Effect of Ball Milling on Spark Sintering Behavior of FeB-10 vol% Ni Hard Materials

FeB-10 vol% Ni compacts were prepared by spark plasma sintering of FeB and Ni powders ball-milled at different durations. The density of the compacts consistently increased with the temperature regardless of the ball-milling time. The sintered compact of powders ball-milled for 21.6 ks exhibited the highest apparent relative density (D) of 0.92. The maximum densification rates of 0.66, 0.68, and 0.71 obtained for powders ball-milled for 7.2, 14.4 and 21.6 ks, respectively, are close to that of pure Ni (0.74). This suggests that good sinter-ability was achieved by ball milling. The grain size of FeB was more effective than the Ni content in increasing the D value of the sintered compacts. The FeB-10 vol% Ni compact prepared using the powders ball-milled for 21.6 ks exhibited the highest relative density of 0.92 and excellent mechanical properties (hardness of 11.9 GPa and fracture toughness of 9.8 MPa·m1/2). This compact exhibited the decrease in grain size and increase of reacted (Fe,Ni)B phase.