Powder metallurgy processing of seven/eight component multi-phase (HfTiZr-Mn/Mo/W/Cr/Ta)B2 high entropy diboride ceramics

This study aims to show the possibility of synthesizing seven- and eight-component high entropy diboride (HEB) ceramics using high energy ball milling-assisted spark plasma sintering (SPS). Metal boride powders, synthesized in laboratory conditions from metal oxide-boron oxide-magnesium powder blends, were combined equimolarly as seven and eight components containing systems. Afterwards, hybridized powders were mechanically alloyed (MA) for 6 h and subjected to spark plasma sintering (SPS) at 2000 °C and under 30 MPa. Detailed phase analysis and physical, microstructural, and mechanical characterization of the samples were performed. ın the sintered products, the main phase belongs to the HEB, and also low amounts of Hf/Zr oxides and secondary phases (W or Ti-rich) occurred. The highest hardness was observed at the (HfTiZrMoWCrTa)B 2 with ∼25 GPa, and the lowest hardness was seen at the (HfTiZrMnCrMoWTa)B 2 with ∼17 GPa. Also, the highest wear resistance was calculated for the (HfTiZrMnCrMoTa)B 2 as 6.05 × 10 −7 mm 3 /Nm. Additionally, (HfTiZrMnMoWTa)B 2 and (HfTiZrMnMoCrTa)B 2 have the highest and lowest Archimedes’ densities, with 7.94 g/cm 3 and 6.91 g/cm 3 , respectively. • High entropy diboride synthesis via mechanical alloying and spark plasma sintering. • Multi-phase high entropy diboride synthesis with seven and eight constituents. • High entropy diboride ceramics with max. 25 GPa high hardness. • High entropy diboride ceramics at around 7 g/cm 3 density. • Wear rate with a minimum value of around 6 × 10 −7 mm 3 /Nm.