Double cemented carbide: Microstructure-property relationships.

摘要

Double cemented (DC) carbide is a creative and new dual composite composed of spherical cemented carbide granules embedded in a continuous metal-matrix. This ‘composite-in-composite’ structure contributes to the special mechanical property combinations of DC carbide and allows more flexible composite design. In the present study, the relationships between microstructure and mechanical properties of DC carbide were investigated. For DC carbide with cobalt matrix. WC particle size and cobalt content within the granules strongly influence the mechanical properties. Higher cobalt content inside granules leads to higher toughness and flexural strength with the sacrifice of hardness and wear resistance. Finer WC particle achieves higher hardness and wear resistance with limited sacrifice of toughness and flexural strength.; Granule size is another important factor influencing mechanical properties of DC carbide. At the same metal-matrix content, toughness and high stress wear resistance increase with granule size, and there is a critical granule size at which low stress wear resistance is minimized. At constant total cobalt content (including both the cobalt within the granules and the cobalt in the metal-matrix), direct mechanical property comparison between DC carbide and conventional cemented carbide is possible, showing DC carbide to have higher toughness and high stress wear resistance, similar hardness, low stress wear resistance and Young's modulus and lower flexural strength.; Mean free path of metal-matrix is the main factor controlling the toughness of DC carbide and the most important microstructural parameter relating DC carbide to conventional cemented carbide. Conventional cemented carbide can be regarded as a special DC carbide with a very small mean free path through the metal-matrix and hence low toughness. In high stress wear, granule protrusion enhances wear resistance. In low stress wear, cobalt, both in the metal-matrix and within the granule, is preferentially removed, giving DC carbide no significant advantage over conventional cemented carbide.