Investigation of Initial and Steady-State Sliding Behavior of a Nearly Frictionless Carbon Film by Imaging 2- and 3-D TOF-SIMS

Abstract

Using imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS), we investigated the initial and steady-state sliding behavior of a nearly frictionless carbon (NFC) film. Specifically, TOF-SIMS images (both 2-D and 3-D) of these surfaces were constructed to highlight the spatial distributions of ionized and molecular species that were present on as-received and friction-tested NFC surfaces and as a function of depth. As a complementary technique, we used X-ray photoelectron spectroscopy (XPS) to gain further insight into the chemical nature of the sliding surfaces. The NFC films were produced on Si wafers and steel substrates in a gas discharge plasma that consisted of 25 vol.% methane and 75 vol.% hydrogen using a plasmaenhanced chemical vapor deposition (PECVD) system. They were then subjected to sliding friction and wear experiments in a pin-on-disk machine under 5-and 10-N loads and at sliding velocities of 0.2-0.5 m/s in dry nitrogen. The initial friction coefficients of the NFC films were in the range of 0.05-0.1, but decreased rapidly to values less than 0.01 at steady state. Positive and negative TOF-SIMS spectra and 2-and 3-D images reconstructed from selected masses revealed that the elemental distribution of certain chemical species differs substantially between undisturbed and tribo-tested areas of the NFC films. Specifically, the tribo-tested areas are essentially made up of carbon and hydrogen, while undisturbed or as-received areas are covered by a layer that is rich in oxygen and other species. These findings correlate well with the initial and steady-state friction coefficients of these films and help further explain their superlubricity in inert test environments.

Ultralow Friction Behaviors of Hydrogenated Fullerene-Like Carbon Films: Effect of Normal Load and Surface Tribochemistry

“…These transformations are advantageous for the decrease of the coefficient of friction of the H-FLC films. It was noticed that the fragment with m/z of 28 should be attributed to the Si element came from Si substrate, which is agreed with the previous literatures [46][47][48]. As the transfer films are born from the carbon films surface and then moved to the ball surface during the sliding process, it is reasonable to infer Fig.…”

Is Ultra-Low Friction Needed to Prevent Wear of Diamond-Like Carbon (DLC)? An Alcohol Vapor Lubrication Study for Stainless Steel/DLC Interface

“…In contrast, the ultra-low friction coefficient in vacuum or dry nitrogen environments results in an extremely low-wear rate of the DLC film. However, the ultra-low friction coefficient is observed after an initial induction period (or called a run-in period) during which the friction coefficient is high and gradually decreases to a low value as the friction test cycle repeats [13]. It is believed that the surface contaminants or the layers with sub-optimum compositions are removed during the induction or run-in period [13].…”

Tribological behavior of DLC films in space and automotive oil under boundary lubrication

“…A new position on the ball/disk was used for each test, and the friction coefficients were collected from the steady-state region (Eryilmaz and Erdemir, 2007).…”