Physicochemical, structural, mechanical, and tribological characteristics of Si_3N_4-MoS_2 thin films deposited by reactive magnetron sputtering

摘要

Si_3N_4 coatings show outstanding performance in wear and corrosion resistance of cutting tools at high temperatures, up to 1000 °C and above. In addition, the incorporation of minor concentrations of MoS_2 in Si_3N_4 could reduce the friction coefficient and preserve sufficiently high hardness values. In the present work, Si_3N_4-MoS_2 thin films were deposited on C and Si (001) substrates by RF and DC reactive deposition magnetron sputtering fromSi and MoS_2 targets in a Ar/N_2 plasma,with different lowMoS_2 amounts. The thin films were characterized by nanoindentation at different temperatures from 23 °C to 400 °C and sliding friction and nanoscratch tests at a constant temperature of 23 °C. Several different analytical techniques were also employed to characterize the thin films. In thewhole layer both Si_3N_4 andMoS_2 compounds are stoichiometric and the structure is amorphous and homogenous. Although the hardness is roughly constant in the here investigatedMoS_2 concentration range at constant temperature, the lowest amount of MoS_2 (0.2 at.%) increases substantially the hardness of Si_3N_4- MoS_2 thin films at 23 °C. The hardness of Si_3N_4-MoS_2 thin films decreases with the increase of temperature. The friction coefficient decreases substantially for MoS_2 concentrations between 0.2 and 0.3 at.% and the annealing process does notmodify such behavior. The 24 h annealing performed during hardnessmeasurements, up to 400 °C, induced thermally-activated processes in the thin films, whichmodify the critical load, hardness, and reduced elastic modulus of the thin film when measured at 23 °C.