Understanding and formalization of the fretting-wear behavior of a cobalt-based alloy at high temperature

TL;DR

This study investigates the high-temperature fretting-wear behavior of cobalt-based alloys, revealing a protective glaze layer formation through tribo-sintering that prevents wear and proposing a predictive formalization for wear behavior.

Contribution

It provides a detailed microstructural, chemical, and mechanical characterization of the tribolayer and introduces a formalized model for predicting glaze layer formation and wear in cobalt-based alloys.

Findings

Formation of a protective glaze layer at high temperature.

The glaze layer prevents wear by re-incorporating debris.

The model predicts wear across various tribological conditions.

Abstract

The purpose of this study is to investigate the mechanisms involved in the wear of cobalt-based interfaces at high temperature. The studied contact is a cobalt-based alloy subjected to fretting against an alumina sample. At high temperature, a protective third body is spontaneously created at the interface and presents excellent tribological properties. The formation of the so-called ''glaze layer'' leads to an absence of wear. The investigation presents on complete description of the hightemperature tribolayer with microstructural, chemical and mechanical characterizations. The glaze layer regime is mainly related to a threshold temperature above which a thin cobalt-rich layer is formed by a tribo-sintering process. A formalization of the tribo-sintering process is proposed to predict the necessary number of fretting cycles N GL to form the glaze layer. The tribo-sintering process prevents wear debris ejection by continuously re-incorporating the wear debris particles in the glaze layer. The re-incorporation of the wear debris may be the reason for the absence of wear of the fretted interface from a macroscopic point of view. Finally, the paper presents an extended friction energy wear approach taking into account tribo-oxidation and tribo-sintering considerations. The formulation is able to predict wear for a large range of tribological parameters (temperature, frequency, sliding amplitude, number of cycles), when applied to the Co-based/alumina contact.