Effects of sintering processes on the mechanical properties and microstructure of Ti(C,N)-based cermet cutting tool materials

In this study, two types of Ti(C-0.7,N-0.3)-based cermet cutting tool materials (Ti(C,N)-Mo-Ni-Co, named as TMNC, and Ti(C,N)-WC-Mo-Ni-Co-TaC-HfC, named as TWMNCTH) were fabricated by the hot pressed sintering process at different temperatures (from 1380 degrees C to 1500 degrees C) for different holding times (from 30 min to 60 min) in a vacuum atmosphere and at a compressive stress of 32 MPa. The polished surface and the fracture surface of the two types of cermets were observed by a scanning electron microscope (BSE/SEM) and energy dispersive spectrometry (EDS), and the relationships among sintering processes, mechanical properties and microstructure were discussed. The experimental results showed that the sintering temperature and holding time both had a great influence on the flexural strength and a small effect on the hardness and the fracture toughness of the two types of cermets. The two cermets both had the optimal comprehensive mechanical properties when they were sintered at 1400 degrees C for 30 min. The sintering temperature and holding time also had a great influence on the microstructure of the two cermets, and the grain sizes increased when the sintering temperature varied from 1400 degrees C to 1500 degrees C and the holding time varied from 30 min to 60 min. The properties and microstructure of the two cermets were also compared. The results indicated that the cermet TWMNCTH had a lower flexural strength, a similar value of fracture toughness, a higher hardness and a thicker rim in the microstructure. (C) 2014 Elsevier Ltd. All rights reserved.