ON THE POSSIBILITY OF OBTAINING HARD ALLOYS FROM MIXTURES OF CARBIDE POWDERS AND METALS BY EXPLOSIVE COMPACTING WITHOUT SINTERING

Abstract

The paper presents experimental results on the possibility of obtaining consolidated powdered hard alloys by the method of explosive compacting without subsequent sintering. Tungsten carbide (WC), chromium (Cr 3 C 2 ) and silicon carbide (SiC) were used as main carbides of alloys; titanium, nickel and copper acted as binder metals. The compression pressure of the powder mixture in shock waves during explosive compacting varied in the range from 5 to 16 GPa, the heating temperature was from 250 to 950°C. The structure, chemical and phase compositions were studied using optical (Axiovert 40MAT, Carl Zeiss), raster (FEI Versa 3D) and transmission (FEI Titan 80-300, Tecnai G2 20F) electron microscopes. The paper demonstrates that powder compositions with a titanium binder are compacted much better than mixtures with copper or nickel. The hardness of materials after explosive compacting reaches 1200 HV. The paper determines a temperature range corresponding to ((0,35÷0,4)t melt (where t melt is the absolute melting point of the main carbide of the alloy), transition through which changes the fracture pattern of samples from intercrystalline to transcrystalline. The paper determines that this is due to the formation of strong boundaries between carbide particles and the metal matrix, which constitute interlayers with a thickness of the order of 80–100 nm having its own crystalline structure different from the structure of main components of the alloy.