Diamond composites consist in the diamond powder mixed with a binder phase, which sintering is carried out by means of the High Pressure-High Temperature (HPHT) techniques. These composites are widely used in the cutters of drillers for the oil industry, and as inserts for machining. In this work was used a mix of diamond + 5% weight cobalt. Sintering was accomplished under the HPHT Lowest Limit conditions: P=7GPa and T=15000C for times of t=10-30-60 seconds, aiming at the densification study under these conditions. Results are shown as a function of the sintered micro-structure evolution, cobalt influence on densification, graphitization, and hardness of the sintered parts.