Nanocomposite oxide and nitride hard coatings produced by pulse magnetron sputtering

In this work, the composition and the microstructure of two-phase hard coatings have been varied by reactive pulsed co-sputtering of two target materials to produce nanocomposite structures. Two material systems have been studied for their potential of improved properties induced by phase segregation: the nitride system Ti–Al–N and the oxide system Al–Zr–O. Both systems combine well-established hard coating materials and hold the potential for nanocomposite formation. The nitride system is known to exhibit enhanced properties when the composition Ti1−xAlxN is in the range x=0.5…0.7. Pulse magnetron sputtering allows tuning of the composition in this range by varying the pulse durations of the two materials sputtered. nc-(Ti,Al)N/nc-AlN films with hardness up to 38 GPa have been produced by optimising composition and microstructure. In the oxide system, nc-Al2O3/ZrO2 coatings with γ-phase Al2O3 of hardness about 30 GPa are obtained only when the ZrO2 content is below 8 at.%. With increasing zirconia content the films become amorphous and exhibit hardness of 10 GPa. At low alumina content, crystalline zirconia is stabilized in its tetragonal phase exhibiting hardness of 17 GPa.