Fresamento de Inconel® 718 com diferentes estratégias de lubri-refrigeração

Abstract

Nickel-based superalloys, such as Inconel® 718, are widely employed in critical sectors, including aerospace, nuclear, and petrochemical industries, due to their high mechanical strength, corrosion resistance, fatigue resistance, creep resistance, and structural stability under extreme conditions. However, these properties also make machining particularly challenging due to high dynamic shear strength, that is maintained at elevated temperatures, low thermal conductivity, work hardening, possibility of built-up edge (BUE) formation, and the presence of hard carbides, which compromise surface integrity and reduce tool life. Given this scenario, the proper application of lubrication and cooling techniques is essential to mitigate these effects. Thus, this study investigates five lubrication and cooling methods in the milling of Inconel® 718 with cemented carbide tools: dry cutting (DC), compressed air (CA), minimum quantity lubrication (MQL), vortex tube (VT), and flood cooling (FC). Four cutting conditions were tested, varying cutting speed and feed per tooth. The study included temperature measurements using the tool-workpiece thermocouple method to assess the interface temperature, as well as analyses of cutting forces, power consumption, and specific cutting energy. Additionally, surface roughness, chip compression degree, and chip morphology were examined. Tool life and wear mechanisms were also evaluated. The collected data were statistically analyzed using analysis of variance (ANOVA) and Tukey’s test. Flood cooling proved to be the most effective method in reducing cutting temperatures, cutting forces, and power consumption, while also increasing tool life because of its good lubri-cooling effect and the absence of thermally induced cracks. In contrast, dry cutting resulted in the highest interface temperatures, leading to greater tool wear, reduced tool life, and increased cutting forces and specific cutting energy. The air-based cooling methods (CA, MQL, and VT) did not exhibit statistically significant differences in temperature reduction, although the VT method demonstrated a lower degree of chip compression. The observed wear mechanisms included adhesion and abrasion on the flank surface and adhesion wear on the rake face. No thermally induced cracks were observed under any lubrication and cooling condition; however, chipping and mechanically induced cracks were present.