Investigation of optimum drill diameter and coating properties in reaming of Ti6Al4V alloy

Reaming is one of the finishing processes widely applied in the manufacturing industry. Reaming of titanium-based Ti6Al4V alloy is an important and current research topic in manufacturing processes. Optimum manufacturing parameters is an important process for machinability of Ti6Al4V alloy. This research focused on finding these optimum parameters based on drill diameter, hole surface roughness values, reamer coatings, wear and ideal hole diameter values. In the experiments firstly, 6 holes were drilled with four different drills which has four different diameters (Ø6.7, Ø6.8, Ø6.8 t_land, Ø6.9). The forces acting on the drills were measured instantaneously by dynamometer holder. After drilling experiment, hole surface roughnesses and hole diameters were measured. Ø7 flat carbide reamer is used for reaming which has two different coatings (AlTiN and ZrN) and uncoated. After the reaming experiment, hole surface roughness and diameters of the holes were measured again. Considering these measurement results, the optimum drill diameter was determined. The maximum force was determined on the Ø6.7 drill, while the minimum force was determined on the Ø6.8 drill. Ø6.8 drill was chosen to continue to experiment. 850 holes were drilled with selected Ø6.8 drill and Ø7 ZrN and AlTiN coated reamers. The uncoated reamer achieved twice the wear rate of the coated reamers at 200 holes. Although the AlTiN coating is 10% less worn than the ZrN coating, ZrN gave better results in hole surface roughness measurements. Therefore, ZrN coating should be preferred for reaming process where surface quality is prominent. Keywords: Reamer, Ti6Al4V Alloy, Optimum Parameter, Coating