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

Abstract

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 (∼1000 °C) on NiCrFeMo super-alloy substrates coated with a stabilized zirconia (8% at Y 2O 3). Electron/optical microscopy, X-ray diffraction and Raman microspectroscopy were used to identify the phases present in the debris. Raman surface and section analysis were performed on the deposits and debris in order to get a step by step description of the impact-friction process and comparison was made with model spinel compositions prepared by a chemical route. The formation of a NiO-rich transient liquid lubricant enhancing the formation of a well-defined groove was also established. A more homogeneous and regular contact was obtained for blade tips covered with a mixture of Ni/BN and an aluminium-rich layer.