| As one of wear-resistant materials with great development prospects,high boron steel has attracted the attention of experts for its high hardness and good wear resistance.However,due to the weak bond energy of the B-B bond along the [002] crystal direction and the network distribution of the boride in steel,leading to severe brittleness in high boron steel.In this paper,based on the modification and high temperature treatment to improve the morphology of boride,the Q&P process in the Fe-C-B system is applied to study the effect of the partitioning process on the microstructure and properties of high boron steel.With the increase of boron content,the network borides in the microstructure of the as-cast sample gradually increases,while the dendrites gradually decreases.Elemental analysis shows that Al and Si were mostly present in the dendrites,while Mn and B elements were widely distributed in the boride.The macro hardness of as-cast samples gradually increases with the increase of boron content,while the impact toughness gradually decreases.The borides in the microstructure appear spheroidization and fracture after austenitizing at 1050? and holding for 2h,and the quenching time?tQ?has an effect on the microstructure in the subsequentQ&P heat treatment process.With the increase of quenching time?tQ?,the volume fraction of tempered martensite?TM?and retained austenite?RA?in high boron steels?1.6wt%B,1.9wt%B and 2.2wt%B?with different boron content increase,and the macro hardness all gradually decrease,while the impact toughness tends to increase first and then decrease.During the partition heat treatment,the increase of quenching temperature?TQ?will cause decrease of the volume fraction of TM and RA in the matrix,while the macro hardness is getting higher,and the impact toughness decreases.The increase of the partitioning time allowes the carbon partitioning process becomes more sufficient,and the volume fraction of RA gradually increases,but the Rockwell hardness decreases.The highest impact toughness of the three high boron steels with different boron content are 7.5 J · cm-2,6.3 J · cm-2 and 5.9J · cm-2,respectively,which are 2,1.9 and 2.4 times of the toughness of as-cast specimens.The wear resistance of as-cast high boron steel increases with the increase of boron content,and reaches the peak when the boron content is 2.2wt%,which is 2.07 times of NM500.After the partition treatment at different tQ,the wear resistance of high boron steel is better than that of as-cast steel,and the existence of a certain amount of RA will cause TRIP effect on the wear subsurface layer,ensuring the good wear resistance of samples even under the condition of reduced macro hardness,but too much volume fraction of RA will deteriorate the wear resistance of high boron steel. |
PDF Full Text Request