Abstract
The aero engine turbine blades made of Inconel 718, have thermal barrier coatings (TBC) to sustain high temperature air stream and cooling holes to reduce severe heat load. The complex physical and chemical properties of metal and ceramic layers pose challenges in a drilling these holes. Therefore, researchers have used laser and electrical discharge machining processes, which are time-consuming, costly, and inflict surface damages in and around the holes. To overcome these drawbacks, conventional micro-holes drilling has been adopted in this work. Drilling thrust distribution over cutting edges of micro-drills while drilling straight and inclined holes, under different cutting conditions has been analysed. The input parameters include: spindle speed, drill feed, and workpiece inclination, each at two levels. Each experiment was performed on TBC IN 718 sheet using a 600 μm TiAlN coated carbide drill under a dry peck-drilling cycle and was repeated twice. The results show that maximum elemental thrust in each experiment was found to be at the chisel edge. It was found to be 50–60% of the total thrust and varied non-linearly along the drill cutting edges, for straight as well as an inclined hole drilling. The unequal radial thrust distribution was observed due to workpiece inclination in case of inclined hole drilling, whereas a straight hole drilling shows an equal radial thrust distribution on each cutting edge.
