Hole drilling with abrasive fluidjets

Small-hole drilling in several materials using abrasive fluidjets—abrasive-waterjets and abrasive cryogenic jets with liquefied nitrogen as the working fluid—were investigated through laboratory tests, numerical simulation, and phenomenological analysis. Drilling is accomplished by an abrasive slurry for abrasive-waterjets and primarily by a stream of dry abrasives for abrasive cryogenic jets as the liquefied nitrogen changes phase after exiting the mixing tube. Scaling factors were successfully derived through analysis of profiles digitized from hole images to collapse the data. For abrasive-waterjets, water is nearly incompressible; a high stagnation pressure inside the blind hole was developed causing delamination in laminates and cracking in the thermal barrier coating. The return abrasive slurry also possesses considerable residue erosion power that could cause damage to the hole entrance due to secondary wear. Neither delamination in laminates nor cracking in the thermal barrier coating is however observed when abrasive cryogenic jets were used.