Effect of Cr alloying on friction and wear of sputter-deposited nanocrystalline (MoxCr1−x)5Si3 films

In the present work, five kinds of nanocrystalline (MoxCr1−x)5Si3(x = 1, 0.78, 0.75, 0.64, 0.57) films with average grain size 8 nm have successfully been prepared on Ti6Al4V alloy by a double cathode glow discharge technique in order to improve its poor tribological properties. The influence of the Cr additions on the mechanical and tribological properties of nanocrystalline (MoxCr1−x)5Si3 films have been studied. The microstructure of the films was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Nanoindentation was used to measure hardness (H) and elastic modulus (E) of the as-deposited films, and the adhesion strength between the as-deposited films and substrate was evaluated by scratch test. The dry sliding wear properties of the as-deposited films were investigated using against different counterbodies (ZrO2 ceramic balls and GCr15 rolling bearing steel) in ball-on-disk system at room temperature. The results indicated that alloying additions of Cr affected considerably the wear performance of nanocrystalline (MoxCr1−x)5Si3 films. The friction coefficients and specific wear rates of nanocrystalline (MoxCr1−x)5Si3 films were significantly reduced by the increasing Cr substitution, and its specific wear rates have been shown to be two orders of magnitude lower than for Ti6Al4V alloy. The dominant wear mechanism of the nanocrystalline (MoxCr1−x)5Si3 films experiences a transition from delamination to tribo-oxidation wear, along with the increasing amount of Cr additions.