Criteria of microstructural assessment of the conventional and new TBC layers

Purpose: The purpose of this paper is to present principles and criteria of microstructural assessment of thermal barrier coatings (TBCs). The conventional layers are described in expert papers, whereas there is no literature on new type of thermal barrier coatings on the basis of RE₂Zr₂O₇ compounds Design/methodology/approach: The study was carried out on the TBC layers, sprayed by using the conventional powders on the basis of yttria stabilized zirconium (YSZ) oxides and by using the powders of pyrochlore structure. Industrial powder type Gd₂Zr₂O₇ was sprayed as a representative of a new group of materials to be sprayed with the APS method. Findings: The carried out analysis allowed to compare guidelines and criteria, which were used to assess the conventional TBC layer and their reference to barrier layers of a new type. The carried out study proved that heretofore used criteria of assessment for the TBC layers by using the conventional powders are sufficient to assess layers of a new type. Research limitations/implications: The carried out study suggests necessity to verify the received results in the case of the TBC layers, sprayed by using the powders of pyrochlore structures of other types. Practical implications: The received results show the possibility of using the heretofore criteria of microstructural assessment of the TBC layers as sufficient to get information on quality of the TBC layers of a new type. Originality/value: The information concerning basic principles in assessment of microstructural layers of a new type, which are sprayed with the APS method on high temperature creep resisting alloys, is an original value presented in this paper.