The Cu matrix cermets remarkably strengthened by TiB2 “in situ” synthesized via self-propagating high temperature synthesis

Abstract

The TiB 2 -Cu cermets with predominant concentration of superhard TiB 2 (from 45 to 90vol.%) were fabricated using elemental powders by means of SHS (self-propagating hightemperature synthesis) process and simultaneously densified by p-HIP (pseudo-isostatic pressing technique). The heat released during highly exothermic SHS reaction was "in situ" utilized for sintering. The combustion occurred even for 50vol.% Cu dilution. According to XRD metallic copper binder was formed in those cermets in whole range of investigated compositions. The TiB 2 volume fraction significantly influenced the properties of fabricated materials, especially grain size and hardness. Both the average grain size and hardness significantly increased with TiB 2 content, so the maximum value of 18GPa was measured for TiB 2 -5vol.%Cu composite. Coarse grains of 6.4µm in size were observed for this composite while TiB 2-based submicro-composites were formed for 40-50% of Cu where the average grain size did not exceed 0.6µm. The Vickers hardness of 16-18 GPa obtained for cermets containing from 85 to 90vol.% of TiB 2 and no radial cracks in Vickers hardness test proved that in term of hardness and fracture toughness the composites might be competitive to WCCo cermets.

Vaporization and Poor Wettability as the Main Challenges in Fabrication of TiB2-Cu Cermets Studied by SPS

“…Therefore, search for effective sintering techniques is a fully justified challenge to be undertaken. Such systems were studied and already reported in several papers [3][4][5]9,10,12], including sintering by SPS, and the results were consistently confirmed. Also compaction of Cu or Cu-based powder mixtures by means of SPS technique has been studied at least several times, using different grain size powders and various sintering conditions [2,13,14].…”

“…Moreover, most modifications will affect the crystallization of additional phases, i.e., intermetallics. The second method to eliminate effects of vaporization and control the chemical composition is by means of fabrication using encapsulated device, as it has been already published [9]. In this case the poor wettability of TiB2 by Cu and weak effect of capillary forces can be compensated by high pressure working on a well-sealed container, which is able to both enhance infiltration and prevent vaporization of Cu.…”

“…For instance, formation of intermetallics at elevated temperature occurs in many systems. Compared to those systems, Cu is a thermodynamically stable binder for TiB2, and intermetallics can be entirely avoided [9], which makes the boride a unique candidate for strengthening of the Cu matrix. Due to the application of very hard TiB2, hardness, strength, as well as wear and erosion resistance can be significantly improved.…”

“…Due to the application of very hard TiB2, hardness, strength, as well as wear and erosion resistance can be significantly improved. By using high volume fraction of TiB2 even the application in cutting tools technology is possible [3,10,11] because remarkably hard cermets can be obtained [7][8][9][10][11].…”

Effect of (Ti:B) atomic ratio on mechanical properties of TiB2–Fe composites “in situ” fabricated via Self-propagating High-temperature Synthesis

“…Particular attention is being paid to Al [15][16][17][18], Cu or Fe as a toughening binder [2,6,8,11,[19][20][21], because cermets can be obtained in these systems. In order to fully utilize the high refractoriness of TiB 2 (melting point of 3225°C), Fe is a better candidate for a metallic matrix.…”