Performance Evaluation of Ceramic Materials and Aspects of Surface Preparation for Gas-Bearings.

摘要

In the first part of this report, silicon nitride and boron carbide were the materials studied for their friction and wear properties. Boron carbide in air gave an average coefficient of friction of 0.11 + or - 0.1 but values as low as 0.03 were observed under certain conditions. Surface chemistry plays a critical role in determining the coefficient values. Wear yielded surface-active debris which became more dense to form packed surface layers. The behavior of these surface layers determines the coefficient of friction. Silicon nitride yielded more wear debris and gave very short stable runs. Packed surface layers were also observed. Coefficients of friction from 0.4 to 0.04 were measured. The most frequently observed value in air was 0.28. In a separate work (Part II) an in-depth study of the surface preparation for gas bearings was done. Surface finish, which results from a complex interaction between system and material, has a very important influence on the performance of the gas bearings.