Enhance diamond coating adhesion by oriented interlayer microcracking

Abstract

In this paper, we report a microcrack toughening mechanism for enhancing the adhesion of diamond coating. The oriented microcracks were formed within the TiC interlayer to dissipate strain energy and accommodate deformation via the crack opening-closing mechanism, thus enhancing the coating/substrate interfacial toughness. The delamination of diamond coating was effectively prevented when the parallel microcracks were confined within the interlayer and arrested at interfaces of coating/interlayer/substrate. Density functional theory calculations revealed that the highly anisotropic fracture strength of the TiC phase energetically favors crack initiation and propagation along (100) planes only, which are 54.7° away from the interface. These microcracks are constrained inside the interlayer by the two strong interfaces in the substrate/interlayer/coating system. The new microcrack toughening mechanism with these combined features has a wide application to enhance the adhesion of thin-film coatings.

Combinatorial Materials Design Approach to Investigate Adhesion Layer Chemistry for Optimal Interfacial Adhesion Strength

“…Figure 7 summarizes the work of adhesion values calculated using the simplified Laugier model as a function of adhesion layer composition and compared to the NCD coating deposited on the bare Si wafer (grey line, labeled 'none'). Despite numerous simplifications, the obtained adhesion energies appear to be a reasonable order of magnitude [46].…”

“…Figure 7 summarizes the work of adhesion values calculated using the simplified Laugier model as a function of adhesion layer composition and compared to the NCD coating deposited on the bare Si wafer (grey line, labeled 'none'). Despite numerous simplifications, the obtained adhesion energies appear to be a reasonable order of magnitude [46]. Since scratch testing is highly dependent on the morphology of each surface, and on the coefficient of friction (COF) value between the two bodies (thin film and indenter tip) [18,22], it is important to use an appropriate value when attempting to quantify the adhesion energy (Equation ( 1)).…”