Tribochemistry Between Water and Si3N4 and SiC: Induction Time Analysis

Published

October 1, 2004

Author(s)

Richard S. Gates, Stephen M. Hsu

Abstract

Avanced ceramics are being considered as one of the potential materials for high temperature steam engines. Silicon nitride and silicon carbide have demonstrated in laboratory bench wear tests that under low loads and medium speed conditions, water is an effective lubricant, achieving extremely low friction and wear. This unusual behavior has been attributed to tribochemical reactions between water and these ceramics. The detailed mechanism for this phenomenon is not clearly understood. Recent data also suggest that the time it takes to enter the tribochemical regime (induction time) for the two ceramics is very different. Silicon carbide takes 5 to 6 times longer to enter this regime than silicon nitride, yet the operating range for silicon carbide is much larger once it enters into this regime.This paper examines the various explanations for why these two ceramics should exhibit different time constants for tribochemistry to occur. Experiments were performed using a ball-on-three-flat geometry in water. A preworn-in procedure was used to control surface roughness and the tribochemical induction times were measured. It was found that wear-particle-induced third body effect prevented the successful entrance into the tribochemical regime. It was postulated that the films formed are very susceptible to third body effect and require smooth surfaces for the tribochemical reaction films to be effective.

Citation

Tribology Letters

Volume

17

Issue

No. 3

Pub Type

Journals

Keywords

ceramics, friction, gel formation, induction time, tribochemistry, water

Citation

Gates, R. and Hsu, S. (2004), Tribochemistry Between Water and Si₃N₄ and SiC: Induction Time Analysis, Tribology Letters (Accessed May 14, 2024)