Superimposition of high power impulse and middle frequency magnetron sputtering for fabrication of CrTiBN multicomponent hard coatings

The combination of superimposition and hybrid target powers using a superimposed high power impulse magnetron sputtering (HiPIMS) power and middle-frequency (MF) power system, together with the hybrid of direct-current (DC) and radio-frequency (RF) powers was adopted in this work to grow CrTiBN hard coatings. The flexibility of tailoring the chemical composition, phase, deposition rate, microstructure and mechanical properties of CrTiBN coatings through the feedback control of reactive N₂ gas flow rate and the corresponding Ti target poisoning status by a plasma emission monitoring (PEM) system was successfully illustrated in this work. Both the peak current and peak power density of Ti target increased with increasing poisoning ratio, i.e., decreasing PEM set point. The 1.64 times higher deposition rate of CrTiBN films can be obtained when the Ti target status changes from poisoning (PEM set point 30%) to transition regime (PEM set point 70%). Fine and compact film microstructure, and a very smooth surface are fabricated for all films. Each coating shows a low coefficient of friction and low wear rate ranging from 0.46 to 0.49 and from 2.06 to 5.73 × 10⁻⁶ mm³ N⁻¹m⁻¹, respectively. The highest hardness of 34.1 GPa, adequate adhesion and wear resistance can be found for the CrTiBN coating as deposited at PEM set point of 40% and Ti target poisoning ratio of 60%.