A Comprehensive Investigation on Nanomechanical, Scratch, and Tribological Characteristics of TaN-Ag Nanocomposite Coating on Ti6Al7Nb Alloy

This investigation explores the improvement in mechanical and tribological properties of the Ti6Al7Nb alloy by depositing TaN-Ag (0.5 at.%) nanocomposite coating using magnetron sputtering. The structural properties, morphology, elemental composition, and surface roughness of nanocomposite coating were studied. The effect of nanoindentation load on the hardness (H) and modulus (E) of the substrate and deposited nanocomposite coating was studied. To determine the coefficient of friction and wear rate, tribological tests were performed on the substrate and coating under the applied load range 0.50-1.50 N. Also, scratch test was performed under progressive loading 0-600 mN to determine the critical loads. The results demonstrated that indentation load significantly affects the H, E, and H/E ratio values. The TaN-Ag coating shows reduced wear rate (10⁻⁵ mm³/N m) compared to substrate (10⁻³ mm³/N m). Cracking due to spallation and fine abrasive grooves were main mechanisms responsible for wear of TaN-Ag nanocomposite coating. Raman spectroscopy also confirmed oxide formation during sliding.