LOW-SPEED SLIDING BEHAVIOR OF METAL-CERAMIC COUPLES AT TEMPERATURES UP TO 800-DEGREES-C

The objective of this work was to select a small number of alloys with favorable tribological characteristics and suitable high temperature properties, and evaluate their sliding performance against ceramics as a function of temperature. Five candidate alloys were chosen. They in cluded four alloys containing cobalt and molybdenum, or tungsten and a nickel-base superalloy with good high-temperature strength. All of th ese alloys are known to form oxide films that protect sliding surfaces from damage at high temperature. These metals were slid against five ceramic flats of different compositions in slow speed reciprocating sl iding tests. The test geometry was a metal pin sliding against a ceram ic flat. Coefficients of friction and wear rates were measured over a temperature range from 25-degrees to 800-degrees-C. Material transfer from the metals to the ceramics played a major role in most of the res ults. In the low-to intermediate-temperature range, the transferred fi lms (with the exception of silicon carbide) coated the ceramic surface and sliding was essentially metal vs. the transferred metal film. At higher temperatures, depending on the alloy composition, the transferr ed films oxidized and provided reasonably low friction and, in some in stances, very low wear.