Influence of Heat Treatment on Microstructure and Mechanical Properties of Ni-Fe-Co Ternary Alloy Prepared via Spark Plasma Sintering

The use of nickel-based superalloys has extended to different fields such as turbines, rocket motors, chemical equipment, space vehicles and power plants due to their excellent mechanical properties. This study investigates the effect of heat treatment on the microstructure and microhardness of spark plasma sintered Ni-Fe-Co ternary alloy. 50wt.% Ni and varying percentages of Fe and Co powders were milled and fabricated by Spark Plasma Sintering (SPS) technique at a temperature of 900 °C, pressure and holding time were kept at 50 MPa and 10 min respectively. The sintered compacts were heat-treated at 1000 °C, soaked for 1 hr and quenched in distilled water for 5 min. Subsequently, the sintered and heat-treated samples were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS) and X-ray Diffraction (XRD) to determine the microstructural evolution and phase transformation accompanying the process. XRD results revealed the evolution of strengthening phases in the heat treated of the samples. The as-sintered and heat-treated compacts Vickers hardness was also investigated before and after the heat treatment. The results show a general improvement in the microstructure after the heat treatment which translated to the observed increase in the hardness of the heat-treated samples. (paper)