Low-temperature sintered (Ti, Zr, Nb, Ta, Mo)C ceramics with improved hardness and toughness by using CrN as sintering additive

Currently, previous studies of low-temperature sintering of high-entropy carbide ceramics (HECCs) have followed the traditional approach to use the low-melting-point metals, such as Co, Ni, and so forth, as sintering additives. However, metallic binders can cause adverse impacts on hardness of HECCs. This study reported an innovation processing method for low-temperature sintering of HECCs, which involved the use of various contents of CrN as sintering additive and spark plasma sintering at 1600 degrees C to obtain dense HECCs. In comparison to the grain size of pure (Ti, Zr, Nb, Ta, Mo)C bulk sintered at 2000 degrees C (3.29 +/- 1.02 mu m), the grain size of samples with the addition of 5-15 wt.% CrN sintered at 1600 degrees C was significantly smaller, ranging from 0.32 to 0.48 mu m. By using only 5 wt.% CrN, dense (Ti, Zr, Nb, Ta, Mo)C ceramics with a high hardness value of 26.73 +/- 0.43 GPa could be obtained. Furthermore, increasing the amount of CrN to 15 wt.% resulted in a fracture toughness of 3.78 +/- 0.10 MPa center dot m1/2. It is anticipated that the (Ti, Zr, Nb, Ta, Mo)C ceramic with an ideally combined hardness and toughness can be achieved at low sintering temperatures by the proper control of CrN content.