Abstract: Diamond-like carbon (DLC) films are synthesized by the plasma immersion ion implantation and deposition (PIIID) technique on the steel substrate surface of aerospace bearing AISI440C. Raman spectroscopy analysis indicates that the DLC consists of a mixture of amorphous and crystalline phases, with a variable ratio of sp²/sp³ carbon bonds in which the sp³ bonds content is more than 10%. Atomic force microscope (AFM) reveals that the DLC film has extremely smooth surface, very high uniformity, and efficiency of space filling over large areas. The rolling contact fatigue (RCF) life results show that the maximum L₁₀, L₅₀, L_a and mean fatigue life L of the treated samples, at 90% confidence level, increase by 10.1, 4.2, 3.5, and 3.6 times respectively.The ANSYS simulation result exhibits that the maximum shear stress is about 2.15 GPa, which is generated in the substrate-film interface inside a certain depth in the film layer. Combined with the scanning electron microscope (SEM) morphology of DLC/AISI440C bearing fatigue pitches, a conclusion can be drawn that the micro-defects in the film interior induce the initiation of rolling contact fatigue pitches, while the action of the maximum shear stress together with the polluted gains in the lubricant oil is the exterior driving force for their final formation. A five phase physical model of PIIID DLC/AISI440C bearing fatigue failure is established under cyclic contact stress conditions.

Key words: plasma immersion ion implantation and deposition (PIIID), diamond-like carbon films, rolling contact fatigue, physical model, bearings