Mechanical properties and oxidation behavior of multilayered Hf-Si-N coatings

Abstract

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.