Research On Microstructure And Properties Of Nano-SiC Whisker Modified Ti(C,N)-based Cermets

The study progress and developmental trend of Ti(C,N)-based cermets and nano SiC whisker have been reviewed, and the influences of nano SiC whisker(nano-SiCw) on the microstructure and mechanical properties of metal and ceramics materials have also been summarized. Based on previous work, the purpose of the dissertation is to improve the transverse rupture strength (TRS), Rockwell hardness (HRA) and fracture toughness (KIC) of the Ti(C,N)-based cermets by adding nano-SiCw.In this study, the fracture morphologies and microstructure have been observed by field emission scanning electron microscope. Composition profiles have been analysed by energy dispersive spectroscopy. And Transverse strength test was conducted by three-point transverse method, Rockwell hardness and fracture toughness property were tested. And relationship among composition, microstructure and mechanical properties has been systematically investigated.The effects of nano-SiCw content and sintering temperature on the microstructure and mechanical properties of Ti(C,N)-based cermets have studied systematically. After being sintered, the carbide phase of the cermets exhibits classical core-rim morphology: core phase, gray surrounding phase and grayish-white binder phase. The microstructure of Ti(C,N) based cermets with nano-SiCw also exhibits the classical core-rim morphology: black core phase, gray surrounding phase, grayish-white binder phase and white SiCw reinforced-phase. Comprehensively, the dissertation indicates that the mechanical properties of the transverse strength and the hardness are the best when the nano-SiCw contention is 7.5vol% and sintering temperature is 1410℃.The effects of nano-SiCw content on the fracture toughness property of Ti(C,N) based cermets has been studied systematically. The fracture toughness of Ti(C,N) based cermets after adding nano-SiCw is higher than that of Ti(C,N)-based cermet. When the nano-SiCw contention is 7.5vol%, the the fracture toughness is up to 11.56MPa·m1/2, which is increasing by 31%.This article emphatically studies the whisker toughening mechanism, the result showed that whisker bridged, whisker pull-out and crack branching improved toughness of Ti(C,N)-based cermets. The whisker impedes the development of crack and postpones the extending speed of the main crack. Some small grains were found to be embedded in binder obstructed the form and extend of crack, in this process, the absorbed energy augmented and the transverse rupture strength of cermet was enhanced.Observations of the fracture morphology of the cermets with different nano-SiCw contents reveal the fracture is a mixed one. Both inter-granular and dimple fractures are in existence, the dimple fracture takes the main part, and the extraction trace of nano-SiCw is obvious.