Utilization of moderate pressure and elevated temperatures in the optimization of Ti2AlC‐cBN composites using SPS technique

Abstract

Abstract The formation reaction mechanism of Ti2AlC cubic boron nitride (cBN) composite materials was investigated using different particle sizes at different volume percentages of cBN (20 and 40 vol%), at a constant moderate pressure while varying time and temperature. The results show that, under the investigated conditions, Ti2AlC decomposed at 1300°C with a simultaneous hexagonalization of the cBN, resulting in the creation of secondary phases including TiB2, TiC, TiN and AlN. It was observed that the optimum time and temperature for fabricating Ti2AlC‐cBN composites, where both phases were abundantly present, was 1250°C for 5 minutes for all composites. Under these conditions, there was no hBN in the resulting composites. Increasing the average particle size of cBN powder enhanced the stability of the Ti2AlC and cBN in the samples. Also, the increase in volume fraction of cBN was observed to further promote the stability of Ti2AlC and cBN in the samples. This was due to the decrease in surface area of cBN, which hampered hexagonalization of cBN. Whatever excess hBN present reacted completely with the MAX phase in the final composites. The secondary phases formed in the samples were TiAl2, Ti3Al, TiCb, TiB2, TiCxNy (in samples containing 100 µm cBN) and TiN (in samples containing 20 vol.% cBN). The reaction area between Ti2AlC and cBN was strongly bonded to the cBN and Ti2AlC phases. A controlled method of simultaneous hexagonalization of cBN and reaction of the resultant hBN with Ti2AlC has proved superior in forming composites of Ti2AlC with cBN.

Keywords

• cBN
• MAX phases
• spark plasma sintering
• Ti2AlC