Phase Evolution, Microstructure and Hardness of TiB2-based Co-containing Composite by SHS under Pseudo-isostatic Pressure

摘要

TiB2-based cermets with various Co contents were fabricated from elemental powders “in situ” by means of the Self-propagating High-temperature Synthesis, SHS, and Pseudo- Hot Isostatic Pressing, P-HIP method. The sample pressed into a cylindrical compact was ignited in a steel can by an external heating element coiling the can. After SHS initiation, which was detected by rapid temperature increase, the samples were quickly pressed pseudo-isostatically under a pressure of 192 MPa and held for 5 min. Samples with predominant concentration of TiB2, which varied from 70 to 85 vol.% with the addition of 5 vol% of Ti, were investigated in this study. Appreciable differences in terms of microstructure, density and hardness were observed depending on the composition. The average TiB2 grain size increased while porosity decreased with rising concentration of TiB2. The material synthesized with increased to 85% concentration of superhard TiB2 grains and minimized concentration of Co exhibited greatest densification, highest hardness of about 2400 HV, and the most homogenous microstructure. The reaction mechanism was reportedly proposed, based on temperature monitoring during combustion and previously reported references.