Crystal structure and high temperature tribological behavior of niobium aluminum nitride films

Abstract

Niobium aluminum nitride (NbAlN) films with various aluminum content were deposited using a reactive magnetron system and the film with 22.3 at% aluminum exhibiting the highest hardness, lowest wear rate and friction coefficient at room temperature was chosen to investigate the tribological properties at elevated testing temperatures. The results showed that from room temperature to 200 °C, the absence of oxide-based tribo-phases led to the reduction in wear rate, but friction coefficient remained stable. As the testing temperature increased from 200–500 °C, there was reemergence of γ-alumina tribo-phase, this resulted in intensified interaction between the wear track and the counterpart leading to an increase in both the wear rate and friction coefficient. A further increase in testing temperature resulted in a phase transition from a porous γ-alumina to a dense α-alumina. This transition aided in the reconstruction of the worn area in the wear track and the improvement in the friction and wear resistance properties.