# Manufacturing Processes of Integral Blade Rotors for Turbomachinery, Processes and New Approaches
## 1 Introduction  
The aeronautical industry is considered one of the strategic sectors of the global market. According to the Spanish Association of Defense, Aeronautics and Space Technology Companies (TEDAE), this sector generates a total revenue of 7.8 billion EUR, from which 11% is assigned to R&D&I (Research, Development and Innovation) activities [1]. For this purpose, it is necessary to work not only on the improvement of new components but also in looking for new innovative processes, alternative to conventional manufacturing processes, and optimizing cutting tools, tool-paths, machining strategies and material properties. Nevertheless, it should not be forgotten that the main objective of performing more productive and efficient processes is reducing machining times and costs along the entire manufacturing chain. Turbomachinery rotary components in aircraft engines, mainly in the compressor and turbine stages, present a complex geometry composed of a series of bladed discs distributed along the same rotor. In some cases, these components are an assembly of smaller pieces, mounting single blades in some rotor section, which in turn is mounted on the final rotor. In the last decades, there was a new trend to integrate blades and the rotor in a monolithic component, that is, to produce the entire components from an starting disc eliminating materials by means of five-axis milling process, reaching a component with the maximum strength and minimum weight. The common definition for this kind of components is integral blade rotor IBR (Integrally Bladed Rotors), or blisk (from blade on disc). In addition, comparing IBRs withassembled discs, the component weight is reduced up to 20-30%, increasing the efficiency considerably, reducing at the same time the fuel consumption and gas emissions. Nonetheless, these components present some difficulties: elevated machining times, cutting tool costs and a surface integrity that must be kept in healthy values, all which are aspects dependent on machine kinematics [2]. With the aim of manufacturing these components and avoiding the former issues, blades are manufactured directly using conventional machining processes (i.e., milling, turning, etc.) over a revolution body, thus obtaining a compact component with more complex geometries because original assembly junctions are avoided. However, turbomachinery integral rotary component manufacturing presents some difficulties, such as accessibility and geometrical complexity, among others. Therefore, manufacturing process optimization is the principal target for large aeronautic engine manufacturers. Blade geometries are complex and present internal cooling ducts. They combine different materials and microstructures for the disc and blades with the aim of improving/optimizing mechanical properties. Figure 1 shows a HF-120 turbofan engine from GE(r) and the differences between IBRs and assembled discs. The selection of machining processes for component manufacturing will depend on the component material and geometry [4]. Due to hard working conditions, there are several materials presented in aeronautic motors [5]. Additionally, with the aim of standing those extreme working conditions, materials should fulfill some extra requirements such as good resistance to impact loads, fatigue and erosion and a high ratio between mechanical resistance and material density [6]. Moreover, depending on the application, different thermal forces and pressures are present. Notable are nickel alloys for the so-called \"hot\" zones such as combustion chamber and turbine inlet and titanium alloys for \"cold\" zones such as compressor inlet and turbine outlet. These materials are known as difficult-to-cut materials, and it is necessary to analyze which is the most appropriate manufacturing process depending on the concrete material and geometry. Integral blade rotors must be made of hard-to-machine alloys (Ti-6 Al-4V and Inconel(r)), which represent a machining technological challenge from the economic and technological points of view.