ABSTRACT
The deposition of ceramic thermal barrier coatings, e.g. coatings based on partially stabilised zirconia, is of great interest for applications in energy converting machines like gas turbines. In this context the EB-PVD technique shows a really high potential because of its benefits in adapting the coatings microstructure to special demands. To achieve the desired columnar microstructure with respect to the optimised thermal cycling resistance, it is important to practice exact control of the substrates temperature.
This paper deals with the possibilities and limits of temperature control in special EB-PVD equipment used at the Materials Science Institute in Aachen. In this case a second electron beam gun was used as a substrate heater which results in a heating source inside the substrates. This direct heating method is seen to be contrary to indirect ones, e.g. radiant heaters. Therefore, accurate temperature control is more difficult to attain.
The pros and cons of the different methods for temperature measurement will be discussed. As a conclusion, the optimum method of temperature control using an electron beam as a substrate heater will be described. Because of the bad reproducability of temperature measurements by thermocouples, the decision was made to use an FEM program to obtain more accurate temperature values of the substrates surfaces, and correlating them to the energy which is converted into heat inside the substrates. Confirmation of the FEM calculation was made by temperature measurements inside the samples. However, additional investigations are necessary and in progress.
