Chapter 10 starts with category and production processes of cemented carbides. Subsequently, case studies for three cemented carbides are demonstrated. In the case of ultrafine cemented carbide, thermodynamic calculations were utilized to select composition and sintering temperature to avoid segregation of the (Ta,W)C phase. Optimal mechanical properties were obtained via adding VC and Cr3C2 inhibitors and the selected sintering temperature and composition. For WC–Co–Ni–Al cemented carbides, calculated phase diagrams and interfacial energy were employed to optimize the composition of Co–Ni–Al binder phase and sintering temperature. The morphology of WC was controlled through phase-field simulation and microstructure characterization. The best trade-off between transverse rupture strength and Rockwell hardness is obtained accordingly. For gradient cemented carbides, thermodynamic and diffusion calculations were performed to select composition and sintering schedule to provide microstructure parameters. A microstructure-based model was then developed to predict the hardness distribution. This simulation-driven materials design leads to development of these products within three years.