Structural and tribo-mechanical properties of AlCrVYON thin films with varying O contents sputtered from either AlCrVY or AlCrY and V targets

Abstract

Incorporating Y and V into AlCrN enhances its oxidation resistance and tribological properties at elevated temperatures. As this improvement stems from the oxide formation of these elements, depositing O-containing AlCrVYN presents a promising approach for thin films with enhanced tribo-mechanical properties for high-temperature applications. Therefore, AlCrVYON with varying O contents were deposited using a hybrid reactive dcMS/HiPIMS process in two distinct approaches. AlCrVYON was either sputtered from two AlCrVY targets or co-sputtered from AlCrY and V targets, with O₂ flow rates varying from 0 to 20 sccm.

Sputtering from AlCrY+V targets results in higher O contents from 1.4 to 31.3 at.% compared to the other target setup (up to 20.7 at.%). Synchrotron XRD showed a cubic CrN phase across all films, independent of O content or target setup. TEM imaging revealed nanolayered structures combining crystalline and amorphous phases, induced by O incorporation. This nanolayered structure results in a high hardness level around 40 GPa and maxima in the H/E ratio were observed at specific O levels for both configurations. High-temperature tribological analyses revealed no significant reduction in the coefficient of friction against Al₂O₃ at room temperature, but improvements were observed at elevated temperatures for most films, except those deposited with an O₂ flow rate of 10 sccm. Annealing the thin films deposited from two AlCrVY targets at 500 and 700 °C demonstrated high oxidation resistance, as no decrease in hardness, nor an increase in O content could be identified post-annealing. However, the thin films sputtered from AlCrY+V targets show a decrease in hardness after annealing at 700 °C.

In summary, the AlCrY+V target configuration produces AlCrVYON with higher O contents, resulting in a significantly different oxidation resistance. Other than that, both configurations show similar trends, demonstrating the advantage of adding small amounts of O into AlCrVYN.