Search

Directed Energy Deposition (DED) processes are known for producing parts close to their final shape where only a post-process finish machining is required. However, geometrical deviations due to thermal effects may occur during the process, which results in the final geometry not being achieved or in the necessity of oversizing the part in order to compensate the distortion in the subsequent machining. In this article, a 3D scanning methodology of the manufactured part will be used to measure the geometry at different stages of the Laser Metal Deposition (LMD) process. In this way it is possible to assist the manufacturing as well as to make a comparison with the theoretical geometry during the process. This results in a higher probability of manufacturing the part without process failures and obtaining a precise reproduction of the geometry to be manufactured, reducing the subsequent post-processing operations and saving manufacturing time and cost.

Metal Matrix Composite (MMC) coatings have become increasingly important in recent years because of their high wear resistance in aggressive environments. These coatings can be efficiently manufactured by Laser Metal Deposition, as it is known to perform well in repair and coating applications due to its low substrate affection. However, there are many challenges to be faced when metallic and ceramic materials are combined. In fact, inhomogeneous material distribution and lack of metallurgical integrity are issues to be addressed. For this purpose, the use of Functionally Graded Materials is proposed. Nevertheless, there is a lack of knowledge regarding the procedure and deposition strategies to follow in order to obtain crack-free coatings. In the present work, the main challenges for the deposition of such coatings have been experimentally identified, particularly for Stellite 6 reinforced with tungsten carbide. To that end, the quality of the deposited coatings and their composition has been assessed. Furthermore, as the dilution of the reinforcement phase has not been studied in depth in the literature when ceramic particles are used, in the present study, an analysis of the dilution of the ceramic phase in the metal matrix is performed when different WC concentrations are fed.

The quality of the powder is a key aspect in the Laser Powder Bed Fusion (PBF-LB/M) process to guarantee manufacturability and quality of the manufactured parts. However, the powder is reused several times and its quality changes during the manufacture process, which affects the quality of the manufactured parts. Throughout this article, the powder and the final part properties will be studied during 25 manufacturing process. Specifically, morphology, granulometry and flowability of the powder were studied, and these results were related with the roughness and the porosity of the manufactured parts. Thanks to this research, it was found that the size of the particles increases when the powder is reused. And this directly affects the flowability of the powder which increases. Furthermore, it has also been shown that this increase in particle size distribution causes an increase in the porosity and roughness of the manufactured parts.

The Laser Material Deposition (LMD) is an additive manufacturing technique that has become one of the most noteworthy methods for coating and repairing components. It is also a key process in hybrid manufacturing systems that combine LMD and machining operations. One of the main difficulties of LMD is the large number of relevant parameters and the complex interdependencies that must be considered. Thus, process fitting is usually based on trial and error techniques. The present work proposes a series of developments based on the numerical modeling of the LMD process, with the aim of reducing the experimental tests to setup the process.

Laser metal deposition is an additive manufacturing process capable of layer by layer construction of solid parts. An incorrect deposition distance between nozzle and substrate can result in height deviations from the ideal building path. The error can be propagated along layers, leading to an irreversible defect. Maintaining an optimal distance between the nozzle and the substrate is therefore a critical aspect. This paper introduces an off-line geometric control system for in-process measurement and build path correction. A structured light based 3D scanner measures the build height from an external, fixed position, providing more precise results than moving measuring systems. The deposition is stopped in certain stages of the process and the piece is scanned generating a three-dimensional point cloud. Processing of the collected data allows the build height determination. A control algorithm was developed to take corrective actions in accordance with the measured error. The system enables an accurate control of the generated geometry and permits the comparison with the original computer design. This approach reduces the required human supervision during the process and the occurrence of non-valid parts. The effectiveness of the method was proved through the contrast of parts built with and without control, showing a more accurate reproduction of the generated solid parts when corrections are applied.

The use of hybrid manufacturing processes that combine additive and machining operations is on increase and an example of it is the fact that the most advanced machine tool manufacturers have developed hybrid machines solutions. Nevertheless, cutting fluid required for machining operations can present several problems for the Laser Metal Deposition (LMD) process. In order to solve this issue, the present work evaluates the influence of the coolants in the LMD process from the point of view of pore generation and clad quality. For this purpose, several tests are performed on a part impregnated with cutting fluid, both directly and after the elimination of the fluid by means of different alternatives.

Laser Material Deposition (LMD) is a near-net-shape additive process. Powder particles are usually employed as filler material, which is injected through a powder nozzle (coaxial or off-axis) and then completely molten by a laser beam. The possibility to add material on complex 3D surfaces makes LMD a key process in the repair and wear/corrosion protection applications. The present work is focused on the improvement of the design & manufacturing of a LMD nozzle, what introduces two main advantages: the possibility to process a wider variety of materials by generating a protective atmosphere and the improvement of the efficiency of the nozzle. The results of numerical simulations are used for optimizing the design of the protective cone of the LMD nozzle, which is then manufactured and experimentally validated. Finally, the proper performance of the resultant nozzle is tested depositing Ti6Al4 V.

Modern aerospace industry demands the union of different Inconel 718 parts ensuring the quality of the joint. Therefore, in the present work a novel fiber laser welding model that considers wobbling strategy is developed. The heat source model definition and solid-liquid phase change phenomena are taken into account as bead is considered liquid zone during the melting, getting a robust-but-simple tool for prediction of bead and heat affected zone geometries depending on process parameters. One of the main drawbacks is the maximum welded bead width, which is limited by the beam spot. In order to overcome this handicap, wobbling strategy allows covering a wider area by combining elliptical and linear motions. Optimal relation between these orbital and translation speeds is defined for minimum overlap among consecutive wobble rings. Likewise, temperature rise at welded joint is estimated by existing and modified heat source models after relying on experimental validation.