Multi-material structure fabrication has the potential to address some critical challenges in today’s industrial paradigm. While conventional manufacturing processes cannot deliver multi-material structures in a single operation, additive manufacturing (AM) has come up as an appealing alternative. In particular, laser-directed energy deposition (L-DED) is preferred for multi-material AM. The most relevant applications envisioned for multi-material L-DED are alloy design, metal matrix composites (MMC), and functionally graded materials (FGM). Nonetheless, there are still some issues that need to be faced before multi-material L-DED is ready for industrial use. Driven by this need, in this literature review, the suitability of L-DED for multi-material component fabrication is first demonstrated. Then, the main defects associated with multi-material L-DED and current opportunities and challenges in the field are reported. In view of the industrial relevance of high-performance coatings as tools to mitigate wear, emphasis is placed on the development of MMCs and FGMs. The identified challenges include—but are not limited to—tightly controlling the composition of the multi-material powder mixture injected into the melt pool; understanding the influence of the thermal history of the process on microstructural aspects, including the interactions between constituents; and studying the in-service behaviours of MMCs and FGMs with regard to their durability and failure modes.

Manufacturing techniques that are applied to turbomachinery components represent a challenge in the aeronautic sector. These components require high resistant super-alloys in order to satisfy the extreme working conditions they have to support during their useful life. Besides, in the particular case of Integrally Bladed Rotors (IBR), usually present complex geometries that need to be roughed and finished by milling and grinding processes, respectively. In order to improve their manufacturing processes, Super Abrasive Machining (SAM) is presented as a solution because it combines the advantages of the use of grinding tools with milling feed rates. However, this innovative technique usually needed high tool rotary speed and pure cutting oils cooling. These issues implied that SAM technique was not feasible in conventional machining centers. In this work, these matters were tackled and the possibility of using SAM in these five-axis centers with emulsion coolants was achieved. To verify this approach, Inconel 718 single blades with non-ruled surfaces were manufactured with Flank-SAM technique and conventional milling process, analyzing cutting forces, surface roughness, and dimension accuracy in both cases. The results show that SAM implies a suitable, controllable, and predictable process to improve the manufacture of aeronautical critical components, such as IBR.

In this paper, a five-axis machining process is analyzed for large spiral-bevel gears, an interesting process for one-of-kind manufacturing. The work is focused on large sized spiral bevel gears manufacturing using universal multitasking machines or five-axis milling centers. Different machining strategies, toolpath patterns, and parameters are tested for both gear roughing and finishing operations. Machining time, tools’ wear, and gear surface are analyzed in order to determine which are the best strategies and parameters for large modulus gear manufacturing on universal machines. The case study results are discussed in the last section, showing the capacity of a universal five-axis milling for this niche. Special attention was paid to the possible affectations of the metal surfaces, since gear durability is very sensitive to thermo-mechanical damage, affected layers, and flank gear surface state.

Cubic boron nitride (cBN), in addition to diamond, is one of the two superabrasives most commonly used for grinding hard materials such as ceramics or difficult-to-cut metal alloys such as nickel-based aeronautical alloys. In the manufacturing process of turbine parts, electroplated cBN wheels are commonly used under creep feed grinding (CFG) conditions for enhancing productivity. This type of wheel is used because of its chemical stability and high thermal conductivity in comparison with diamond, as it maintains its shape longer. However, these wheels only have one abrasive layer, for which wear may lead to vibration and thermal problems. The effect of wear can be partially solved through conditioning the wheel surface. Silicon carbide (SiC) stick conditioning is commonly used in the industry due to its simplicity and good results. Nevertheless, little work has been done on the understanding of this conditioning process for electroplated cBN wheels in terms of wheel topography and later wheel performance during CFG. This work is focused, firstly, on detecting the main wear type and proposing a manner for its measurement and, secondly, on analyzing the effect of the conditioning process in terms of topographical changes and power consumption during grinding before and after conditioning.