Solid-state bonding shows irreplaceable advantages in joining similar and dissimilar materials with poor weldability compared with fusion welding methods. To widen its applications in manufacturing safety-critical structural parts, a sound bonding quality must be achieved under less strict conditions. In this work, the metallurgical bonding is formed by hot compressing two Inconel 718 parts to different strain levels at the temperature of 1150 °C, strain rate of 0.1s−1 under a low vacuum. Full tensile strength and ductility comparable to the parent materials have been achieved for the first time by 0.5 engineering strain. The severe plastic deformation at hot temperature rapidly bonds the two parts by effectively closing the interface micro-voids, breaking up the oxide film, and in the meantime, accelerating the grain boundary(GB) migration through the dynamic recrystallization(DRx). Based on these observations, a theoretical model is proposed to describe the bonding process under hot deforming condition and the achieved relative interface bond quality, in which the cohesion between oxide-oxide and oxide-metal is assumed, and impairing effect of remaining dispersed oxides is minimized with the attempt of introducing a strain-amplifying factor. The insights and model provide the basis for further understanding of the solid-state bonding-by-hot-deforming under practical conditions and explore its wider application with ideal joint integrity.