Machining Performance Response of Inconel 718 Under High-Moderate-Low Cutting Speeds

Nickel-based superalloy Inconel 718, renowned for its high yield strength and fatigue resistance at elevated temperatures, has found extensive application in various critical aviation structures, such as combustion chambers and turbine blades in aero engines. As the range of applications expands, the demand for machining Inconel 718 is increasing rapidly. However, it is the high strength and hardness of this alloy, along with its tendency to work harden, that make it difficult to cut. Therefore, it is crucial to examine how cutting speed influences the characteristics of 718 superalloy. This study systematically examined the influence of increasing cutting speed on key machining parameters, including cutting force, surface roughness, and microhardness. Additionally, a thorough analysis was performed on surface morphology and chip formation characteristics. As the cutting speed increases within the range of 20–100 m/min, both the surface roughness and cutting force exhibit an initial rise followed by a subsequent decline. Notably, the minimal cutting force is observed when the speed reaches 90 m/min, whereas the best surface finish is attained at 100 m/min. Additionally, a noticeable change in the chip morphology is also witnessed with the increase in cutting speed. Especially above 60 m/min, the chip shape gradually transitions from spiral to nonspiral arcuation chips, and the chip edges are observed to change from a continuous state to a periodic serrated state and then to a torn serrated state. This study can provide valuable guidance for high-efficiency and high-quality processing of Inconel 718.