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Scientific Reports volume 15, Article number: 1171 (2025 ) Cite this article p205 bearing
Since the rings of the angular contact ball bearings (ACBBs) are typical highly sensitive quenching thin-walled structure, the microstructure and properties variation of the rings during the heat treatment process are often difficult to be controlled precisely, and then the service life of the bearings is reduced. Therefore, in this study, the combination of the numerical simulation and experimental was carried out during the quenching and tempering process of ACBBs (7008C), the phase transformation of the inner and outer ring during the heat treatment process were explored, and the law of the microstructure evolution and the mechanical properties variation were revealed. Firstly, based on the multi-field coupling theory of temperature, microstructure and stress–strain field, the numerical simulation model of the heat treatment process of the bearing rings was established. Secondly, the content of each element of the rings was measured by a direct reading spectrometer (SPECTRO M12), and the thermophysical characteristics parameters of the material were calculated by the JMatPro software. Besides, the numerical simulation of the process was carried out by the Deform software. The evolution process of the temperature, microstructure, and properties during the heat treatment of the rings was investigated. Finally, the microstructure and mechanical properties of the heat-treated rings were obtained by optical microscopy, SEM and hardness tester. The results showed that the microstructure of the inner and outer ring after heat treatment process was cryptocrystalline martensite, and the average sizes of spherical carbides precipitated at grain boundaries were 0.39 μm and 0.38 μm, and corresponding hardnesses were increased to be 62.5 HRC and 62.7 HRC. The evolution of temperature-microstructure-mechanical properties during the heat treatment process of the ACBB rings are revealed, which can provide an important theoretical and technological support for the heat treatment process of the bearing rings for high-quality production.
As an important mechanical transmission element, angular contact ball bearings (ACBBs) are widely used in industrial equipment with high loads and high speeds. The contact fatigue failure can occur when bearing surfaces are subjected to high axial and radial loads. The observation of the microstructure of the bearing surface, it is found that the crack initiation is preferentially observed in the nano-grains layer, at primary carbides/matrix interfaces1. There are also unique microstructural alterations at the subsurface such as light etching region, white etching band and white etching area2. These cause a rapid reduction in the life of the bearings. The quenching and tempering process is commonly used as an important technology to improve the surface hardness and wear resistance of the bearing rings. The quenching and tempering process can improve the surface quality, refine the subsurface microstructure of the bearing rings, reduce the rolling contact fatigue damage on the surface, and increase the reliability of the bearings3.
In order to improve the microstructure and mechanical properties of the key components after the heat treatment process, the different heat treatment processes and the cooling methods have been studied by scholars. Reddy4 used seven different cooling methods to vary the cooling rate of low-carbon AISI 1020 steel during the heat treatment process. The changes in the microstructure and grain structure of the steel were analyzed. The stepped cooling procedures (e.g., sand + water, sand + oil) were found to be effective in preventing martensite formation, resulting in a reduction in the hardness of the material. Sharma5 analyzed the microstructure and mechanical properties of AISI 1020 steel by varying the cooling method during the post weld heat treatment process, it was found that the sand cooled specimens have a 7% reduction in the hardness and an 85% increase in the tensile strength due to the presence of coarse α + Fe3C. Besides, the specimens have no obvious defects and oxides formation after heat treament. A quenching-critical quenching-tempering heat treatment process has been proposed by Li et al.6. Compared with the conventional quenching and tempering process, the grains were refined by this process. The tensile strength, yield strength and impact toughness of the experimental steel were increased by 5.4%, 3.2% and 20.7%, respectively. The combination of pre-straining and heat treatment process was adopted by Zhou et al.7, the recrystallisation in the pre-strained region was promoted and the average grain and martensite size of BG 801 steel was reduced. The results show that higher pre-strain was beneficial for obtaining finer austenite and martensite grains, as well as lower residual austenite content. Different austenitization temperatures were adopted by Li et al.8. When the holding the heat is 740 °C, the nucleation latency of the austenite phase change was shortened. As a result, the rapid growth of the austenite in some areas was suppressed, and the carbides in the austenite grains were uniformly dissolved. This effectively reduces the stress concentration during impact loading, resulting in the impact