compared to other BZ and pile-ups were appears around the nanoindents in all bonding zones as analyzed with atomic force microscopy (AFM).