Self-lubrication of nuclear graphite in argon at high temperature
Lorenzo Vergari, J. Quincey, G. Meric de Bellefon, T. Merriman, Micah J. Hackett, Raluca O. Scarlat
Abstract
Tribology studies in argon of nuclear graphite previously degassed at 600 °C show lower friction and wear at 600 °C than at room-temperature: the COF decreases from 0.55(14) to 0.33(5) and the specific wear rate decreases from 0.4(3) to 0.06(3) μg/Nm. Microstructural characterization of the wear spots via digital, polarized, and electron microscopy and Raman spectroscopy suggests formation of a Tribo-film formed by fracture perpendicular to the basal planes that exhibits crystallite alignment. The improved self-lubrication at high temperature results from the presence of a thicker and more continuous Tribo-film, attributed to the increase with temperature in the tensile strength and in the anisotropy of the chemical reactivity of graphite crystallites.