Effect of Different Cutting Conditions on Tool Wear and Chip Formation in Drilling of Cobalt Chromium Molybdenum

Cobalt-Chromium Molybdenum (CoCrMo) alloy is categorized under hard to cut material due to its unique combination characteristics such as high strength and low thermal conductivity. However, there was a problem during machining hard alloy material which is rapid tool wear. The tool wear will cause changes at tooltip geometry consequently has significant influence on the chip forming. There are some factors that influence tool wear which are cutting parameters, type of drill bit, and cutting fluids. In this study, a series of experiment were conducted to investigate the effect of cooling conditions on tool wear and chip formation during drilling this material. The cooling conditions used were dry, pure Karanja oil (MQL condition), and combination of Hexagonal boron nitride (hBN) nanoparticles with Karanja oil (MQL condition). The experiment was conducted under constant cutting speed of 20 m/min, and feed rate of 0.07 mm/rev through holes. Each hole was inspected when the tool wear reached 0.3 mm. The result showed that mixed of hBN with Karanja Oil (MQL condition) had lowest growth of flank wear and produced more holes compared to dry and pure Karanja oil condition. In addition, for chip formation, the size of lamellae produced was finest compared to other conditions.