In-situ NbC/H13 Steel Matrix Composites For Wear And Corrosion Resistance

As a key component in tunnel boring,the working environment of shield machine hob is harsh,often accompanied by wear and corrosion,and the hob ring is highly susceptible to damage.Therefore,the hob cutter ring must not only have excellent mechanical properties,but also put forward high requirements on its corrosion resistance.Ceramic/metal matrix composites have been widely studied for their excellent wear and corrosion resistance.In-situ ceramic/metal matrix composites are formed in-situ inside the metal matrix,so the interface between the reinforcing phase and the metal matrix is clean and free of contamination and well bonded,and the good wear and corrosion resistance of the ceramic reinforcing phase significantly increases the service life of the composite material.In this paper,NbC/H13 steel matrix composites were prepared based on the in-situ reaction casting method,and the effects of different volume fractions of NbC on the organization and properties of the composites were systematically investigated.The effects of different volume fractions of NbC on the composite structure,mechanical properties,dynamic and static load abrasive wear properties and corrosion performance were investigated by in-situ autogenous generation of 1%,3%and 5%NbC ceramic reinforced phases in the material.It was found that with the increase of the volume fraction of NbC reinforced phase,the morphology of NbC reinforced phase gradually changed from reticulated to small rod and granular.the introduction of NbC reinforced phase decreased the tensile strength and impact toughness of the composites compared with the metal matrix material,but the hardness of the composites was mentioned to be increased,which improved the wear resistance.Dynamic and static load abrasive wear tests were performed on the composites,and the effects of the NbC-reinforced phase on the wear resistance of the materials were discussed.In the impact abrasive wear tests,the in-situ autogenous NbC reinforced phase resulted in an effective improvement of the impact abrasive wear resistance of the material,and the best impact abrasive wear resistance was achieved when the volume fraction of the NbC reinforced phase reached 5%,which was 1.8 times higher than that of the metal matrix material.The effect of in-situ autogenous NbC/H13 steel matrix composite three-body abrasive wear performance is closely related to the volume fraction of the formed reinforcing phase,as shown by the reciprocating three-body abrasive wear test.The best wear performance is achieved when the volume fraction of the reinforcing phase reaches 5%,which is 2.1 times higher than that of the metallic matrix material.The corrosion behavior of the composites was investigated in three typical corrosive media solutions:acidic（H₂SO₄ solution）,alkaline（Na OH solution）,and neutral（Na Cl solution）.The results showed that the NbC/H13 steel matrix composite had the best corrosion resistance in Na OH solution and the worst corrosion resistance in H2SO4 solution.In the three typical corrosive media solutions,the corrosion resistance of NbC/H13 steel matrix composites gradually improved as the volume fraction of NbC reinforced phase increased.in Na Cl and Na OH solutions,the oxygen absorption reaction became the dominant factor in the overall electrochemical reaction;in H₂SO₄ solution,the hydrogen precipitation reaction became the dominant factor in the overall electrochemical reaction.