toughness of the steel was improved by 37% after the quenching and low temperature process. Su9 found that the bearing steels treated with vacuum graded isothermal quenching were able to form a bainite phase, and the uniform and fine carbides were precipitated after tempering. The impact toughness was 50.6% higher than that of the steel treated only by vacuum hardening and tempering. The effect of deep cryogenic treatment and laser peening on surface hardness and wear resistance of GCr15 bearing steel was studied by Feng et al.10. It was found that a large number of twins, high density dislocation structures and ultrafine particles were generated on the surface of the specimens treated by this process. The microhardness of the specimens increased by 49.9% and the wear was reduced by 55.2%. It has been found that the microstructure and mechanical properties of key components can be significantly affected by the different heat treatment process parameters. The effect of quenching temperature and tempering temperature on the mechanical properties of 45Mn2 bainitic steel was studied by physical tests11. The microstructure of the steel was found to be lower bainite + ferrite + residual austenite + M/A at a quenching temperature of 910 °C and a tempering temperature of 240 °C, and the hardness and wear resistance were highest. With the development of the numerical simulation, the heat treatment processes have been numerically modelled and simulated by scholars to reveal the phase transitions and mechanical property evolution of key components during the heat treatment process. The relationship between the carburising and quenching process parameters and the depth of the hardened layer of the components was modeld by Liang12. The carburising and quenching process parameters were optimised by genetic algorithm. The evolution of the residual stresses, temperature and phase fractions during the quenching process of low-alloy steel tubes was simulated by Brunbauer13. It was found that discontinuous cooling has little effect on residual stress, but it can lead to local self annealing and a decrease in hardness. The material model of steel based on the phase transformation kinetics and mechanical properties testing has been established by Zhang et al.14. The phase transition, temperature variation and deformation during the quenching process of spiral bevel gears were studied by the finite element method. The results show that the final microstructure of low-carbon steel was bainite and the final microstructure of high-carbon steel was a mixture of bainite and ferrite. The experimental and simulation results were highly consistent, it was great significance in revealing the evolution of the microstructure and mechanical properties of the components during heat treatment.
The evolution of the microstructures and mechanical properties of the heat treatment process of the key components has been studied by many experts and scholars. But the microstructure evolution during heat treatment is affected by the structure of the components, as well as the coupling effects of temperature variation, microstructure transformation and stress–strain. In particular, the rings of the ACBBs with thin-walled structure and high quenching sensitivity, the phase transformation process during heat treatment process are often difficult to obtain through experiment. The heat treatment processes of the bearing rings with the thin-walled, small size and high quenching sensitivity have rarely been investigated.
To sum up, to solve the above problems, the rings of ACBBs (7008C) were taken as the research object in this study, and the evolution of temperature, microstructure and mechanical properties of bearing rings during the heat treatment process were investigated through the combination of numerical simulation and experiment. Firstly, based on the coupling principle of the temperature, microstructure and stress–strain field, a numerical simulation model of the heat treatment of the bearing rings was established. Secondly, the content of each element in the bearing rings was obtained by the infrared absorption method on a direct reading spectrometer, and a material model of GCr15 was established based on JMatPro software. The heat treatment process of the bearing rings was calculated based on Deform software. Finally, the microstructure morphologies of the bearing rings were observed under the metallurgical microscopy and SEM, and the content of retained austenite and hardness of the bearing rings were tested by X-ray diffractometer and Rockwell hardness tester. The evolution of microstructure and mechanical properties of the bearing rings during the heat treatment process were revealed. This research provides theoretical reference and guidance for the production of heat treatment of the bearing rings with the thin special-shaped.
Due to the complex interaction between the temperature, microstructure and stress–strain field, the following assumptions are made about the model to highlight the key issues, improve the solution efficiency and facilitate the modeling process.
The initial setting microstructure is pearlite, the hardness is 30 HRC, the temperature is 25 °C, and the stress is 0 Mpa of the bearing rings.
The distribution of atoms in the material is uniform, continuous and isotropic, and the uniform quenching can be realized.
