Effect of conditions of quasiisostatic hot peessing on the densification and steuctueal characteeistics of Cr3C2-15% Ni haed metal

Abstract

The investigation has shown that a hard metal based on chromium carbide with a 15% nickel binder addition (KKhN-15) can be effectively shaped by the QHP method. The optimum process parameters, ensuring the formation of a high-density structure, were found to be a process temperature of 1510–1540°K and a pressing, pressure of 800–1000 MPa. Uneven triaxial compression combined with the application of a high isostatic pressure enabled high densities (up to 80% of the theoretical) to be attained in Cr2C3-15% Ni hard metal specimens in the unsintered condition. A study was made of the effect of QHP conditions (temperature and pressure) on the stereological characteristics of the structure of Cr3C2-15% Ni hard metal: carbide phase grain size, sizes of the interfaces of the structural components, and structural coherence parameters. It has been established that the structure produced under conditions of quasiisostatic hot pressing is more fine-grained and has better developed interfaces than that obtained in vacuum sintering. The structure of hot-pressed Cr3C2-15% Ni alloy is characterized by a larger specific perimeter of carbide grain contacts and smaller nickel phase interlayers compared with a vacuum-sintered alloy. With both methods of alloy preparation, the number of contacts per carbide grain changes only slightly. The hypothesis is advanced that, like the coherence of the carbide skeleton as a whole, this characteristic depends more on the character of the structure of the material than on the method of its preparation.