Synthesis and characterization of multilayered TiC/TiB₂ coatings deposited by ion beam assisted, electron beam-physical vapor deposition (EB-PVD)

Polycrystalline 4 μm and 14 μm thick multilayer TiB₂/TiC coatings with varying number of total layers (2-20) were deposited by ion beam assisted, electron beam-physical vapor deposition (IBA, EB-PVD) on WC-6wt.%Co-0.3wt.%TaC substrates. The average Vicker's hardness numbers were found to increase with increasing total number of layers and ranged from 3215 VHN_0.050 to 3726 VHN_0.050 and 3294 VHN_0.050 to 3991 VHN_0.050 for the 4 μm and 14 μm thick multilayer TiB₂/TiC coatings, respectively. The adhesion of the multilayer coatings was found to be greater than 50 N for a 4 μm thick film and less than 30 N for the thicker films. The degree of crystallographic texture was found to change with varying total number of layers, as well as the orientation of both materials within the multilayer system. The grain size and amount of residual compressive stress was found to decrease with increasing number of layers. In addition, the fracture toughness was found to decrease with increasing total number of layers. This paper discusses the effect of changing the individual layer thickness (i.e. total number of layers) for TiC/TiB₂ multilayer coatings deposited on WC-6wt.%Co-0.3wt.%TaC cutting inserts on the average Vicker's hardness number, 2 adhesion, stress, fracture toughness, argon impurities, average crystallite size, crystallographic texture, surface morphology and microstructure using a variety of characterization techniques.