# Deposition of 3 YSZ-TiC PVD Coatings with High-Power Impulse Magnetron Sputtering (HiPTMS)
## 2 Materials and Methods  
The parameter study consisted of two parts. First, preliminary tests with the yttri-stabilized zirconia (3 YSZ)-titanium carbide (TiC) target on the impact of the working gas flow of argon and krypton on the maximum substrate table current were conducted. In the preliminary tests, the gas flow of argon with respect to krypton varied between 0 and 650 sccm in intervals of 50, which added up to 14 \(\times\) 14 = 196 individual tests. The frequency was 800 Hz, the on-time of the cathode and the bias was 40 \(\upmu\)s, and the offset of the bias was 20 \(\upmu\)s.  
Secondly, the main experiments with the 3 YSZ-TiC target on the influence of the working gas flow, pulse frequency, cathode on-time, bias on-time and bias offset on the maximum table current were conducted, as shown in Table 1.  
Combined with the four gas mixes picked out for our preliminary tests (150 sccm Ar/0 sccm Kr, 100 sccm Ar/50 sccm Kr, 50 sccm Ar/200 sccm Kr and 0 sccm Ar/550 sccm Kr), we did 4050 tests for our main experiments. The target power was kept constant for the preliminary and main experiments at 4 kW, and the bias voltage was also kept constant at 70 V.  
The maximum substrate table current was measured with a Picoscope 4824 oscilloscope produced by Pico Technology Ltd., Saint Neots, United Kingdom, connected to a standard CC800 HiPIMS coating unit produced by CemeCon AG, Wurselen, Germany. In order to prevent the DAE and stabilize the coating process, an electrically conductive carbide ceramic (TiC) was added to the 3 YSZ target material. The 3 YSZ-TiC target contained 30 vol.-% TiC. The 3 YSZ-TiC target was hot-pressed and indium bonded by Avaluxe International GmbH, Furth, Germany. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Unit** & **Values** \\ \hline Frequency & Hz & 400, 500, 800, 1000 *, 2000 * \\ On-time cathode & us & 20, 30, 40, 50, 60 \\ On-time bias & us & 20, 30, 40, 50, 60 \\ Offset bias & us & 0, 10, 20, 30, 40, 50, 60, 70, 80 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of the high-power impulse magnetron sputtering (HiPIMS) parameters examined in this study. * Marked parameters were not measured with a gas mix of 150 sccm Ar/0 sccm Kr. By measuring the maximum substrate table current, we expected to see which gas flow mix and HiPIMS parameters produced the highest ionization rate of the 3 YSZ-TiC target atoms. High ionization is known to lead to better mechanical properties in coatings [14]. To conclude, we prepared coated tungsten carbide specimens with 9 wt-% Co with fixed parameters based on our preliminary experiment, as shown in Table 2.  
Because of non-uniform batch load in production applications (e.g., coating of cutting tools), the average power was kept constant. Peak power and other modes of operation led to deviations in the behavior of the cathode. Big deviations could lead to a security stoppage by the machine system. To measure the maximum table current at a constant set-up, we stopped the table rotation. The batch load was uniform for our measurements. The coatings were analyzed to measure the coating thickness, hardness, Young's modulus and elemental composition. Elemental composition was also measured on the target material of 3 YSZ-TiC. The thickness measurement (Calo test) was prepared with a Kalottchen/L produced by CemeCon AG, Wurselen, Germany and measured with an Olympus BXM-LEDR light microscope and Olympus Stream software produced by Olympus Europe, Hamburg, Germany. For the hardness and Young's modulus, we did nanoindentation with a Micro-Combi. Tester produced by CSM (now Anton Paar) in Graz, Austria. A total of 24 indentations were executed with a Berkovich indenter. Every indentation was executed with a linear load from 0 to 10 mN at a load rate of 20 mN per minute. The elemental composition was measured with an XFlash Detector 610M energy dispersive X-ray spectroscope (EDX) produced by Bruker Nano GmbH, Berlin, Germany.