Microfracture and Limited Tribochemical Wear of Silicon Carbide During High‐Speed Sliding in Cryogenic Environment

Abstract

In an effort to develop an understanding of the tribological properties of silicon carbide (SiC) in a cryogenic environment, this contribution reports on the results of the sliding wear properties of the self‐mated SiC in liquid nitrogen (LN2). Two sets of sliding wear tests were conducted in a planned manner in LN2 under varying combinations of operating conditions, using a specially designed high‐speed cryo‐tribometer. In the first set, the sliding velocity is varied up to 1.1 m/s, for 600 s, at a constant load of 5 N; while the second set of experiments were conducted with loads of 5, 10, and 15 N, at a constant speed of 3.3 m/s for 900 s, thereby enabling to evaluate tribological potential over a broad spectrum of operating conditions. In our experiments, high coefficient of friction (COF) (0.28–0.40) and high wear resistance (∼10−7–10−6 mm3/N m) have been measured for self‐mated SiC. The topographical observations using a scanning electron microscope reveal that limited tribochemical layer formation, as well as grain boundary microfracture‐induced damage mechanisms, contribute to the wear of self‐mated SiC. The experimental results are critically analyzed with reference to flash temperature and contact stress conditions, as well as compared with some baseline experiments, conducted under ambient conditions. A comparison with our earlier research results, obtained with self‐mated Al2O3 or ZrO2, establishes the good tribological potential of self‐mated SiC in LN2, in terms of exhibiting a better combination of COF and wear rate.

Tribological characteristics of SiC ceramics sintered with a small amount of yttria

“…The sliding wear resistance of SiC ceramics was superior under high humid (60% RH) conditions as compared in dry or moderate humid (30% RH) conditions [18]. The sliding wear resistance of SiC ceramics in liquid nitrogen (cryogenic environment) was better than that under ambient condition [24]. The sliding wear resistance of a SiC ceramic in deoxygenated water decreased at elevated temperatures at given sliding speed, but decreased with increasing sliding speed at 120 1C and 300 1C [25].…”