# Five-Axis Finish Milling Machining for an Inconel 718 Alloy Monolithic Blisk
## 1 Introduction  
A monolithic blisk is a critical component of an aircraft engine (aero engine). In contrast to the traditional fan design, in which multiple removable blades are assembled on an individual disk, the design of a blisk considers the blades and their holder disk as a monolithic construction. This design can reduce weight, improve stability during high-speed revolutions, and improve the performance of engines. Moreover, the design obviates the necessity of assembling the blades and the disk during the production process, which improves manufacturing efficiency. Blisks can be manufactured using various methods; the most common method involves machining from solid material by using machine tools. It must be emphasized that a blisk presents a complex geometry, so the machining costs are pretty high. It operates at high temperatures, thus blisks material must have excellent mechanical properties to ensure its high durability. The requirements for material selection, processing environment, and precision in the manufacturing process are strict. Blisks are usually made from difficult-to-cut materials such as titanium and nickel-based alloys and require the use of multiaxis machine tools and complex toolpath planning equipped with suitable tools that operate on well-chosen cutting parameters. Inconel 718 has been used frequently as blisk material quality because of its superior mechanical properties. However, the machinability of Inconel 718 is relatively low owing to its extreme performance. This thermal-resistant alloy exhibits high strength and tends to exhibit strain hardening even at high temperatures, resulting in high cutting forces and extreme temperatures during machining. Traditional carbide tools wear quickly during machining, especially uncoated tungsten carbide inserts employed under dry conditions. Research has focused on improving the machining efficiency of Inconel 718 through the use of tool coatings, the use of coolants, and the optimization of cutting parameters [1]. Liquid coolants, also known as cutting fluids, are used to cool the tool and workpiece by removing the heat generated during machining. [PERSON] et al. proposed the use of external MQL lubrication (CryoMQL) with CO\({}_{2}\) as an internal coolant for the cryogenic cooling of Inconel 718 during milling [2]. This ambient cooling method was demonstrated to engender increased tool life [3]. [PERSON] et al. conducted cryogenic heat treatment on cemented carbide tools to increase their wear resistance and thus improve their cutting performance [4]. Scholars have extensively discussed the effect of cutting conditions, including the tool material and geometry, feed rates, and radial depth of cuts, on tool life [5]. Different cutting methods with various cutting parameters and machining strategies have been proposed for controlling tool wear [6]. Moreover, a study introduced a laser preheating-assisted system and an ultrasonically assisted system for optimizing cutting parameters and improving cutting performance [7]. The computer-aided engineering (CAE) software with the commercial SOLIDWORKS(r) 2014 was also used to predict the deformations and stresses of the spindle and cutting tools under external loads to evaluate the rationality of cutting conditions [8; 9]. The first step of blisk machining entails rough milling, followed by the establishment of a boundary contour on the free surface of the blade [10] and then the control of the tool axis and cutting path to remove the groove material [11]. Traditional flank mills or barrel cutters are often used for machining [12]. In rough machining, efficiency is essential. Studies have presented a plunge milling strategy or four-axis cycloid path for material removal to improve efficiency [13]. Although most studies on blisk machining have discussed roughing processes [14], the finishing operation is also of increased importance in order to achieve the prescribed geometrical precision and surface roughness.