Use of silicon or carbonitriding interface in the adhesion of Ag-DLC film on titanium alloy: a comparative study

Abstract

A Hollow Cathode Plasma Enhanced Chemical Vapor Deposition (HC-PECVD) reactor was used to deposit silver doped Diamond-Like Carbon (Ag-DLC) films on Ti6Al4V alloy employing two methodologies: i) producing a silicon interlayer, using tetramethylsilane (TMS) as silicon precursor, varying the argon flow of the hollow cathode; and ii) carbonitriding the substrate. Profilometry, Raman, and Secondary Ion Mass Spectrometry (SIMS), as well as nanohardness, micro-scratch, scratch, and VDI 3198 indentation tests were used to evaluate the characteristics of the films and their adhesion on the substrates. The results demonstrated that the argon flow can be used for tuning the Ag-DLC film’s hardness, toughness, and adherence on silicon interlayers. The carbonitriding process, in turn, provided an improvement in the film toughness compared with non-carbonitrided samples. Considering the lower cost and easier handling of N₂ compared to the silicon precursors commonly available (TMS, HDMSO, SiH₄, etc.), the carbonitriding process proved more appropriate to improve the adhesion of the Ag-DLC films on the Ti6Al4V alloy.

Keywords:
diamond-like carbon; PECVD; hollow cathode; carbonitriding; titanium; scratch