Nano and Micro indentation studies of bulk zirconia and EB PVD TBCs

Abstract

In order to model the erosion of a material it is necessary to know the material properties of both the impacting particles as well as the target. In the case of electron beam (EB) physical vapour deposited (PVD) thermal barrier coatings (TBCs) the properties of the columns as opposed to the coating as a whole are important. This is due to the fact that discrete erosion events are on a similar scale as the size of the individual columns. Thus nano * and micro * indentation were used to determine the hardness and the Young's modulus of the columns. However, care had to be taken to ensure that it was the hardness of the columns that was being measured and not the coating as a whole. This paper discusses the differences in the results obtained when using the two different tests and relates them to the interactions between the indent and the columns of the EB PVD TBC microstructure. It was found that individual columns had a hardness of 14 GPa measured using nano indentation, while the hardness of the coating, using micro indentation decreased from 13 to 2.4 GPa as the indentation load increased from 0.1 to 3N. This decrease in hardness was attributed to the interaction between the indenter and a number of adjacent columns and the ability of the columns to move laterally under indentation.

Nanoindentation study of microplasma sprayed hydroxyapatite coating

“…However, in a practical situation, the hardness using similar indentations is found to vary with the load. The increase in hardness with decreasing load, which is known as indentation size effect, is often observed in bulk ceramics [36][37][38][39], physically and chemically vapour deposited ceramic coatings [40,41] as well as in plasma sprayed ceramic coatings [21,31,42,43]. In the present work, ISE also was observed ( Fig.…”

Porosity influence on the mechanical properties of polycrystalline zirconium nitride ceramics

“…From these figures, the nanoindentation size is of a sub-micro scale, which is remarkably smaller than the grain size. In this case, the nanoindentation is scarcely affected by the porosity [10,11] because the nanoindentation is just performed in the grain. For instance, the diamond tip does not touch the grain boundary or the pores.…”

Influence of porosity on hardness and Young's modulus of nanoporous EB-PVD TBCs by nanoindentation

“…The mechanical properties of EB-PVD TBCs were reported by nanoindeatation technique [12,13]. Because EB-PVD TBCs generally have a textured, columnar structure, the mechanical properties in the vertical and horizontal directions of the coatings are completely different.…”