Effect of titanium and deposition parameters on microstructure and mechanical properties of W-Ti-B thin films deposited by High Power Impulse Magnetron Sputtering

Abstract

Tungsten diboride alloyed with transition metals provides an opportunity to obtain exceptional mechanical, physical, and chemical properties. We report a strategy for designing and synthesizing of superhard and low-compressible ceramic thin films with increased toughness and lowered residual stresses (σ < −0.9 GPa) deposited with high-power impulse magnetron sputtering (HiPIMS) from one target. The addition of 7–12 % titanium promotes additional strengthening mechanisms of the layers in one material, leading to the improvement of wear resistance compared to an alloyed WB2-z yet at even higher hardness 43.8 ± 2.1 GPa and nanoindentation toughness 4.9 ± 0.2 MPa√m. The compression of the micropillar shows that titanium addition changed the type of nanoindentation from cracking along the slip plane to bulging on the top of the pillar and next the crack initiation along column boundaries. The highest adhesion of the layers is obtained for addition of 7 % titanium and in all cases the wear has abrasive character. The controlled use of 200 μs pulses during synthesis with HiPIMS allows for an increase in the deposition rate and maintaining exceptional mechanical properties of the layers even at a substrate temperature of 300 °C.