Investigation of the microstructure and characterizations of TiN/CrN nanomultilayer deposited by unbalanced magnetron sputter process

In this study, TiN, and CrN, monolayer thin films and a TiN/CrN multilayer thin film were deposited onto WC substrates by unbalance DC magnetron sputtering. Single-layer TiN and CrN thin films were prepared at various nitrogen flow rates (20-30 sccm). TiN/CrN multilayers with a monolayer thickness of 4 nm were also deposited on the WC substrates. The morphology, and crystalline structures of the as-prepared films were characterized by SEM and XRD, and their mechanical properties and thermal stabilities were also evaluated. The experimental results show that the grain size of the columnar structure increased with the nitrogen flow rate. The increase in the size of the grains in the columnar structure, however, can be minimized with an applied bias voltage of 100 V. When the nitrogen flow rate was increased from 20 to 30 sccm, β-Cr2N transformation to CrN was observed, while the TiN structure remained unchanged. The hardnesses of the TiN and CrN thin films were ~ 23.9 and 21.4 GPa, respectively. A significant increase in the hardness of the TiN/CrN multilayer thin film to 34.9 GPa (4 nm interval) could be observed. Scratch test results also show that the multilayer has more desirable properties than the monolayers. The critical load for the TiN/CrN multilayer thin film (45.0 N) was higher than that for the TiN (~ 24.8 N) or CrN (~ 37.3 N) monolayer thin films. After annealing at 800 °C, no significant phase transformation and decrease in mechanical properties of the TiN/CrN multilayer thin film could be observed.