Effect Of Mo Content And Heat Treatment On Structure And Properties Of Wear-resistant High-molybdenum Cast Steel

Chromium white cast iron is widely used due to its excellent wear resistance,but its application range is limited by the reduction of toughness due to the large strip like M7C3carbide splitting the matrix structure.Based on the composition of medium chromium white cast iron,a new wear-resistant material high molybdenum wear-resistant steel was designed by reducing carbon content and adding more molybdenum content.The effects of molybdenum content and heat treatment process on the microstructure and properties of high molybdenum wear-resistant steel were studied.(1)The as cast matrix structure of high Mo wear-resistant steel is mainly acicular martensite,lath martensite,austenite and more carbides segregate along grain boundaries.With the increase of Mo content,the carbides at grain boundaries increase first and then decrease,the Rockwell hardness decreases first and then increases,and the impact toughness increases first and then decreases.After quenching,the secondary carbides begin to appear in the structure.With the increase of Mo content,the network carbides in the structure of high Mo wear-resistant steel transform into massive carbides.After tempering at 480?,the structure mainly contains tempered martensite Retained austenite,primary carbide and secondary carbide.The primary carbides are mainly Mo and V carbides,and the secondary carbides are mainly Mo,Cr,V and Fe precipitated in the grain after tempering.With the increase of Mo content,the transformation from austenite to martensite is hindered.The Rockwell hardness of high Mo wear-resistant steel decreases with the increase of Mo content,and the impact toughness of high Mo wear-resistant steel first decreases and then increases with the increase of Mo content.(2)With the increase of tempering temperature,the driving force of transformation from austenite to martensite increases,the content of martensite in matrix increases,the hardness of high molybdenum wear-resistant steel with 6%and 8%molybdenum content increases gradually,and the impact toughness decreases gradually,There are obvious furrows,creases and scratches along the wear direction on the wear surface of high molybdenum wear-resistant steel after three body abrasive wear,and there are abrasive embedded in some parts.On the whole,with the increase of tempering temperature,the mass loss rate decreases mainly,and the wear resistance increases with the increase of post tempering temperature,which corresponds to the mechanical energy.(3)After oxidation test,the oxidation resistance of high molybdenum wear-resistant steel with different molybdenum content decreases with the increase of molybdenum content.The increase of molybdenum content is not conducive to the high-temperature oxidation resistance of high molybdenum wear-resistant steel.SEM-EDS analysis results show that the outer oxide film is mainly composed of Fe₂O₃,Mn₂O₃,Fe VO₄and Fe Cr₂O₄,while Mo containing oxides gather at the interface between the outer oxide film and the matrix alloy.The overall oxidation resistance at 900?is not very good,which needs further study.