Industrial reactive sputter deposition of TiZrN coatings: The role of nitrogen partial pressure

Abstract

Reactive sputter deposition of TiN, ZrN, and TiZrN coatings at different nitrogen partial pressures was performed under industrial conditions using a combinatorial approach. For all coatings, the nitrogen content rose with increasing nitrogen partial pressure and then leveled off above a given pressure. The ZrN coatings exhibited a columnar structure irrespective of the nitrogen pressure used. In contrast, the microstructure of TiN and TiZrN varied depending on the nitrogen partial pressure. A different behavior of the crystallite size as a function of the nitrogen partial pressure was observed for TiN and ZrN. A strong dependence was noticed for TiN. This contrasted with the behavior of ZrN which had much smaller crystallites. Smaller crystallites were also observed in the TiZrN coatings and the influence of the nitrogen partial pressure and the Ti/(Ti + Zr) ratio on these coatings was weak. The coloration of the coatings was notably influenced by nitrogen partial pressure. The level of red for the TiN and TiZrN coatings and the yellow hue for the ZrN coatings significantly increased with nitrogen partial pressure. The hardness of all TiZrN coatings peaked at intermediate nitrogen partial pressures, which indicates that nitrogen partial pressure enables the optimization of mechanical properties. The highest measured hardness (31 GPa) was obtained at a Ti/(Ti + Zr) ratio of 0.50 although similar values were obtained irrespective of the metallic elements. This study demonstrates the potential to enhance the mechanical properties of TiN by incorporating Zr provided the correct nitrogen partial pressure is selected.