Abstract — This paper presents a review on sintered nickel based alloys. Nickel-based superalloys are an unusual group of metallic materials, showing an extraordinary combination of high temperature strength, toughness and surface stability in corrosive or oxidative environment. Therefore, these alloys play an extremely important role in gas turbine engines, aircraft, marine, nuclear reactors, steam power plants, petrochemical equipment and other high-temperature applications. Their resistance to temperature is achieved through a mixture of dispersion hardening, precipitation hardening and solid solution strengthening. To overcome or reduce probability of segregations, difficulties of forming and machining, often associated with or present in cast ingots, powder metallurgy has been of great consideration recently. In addition, powder metallurgy enables the alloying with refractory elements for high temperature strength. Index Terms— Sintered nickel based alloys, Microstructure, Powder metallurgy. I. INTRODUCTION The application of novel high temperature alloys in aerospace, automotive, and power industry have seen increased with recent developments. One such material that meets the need of resisting mechanical loads under high operating temperatures is nickel alloys (Jovanović et al., 2011; Singh, 2016). Their temperature resistance is achieved through a mixture of dispersion hardening, precipitation hardening and solid solution strengthening (Zacherl et al., 2012; Singh, 2016). As compared to any other commercially available materials, nickel-base superalloys can be used to a higher fraction of their melting points (Singh, 2016). These materials contain larger volume Isaac M. Makena is with the Institute for NanoEngineering Research, Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa (email: makenaisaac@yahoo.co.za) Mxolisi B. Shongwe is with the Institute for NanoEngineering Research, Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa (email: m.shonwgem@gmail.com) Munyadziwa M. Ramakokovhu is with the Institute for NanoEngineering Research, Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa (Email: RamakokovhuM@tut.ac.za) Moipone L. Lethabane is with the Institute for NanoEngineering Research, Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa (LethabaneL@tut.ac.za) The financial assistance of the Department of Higher Education and Training [DHET] funding under the Tshwane University of Technology, Emerging Program Grant. This work is based on the research supported in part by the National Research Foundation of South Africa for the grant, Unique Grant No. 99348. fractions of strengthening γ ’ precipitates and refractory elements than conventional superalloys, thereby offering higher strength at high temperatures (Akca and Gursel, 2015). However, despite their superior properties, nickel alloys are being reported by Yamanoglu et al., (2014), as one of the most difficult to machine materials in order to satisfy production requirement. In addition, these alloys have become more complex with more alloying elements designed for higher strengths and deforming the alloys by mechanical methods with the cast and wrought route has become more difficult (Mignanelli, 2012; Singh, 2016). Therefore, many studies have been conducted recently on the machinability of nickel based alloys. The fabrication of near net shape components by powder metallurgy (PM) offers important advantages in terms of material yield and number of production stages (Ozgun et al., 2013). Furthermore, PM of superalloys has attracted great attention in recent years (Ozgun et al., 2013). This is from the fact that PM overcome problems that adversely affect part-related characteristics and increase cost of production encountered in the production of the superalloys by traditional methods such as segregation, difficulties of forming and machining (Ezugwu et al., 1999; Pusavec et al., 2011; Ozgun et al., 2013). The process (PM) is reported (Lall, and Starr, unknown year) to manufacture components that can result in highly ductile (>30% elongation) or very strong (>1500 MPa UTS) products. This wide range of properties is attributed to the relative ease with which compositions can be tailored and that various processing parameters (compaction pressures, sintering time and temperatures, post-sinter operations, heat treatment, surface modifications, etc.) can be varied for the optimum microstructural evolutions. Spark plasma sintering (SPS) is a novel powder metallurgy sintering technique that is reported to be more effective as compared to the conventional sintering techniques (Garcia et al., 2010). The duration of the high-temperature stage is reduced, thus, lowering the overall sintering time. Sintering is conducted at comparatively lower temperatures with shorter dwell times reducing the threat of vaporization and resulting in dense, fine grain structures exhibiting high strength (Luke, 2010; Yamanoglu et al., 2014; Shongwe et al., 2015;). Detailed information on this technology (SPS) are presented in Refs (Shongwe et al., 2015; Makena et al., 2017a). In most cases nonreactive environments such as vacuum or an inert gas are used to avoid contaminations. Characteristics of the starting powders, such as degree of oxidation, segregation, morphology, and purity, are generally of significance prior to sintering. During sintering, it is reported by Davis, (2000), that loosely packed beds or A Review on Sintered Nickel based Alloys Isaac M. Makena, Mxolisi B. Shongwe, Munyadziwa M. Ramakokovhu, and Moipone L. Lethabane Proceedings of the World Congress on Engineering 2017 Vol II WCE 2017, July 5-7, 2017, London, U.K. ISBN: 978-988-14048-3-1 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) WCE 2017