Influence of the substrate bias voltage on the crystallographic structure and mechanical properties of Ti6Al4V coatings deposited by rf magnetron

Abstract

Physical and mechanical properties of pure titanium are improved when the material is mixed with aluminum and vanadium at specific concentrations. Specifically, the alloy composed by 90% of titanium, 6% of aluminum and 4% of vanadium (Ti-6Al-4V) is highly resistant to fatigue and corrosion titanium and their alloys can be deposited by two techniques: Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD). However, some problems are generated when carbonated steel substrates are used under the CVD technique, mainly because those substrates lost its carbon as a result of the high substrate temperature used during the deposition process. Alternatively, PVD (magnetron sputtering, ion plating) is a low temperature substrate process and also has the advantage that substrate bias can promote structure refinement through resputtering effects. Substrate bias influence on the crystalline structure of Ti6Al4V thin films prepared by rf magnetron sputtering are presented in this work. Samples were grown onto common glass and AISI 420 steel substrates using a Ti6Al4V (99.9 %) target. Substrate bias was varied from –100 V to –200 V. Samples were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDXS), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). Thin films stoichiometry were studied by EDX in agreement with the Ti-6Al-4V target. Finally, the studies of the mechanical behavior of the films on steel showed that the hardness increased 1100 Knoop when the bias voltage is raised to –160 V. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)