Powder Bed Fusion Additive Manufacturing of Ni-Based Superalloys: Applications, Characteristics, and Limitations

Powder Bed Fusion Additive Manufacturing of Ni-Based Superalloys: Applications, Characteristics, and Limitations

Evren Yasa, Ozgur Poyraz
Copyright: © 2020 |Pages: 22
DOI: 10.4018/978-1-7998-4054-1.ch013
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Emerging additive manufacturing technologies have been gaining interest from different industries and widened their fields of application among aerospace and defense. The introduction of powder bed fusion processes was one of the significant developments in terms of direct metal part manufacturing of different materials and complex geometries, presenting good properties, and decreasing the need for tooling to allow fast product development as well as small-volume production. In this respect, nickel-based superalloys are one of the most employed material groups for aerospace and defense applications due to their mechanical strength, creep, wear, and oxidation resistance at both ambient and elevated temperatures. Nevertheless, the use of some materials has not become widespread due to several reasons such as processing difficulties, absence of design criteria or material properties. This chapter presents a comprehensive benchmark for powder bed fusion additive manufacturing of nickel-based superalloys considering applications, characteristics, and limitations.
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Powder bed fusion (PBF) additive manufacturing (AM) technologies, which are categorized as one of the seven main AM groups according to International Standards Organization (2015), include various processes employing different energy sources such as laser, electron or heat. Electron Beam Melting (EBM), Selective Laser Melting (SLM), Selective Laser Sintering (SLS) and Selective Heat Sintering (SHS) are the most commonly known powder bed fusion processes. SLM is also known with different commercial names from different machine vendors such as Direct Metal Laser Melting (DMLM), Direct Metal Laser Sintering (DMLS) and Laser Cusing, Laser-based powder fusion, etc. Like other AM technologies, these processes are used for production of 3 dimensional (3D) parts based on a Computer Aided Design (CAD) model file and can be applied for a wide range of powder materials. Many metallic alloys are included among the wide material range such as aluminum, cobalt, copper, nickel, steel and titanium alloys. With the proper use of PBF AM technologies, many of these alloys can be processed to obtain fully functional parts, prototypes and tools. The technology may offer various advantages such as low material consumption, good material and dimensional properties, design freedom to enable production of complex geometries with improved functionality and internal features, decreased need for tooling, reduced production times and thus easy transition from design to manufacturing and testing. However, it is only possible to benefit from all advantages offered by AM technologies with certain alloys while others still remain as a challenge for research and industrial organizations. Nickel-based superalloys, which are of great interest to aerospace and defense industries, are such an example. Initially developed for conventional manufacturing processes such as casting, forging or welding, several nickel based superalloys are easily adopted to PBF AM technologies, while the scientific or industrial trials still remain unsuccessful for other ones. Diverse reasons lead to problems for adopting nickel-based superalloys for PBF AM technologies such as absence of materials in powder form fulfilling the AM requirements, processing difficulties, material defects and cracks, residual stresses, the need for support structures, lack of knowledge on property enhancement processes (heat treatment, hot isostatic pressing), etc. On top of these, there is a lack of material property – processibility benchmarks, and material selection - design criteria are not fully set for PBF AM of nickel-based superalloys. This chapter presents a comprehensive benchmark for PBF AM of nickel-based superalloys considering applications, characteristics and limitations. The rest of this chapter is arranged as follows: Development of nickel based superalloys and PBF AM technologies are presented in the background section. The subsequent section describes the PBF AM in detail and discusses results of research on various nickel based superalloy types by demonstrating the issues and problems. Following this, the next section provides solutions and recommendations for the encountered problems. Last two sections emphasize the future research directions and conclude the chapter by summarizing the presented information.

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