Material Additive Process Research Articles

Modeling and simulation of surface generation in manufacturing

The paper describes the state-of-the-art in modeling and simulation of surface texture and topography generation at micro and nano dimensional scales. Three main classes of manufacturing processes used for the generation of engineering surfaces are considered: material removal processes, material conservative processes, and material additive processes. Types of modeling techniques for the simulation of surface generation are reviewed and discussed including analytical models, numerical multi-physics models, and data-driven methods. After presenting the application of those modeling techniques for the prediction of characteristics and geometry of surfaces generated by different manufacturing processes, their performance, implementation, and accuracy are discussed. Finally, a roadmap for the realization of a complete surface generation digital twin in manufacturing is outlined.

Manufacturing and Machining Challenges of Hybrid Aluminium Metal Matix Composites

Manufacturing which involves material removal processes or material addition processes or material transformation processes. One or all the processes to obtain the final desired properties for a material with desired shape which meets the required precision and accuracy values for the expected service life of a material in working conditions. Researchers found the utility of aluminium to be the second largest after steel. Aluminium and its metal matrix composite possess wide applications in various applications in aerospace industry, automobile industry, Constructions and even in kitchen utensils. Hybrid Al-MMCconsist of two different materials, and one will be from organic origin along with the base material. In this paper an attempt is made to bring out the importance of utilization of aluminium and the challenges concerned in manufacturing and machining of hybrid aluminium MMC.

A unit sphere discretization and search approach to optimize building direction with minimized volumetric error for rapid prototyping

As a material-additive process, rapid prototyping (RP) has shown its capability in creating complex geometries that traditional material-removal processes cannot accomplish. However, its layer manufacturing nature still subjects itself to undesired staircase effects. It has been shown that staircase effects have relationship with the building orientation in RP processes. In order to minimize staircase effects, the building orientation has to be properly selected prior to the implementation of RP processes. This paper presents a method to select the optimal building direction in RP processes that leads to the minimized volumetric error. In order to explore the global directional space, a unit sphere is uniformly discretized first to represent the potential directions in a 3-dimensional (3-D) space. Following that, each facet comprising the STL geometric model is mapped onto the discretized unit sphere as a great circle individually, which represents the optimal directions for that facet. In order to find the globally optimal solution, both an exhaustive search and a genetic algorithm (GA)-based searching strategy are presented to identify the globally optimal direction for building the 3-D geometry. At the end of the paper, examples are presented to show the effectiveness of the method.

Experimental studies on process-induced morphological characteristics of macro- and microstructures in laser consolidated alloys

Laser consolidation (LC) developed by National Research Council’s Industrial Materials Institute (NRC-IMI-London) since mid-1990s, is a laser cladding based rapid manufacturing and material additive process that could fabricate a “net-shape” functional metallic shape through a “layer-upon-layer” deposition directly from a computer aided design model without using molds or dies. In order to evaluate the LC processability of different materials, some representative nickel-based superalloys (IN-625, IN-718, IN-738, and Waspaloy), stainless steels (austenitic SS316L and martensitic SS420), and lightweight alloys (Ti–6Al–4V titanium alloy and Al-4047 aluminum alloy) have been investigated. Like other laser cladding based processes, due to process-induced rapid directional solidification, the LC alloys have demonstrated certain unique morphological characteristics. Moreover, the “as-consolidated” LC alloys, in nature, are in the “as-quenched” state, and some precipitation processes from their matrices, which are sometimes critical to the development of mechanical performance of the materials, could be effectively suppressed or retarded. Post-heat treatments, therefore, could necessarily facilitate the process of achieving their required operational microstructures. In this article, a comprehensive investigation was performed including metallurgical soundness and process-induced morphological characteristics of the LC materials, and microstructure development brought by post-LC heat treatments using optical microscope, scanning electron microscope, and X-ray diffraction. The implications on the mechanical performance of the LC materials were discussed as well in order to provide essential information for potential industrial applications of the LC materials.

Process-induced microstructural characteristics of laser consolidated IN-738 superalloy

Laser consolidation (LC) is a laser cladding based material additive process that could fabricate a “net-shape” functional metallic part through a “layer-upon-layer” deposition directly from a CAD model. The LC process can produce nickel-base IN-738 superalloy with metallurgical soundness. Nevertheless, due to process-induced rapid directional solidification, the LC IN-738 alloy demonstrates certain unique microstructural characteristics, such as, the presence of non-uniform coarse columnar grains (a majority of the grains is in the range of about 56–158 μm in diameter; but their lengths could vary from several hundred μm to the height of the wall being built up) in combination with exceptionally fine directionally solidified dendrites inside (the secondary dendritic arm spacing is about 1.7 μm). Moreover, the “as-consolidated” LC IN-738 alloy, in nature, is a supersaturated γ solid solution, and any precipitation of γ′ particles from the γ matrix is effectively suppressed. Post heat treatment, thus, is essential to achieve the required operational microstructure. On the other hand, the nature and role of conventional “solution plus aging” treatment to the LC IN-738 alloy seem to be different as compared to “as-cast” or wrought IN-738 alloy. In this paper, process-induced microstructural characteristics of the LC IN-738 alloy and its development brought by post heat treatment were fully investigated. The implication on high-temperature mechanical performance of the LC alloy was discussed as well.

Complex cast parts with rapid tooling: rapid manufacturing point of view

Rapid manufacturing techniques are typically either material addition or material subtraction processes. Direct metal laser sintering (DMLS) is a material addition process that enables the rapid creation of complex parts via laser sintering (or electron beam melting) whereby layers of powder are deposited and then partially or totally melted using a laser. This technique is directly challenging other more rapid, but subtractive manufacturing processes like high-speed milling (HSM) and electro-erosion. In terms of machining, the capacity of rapid tooling to quickly manufacture complex shapes, like conformal cooling channels, is an advantage (Boillat in J Phys IV 12(Pr 11):27–38, 2002, Au in Int J Adv Manuf Technol 34:496–515, 2007). On the other hand, the dimensional accuracy of this process is definitely lower than that obtained using HSM. To our knowledge, no systematic study of the dimensional capacities of this process has yet been carried out. In this article, through the geometrical study of the quality of the obtained parts, the capability of this process is studied and verified with respect to the required constraints of the die casting method.

Laser Based Flexible Fabrication of Functionally Graded Mould Inserts

A CO 2 laser-based freeform fabrication process with emphasis on difficult-to-shape and functionally effective materials was investigated with regard to fabrication of dies and moulds. Square and circular moulds were built by use of a material additive process of layers of TiC and Ni-alloy composite. The effects of laser processing on the quality, microstructures, and hardness of the moulds were determined. Additionally, the mould performance was evaluated in die-casting, injection moulding, and in a thermal fatigue environment. The TiC core-Ni-alloy shell mould outperformed moulds made of hardened H13 die steel, 304 stainless steel, and TiC-coated stainless steel in withstanding stresses and in retaining dimensional stability at elevated temperatures.