The temperature of the quenching oil is maintained at 70 °C during the quenching process, this is determined based on the heat treatment production process of an enterprise for this type of bearing ring. The effect of the bearing rings temperature on the temperature of the quenching medium is not taken into account.
The variation in workpiece temperature during the heat treatment process involves three basic forms of heat transfer: heat conduction, heat convection, and heat radiation. According to the law of energy conservation and Fourier’s law, the governing equation of transient heat conduction in solid three dimensions can be derived as follows:
where T is the workpiece temperature, t is the temperature conduction time, k is the thermal conductivity, ρ is the material density, qv is the heat generation rate from the steel phase transformations, Cp is the specific heat capacity.
The heat transfer between the surface of the workpiece and its surroundings can be expressed by:
where ∂T/∂n is the temperature gradient of the surface layer of the workpiece, H is the total heat transfer coefficient (H = Hk + Hs), Hk is the convection heat transfer coefficient, Hs is the radiation heat transfer coefficient. Tg is the workpiece temperature, Tc is the ambient temperature of 25 °C.
The mathematical models used to describe the transformation of phase during heat treatment process can be divided into two categories, one class is the diffusive phase transformation from pearlite to austenite, that is:
where ξA is the amount of austenite transformation, Ts and Te are the temperatures at the beginning and the end of the austenite transformation. A and D are constants, calculated by JMatPro software to obtain Ts is 722 °C, Te is 816 °C, A is − 4, and D is 2.
Since the transformation of austenite to martensite occurs through atomic shear and rotation, this process is a non-diffusive phase transformation, and the amount of transformation depends on the temperature, independent of time:
where ξM is the amount of martensite transformation, T is the temperature, η1 and η2 are martensite transformation scale factors, based on the temperature at which the martensite transformation begins and the temperature required for half of the martensite transformation, η1 is calculated to be 0.016 and η2 to be − 5.18.
Taking into account the stresses and deformations generated by temperature variations and microstructure transformations during heat treatment, thus the total strain of the material is calculated by linear superposition of individual strains:
where εij is the total strain, \(\varepsilon _{{ij}}^{e}\) is the thermoelastic strain, \(\varepsilon _{{ij}}^{p}\) is the plastic strain, \(\varepsilon _{{ij}}^{th}\) is the thermal strain, \(\varepsilon _{{ij}}^{tr}\) is the phase transformation strain, \(\varepsilon _{{ij}}^{tp}\) is the phase transformation plastic strain.
The dimensional structure of the ACBB rings (7008C) is shown in Fig. 1, and the dimensional structure of the inner ring is shown in Fig. 1a, which has an inner diameter of 40 mm, a width of 15 mm and a max-wall thickness of 5.2 mm and a min-wall thickness of 4 mm. The dimensional structure of the outer ring is shown in Fig. 1b, which has an outer diameter of 68 mm and a width of 15 mm.
The rings of ACBBs (7008C) dimensional structure: (a) inner ring, (b) outer ring.
The detailed process of heat treatment is shown in Fig. 2, and the corresponding process is as follows: the heating and holding temperature of quenching is 830 °C, and the heating and holding time is 1 h, then cooling in quenching oil at 70 °C, the bearing rings are cleaned after cooling. A tempering treatment with a temperature of 160 °C for 3 h, and followed by air cooling.
The heat transfer coefficient is an element that describes the phenomenon of heat transfer during the heat treatment process15. As shown in Fig. 3a, it represents the heat transfer rate between the quenching medium and the surface of the workpiece, which can intuitively reflect the cooling characteristics of the medium. The heat transfer coefficient of the quenching oil used in this study is shown in Fig. 3b16.
The heat transfer coefficient of quenching oil.
According to the actual heat treatment production process of bearing rings, to ensure the accuracy of the simulation results, the integral bearing rings structure were selected as the simulation object. Tetrahedral meshing is used for the inner and outer ring, and the mesh number of the inner and outer ring are 69,984 and 56,768, with the min-element size of 0.555 mm and 0.74 mm, and the max-element size of 1.110 mm and 1.48 mm.
