Evaluating tool wear mechanisms, hole integrity and drilling performance of indexable and solid carbide tools on GFRP-Steel stacked composite

Abstract

Engineers are exploring GFRP-steel hybrid materials for various applications due to their superior mechanical properties with lightweight. However, machining these materials poses significant challenges due to mismatch leading towards accelerated tool wear and compromised surface quality. Therefore, the present study reports a comprehensive analysis of drilling GFRP-steel stacked composite using indexable inserts and solid carbide drills in dry conditions. The experiments were designed by varying key process parameters such as feed rate (10–20 mm/min) and spindle speed (2400–4800 rpm). While, five significant response variables of this study were investigated as surface roughness (Ra in μm), tool wear (TW in μm), diametric error (DE in μm), delamination factor (Fd) and drilling temperature (Td in °C). Key findings revealed that indexable drill exhibited superior TW due to its robust design and efficient cutting-edge geometry, reducing localized stress and heat. TW significantly increased by increasing the feed rate and spindle speed. SEM analysis of solid carbide drills and the indexable inserts revealing grooves, adhesion, and coating delamination at higher spindle speed and feed rate, but lower for indexable inserts. Roughness analysis highlighted that indexable inserts resulted reduced Ra of 0.09 μm at 10 mm/min feed rate and 3600 rpm spindle speed compared to the solid carbide drill (Ra 1.28 μm). The indexable drill ensured better accuracy with a minimum DE of 10.33 μm compared to 42.94 μm for the solid carbide drill, attributed to enhanced chip evacuation and reduced thermal stress. Delamination control was more effective at 10 mm/min feed and 3600 rpm spindle speed, minimizing material separation, whereas higher settings (20 mm/min, 4800 rpm) amplified delamination. The indexable inserts maintained consistently lower drilling temperatures, with the solid carbide drill reaching a peak of 482 °C due to higher frictional heat generation, underscoring its superior thermal stability and wear resistance.