Mechanical micro-drilling of nimonic 80A superalloy using uncoated and TiAlN-coated micro-drills

ABSTRACT

Micro-drilling is a complex mechanical machining process. Micro-drilling experiences an early tool damage which is a major drawback for nickel-based superalloy. This paper examines the wear condition on the micro-tool cutting edge, surface roughness of machined holes, and hole diameter analysis in micro-drilling of Nimonic 80A, using two types of micro-drills (uncoated and TiAlN coated) with 0.79 mm diameter. Micro-drilling tests, using cutting speed (V_c), feed rate (f_z), and the micro-drill diameter as experimental parameters were carried out to bring out the best optimized machining conditions in micro-drilling of Nimonic 80A. Wear on the tool cutting edge and burr height occurring at the entrance of drilled holes were measured at constant period to give the lastingness of micro-drill. Quality of holes were analyzed in terms of surface roughness inside the hole and the hole diameter after every five drilled holes. The result obtained from the above analysis showed that TiAlN-coated micro-drill performs way better than the uncoated micro-drill in terms of wear, surface roughness, hole quality, and burr. Thus, the above performed study gives the knowledge to select micro-tool for machining of Nimonic 80A which could be useful in the aerospace industry.

KEYWORDS:

• Burr
• coating
• drilling
• machinability
• nickel
• quality
• Wear

Acknowledgements

The authors thank the director, NAL, for permitting us to publish this paper. Thanks are due to Mr. Siju and Mr. Jakeer Khan for their help in giving relevant inputs. Dr. Naga Hanumaiah and Dr. S. S. Joshi are thanked for stimulating discussions.