Because of the elastic–plastic body of the bearing rings, the elastic–plastic deformation would be generated during the heat treatment process. It is necessary to define fixed node boundary conditions. Four nodes are fixed in the X direction and two nodes in the Y and Z directions in the inner and outer ring. The finite element mesh model and fixed nodes are shown in Fig. 4. The total step length of the simulation is 3824 and the total time is 29,040 s. The temperature variation per step is set to 2 °C, and the max-time per step is 10 s and the min-time per step is 0.001 s, the step increment is 10.
The finite element mesh model and fixed nodes schematic diagram of fixed nodes: (a) inner ring, (b) outer ring.
The material of the ACBB rings (7008C) are GCr15, the direct reading spectrometer (SPECTRO M12) was used to obtain the content of elements in the bearing rings17. The tested value and the standard value on the content of each element of GCr15 steel18 are as shown in Table 1.
The thermophysical characteristics of the materials changed with the temperature during the heat treatment process, and the simulation results would be distorted if invariant thermophysical characteristics parameters were used19. The thermophysical characteristics parameters of GCr15 steel were calculated by JMatPro software, and the results are shown in Fig. 5.
The thermophysical characteristics parameters of materials: (a) density, (b) Poisson’s ratio, (c) elastic modulus, (d) specific heat, (e) thermal conductivity, (f) linear expansion.
Before the heat treatment, a mixture of detergent and water was used to clean the surface dirt of ACBBs (7008C) rings. The cleaned bearing rings were dried at 120–150 °C. The controlled atmosphere production line with the roller mesh belt was selected as the heat treatment equipment, its temperature control accuracy was ± 1 °C. The automatic feeding, quenching, tempering and other processes can be realized. The heating and holding temperature of the bearing rings was set at 830 °C for 1 h. The oil temperature was kept at 70 °C during the cooling process. Subsequently, the bearing rings were placed in the tempering furnace for the tempering, and the tempering temperature and time were set to 160 °C and 3 h, and the detailed process flow is shown in Fig. 2. The experiment process and characterization analysis are shown in Fig. 6.
The bearing rings were cut off in the longitudinal direction using wire-electrode cutting after the heat treatment. Four specimens were taken out along its circumferential direction, they were pre-grinded with 400 #, 800 #, 1500 # and 2000 # sandpaper, and polished with 5 μm and 1 μm diamond polish. Finally the metallographic microstructure was shown by etching with 4% nitric acid alcohol solution. The martensite morphology was observed by metallurgical microscope (O-LYMPUSGX71). The microstructure of the bearing rings was analyzed by field emission scanning electron microscopy (JSM-6700F), and the volume fraction and size of carbides were statistically counted by the Image Pro software.
The square specimens with an area of about 1.5 mm2 and a thickness of about 1 mm were cut by wire-electrode cutting, and then ground and mechanically polished. Since a deformation layer was generated on the surface during grinding and polishing, electrolytic polishing was performed using a 10% perchloric acid alcohol solution electrolyte. XRD diffraction experiments were carried out and the data were processed by MDI Jade 6.0 software. The integral intensities of the austenite and martensite diffraction peaks in the bearing rings were obtained. The volume fraction of retained austenite in GCr15 steel is calculated by the following20:
where VA is the volume fraction of retained austenite, VC is the volume fraction of carbides, IM(hkl)I is the integral intensity of the a-phase diffraction peak, IA(hkl)j is the integral intensity of the γ-phase diffraction peak, G is the ratio of crystal strength factor of austenitic and martensitic crystal faces.
The microhardness of the bearing rings after the heat treatment process was measured by rockwell hardness tester. Three sets each of inner and outer ring after the heat treatment process were selected and three specimens were taken on each rings. During the specimen preparation process, the effects of heat and cold working on the surface hardness of the specimen should be avoided. The finish of the test surface must be ensured to accurately measure the indentation diameter. The thickness of the specimen should be not less than eight times the depth of the indentation. The Rockwell hardness measurements should be made using the methods in the referance21.
