Research On The Effect Of In-Situ Synthesis TiC Reinforcement On The Wear Resistance Performance Of HB400 Steel

Under the background of "double carbon",it is of great significance to explore and develop high-performance green steel products with higher wear resistance and longer life,and realize the iterative upgrading of wear-resistant steel to reduce the economic loss and resource waste caused by wear.In recent years,the new TiCreinforced wear-resistant steel developed by the in-situ synthesis method has significantly improved the wear-resistant performance compared with the traditional steel with the same hardness,but its wide application is restricted by the problems of reduced toughness and increased residual stress that caused by the introduction of TiC.In this paper,in-situ synthesis TiC-reinforced HB400 wear-resistant steels were studied.The microstructure and properties of the experimental steels were analyzed by scanning electron microscopy(SEM),transmission electron microscopy(TEM),electron backscattering diffraction(EBSD),X-ray diffractometer(XRD)and nanoindentation and other microstructural or performance characterization techniques.The effect of microstructure type,the content,and the size of TiC reinforcement on the wear resistance performance of the steel were systematically studied.The formation of TiC reinforcement during solidification and the evolution of TiC/matrix interface characteristics before and after thermal deformation were revealed.The mechanism of the influence of TiC reinforcement on the residual stress of steel was explored.The main conclusions are as follows:HB400 wear-resistant steels with the volume fraction of 0%(0TiC),0.4%(0.4TiC),0.7%(0.7TiC),and 1.1%(1.1 TiC)were designed.After quenching at 900℃and tempering at 220℃,the microstructure of these four experimental plates of steel was lath martensite.Their hardness is in a range of 426～450 HV.The introduction of TiC improves the wear resistance of the steel,and with the increase of TiC volume fraction,the wear resistance performance increases gradually.Under the condition of two-body abrasive wear,the wear resistance performance of 0.4TiC,0.7TiC and 1.1 TiC test steel is 1.1 7.1.32,and 1.48 times of 0TiC steel,and 1.15.1.31.and 1.50 times for the condition of three-body abrasive wear.respectively.For 0.4TiC steel,the formation mechanism of TiC reinforced phase during solidification was defined,the evolution of matrix structure,TiC size,and TiC/matrix interface of the steel under different thermal deformation processes was analyzed,and the influence on the wear resistance of steel was also investigated.TiC forms in the solidification process of molten steel and is eutectic with some austenitic phase(γ)near the end of solidification,which follows the cube-cube orientation relationship.With the decrease in temperature,there is a K-S(or N-W)orientation relationship between the new ferrite phase(α)and the original γ,thus the K-S(or N-W)orientation relationship between TiC and a in the solidified sample can be observed.In the process of thermal deformation,the microstructure of the TiC-reinforced steel is mainly affected by the thermal deformed temperature.The 1050℃ samples have better wear resistance because of the smaller size of martensitic laths and higher uniformity of microstructure.The size and interface characteristics of TiC reinforcements are mainly affected by the deformation amount.The increase of the deformation not only makes TiC reinforcements become smaller and dispersed,but also changes the orientation relationships and the interface characteristics between TiC and matrix.Increasing the size of TiC and maintaining the K-S or N-W interface characteristics between TiC and the matrix is beneficial to improve the wear resistance of the steel.The effects of quenching temperatures and tempering temperatures on microstructure,mechanical properties,and wear resistance of reinforced steel were studied.After quenching at 830～950℃ and tempering at 220℃,the wear resistance of the experimental steel increases first and then decreases with the increase of quenching temperature.After quenching at 900℃ and tempering at 160～600℃,the toughness of the test steel decreases first and then increases with the increase of tempering temperature,and the hardness and residual stress show a monotonously decreasing trend,while the wear resistance of the reinforced steel increases first and then decreases,indicating that the wear resistance of the reinforced steel is affected by the hardness,toughness and residual stress together.The tensile strength of the experimental steel quenched at 900℃ and tempered at 220℃ is 1418 MPa,the elongation is 10.2%,the impact energy is 18 J at-20℃,and the weight loss of the two-body abrasive in 15 min is 0.2049 g,showing relatively excellent comprehensive mechanical properties and wear resistance.The residual stress in TiC-reinforced steel was investigated by means of nanoindentation,XRD,and numerical simulation.Due to the difference in thermal expansion coefficient between the matrix and TiC reinforcement in the cooling process,the matrix near the TiC reinforced phase generally shows residual tensile stress,while the TiC reinforced phase shows residual compressive stress.The introduction of TiC reinforcements results in the larger fluctuation of nanohardness,the more complex microstress,and the greater macroscopic stress of steel.The static load relaxation method(small deformation at an appropriate amount)can improve the stress uniformity and reduce the macroscopic residual stress of the reinforced steel.Based on the research above,combined with the equipment conditions of the factory,the industrial trial productions were carried out and performance evaluations were completed.The billet with good quality was obtained when casting with superheat at 10～15℃.The TiC-reinforced steel plate with a tensile strength of 1452 MPa,hardness of 439 HV,and low residual stress was obtained by TMCP rolling process,quenching at 900℃,and tempering at 200℃.The maximum wear resistance performance of the TiC reinforced steel is up to 1.31 times that of traditional steel.This study provides technical support for the popularization and application of TiC reinforced wear-resistant steel.