Towards tailorable interface microstructure through Solid-state interface reaction between synthetic diamond grits and sputtered Ni-Cr binary alloy

Abstract

In this work, the solid-state (S/S) interface reaction between single-crystal synthetic diamond grits and binary Ni-Cr alloys has been comprehensively studied on (100) and (111) crystal planes using Raman spectroscopy, SEM, TEM, and XPS techniques, in combination with first-principles calculation. The early-stage interfacial chromium carbides formation was found to be dependent on crystal orientation of synthetic diamond, which can be explained by geometric optimization that explores the underlying catalytic mechanisms of Ni-Cr alloys on the relaxation and bonds construction of C atoms on (100) and (111) crystal planes of diamond. More importantly, a unique interfacial microstructure, namely a Ni-rich layer instead of interfacial carbides was formed directly on diamond surface of S/S reaction samples at 700 and 900 °C. In addition, the phase transformation between Ni-rich phase and chromium carbides formed in the S/S interface reaction between Ni-Cr alloy and synthetic diamond were comparatively examined at 700 and 900 °C and investigated through a careful TEM lattice mismatches analysis. Ultimately, a mechanism to tailor the S/S interface microstructure by simply designing alloy compositions and reaction temperatures was proposed with experimental validation.