# Manufacturing Processes of Integral Blade Rotors for Turbomachinery, Processes and New Approaches
## 2 Monolithic Components: Manufacturing Processes
### Additive Manufacturing (AM)  
Over the last three decades, Additive Manufacturing (AM) has become a competitive alternative or compliment in such a strict sectors as the aeronautical and the automotive. This technology is still in early stages; however, it presents many new opportunities in terms of material waste and sustainability. By the end of the 80s, the first generation of Material jetting (MJ) commercial 3D system rapid prototyping machine was developed. During the early 90s, the MIT (Massachusetts Institute of Technology) developed the first Binder Jetting (BJ) method with a powder bed similar to the actual Powder Bed Fusion (PBF) processes [30].  
At the beginning, this technology was utilized for prototyping and small fixtures, but step by step, it has been expanding and replacing other manufacturing processes for small batches. Among different AM processes, processes most commonly used for entire part creation consist in placing a flat powder layer of the part material, which is then heated and solidified using electron beam (Electron Beam Melting or EBM) or laser [31]. Thus, the final desired form is generated by overlapping of single layers.  
The main challenges for these technologies reside on good heat dissipation generated during the process and reducing distortions. On the contrary, these technologies offer advantages as the good powder utilization reducing material waste and the possibility of generating complex geometries, which are impossible to other technologies. They achieved tolerances for Ti and Ni based superalloys with material components using AM in the order of 100 \(\upmu\)m or higher. It should be pointed that, in the case of using AM for Ti alloys, it is necessary to consider this material tendency to oxidation; that is why EBM technology is preferred, helped by an inert gas [32; 33]. Overall, the process does not have the capability of achieving the tough finishing dimensional requirements, a finishing stage being needed with a material removing manufacturing process [34].  
In 2015, Boeing Company filed a patent application for defining airplane components that are going to be produced by AM, covering 300 part numbers on 10 different aircrafts [35]. Airbus is also promoting AM components in their aircrafts; on 30 March 2017, the first fully 3D printed hydraulic spoiler manifold fle in an A380 [36].  
Figure 6: **(a)** Electro Chemical Machining (ECM) method definition for a blisk and **(b)** blades in Ti60 blisk using ECM [27].  
Another AM technology that is an outstanding process in the aeronautical sector is the Direct energy deposition (DED). In this technology, a laser is in charge of melting the substrate meanwhile a nozzle injects the metallic powder to be added in the area of the melting pool. During the process, it is protected by inert gas streams to avoid interactions between melted materials and the oxygen [37]. Creating consecutive clades, a layer or coating is generated and, consequently, when overlapping layer over layer, it results into the 3D final desired geometry.  
The LMD main applications are direct blades fabrication for small blisks and for damaged area repairing process (Figure 7). For repairing operations, LMD process requires previous stages: component damaged area inspection, repairing tool-path strategy definition, studying repairing necessities and feasibility and, finally, a measuring and control stage for the final obtained geometry and the material properties [38]. In both, direct blade manufacturing and damaged component repair through LMD [39], a posterior stage of machining is required to achieve the final desired geometry accomplishing tolerance requirements. Hence, this additive manufacturing process provides an initial geometry closer to the final geometry, so it is addressed inside the \"Near-Net-Shape\" concept [40].