Evaluation on the microstructure and corrosion properties of in situ prepared FeCrNiCo-boride cermet by hot press sintering

Traditional studies on boride cermet have rarely considered the effects of the synergistic interactions among their multiple components on their microstructure and properties. In this study, FeCrNiCo-boride cermet is prepared for the first time via hot-press sintering. The microstructure evolution and corrosion resistance of the cermet are investigated for sintering temperatures in the range of 1000–1300 °C. The results show that the phase comprises Mo₂FeB₂, MoB₂, and FCC phases (including that of FeCrNiCo or various intermetallic solid solutions formed by FeCrNiCo decomposition). Owing to its low Gibbs free energy, Mo₂FeB₂ occurs in the hard phase. Cr atoms dissolve into the crystal lattice and stabilise the Mo₂FeB₂ crystals. A certain amount of MoB₂ is also present in the hard phase. The bond phase is formed by alloying elements and solid solutions. The cermet sintered at 1100 °C exhibits the least structural defects, highest cermet content, and best corrosion resistance; the porosity is 9.94% and phase ratio of cermet is 48.9 %. The cermet phase has the smallest grain size of 5.96 μm. The equilibrium potential (E_corr) is -0.52 V, corrosion current density (I_corr) is 2.07 × 10^-6 A/cm², and open-circuit potential (OCP) in a 3.5% NaCl solution is -0.34 V.