Thermomechanical properties and oxidation resistance of Ce–Si alloyed Ti–Al–N thin films

Abstract

Within this study, we show that single-phase face centered cubic (fcc) Ti0.47Al0.46Ce0.02Si0.05N coatings (sputtered from Ti0.37Al0.57Ce0.02Si0.04 targets plus the addition of Ti) outperform their single-phase fcc Ti0.49Al0.51N counterparts (sputtered from Ti0.40Al0.60 targets plus the same addition of Ti). The deposition rate increases by more than 43% and also the hardness of as-deposited Ti0.47Al0.46Ce0.02Si0.05N coatings is with 39.9 ± 1.2 GPa (on sapphire) 13% higher. Furthermore, this Ce-Si alloyed coating shows a remarkably higher thermal stability, represented by a higher annealing temperature (1200 °C instead of 900 °C) after which hexagonal structured wurtzite-type AlN (w-AlN) can be detected. They also show a more parabolic like oxide growth rate (4.13·10−7 and 1.13·10−5 μm2/s at 850 and 950 °C) during the 10-h-oxidation experiment, whereas that of Ti0.49Al0.51N is close to linear already at 850 °C (especially after ∼2 h). The postponed w-AlN formation guarantees that the hardness of Ti0.47Al0.46Ce0.02Si0.05N is still 40.8 ± 1.6 GPa even after annealing at 1100 °C. Our results clearly demonstrate that the addition of 2 mol% CeSi2 to Ti-Al targets allows to increase the sputter rate and leads to Ce-Si alloyed nitride coatings with improved thermomechanical properties and oxidation resistance.