In order to improve the uniformity of microstructures,and thus enhance the mechanical properties,espe-cially the impact toughness,of 52100 bearing steels,modified quenching heat treatments with different austenitizing...In order to improve the uniformity of microstructures,and thus enhance the mechanical properties,espe-cially the impact toughness,of 52100 bearing steels,modified quenching heat treatments with different austenitizing processes have been designed.The results show that 740°C is the optimal holding tem-perature(approaching Ac 1=750°C)to improve the impact toughness of the steel by 37%after quench-ing and low-temperature tempering.Microstructure observations reveal that 740°C holding shortens the nucleation incubation period of austenitization phase transformation,and inhibits the overfast growth of austenite in some regions,which leads to simultaneous nucleation and growth of austenite during austen-itizing,and homogeneous dissolution of carbides in different austenite grains.The changes in microstruc-ture evolution improve the microstructure uniformity(carbide and grain size)after quenching.Uniformly distributed carbides and grain size effectively reduce stress concentration and retard crack propagation during impact loading,thus resulting in high impact toughness.展开更多
基金the National Natural Science Foundation of China(No.52031013)the Strategic Pri-ority Research Program of the Chinese Academy of Sciences(No.XDC 04010300).
文摘In order to improve the uniformity of microstructures,and thus enhance the mechanical properties,espe-cially the impact toughness,of 52100 bearing steels,modified quenching heat treatments with different austenitizing processes have been designed.The results show that 740°C is the optimal holding tem-perature(approaching Ac 1=750°C)to improve the impact toughness of the steel by 37%after quench-ing and low-temperature tempering.Microstructure observations reveal that 740°C holding shortens the nucleation incubation period of austenitization phase transformation,and inhibits the overfast growth of austenite in some regions,which leads to simultaneous nucleation and growth of austenite during austen-itizing,and homogeneous dissolution of carbides in different austenite grains.The changes in microstruc-ture evolution improve the microstructure uniformity(carbide and grain size)after quenching.Uniformly distributed carbides and grain size effectively reduce stress concentration and retard crack propagation during impact loading,thus resulting in high impact toughness.
