Oxidation study of cobalt- base super alloys at high temperatures in molten salt of Na2SO4

Abstract EN

The major objective of this study was to understand the mechanisms controlling the thermal barrier coatings (TBCs) and use this understanding to develop new TBCs with improved performance characteristics.

The system studied consisted of the Cobalt-Base superalloy as a substrate and yttria-stabilized Alumina as a ceramic topcoat.

A second objective of the study was to see the degradation behavior of the systems during thermal cycling (three hour cycles in a bottom-loading furnace).

The failure mode for the aluminized because of the defects at the coating-thermally grown oxide (TGO) interface and at the TGO bond coat interface.

The fractures then propagated along the interface between the bond coat and the TGO.

The failure the aluminide was found a coat interface and a deformation mode of the bond coat.

The effect of cycle frequency on the spallation failure of the state TBCs was also found small degradation.

The molten salt of (Na2SO4) conditions affect the lifetimes of the coatings.

Exposure temperature was found to have a strong effect, which is consistent with TGO growth being a first order variable in scale failure.