Preparation Of Ti(C,N)-based Cermet Materials With Dual-core Ring Structure

Ti?C,N?-based cermets represent the best choice of the material c for the manufacturing and military products,and are also considered as one of the potential alternatives to hard alloys such as WC because of their excellent resistance to high temperatures,corrosion,and wear And other properties,However,due to its hard sintered phase is polycrystalline sintered material,its fatal weakness is insufficient brittleness and toughness.In this paper,Ti?C,N?-based cermets with two kinds of core ring structures,that is,black core/white rim and white core/grey rim,were prepared mainly by adding Cobalt wih face-centered cubic structure and?Ti,W,Mo,Ta??C,N?solid solution powder into the raw materials to enhance the mechanical properties of cermet.Firstly,CoCl₂·6H₂O and Na₂Co₃ were used as raw materials to prepare the face-centered cubic structure of the?-Co by high-energy ball milling?spray drying and thermal decomposition.Solid solution powder?Ti,W,Mo,Ta??C,N?was prepared by the combination of solid phase chemical reaction and carbothermal reduction reaction.Then samples A of Ti?C,N?-WC-Mo C-TaC-??-Co?,samples B of Ti?C,N?-WC-Mo C-TaC-??-Co?,and Sample C of Ti?C,N?-?-Co-?Ti,W,Mo,Ta??C,N?are prepared by sintering.The phases and specimens were analyzed using a Japanese D/MAX2500 X-ray diffractometer.The morphologies and microstructures of the samples were observed with a Jeol-6490LV scanning electron microscope.The transverse fracture strength?TRS?of each sample was tested with a We-100b universal material testing machine,and the three-point bending method was adopted.The size of the sample was 20×6.5×5.5mm?length width and height?,the span was 30 mm,and the loading speed was0.5mm·min^-1.The Rockwell hardness of each sample was measured with an AR-600Rockwell hardness machine.The Vickers hardness of each sample material was tested with a HV-50 tester,and the fracture toughness values were calculated using the Shetty fracture toughness formula.The results is as follows:?1??-Co microspheres obtained by the solid-phase reaction of high-energy ball milling have high activation energies and good wettability,which accelerate solid-phase diffusion,promote atomic diffusion,and accelerate the solid-solution speed during sintering.These greatly improve the wettability of the ceramics phase and increase the solidsolution strengthening effect.?2?The?Ti,W,Mo,Ta??C,N?solid solution can be prepared by the carbothermic reduction-nitridation method?N₂ atmosphere protection,heating temperature of1600°C?.?3?Cermets were prepared using?-Co as the binder phase and using?Ti,W,Mo,Ta??C,N?solid instead of single metal carbide,which resulted in two kinds of core-rim structures with fine cores and thick rims.With this structure,when the cermets are acted on by an external force,stress transfer is alleviated and crack deflection is improved,which means the toughness of the cermets is improved.?4?The properties of the new cermet were compared with those of traditional cermets.The former's transverse fracture toughness?KIC?has been improved by 7%compared with ordinary ones,and the bending strength?TRS?has been increased by 10%.