| AVS 57th International Symposium & Exhibition | |
| Advanced Surface Engineering | Tuesday Sessions |
| Session SE-TuM |
| Session: | Hard and Nanostructured Coatings |
| Presenter: | C. Mitterer, University of Leoben, Austria |
| Authors: | R. Franz, University of Leoben, Austria J. Schnoeller, Vienna University of Technology, Austria H. Hutter, Vienna University of Technology, Austria C. Mitterer, University of Leoben, Austria |
| Correspondent: | Click to Email |
In the commonly applied procedure to study the oxidation behavior of hard nitride and carbide coatings, the sample is heated to a certain temperature and exposed to an oxygen-containing atmosphere during a defined period of time. Subsequently, the oxidized specimen is analyzed as to the thickness and morphology of the oxide layer or the composition and chemical nature of the oxides. In order to gain more information about the mechanisms active during oxidation the procedure can be split into two stages where different isotopes, 16O and 18O, are introduced in each step. An analysis by means of secondary ion mass spectrometry depth-profiling with its inherent isotope selectivity allows for an investigation of the general oxidation behavior as well as the oxygen diffusion during the oxidation process. In the present case, two AlCrVN coatings of equal composition but different crystal structure were studied. The single-phase coating with its face-centered cubic (fcc) structure presents a higher oxidation resistance as compared to the dual-phase coating containing a wurtzite and a fcc phase. After the annealing treatment, the surface of the latter is entirely covered by VO2 and V2O5 as evidenced by Raman spectroscopy. The single-phase coating, on the other hand, reveals unoxidized coating material and AlVO4 crystals. However, even though exhibiting a significantly different oxidation resistance, the oxygen diffusion is similar. In both cases peak values of 18O, which was introduced in the second stage, were found near the oxide-nitride interface indicating that O atoms diffused through the already formed oxides. Additional experiments using a gas mixture comprising natural water vapor H216O and 18O2 revealed that mainly the molecular oxygen serves as source for the formation of oxides as with increasing water vapor partial pressure the oxide layer thickness was significantly reduced.