Influence of TiN nanoparticle addition on microstructure and properties of Fe22Cr alloy fabricated by spark plasma sintering

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 Cr₂N 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.