Measurement of grit wear in abrasive c-BN electroplated tipped blades for gas turbines applications

Abstract

The increasing use of ceramic abradable seal systems in the High-Pressure Turbine section of gas turbines, aimed at improving efficiency and reducing fuel consumption, introduces new challenges in performance evaluation. This work proposes a standard method to quantify wear on c-BN electroplated tipped blades, which function as abrasive coatings on rotor blades. The approach relies on 3D metrology scanner to capture surface data of the blade and converting them into measurable parameters that allow for consistent comparison between blades from rig testing. Key metrics include grit density, the volume occupied by abrasive particles, and the corresponding void volume and void density resulting from wear. An additional parameter is proposed to account for debris accumulation and its effect on the proposed wear-related metrics. The results demonstrate consistent trends across the proposed parameters, both in pristine and tested blades, regardless of their initial grit density as well as with grit wear patterns. The proposed Positive Volume Variation (PVV) and Grit Density Variation (GDV) metrics exhibited a strong mutual correlation (r = 0.950), a result supported by their shared underlying physical basis. In contrast, the Mean Height Variation (MHV), typically applied to bare blades, demonstrated weaker correlations with both PVV (r = 0.893) and GDV (r = 0.745).