Some Trends in Improving WC–Co Hardmetals. II. Functionally Graded Hardmetals.

Research efforts on the development of hardmetals with a gradient structure, i.e., a structure that changes smoothly over the cross-section or volume of a sample, have been analyzed. These materials are called functionally graded hardmetals and are characterized by increased wear resistance at set hardness. Three approaches to the development of functionally graded hardmetals that are implemented in Ukraine, Europe, and the USA are discussed. These approaches are based on one phenomenon, such as the migration of molten cobalt from one to another hardmetal region that differs in the size of tungsten carbide particles, liquid phase amount, and carbon content. The approaches differ by process features in preparing and sintering the samples that acquire a gradient structure. In addition, different methods to produce hardmetals with a gradient structure are described. New capabilities of the extrusion process for the production of parts with uneven cross-sectional structure are studied. Conditions of obtaining long-length products from hardmetals with a cellular or 'honeycomb' structure by extrusion of structural elements through a die with openings of specific shape are presented. [ABSTRACT FROM AUTHOR]