Abrasive water jet piercing of straight and inclined holes on Yttria-Stabilized Zirconia coated Ni-based superalloy

The present work investigates the Abrasive Water Jet (AWJ) drilled holes with different hole angles such as 0 degrees, 15 degrees, 30 degrees, and 45 degrees on Yttria-Stabilized Zirconia (YSZ)-coated nickel-based superalloy using a piercing mode of operation. These types of holes were used as film cooling holes for the aero engine modules. The water jet pressure, hole piercing angle, and garnet flow rate were taken as variable operational parameters. The effect of these factors on hole features, such as entry and exit hole diameters, taper angle and coating removal rate, was analyzed. The machining time and surface roughness were also investigated. The results indicated the water jet pressure and hole piercing angle having significant effects on the hole geometrical features. Lower water jet pressure produced the exit hole cap, hairline burrs on the exit hole, and surface chipping. However, these defects were not found with an increment in the water jet pressure. Besides, circular and oval shape hole profiles were observed at different hole angles for film cooling applications. The AWJ pierced hole was seen having free of cracks, delamination, and other material defects. However, removal of excess YSZ coating was noticed near the hole by lateral erosion. This could be significantly reduced by optimizing the operational parameters for making quality holes on the ceramic-coated nickel-based superalloys.