ICMCTF2015 Session Ex: Exhibition Keynote Lecture
Time Period TuEx Sessions | Abstract Timeline | Topic EX Sessions | Time Periods | Topics | ICMCTF2015 Schedule
Start | Invited? | Item |
---|---|---|
11:00 AM | Invited |
Ex-1 Synthesis of Oxides by Reactive Cathodic Arc Evaporation: Cathode Surface and Coating Properties
Jürgen Ramm (Oerlikon Balzers Coating AG, Liechtenstein) Reactive cathodic arc evaporation is an attractive method to produce thin oxide coatings at moderate substrate temperatures. Characteristic for this deposition method are two distinctive features which influence the crystalline phases of the synthesized coatings: the freedom to select the chemical composition of the compound cathodes and the control of the metal-to-oxygen ratio during the deposition. An attempt is made to predict the phase formation generated by the arc at the cathode (target) surface and correlate it with the phases of the synthesized coating. The development of the phases at the target surface depends on the oxygen partial pressure and on the particle size utilized to fabricate the powder metallurgical targets. A comparison of the processes at the target surface with the coating synthesis unveils correlations. This knowledge is helpful in the designing of oxide coatings for dedicated applications. The influence of the chemical composition of the targets and the oxygen partial pressure on the formation of the binary and ternary oxide phases was investigated for the Al-Cr, Al-Hf and Al-Ni material systems. The application of oxide coatings in high-temperature environments as oxidation and diffusion barriers is of particular interest. The oxidation process was studied for intermetallic coatings during annealing in ambient atmosphere with temperatures up to 1300°C. The spontaneous selective oxide growth in these materials was investigated by in-situ high-temperature XRD and explains the mechanical malfunctions of the coatings. In search of oxidation barrier coatings for these intermetallic layers, oxide coatings were synthesized for which the metallic components correspond to the metallic components in the underlying intermetallic layer. These coatings showed improved thermal stability which is a result of the pre-formation of high-temperature oxide phases during oxide synthesis already at a substrate temperature of 550°C. Outstanding barrier quality was found for the solid solution of (Al,Cr)2O3 in corundum structures for several applications. |