EB-PVD zirconia thermal barrier coatings for experiments in space

Ceramic thermal barrier coatings based on partial stabilised zirconia (psz) are commonly known for applications in energy converting machines like gas turbines and, therefore, such coatings have been developed to meet these high demands. However, it is appropriate to use pst-coatings for other applications, as will be presented in this paper. The paper deals with zirconia coatings on W26Re substrates, which are used as covers for small crucibles. In these crucibles metallic molten material, e.g. Cu, Ni and Zr, will be investigated concerning its behaviour under microgravity. Therefore, the following demands an required: electrical isolation during the entire experiments, thermal shock and thermal cycling resistance up to the highest temperatures as well as a low light reflection coefficent. As a ceramic coating material for metallic W26Re substrates, partial stabilised zirconia was chosen because of its distinct properties. As a deposition process, which results in a coating with a very high potential concerning thermal cycling resistance, the electron beam-physical vapour deposition (EB-PVD) process was used. Finally, the coated substrates were examined concerning the special demands listed above, to ensure their practical value under microgravity. This paper describes the special application and the developed coating process as well as the results of the testing procedures.