Effect of high-temperature annealing on mechanical properties of spark plasma sintered TiCN-15WC-5Cr3C2-5 nano-TiB2 cermets modified with cobalt

Abstract

This paper reports the effect of high-temperature annealing on the mechanical properties of spark plasma sintered TiCN-15WC-5Cr₃C₂-5 nano-TiB₂-based cermet modified with the addition of different percentages of cobalt (0 to 15%). The microstructure and mechanical properties such as hardness and toughness of the as sintered cermets were reported. The cermets were heated to different annealing temperatures (800 °C and 1000 °C) for the holding time of 4 h and 6 h. The effect of high-temperature annealing on the mechanical properties was evaluated by measuring the hardness, toughness and weight gain/loss. The results showed that the hardness and toughness decreased with an increase in the annealing temperature and time. The presence of Co in the cermets with 10% and 15% showed better hardness values after annealing at 800 °C and 1000 °C for 4 h and 6 h. The fracture toughness values did not change much compared to the blank and cermets with 5% Co. The cermet with 15% Co showed better mechanical properties compared to the blank. The weight gain increased with annealing temperature and time. The SEM analysis revealed that the microstructures were changed with respect to the annealing temperature and time. Annealing at 1000 °C for 4 h and 6 h showed a newly formed oxide layer and coarsening of grains. The new phases formed during annealing were examined by XRD, and it was found that the formation of different oxides leads to deteriorate the thermal stability of the cermets.