Nickel-based superalloys, such as In718 and Waspaloy, are widely used in high-performance aerospace applications due to their exceptional thermal stability, high-temperature strength, hardness, corrosion resistance, and wear resistance. These materials are considered difficult to machine, especially when manufacturing critical components like turbine disks. Turbine disks are subjected to extreme stress, temperature, and harsh operating conditions, making them prone to fatigue failure. As a result, the material selection and manufacturing techniques for turbine disks are crucial in developing advanced aeroengines. The shaped holes on turbine disks are complex, consisting of multiple arcs and straight lines, requiring precise positioning and smooth transitions during machining. The surface roughness must meet strict process requirements, which makes the machining of these holes particularly challenging. Currently, electric discharge machining (EDM) is commonly used to create these intricate features in nickel-chromium alloys. However, EDM generates heat-affected layers that are difficult to remove through conventional grinding or polishing methods, often requiring additional processes like abrasive jetting. This increases both processing time and production costs. To address these challenges, this study explores alternative machining methods for nickel-based superalloy shaped holes, focusing on the combination of drilling, milling, and grinding. The goal is to evaluate the feasibility of replacing EDM with more efficient and cost-effective machining techniques. Through experimental testing, different machining sequences were analyzed, including drilling followed by milling, grinding, and a combined approach of milling and grinding. The test conditions involved using a machining center to produce shaped holes with a cross-section composed of six arcs and two straight lines, with a depth of 10 mm. Three different machining processes were compared: drilling followed by milling, drilling followed by grinding, and drilling followed by milling and then grinding. Each process had specific tooling and cutting parameters, as detailed in Table 1. The results showed that the drilling → milling → grinding sequence produced the lowest surface roughness, while the drilling → grinding method resulted in the highest roughness. Milling alone was also found to be capable of achieving acceptable surface quality, although it required further grinding to meet the final specifications. Additionally, the wear behavior of the milling cutters and grinding wheels was analyzed, revealing that tool degradation occurred under varying cutting conditions, affecting the overall machining performance. Further experiments were conducted on Waspaloy, another nickel-chromium superalloy, to assess the geometrical accuracy, surface roughness, and microhardness of the machined holes. The results indicated that the drilled and milled holes met the required dimensional tolerances, and the surface roughness values were within acceptable limits. However, the microhardness of the machined surface showed some softening near the surface, likely due to plastic deformation and localized heating during the milling process. In terms of machining efficiency, the drilling-milling process significantly reduced the total processing time compared to traditional EDM and abrasive jetting methods. This not only improved productivity but also minimized the need for post-processing steps, leading to cost savings. In conclusion, the study demonstrated that the drilling-milling process can effectively replace EDM for machining shaped holes in nickel-based superalloys. It offers better control over surface finish, reduces processing time, and improves overall efficiency. By optimizing cutting parameters and using advanced coated tools, further improvements in machining performance can be achieved, making this approach a viable alternative for high-precision aerospace component manufacturing.

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