Study On Preparation And Properties Of The Network Ceramic/steel Composites

The Al₂O₃/steel matrix composite as a part of ceramic/metal matrix composite, it has the excellent properties both the ceramic materials and steel materials, such as wear resistance、high temperature resistance、high modular ratio、high strength ratio、low density、good toughness、good electric and thermal conduction. The steel and ceramic in three-dimensional network Al₂O₃/steel shows three-dimensional network structure in space, compared to the traditional fiber reinforced and particle reinforced composite materials, its properties have been greatly improved, but the wettability between ceramic and steel is poor, so how to improve the wettability between the two has become a concern of the majority of researchers.This research deposits titanium coating on the porous ceramic skeleton and its surface by the CVD method, which improves the wettability between the Al₂O₃ ceramic and the steel,the Al₂O₃ ceramic /Ti/ steel composite material is prepared by the method of vacuum evaporative pattern casting; it investigated the interfacial bonding strength and the mechanical properties of the composite materials, and also discussed the influence on the properties of composites with different bonding interface.The results show that: both the outer surface and skeleton of the network ceramic can obtain the flat and uniform titanium coating, the melting steel liquid can be completely induced into the pore of the ceramic network skeleton induced by titanium coating, and occupies the micro triangular pores of network ceramic, to prepare Al₂O₃ ceramic/Ti/steel composite material without internal collapse、macro holes but close bonding interface. There are two mechanisms of the bonding interface of Al₂O₃ ceramic/Ti/steel composite material:mechanical binding and metallurgical binding, between Fe, Ti and Al₂O₃ three phases will react under the condition of high temperature, generate new intermetallic compounds Fe2AlTi、FeAlTiO5 and Fe2 Ti etc, which formed a tight binding interface. The increase of volume fraction of ceramic leads to the decrease of the tensile strength of the composite, the tensile strength of the composite is slightly lower than that of the steel but higher than that of the solid Al₂O₃ ceramic. With the increase of the volume fraction of ceramic, flexural strength of the composites gradually decreases. Interface combinations of titanium coated Al₂O₃/steel composite are metallurgy bonding and mechanical binding, Interface combination of nickel coated Al₂O₃/steel composite is mechanical binding, the flexural strength of the former was significantly higher than that of the latter. The interface cracks of composites in the process of tensile and bending start at the bonding interface of ceramic and steel, enhancement of theinterface strength of Al₂O₃ ceramic/steel composite can improve the whole mechanical properties.