ORIGINAL ARTICLE Influence of TiN nanoparticle addition on microstructure and properties of Fe22Cr alloy fabricated by spark plasma sintering Samuel Ranti Oke 1,2 & Oladeji Oluremi Ige 1,3 & Oluwasegun Eso Falodun 1 & Avwerosuoghene M. Okoro 1 & Mahlatse R. Mphahlele 1 & Peter Apata Olubambi 1 Received: 1 February 2019 /Accepted: 13 May 2019 # Springer-Verlag London Ltd., part of Springer Nature 2019 Abstract Duplex stainless steel (SAF 2205) reinforced with various weight percent of titanium nitride (TiN) nanoparticles is fabricated in vacuum via spark plasma sintering (SPS) using optimized SPS process parameter of 1150 °C for 10 min and 100 °C/min. The influence of TiN addition on the densification mechanism, microstructure, hardness, and fracture surface of the fabricated duplex stainless steel composite fabricated is evaluated. The results indicate even dispersion of the TiN nanoparticles in the steel matrix during turbular mixing. The displacement and shrinkage rates show three densification stages relating to micro-nanoparticle rearrangement, plastic deformation of the particles, and rapid densification of the composite. The microstructure revealed ferrite, austenite, and TiN phase at grain boundaries. There was phase transformation of ferrite to austenite with the addition of TiN nanoparticles due to diffusion of nitrogen as austenite stabilizer. The evolution of Cr 2 N nitride precipitates along grain boundary, and a dendrite-like austenite structure was evident during sintering. The hardness of the composite was enhanced while the density decreased with TiN content. The fracture surface analysis showed a transition from ductile to brittle fracture with increase in TiN addition. Keywords Spark plasma sintering (SPS) . Densification . Microstructure . Fe22Cr alloy . TiN nanoparticles 1 Introduction Ceramic-reinforced metal matrix composites have been rec- ognized for their appealing properties such as high specific strength, strength-to-weight ratio, temperature stability, and wear resistance coupled with their wide range of applications in the aerospace, automobile, and electronic industries [1, 2]. The synthesis of micro- and nanosized ceramic-reinforced metals by conventional melting and casting technique poses some challenges due to the differences in density, melting point, and thermal conductivity between the ceramics and metal matrix [3, 4]. This often results in inhomogeneous struc- ture with weak matrix/reinforcement interfacial bonding. To overcome this challenge, the powder metallurgy (PM) route has been proven to be a viable alternative [5]. Several PM techniques such as hot pressing, powder extrusion, hot isostat- ic pressing (HIP), high pressure-high temperature (HP-HT), and spark plasma sintering (SPS) have been used to consoli- date metal matrix composite [6, 7]. Powder metallurgy has been successfully used to fabricate different metallic alloys such as Al, Ti, Cu, Fe-Cr, and Mg reinforced with various carbide-, oxide-, nitride-, and boride- based ceramics. For instance, Hosseini Monazzah et al. fabri- cated Al6061/SiCp laminates via powder extrusion route and studied its fracture resistance and interfacial bonding; the au- thors reported that the rolling strain during powder extrusion influenced the extent of interfacial adhesion and damage tol- erance of the composite [8]. The role of fabrication process and reinforcement on interfacial bonding and effective load transfer from matrix to reinforcement has been reported for composites [9]. Recently, Hosseini Monazzah et al. intro- duced Al1050 ductile interlayer to improve the interfacial bonding of Al-Mg-Si/SiC composites fabricated via PM. Their findings revealed weak interfacial bonding of layers * Samuel Ranti Oke sroke@futa.edu.ng; sroke99@outlook.com 1 Center for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa 2 Department of Metallurgical & Materials Engineering, Federal University of Technology Akure, Akure, Ondo State, Nigeria 3 Department of Materials Science and Engineering, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-019-03873-1