Bio-coolants for sustainable friction drilling process: A machine learning approach to temperature reduction

• The potential of novel bio-coolants such as fenugreek solution, coconut water, and their combinations, as sustainable alternatives to conventional coolants in green flow drilling applications. • A decision-tree platform is used to analyze the effects of bio-coolants at different friction-drilling speeds, providing optimal parameters for better machining results. • Fenugreek solution is identified as a promising candidate for cleaner manufacturing reducing the peak temperature to 216.3 °C at 550 rpm, demonstrating its potential for efficient temperature management. In current research, green friction-drilling is being used as a possible alternative to conventional drilling and environmentally friendly coolants are deployed. The current work envisages novel bio-coolants such as fenugreek solution, rose water solution, buttermilk solution, coconut water, fenugreek-coconut water solution and fenugreek-buttermilk solution. The decision-tree platform is employed to investigate the effects of bio-coolants on the peak temperature of friction-drilling at different friction-drilling speeds, showing the potential impact on machining. Regardless of the friction-drilling speed, fenugreek proves to be an efficient, environmentally friendly coolant for temperature reduction compared to other coolants used. The lowest temperature that could be achieved at 550 rpm was 216.3 °C. Plastic flow lines have been witnessed 1 mm in horizontal direction from inner edge of the bush and observed four to five mm downwards. Subsequently, brittle transition is explored due to friction generated heat and least material is occurred at the brittle region. Coolant application diminishes brittle formation and facilitates smooth bush formation. Decision-tree based analyses not only show optimal results, but also the different parameter combinations as options for the chosen process. Microstructural investigations are carried out in the cross-sectional area of the bushing obtained by using fenugreek as a coolant at 2100 rpm and compared with dry drilling. Investigations at the microscopic level show the effectiveness of the fenugreek solution in preventing ear defects (wavy edges) and reducing brittleness.