Characterization of microstructure and mechanism of rolling contact fatigue of high nitrogen stainless bearing steel
High nitrogen stainless bearing steel(HNSBS),as a third-generation bearing steel material,is widely used in fields such as fuel pump bearings for aerospace shuttles and aircraft engine spindle bearings.It has become a key basic material for aerospace.However,there is almost no research on the rolling contact fatigue(RCF)performance of HNSBS in China.Therefore,different tempering temperatures for heat treatment of HNSBS prepared by pressur-ized electroslag smelting process were used,and conducts mechanical properties testing,microstructure characteriza-tion,and RCF testing.The results show that the tensile strength of the test steel quenched at 1 030℃ and tempered at 180℃ is 1 899.7 MPa,with a hardness of 60.7HRC.After tempering at 500℃,the hardness is equivalent to 180℃,and the tensile strength is increased to 2 213.5 MPa.By characterizing the matrix of the 500℃ tempered sample,it was found that the nanoscale Cr-N precipitation in the matrix is the main reason for the occurrence of sec-ondary hardening phenomenon.The RCF life L10 of the 180℃ tempered sample is 1.67×107,while the L10 of the 500℃ tempered sample is 2.85×107,which is 70%higher than that of the 180℃ tempered sample.Through in-depth characterization of fatigue spalling in the matrix of two specimens,it was found that intergranular fracture in the subsurface layer of the 180℃ tempered specimen is the main cause of RCF crack initiation.Based on the analysis of the results of residual stress in the matrix,the residual tensile stress after high-temperature tempering at 500℃ is 41 MPa,which is lower than 101 MPa after tempering at 180℃.The nanoscale Cr-N precipitated in the high-temperature tempered specimen can reduce the mobility of dislocations and weaken the stress concentration inside the matrix,resulting in a decrease in the tendency of intergranular fracture in the subsurface layer of the raceway and significantly improves the RCF life.Through in-depth research and analysis on the microstructure,RCF,and crack initiation mechanism of HNSBS under different tempering processes,providing experimental and theoretical basis for the for-mulation of heat treatment processes,research on fatigue resistance mechanisms,and material development and appli-cation of HNSBS.
high nitrogen stainless bearing steelmicrostructurerolling contact fatiguefatigue spallingfatigue crack initiation
NETL
NSTL
万方数据
