Abstract
The cutting tools used to machine metallic ingots are produced using hard metals with excellent wear resistance. These hard metals consist of hard phases (transitional metal carbides) and tough phases (metallic phases), though microstructural variables such as grain size, mean free path, and coherency in interfaces between the phases will also affect the properties of the hard metals. Accordingly, the mechanical properties of hard metals can be improved by strengthening both phases, or by adjusting various other factors that affect the microstructure and mechanical properties of the hard metals. In this paper we review the factors that have been identified as controlling the microstructure and associated properties, as well as the diverse research concerning the improvement of hard metals. We ultimately conclude that fine grains of solid-solution strengthened carbides with hard metallic phases are necessary for producing hard metals with superior mechanical properties, as is the formation of a coherent interfacial structure, as the interfacial area is relatively weaker than the grain inside.