# Study on the Machinability of Ni-Based Superalloy by
## 1 Introduction  
Superalloy has an excellent service performance, and it is a typical difficult-to-machine material via its poor machinability, mainly manifested in large milling forces, serious work hardening phenomenon, and high cutting temperatures [1; 2; 3]. Superalloy can work under the condition of gas corrosion, and has excellent high temperature strength, thermal stability, and thermal fatigue resistance; thus, it can ensure the overall performance and working stability of the aeroengine [4; 5]. To reduce the machining area temperature and milling force effectively, irrigating cutting fluid is used for cooling. Due to the high-speed rotation of the tool, the gas barrier formed between the tool and the workpiece makes it difficult for the cutting fluid to enter, and the effective flow rate of the cutting fluid is only 5-40%. The lubrication fluid aerosol can penetrate into the machining area, so the minimal quantity lubrication (MQL) technology can avoid the above problems availably [6; 7; 8]. The capillary phenomenon and pumping effect of the cutting tool and chip result in the lubrication fluid aerosol moving towards the cutting edge. Meanwhile, the lubrication liquid is atomized into nanoscale droplets and sprayed onto the machining area under the action of high-pressure air for achieving the purpose of cooling and lubrication. Scholars have widely researched the milling machinability of Ni-based superalloy. [PERSON] et al. [9] conducted experimental research on the cutting force in end milling Inconel 718 and found that the milling force increased with the increase in the tool feed speed and cutting depth. [PERSON] et al. [10] carried out milling experiments on Inconel 718 with the Taguchi method, and the results showed that the cutting depth andfeed speed had a great influence on the cutting force. [PERSON] et al. [11; 12] made an attempt to use the Taguchi method to study the machinability performance of Inconel 718 and determined the significant machining parameters using analysis of variance. Based on the DD5 Ni-based superalloy characteristics, [PERSON] et al. [13; 14] executed the milling tool proper selection considering the wear characteristics and failure mode of the tools with different coating materials. [PERSON] et al. [15] studied the failure behavior of shear bands during chip formation in the cutting process of Inconel 718 through cutting experiments, numerical simulation, and theoretical analysis. [PERSON] et al. [16] investigated the effects of the cutting speed, machining time, and cooling conditions on tool wear, the cutting force, and the surface finish of Ni-based superalloy. [PERSON] et al. [17; 18] studied the effects of the cutting speed and the hardness of material on the flank wear of tools and the surface finish of the Inconel 718 workpiece. [PERSON] et al. [19] discussed the evolution process of the cutting force in the process of tool wear and conducted an in-depth study on cutting performance. [PERSON] et al. [20] carried out a single-factor milling experiment on GH4169 at room temperature and studied the cutting performance in terms of the cutting chip, cutting force, and tool wear. The results showed that the milling machinability of Ni-based superalloy was significantly affected by temperature. The above scholars have carried out various studies on Ni-based superalloys, but there is a lack of systematic research on the milling machinability of GH4169 under MQL conditions and different cooling methods. In this paper, the milling machinability of GH4169 Ni-based superalloy with milling parameters and cooling methods under MQL conditions were studied. Based on the single-factor experiment method, the mapping relationship of the workpiece surface roughness, milling force, and surface hardness were constructed with the cutting speed, feed per tooth, and radial depth of cutting as variables. The milling machinability of GH4169 Ni-based superalloy under different cooling methods of dry cutting, air cooling, MQL, and nanofluid MQL was investigated.