Thickness study of vanadium carbide interface for deposition of DLC films

Abstract

PECVD (Plasma Enhanced Chemical Vapor Deposition) technique allows growth of wear-resistant and antifriction hard DLC films, with prevalence of sp 3 bonds in relation to hydrogen bonds. This paper presents an experimental evaluation of vanadium carbide layer (VC) thickness formed by reactive thermodiffusion process (TRD) for subsequent deposition of DLC. The salt bath is prepared by mixing the reagents: sodium tetraborate decahydrate, vanadium pentoxide and boron carbide. A crucible with lid was used, with capacity of 25 grams. The PECVD parameters used: 200 Torr vacuum, argon at 1.5 sccm, -600V at 0.05 Torr for 20 minutes; acetylene at 1sccm, -750V for 40 minutes at 0.07 Torr and 180 °C. AISI H13, D2 and O1 tool steels were used as substrates. The layers of VC were characterized by SEM, EDX and XRD, and the DLC films were characterized by SEM, EDX, indentation tests and Raman spectroscopy. The oxygen showed to be harmful to the growth of VC layers on steel substrates by reactive thermodiffusion process. The utilization of conical internal geometry with lid crucible were effective and contributed to the stabilization of thermodiffusion process, restricting oxygen environment and ensuring complete immersion of the sample, and allowing the growth of uniform and homogeneous VC layers suitable for subsequent deposition of DLC films.