Identification of the high-temperature impact/friction of aeroengine blades and cases by micro Raman spectroscopy

The impact-friction of the tip of a blade coated either with a NiCoCrAlYTa alloy or with a Ni/BN-Al deposit and accelerated to high linear speeds (300 -500 m/s) has been studied in high temperature gases (similar to 1000 degre es C) on NiCrFeMo super-alloy substrates coated with a stabilized zirconia (8% at Y2O3) Electron/optical microscopy, X-ray diffraction and Raman micro spectroscopy were used to identify the phases present in the debris. Raman surface and section analysis were performed on the deposits and debris in o rder to get a step by step description of the impact-friction process and c omparison was made with model spinel compositions prepared by a chemical ro ute. The formation of a NiO-rich transient liquid lubricant enhancing the f ormation of a well-defined groove was also established. A more homogeneous and regular contact was obtained for blade tips covered with a mixture of N i/BN and an aluminium-rich layer. (C) 1999 Editions scientifiques et medica les Elsevier SAS.