Microstructure and mechanical properties of TiAlSiN nano-composite coatings deposited by ion beam assisted deposition

TiAlSiN nano-composite coatings with Silicon contents from 4.1 to 23.9 at.% were deposited on Silicon wafers. The nanohardness, microstructure, and adhesion force of the coatings were deeply affected by Silicon contents. The TiAlSiN with 9.0 at.% Silicon has a maximum hardness of 40.9 GPa, a highest adhesion force of 67 N and a lowest friction coefficient of 0.5. Microstructures show that Silicon doping increases the hardness of coating due to solid solution hardening effect and grain boundary enhancement effect. The amorphous Si3N4 matrix, which contains (Ti,Al)N nano-crystals, is formed as the Silicon content is increased. The matrix contributes to the nano-hardness and helps to resist surface oxidization. Especially, the matrix induces low surface roughness and decreases the friction coefficient.