Densification during spark plasma sintering of Ni powder containing dispersed MgO particles

It is known that metal powders containing dispersed oxide particles are dif ficult to sinter by the conventional process. Spark Plasma Sintering (SPS) method was tried for making the dense sinter tablets from Ni powders contai ning MgO. The high-temperature hardness of the sinter tablets were examined from room temperature to 1173 K. The results were summarized as the follow s. The relative density of the tablets increased with an increase in sintering temperature. The relative density of more than 97% was obtained at higher temperature than 1273 K with MgO contents of 0, 2.5, 5 and 10%. The Vickers hardness of the sinter tablets increased with an increase in MgO contents and an increase in sintering temperature. The maximum hardness of about 270 Hv, which corresponded to more than 2.5 times of pure Ni, was obtained wit h 10%MgO at 1273 K sintering. These high relative density and hardness can be obtained by SPS method but not by the conventional sintering. The high-temperature hardness decreased with an increase in the temperature . Plotting the logarithm of hardness against the temperature, two straight lines were obtained. The reflection point which showed the change in deform ation mode was shifted to high-temperature side by the dispersion of MgO pa rticles. The high-temperature hardness straightly increased against a recip rocal of a space between MgO particles.