Influences of target poisoning on the mechanical properties of TiCrBN thin films grown by a superimposed high power impulse and medium-frequency magnetron sputtering

Abstract

Five TiCrBN coatings have been successfully fabricated by adopting hybrid co-deposition and superimposition concepts into high power impulse magnetron sputtering. The medium-frequency (MF) pulses were superimposed during the off-time of HiPIMS pulsing to Ti target. The direct-current (DC) and radio-frequency (RF) powers were connected to TiB2 and Cr targets, respectively. A plasma emission monitoring (PEM) system was used to grow thin films by tailoring the Ti target in transition and poisoning regimes, respectively. The different PEM set points, i.e., different target transition or poisoned regions, were selected to study their effects on the properties of deposited TiCrBN film. The deposition rate of TiCrBN films increased 1.64 times higher when the Ti target status changed from poisoning to transition regime by selecting PEM set points tuning from 30% to 70%. All samples exhibited a fine and dense microstructure, and a very smooth surface with the average roughness <1nm. The coefficient of friction and wear rate of each coating were in the ranges of 0.47–0.58 and 1.59–9.82×10−6mm3N−1m−1, respectively. The highest hardness of 38.9GPa, elastic modulus of 374GPa, acceptable adhesion quality of HF3 and upper critical load of 30N were obtained for T50% sample, which was grown at the PEM set point of 50%, in the transition region of Ti target and under the highest HiPIMS peak power density. This study also demonstrates the potential application of PEM apparatus attached to a superimposed HiPIMS-MF deposition technique for tailoring the growth of multicomponent metal nitride hard coatings.