Tribological Evaluation of an Al2O3-SiO2 Ceramic Fiber Candidate for High Temperature Sliding Seals

A test program to determine the relative slitting durability of an alumina-silica candidate ceramic fiber for high temperature sliding seal applications is described. Pin-on-disk tests were used to evaluate the potential seal material by sliding a tow or bundle of the candidate ceramic fiber against a superalloy test disk. Friction was measured during the tests and fiber wear, indicated h the extent of fibers broken in the tow or bundle, was measured at the end of each test. Test variables studied included ambient temperature from 25° to 900°C, loads from 1.3 to 21.2 N, and sliding velocities from 0.025 to 0.25 m/sec. In addition, the effects of fiber diameter and elastic modulus on friction and wear were measured. Thin gold films deposited on the superalloy disk surface were evaluated in an effort to reduce friction and wear of the fibers.

In most cases, wear increased with test temperature. Friction ranged from 0.36 at 500°C and low velocity (0.025 miser) to over 1.1 at 900°C and high velocity (0.25 m/sec). The gold films resulted in satisfactory lubrication of the fibers at 25°C. At elevated temperatures diffusion of substrate elements degraded the films. These results indicate that the alumina-silica (Al₂O₃SiO₂) fiber is a good candidate material system for high temperature sliding seal applications. More work is needed to reduce friction.