Two testing samples each with different additive amount were sintered in the same furnace with the same sintering process and then tested for their strength. The resulting physical and mechanical properties of them are different. The thickness and area of the metallic carbide generated from different additives on the interface between the diamond and the metallic matrix were observed and measured under high power electronic microscopes. The proper amount of different additives is determined through analysis of the metallurgical system of the samples and observation of its crystal organization and particle distribution.