Twist Drilling of Haynes 282 Superalloy

Experimental work is presented detailing tool wear and workpiece integrity results when drilling next generation Haynes 282 aeroengine casing material using coated carbide tooling with high pressure (50 bar) cutting fluid. Testing involved variation in cutting speed and feed rate typically used for Ni-based superalloys. At lower combinations of operating parameters, flank wear was generally uniform however extensive wear/fracture of the tool corner chamfer was evident in the majority of tests. Adhered material up to ∼250 μm long was observed on all machined surfaces, which increased with worn tooling and at higher operating conditions. Microhardness results showed an increase in hardness (up to 50 HK0.05 above the bulk) within the first 50 μm. Surface/subsurface microstructural damage consisted of deformed grain boundaries up to a depth of ∼15 μm with a discontinuous white layer of up to ∼6 μm from the surface.