Influence of Si Content on Microstructure, Mechanical Properties and Tribological Properties of VAlSiN Coatings

VAlSiN coatings with different Si contents were deposited at 300℃ by reactive magnetron sputtering. The effect of Si content on the microstructure, growth morphology,chemical state, mechanical properties,friction and wear properties was investigated. The results show that the VAlN coating exhibits a single-phase NaCl structure with (111) preferred orientation. The VAlSiN coatings gradually lose their structure of (111) preferred orientation and transfer into amorphous structure with the increase of Si content. The VAlSiN coatings which Si content is more than 1.8% (atom fraction,same as below) are multi-phase composite coatings consisting of nc-VAlN and a-Si3N4. Compared to VAlN coating, the density of VAlSiN coatings with small amount of Si (0.8%) is increased significantly as well as the hardness that reaches 30.1GPa,while the grain size is decreased. Further increasing Si content, the growth of columnar grains is interrupted, concomitant of the hardness gradually declines and tends to be stable at 22GPa. The friction coefficient of the VAlSiN coatings decreases first and then increases with the increase of Si content. The wear rate reaches the lowest value of 1.2×10-16 m3·N-1·m-1 is obtained when Si content is 0.8%.