In situ remote hot erosion scar measurement

When particles of grit, oxide or other contaminants get entrained in high speed gas or steam sections of power or aero turbines they can damage components through repeated impact of particles with the surface. This erosion in turn produces additional debris which can damage other surfaces further down-stream. An instrument to evaluate and quantify high temperature solid particulate erosion (HTSPE) is being designed and built at the National Physical Laboratory (UK). In order to speed up the measurement of the erosion scars, a system is required that can measure the shape and depth of scars on test coupons of materials without the need to remove them from the HTSPE system to perform the measurement. This paper deals with the optical technique that has been developed and validates its performance against a specially prepared test artefact containing 'erosion pits' of several different depths as well as on actual erosion scars produced with a particulate erosion system.