Mechanical Properties and Oxidation Behavior of Multilayered Hf–Si–N Coatings

Monolithic Hf–Si–N coatings and multilayered Hf–Si–N coatings with cyclical gradient concentration were fabricated using reactive direct current magnetron cosputtering. The structure of the Hf–Si–N coatings varied from a crystalline HfN phase, to a mixture of HfN and amorphous phases and to an amorphous phase with continuously increasing the Si content. The multilayered Hf48Si3N49 coatings exhibited a mixture of face-centered cubic and near-amorphous phases with a maximal hardness of 22.5 GPa, a Young’s modulus of 244 GPa and a residual stress of −1.5 GPa. The crystalline phase-dominant coatings exhibited a linear relationship between the hardness and compressive residual stress, whereas the amorphous phase-dominant coatings exhibited a low hardness level of 15–16 GPa; this hardness is close to that of Si3N4. Various oxides were formed after annealing of the Hf–Si–N coatings at 600 °C in a 1% O2–99% Ar atmosphere. Monoclinic HfO2 formed after Hf54N46 annealing and amorphous oxide formed for the oxidation-resistant Hf32Si19N49 coatings. The oxidation behavior with respect to the Si content was investigated by using transmission electron microscopy and X-ray photoelectron spectroscopy.