Rolling contact fatigue behavior of ceramic balls lubricated by lubricants with extreme pressure additives

An experiment is conducted to investigate the effects of lubricant 10#, which contains extreme pressure additives T304 and T305, on the rolling contact fatigue (RCF) life of the contact pairs of a Si₃N₄ ceramic ball and a steel rod. The experimental investigation is carried out using a ball-rod RCF test rig. The results show that the extreme pressure additives increase the anti-contact-fatigue performance of ceramic balls; When the content of the additives varies from 1% to 5%, the increasing gradient of the RCF life curve decreases; And the oil sample with 1% T305 additive corresponds to the maximal gradient of the RCF life curve, with the RCF life being increased by about 10.77 times. The fatigue surface of the ceramic ball is analyzed with scanning electron microscopy (SEM) and X-ray electron dispersion analysis (EDAX), and the physical model of extreme pressure additive increasing the RCF life of the ceramic ball is proposed. It is found that the extreme pressure additives form a corrosive film and a transfer film on the surface of the ceramic ball, which decrease the surface tangential stress, and to increase the surface energy is the most effective means for increasing the RCF life.