Fretting friction and wear of diamond-like carbon multilayer films with silicon and boron nitride

Introduction: Our aim is to evaluate the tribological properties of nano-scale multilayer diamond-like carbon (DLC) films through fretting test under different friction amplitudes and lubrication conditions.

Materials and methods: In this study, a bias sputtering apparatus was employed to create nanoperiod multilayer films composed of DLC alternating with silicon (Si) or boron nitride (BN) to improve friction and wear properties. Testing indicated significant differences in friction behavior: traditional DLC films maintained a high coefficient of friction, particularly at high amplitudes such as 500 μm, leading to fractures. In contrast, the (DLC/BN)n and (DLC/Si)n nanoperiod multilayer films displayed a decreasing friction coefficient with different amplitude conditions, with (DLC/Si)n films showing enhanced wear resistance at lower amplitudes like 50 and 20 μm and (DLC/BN)n films excelling at higher amplitudes of 100 and 500 μm. Moreover, wear mechanisms differed; the (DLC/BN)n film’s wear depth increased with load, while the (DLC/Si)n film exhibited bulging without wear.

Results: The structural design influenced the films’ elastic modulus and hardness, with the (DLC/BN) films demonstrating superior tribological properties and the (DLC/Si)n films showing high hardness and Young’s modules, making them resistant to plastic deformation. Raman spectroscopy analysis revealed that (DLC/BN)n and (DLC/Si)n films exhibited different D- and G-band peaks.

Conclusions: Therefore, their friction surfaces showed significant differences, attributed to varying degrees of disorder and graphitization on the film surfaces after the friction test. Furthermore, under Poly alpha-olefin (PAO) lubrication conditions, friction coefficients decreased for both films, with diminishing amplitude effects, suggesting the improvement of their application for variable loading environments due to lubrication oil addition.