Investigating failure mechanisms in cutting tools used in advanced industries like biomedical and aerospace, which operate under extreme mechanical and chemical conditions, is essential to prevent failures, optimize performance, and minimize financial losses. The diamond-turning process, operating at micrometer-length scales, forms a tightly bonded built-up edge (BUE). The tribochemical interactions between a single-crystal diamond and its deformed chip induce inter-diffusion and contact, rapidly degrading the cutting edge upon BUE fracture. These effects intensify at higher deformation speeds, contributing to the observed rapid wear of diamond tools during d-shell-rich metal machining in industrial settings. In this study, these interactions were studied with niobium (Nb) as the transition metal. Tribochemical effects were observed at low deformation speeds (quasistatic; <1 mm/s), where thermal effects were negligible under in situ conditions inside the FEI /SEM vacuum chamber room. The configuration of the interface region of diamond and transition metals was characterized and analyzed using focused ion beam (FIB) milling and subsequently characterized through transmission electron microscopy (TEM). The corresponding inter-diffusion was examined by elucidating the phase evolution, element concentration profiles, and microstructure evolution via high-resolution TEM/Images equipped with an TEM/EDS system for elemental characterization.