High Temperature Sliding Wear and Glaze Formation in Nickel- and Cobalt-based Superalloys

The tribological behaviour of nickel- and cobalt-based superalloys within gas turbine combustion chambers plays a vital role in determining component longevity and engine performance. These materials operate under exceptionally demanding conditions, with gas temperatures approaching 2100 °C and components being subjected to unlubricated contact, severe oxidation and rapid surface degradation. The mechanisms governing their wear behaviour under realistic service conditions require further investigation. A key protective phenomenon observed during high temperature sliding is the formation of a glaze layer, a glassy oxide film produced from compacted and sintered wear debris. This layer can significantly reduce friction and wear, facilitating a transition from severe to mild wear. Current understanding of glazing is largely restricted to temperatures below 800 °C, which does not reflect the true operating environment of modern combustors that routinely reach 1000 °C.

This PhD research project aims to address these gaps by experimentally investigating glaze behaviour beyond the temperature range typically explored in the literature. The work focuses on clarifying the mechanisms driving glaze initiation, growth, stability and degradation on relevant superalloys subjected to novel high temperature tribological testing.

The outcomes of this study are expected to advance fundamental understanding of high temperature wear processes and support the development of improved materials, component designs and surface protection strategies for next-generation gas turbine engines.