Full Densification of Molybdenum Powders Using Spark Plasma Sintering

Pure molybdenum powder was sintered using spark plasma sintering (SPS) under various temperatures and holding times, under a pressure of 77 MPa and a heating rate at 700 K/min (700 °C/min). After sintering, a carbide layer was observed at the surface. The carbide layer thickness, the relative density of the sample as well as the microhardness, and the grain size of Mo were measured. The carbide thickness depends on time and temperature, and it was found that the carbide layer grows in a parabolic manner, with the activation energy of carbon diffusion in Mo being equal to 34 Kcal/mol. The densification of Mo is controlled mainly by the sintering temperature and the holding time. The molybdenum powder was successfully consolidated by SPS in short times. A relative density of 100 pct is achieved at a sintering temperature of 2123.15 K (1850 °C) and a holding time of 30 minutes. It was shown that the hardness decreases slightly with temperature and time. It should be related to the increase in grain size with the sintering temperature and time.