| Bearings play an important role in the development of the aerospace industry.The requirement of the bearings’high-temperature performance becomes higher with the development of the aerospace industry and universe exploring.For instance,the high-temperature bearing materials are currently subjected to severe challenges such as high-speed,high-temperature,corrosion and other co mplex working environments.Therefore,people put forward higher requirements for the performance of high-temperature bearing materials because of the complex working environment.The experimental material used in this paper is a high Cr-Co-Mo high temperature bearing steel with low carbon martensite as matrix and adding secondary hardening alloy elements to produce secondary hardening effect during tempering.In this paper,the metallographic microscope,scanning electron microscope,transmission electron microscope,X-ray diffractometer,and thermal simulation tester were used to study the thermal deformation behavior of high-Cr-Co-Mo high-temperature bearing steels and the relationship between the structural evolution and mechanical properties during heat treatment.Getting the following results:1.In the process of thermal deformation,the deformation rate mainly affects the dynamic recrystallization time,and the effect is more obvious with the increase of deformation temperature.When the temperature and strain are constant,the degree of recrystallization and the grain size are directly proportional to the deformation rate.When the deformation rate and strain are constant,the degree of recrystallization and the grain size are directly proportional to the deformation temperature.The increase of the deformation rate and the decrease of the deformation temperature both increase the flow stress.2.The constitutive equations of high-Cr-Co-Mo high-temperature bearing steels were established by deformation activation energy（Q）,flow stress（σ）,deformation rate（?）and deformation temperature（T）.The thermal deformation activation energy of this experimental steel is 489.275 k J/mol;Based on the flow stress curve and recrystallization microstructure analysis,a hot workin g chart of high Cr-Co-Mo high temperature bearing steel was established and the optimal hot working process parameters were obtained.3.The results show that there is no carbide precipitated from the martensitic matrix when the sample was tempered at 480℃.However,when the sample was tempered at 540℃,a large number of stable spherical M6C carbides precipitated in the test steel.Nevertheless,there are three types of carbides precipitated from the matrix including M6C,M2C and M23C6 carbides when the t empering temperature reach to 600℃.4.In addition,the austenitic layers with a thickness of about 30 nm have been obtained between the martensite laths after 600℃tempering.The austenitic layers will produce transformation-induced plasticity（TRIP）e ffects to improve the toughness of the steel. |
