Indentation creep of free-standing EB-PVD thermal barrier coatings

Abstract

The indentation creep behavior of a free-standing 7 wt%Y-ZrO2 thermal barrier coating (TBC) prepared by electron beam physical vapor deposition (EB-PVD) has been investigated. The specimens in the form of discs with 5mm in diameter and 1.2mm thickness were used for experiments in the temperature ranging from 1100 to 1300 ◦C and at stresses from 30 to 70MPa, in air. A flat-ended cylindrical indenter has been used. The strain–time relationship was recorded, and the creep exponents and activation energies of the creep have been calculated. The creep micromechanisms have been also studied by means of scanning electron microscopy. The obtained creep stress exponent varied from 0.05 to 1.12 and the obtained activation energy in the interval from 215 to 329 kJ/mol. The main creep mechanisms are densification of the sub-layers with fine columnar crystals, bending of crystals and leaning down of sets of crystals.