The temperature variations, austenite microstructure evolution and hardness variation of the inner ring during the heating process are shown in Fig. 7. At the beginning of heating process, the temperature at the thinner position of the wall thickness of the inner ring is raised first. There is a small temperature difference between the core and the surface. Since the temperature of the inner ring does not reach the austenite transformation temperature, the hardness remained unchanged, as shown in Fig. 7a. The inner ring temperature, austenite microstructure and hardness distribution at a heating time of 736 s (Fig. 7b), and the temperature of the inner ring is 781 °C. Although the austenite content of the inner ring surface is higher than that of the center, the difference between them is small, which in turn leads to a low hardness of 22.1 HRC for both the center and surface. As shown in Fig. 7c, the temperature of the inner ring reaches up to 830 °C at the end of the heating process, and the volume fraction of austenite is about 99.5%, and the hardness is about 20.1 HRC.
The temperature variations, austenite microstructure evolution and hardness variation laws of inner ring during heating process: (a) heating time of 15 s, (b) heating time of 736 s, (c) at the end of the heating process.
The variations of the temperature, austenite microstructure evolution and hardness of the outer ring during the heating process are shown in Fig. 8. As shown in Fig. 8a, it can be seen that the temperature of the outer ring is higher at the position of its thinner thickness after heating for 15 s. The centeral temperature of the outer ring is lower. Since the outer ring does not reach the austenite transformation temperature, and its austenite content is 0%, while the hardness is the initial hardness of 30 HRC. As shown in Fig. 8b, the temperature of the outer ring is 786 °C after heating for 695 s. The austenite microstructure has begun to transform, and the content of austenite on the outer surface of the outer ring is higher than that on the inner surface. Therefore the hardness of the inner surface is lower than that on the outer surface. When the temperature of the outer ring has reached 830 °C at the end of the heating process, and the austenite content is about 99.5%, the hardness is about 20.1 HRC, as shown in Fig. 8c.
The variations of temperature, austenite microstructure evolution and hardness of outer ring during the heating process: (a) heating time of 15 s, (b) heating time of 695 s, (c) at the end of heating process.
The variation of the temperature, microstructure and hardness of the inner ring with time during the heating process, (a) position of feature points selection, (b) the variation of temperature and microstructure over time, (c) the variation of microstructure transformation over time, (d) The variation of microstructure and hardness over time.
The variation of the temperature, austenite microstructure and hardness in inner ring during the cooling process of quenching are shown in Fig. 10. At the beginning of the cooling process, the cooling rate of the inner ring is faster at the position of the thinner wall thickness, and the temperature difference between the inner ring center and the surface is larger. At this time, since the inner ring temperature has not yet reached the martensite transformation temperature, the austenite content is higher, which leads to lower hardness, as shown in Fig. 10a. The cloud diagrams of the inner ring temperature, austenite microstructure and hardness when cooling to 14 s are shown in Fig. 10b. The temperature of the inner ring is reached to the martensite transformation temperature, the martensite microstructure on the surface of the inner ring is transformed first, which leads to the temperature difference between the center and the surface being reduced, and the austenite content on the surface is lower than that on the center, and the hardness of the center is lower than that of the surface. When the inner ring is cooled to the quenching oil temperature of 70 °C, and the retained austenite content is about 1.7%. However, the martensite content is highest at this time, resulting in an inner ring hardness of 63.4 HRC, as shown in Fig. 10c.
The variation of the temperature, austenite and hardness during the cooling process of inner ring: (a) cooling time of 3 s, (b) cooling time of 14 s, (c) after cooling.
The variation of the outer ring temperature, austenite microstructure and hardness during cooling process of quenching is shown in Fig. 11. As shown in Fig. 11a, it can be seen that after cooling the outer ring for 3 s, there is a huge temperature difference between the two sides of the end face and the center. Since the temperature of the outer ring has not yet reached the martensite transformation temperature, the austenite content is more, and the hardness is lower. As shown in Fig. 11b, after the outer ring is cooled for 14 s, the temperature of both sides of the end face is lower than that of the center, and meets the conditions of martensite transformation. Therefore, the austenite content of the two sides of the end face is lower than that of the center, resulting in the hardness of the two sides of the end face is increased. When the outer ring is cooled to the quench oil temperature of 70 °C, the retained austenite content is about 1.73%, resulting in a hardness of 63.4 HRC for the outer ring (as shown in Fig. 11c).
