Abrasive-Waterjet Drilling of High Temperature Jet Engine Parts

Abstract

An experimental investigation was performed to demonstrate the AWJ process capability for precision drilling of small diameter cooling holes in TBC-coated samples and full scale parts used in jet engines. All holes were drilled from the TBC side. Both qualitative and quantitative hole results issues were addressed. These include chipping of TBC, gouging inside the hole at the ceramic-metal interface, feathering at the exit side of the hole, tear drop shape, hole size and its consistency, overall drilling time, and potential systems productivity. It was observed that the AWJ produces high quality holes free from chipping or gouging. However, feathering may occur depending primarily on whether the substrate material is cast or rolled and can be substantially reduced or eliminated by adjusting the drilling parameters. It was also demonstrated that holes of about 0.025-ich can be drilled at 30 with less than 0.001-inch standard deviation. Air flow measurement results have also confirmed that less than 6% variation can be obtained from one set of holes (270 holes) to another. Drilling times below 10 seconds hole to hole were observed for drilling 0.060-inch thick metal substrates with 0.020-inch thick TBC thickness at 30 degrees. This time can be reduced to 3–4 seconds with improved systems. Although AWJ is still slower than laser, produced holes are of superior quality and do not need any additional processing. Future research efforts will focus on improving the drilling time.