Controlled Removal of HVOF Hard Coatings by Abrasive Water Jet

This paper presents development of adaptive Abrasive Water Jet (AWJ) removal method for HVOF hard coatings. High pressure water jet using Al₂O₃ powder was used to remove WC-CoCr and Cr₃C₂-NiCr HVOF coatings in a controlled manner. As a result, coating thickness was reduced down to 10-20 µm without damaging the base material. With this novel method use of environmentally problematic chemicals can be avoided or reduced in coating stripping process. To control the coating removal process and to prevent unwanted base material erosion through jetting, a system capable of measuring the coating thickness non-destructively with adequate accuracy was integrated to the AWJ removal cell. Depending on the substrate and coating materials used, the applied measurement technique is based on the eddy current or X-ray fluorescence methods.