Preparation And Mechanical Properties Of NbC/Fe Reinforced Steel-matrix Laminated Composite

Iron and steel materials have excellent comprehensive properties.High-carbon steel,as the most widely used type of tool and die steel,has good strength,hardness and wear resistance,but the increasingly stringent working environment requires it to increase strength while enhancing bending resistance.Reduce fracture failure,so it has important practical significance for improving the strengthening and toughening of high carbon steel.In this paper,T10 steel sheet,niobium powder,graphite powder,and iron powder are used as raw materials,and the reinforcement layer(RL)is obtained by ball milling and cold pressing.Then,the NbC/Fe reinforced steel-based lamelleted composite material is prepared by in-situ hot press sintering with the steel sheet and RL at(1220?×6 h),realizing the controllable preparation of particle-enriched NbC hard mass and lamelleted structure.The effects of different time and different niobium-carbon ratios on the reaction process and phase of Nb particles in NbC/Fe reinforced steel-based lamelleted composites were studied;the effects of secondary normalizing heat treatment on the bending properties of NbC/Fe reinforced steel-based lamelleted composites and The structure evolution law,formation mechanism,bending performance and toughening mechanism of the NbC hard mass formation process are explored.The research results show that:(1)The phase composition of the NbC/Fe reinforced steel matrix composite is mainly NbC and ?-Fe,and the structure of the NbC/Fe reinforced layer is ferrite and pearlite.In the process of sufficient carbon reaction,three characteristic structures can be observed,namely Laves phase Nb2C,NbC/iron-rich zone,NbC/iron-poor zone,the main phases are ?-Fe,Nb,NbC;in the carbon-poor reaction process.There are also three layers of microscopic features,namely Laves phase Nb2C,NbC and a small amount of iron,Laves phase Fe2Nb,and the main phases are ?-Fe,Nb,NbC and Fe2Nb.The formation of NbC hard masses is manifested by the continuous advancement of the NbC/Nb interface to the center.(2)After normalizing,the maximum flexural strength of the three-layer composite is 1609.5MPa and the maximum deflection is 0.79mm;the maximum flexural strength of the five-layer composite is 2054.41MPa and the maximum deflection is 0.79mm.Compared with normalizing T10 steel,the flexural strength of the three-layer composite material is increased by about 1.34 times,and the deflection is also increased by about 1.34 times;the flexural strength of the five-layer composite material is increased by about 1.41 times,and the deflection is also increased by about 1.16 times.(3)The toughening mechanism of lamelleted composite materials is:delamination cracking at the interface,main cracks and secondary cracks encountering NbC hard groups will cause crack blunting and crack deflection;in the NbC/Fe reinforced layer,ferrite Crack bridging occurs,the secondary cracks are dispersed into a large number of micro-cracks,the crack propagation path increases,a large amount of energy is absorbed,the fracture work of the composite material is improved,and the strength and toughness of the composite material is improved.