Wear behaviour and rolling contact fatigue life of Ti/TiN/DLC multilayer films fabricated on bearing steel by PIIID

In order to improve the friction and wear behaviours and rolling contact fatigue (RCF) life of bearing steel materials, Ti/TiN/DLC (diamond-like carbon) multilayer hard films were fabricated onto AISI52100 bearing steel surface by plasma immersion ion implantation and deposition (PIIID) technique. The micro-Raman spectroscopy analysis confirms that the surface film layer possess the characteristic of diamond-like carbon, and it is composed of a mixture of amorphous and crystalline phases, with a variable ratio of sp2/sp3 carbon bonds. Atomic force microscope (AFM) reveals that the multilayer films have extremely smooth area, excellent adhesion, high uniformity and efficiency of space filling over large areas. The nanohardness (H) and elastic modulus (E) measurement indicates that the H and E of DLC multilayer films is about 32 GPa and 410 GPa, increases by 190.9% and 86.4%. The friction and wear behaviours and RCF life of DLC multilayer films specimen have also been investigated by ball-on-disc and three-ball-rod fatigue testers. Results show that the friction coefficient against AISI52100 steel ball decreases from 0.92 to 0.25, the longest wear life increases nearly by 22 times. In addition, wear tracks of the PIIID samples as well as wear tracks of the sliding steel ball were analyzed with the help of optical microscopy and scanning electron microscopy (SEM). The L10, L50, La and mean RCF life L of treated bearing samples, in 90% confidence level, increases by 10.1, 4.2, 3.5 and 3.4 times, respectively. Compared with the bearing steel substrate, the RCF life scatter extent of Ti/TiN/DLC multilayer films sample is improved obviously.