Composition and mechanical properties of B-C-W and B-C-Ti thin films prepared by pulse magnetron sputtering

Abstract

In the present work, coatings in the material systems B-C-W and B-C-Ti have been synthesized by pulse magnetron sputtering, to exploit their potential as coatings for hard, wear resistant applications. These layers offer interesting properties, because of the possible amounts of carbides and borides that can form in the non-equilibrium deposition processes. Especially the amount of tungsten in the layers promises high wear resistance and corrosion protection at elevated temperatures.The B-C-W and B-C-Ti thin films have been deposited by pulsed magnetron co-sputtering in bipolar mode, using a boron carbide (B4C) target and a metal target (W or Ti) with a maximum total power input of 12.9W/cm2. The amount of metal in the layers has been varied by adjusting the sputtering pulse length of the respective target material. The influence of bias voltage on the properties of B-C-W coatings has been investigated and it was found out that bias voltages of −60V … −100V lower the hardness of the coatings.The hardness and the Young's modulus of the layers have been determined by nanoindentation. Whereas the majority of coatings exhibits hardness around 20GPa or lower, maximum hardness of 28GPa and Young's modulus of 420GPa are observed in a certain compositional range, in which coatings also distinguish by good thermal stability. Their composition has been analysed by using optical glow discharge emission spectroscopy (GD-OES) and Rutherford backscattering spectrometry (RBS).