Carbon and titanium diboride (TiB2) multilayer coatings.

摘要

Titanium Diboride, (TiB2) is a metal-based refractory ceramic material that hasbeen investigated in industrial applications ranging from, cutting tools to wearparts and for use in the aerospace industry. The unique properties which makethis material so fascinating are, its high hardness, high melting point and itscorrosion resistance. TiB2 is prevented from wider mainstream use because of itsinherent brittle nature. With a view to overcome this in coating form and withthe aim of providing in addition inherent lubricity, in this study 50 layerTiB2/C multilayer stacks have been fabricated, with varying volume fractions ofceramic, whereby the interfaces of the layers limit crack propagation in theTiB2 ceramic. TiB2 has been multilayered with carbon, to make use of the uniqueand hybrid nature of the bonding in carbon coatings. DC magnetron sputteringwith substrate bias was the preferred route for the fabrication of thesecoatings. AISI tool steel has been used as the substrate material. By varyingthe amount of TiB2 ceramic from 50% to 95%, the Hardness of the coating is seento increase from 5 GPa to 17GPa. The Hardness is observed to decrease as afunction of increasing carbon content, agreeing with other studies that thecarbon layers are not load-bearing. The graphitic nature of the sp2 bond,however, acts as a lubricant layer.