The variation of the temperature, austenite and hardness during the cooling process of the outer ring: (a) cooling time of 3 s, (b) cooling time of 14 s, (c) after cooling.
The variation of the temperature, microstructure and hardness of inner ring with time during cooling process of quenching, (a) position of feature points selection, (b) the variation of temperature and microstructure with time, (c) the variation of microstructure transformation with time, (d) The variation of microstructure and hardness over time.
The cloud diagram of the retained austenite and hardness after the tempering of the bearing rings are shown in Fig. 13. As shown in Fig. 13a, it can be seen that the retained austenite content of the inner ring after the temping process is 0.834%, and the hardness of the inner ring is about 63.1 HRC. As can be seen from Fig. 13b, the difference in retained austenite content and hardness between the outer ring and the inner ring after the temping process is small, the minimum retained austenite in the inner ring is larger than the min-value of retained austenite in the outer ring, the retained austenite content on the raceway of the inner ring is smaller, and the retained austenite content at the edges of both sides of the outer ring is smaller. This is due to the structure of the inner ring and the outer ring dimensions being inconsistent, and the temperature variation rates are inconsistent during the heat treatment process, resulting in the transformation of phase of the situation being also different.
The cloud diagram of the retained austenite microstructure and hardness after the tempering of the bearing rings: (a) the inner ring, (b) the outer ring.
The mechanical properties of the bearing are determined by the morphology and distribution of the microstructure, and the different morphology of martensite has a great impact on the hardness of the inner ring22,23,24. The OM and SEM images of the bearing rings after the heat treatment process are shown in Fig. 14. The OM images of the inner and outer rings are shown in Fig. 14a and b. The microstructure of the inner and outer rings can be seen in the images as cryptocrystalline martensite structure25,26 and uniformly distributed carbides. The microstructure of the bearing rings surface and center observed under the optical microscope has similar characteristics. The SEM images of the inner and outer rings are shown in Fig. 14c and d. It can be seen that on the cryptocrystalline martensite matrix there is a uniform distribution of fine spherical carbides and a few coarse block carbides. The fine uniform spherical carbides can hinder the growth of grain, the grain size is finer and more uniform after the heat treatment process, so the bearing rings have higher mirohardness. From the SEM images, it can be seen that there is little variation in the carbide kind and particle size at the surface, subsurface and center of the bearing rings.
The OM and SEM images of the bearing rings: (a) OM images at different zone of the inner ring, (b) OM images at different zone of the outer ring, (c) SEM images at different zone of the inner ring, (d) SEM images at different zone of the outer ring.
The size and distribution of the carbides also have a great effect on the bearing life, and the residual carbides are small, which is beneficial for improving the fatigue life27,28,29. The carbides distribution of the rings is shown in Fig. 15. As shown in Fig. 15a, the average value of the carbide size of the inner ring is 0.39 μm, and the statistical distribution of carbides from 0.2 to 0.6 μm is 81%. As shown in Fig. 15b, the average value of the carbide size of the outer ring is 0.38 μm, and about 73% of the carbide sizes are between 0.1 and 0.6 mm. The variance of the carbide size of the inner and outer ring is 0.27 and 0.34, which indicates that the inner ring carbide is uniformly distributed and its mechanical properties are better.
The carbide size of bearing rings: (a) inner ring, (b) outer ring.
The X-ray diffraction pattern of the rings is shown in Fig. 16, the G values for the different diffraction lines are shown in Table 2, and the integrated intensities of the diffraction peaks of the martensitic phase in the rings are shown in Table 3. The integrated intensities of the diffraction peaks of the austenitic phase are shown in Table 4. From the diffraction pattern of the bearing rings, it can be seen that its main phase is α-phase (namely martensitic phase), but a small amount γ-phase (namely austenitic phase) is also found inside it. At the same time, there are some miscellaneous peaks in the XRD pattern, which are compounds of Fe30,31,32.
X-ray diffraction patterns of bearing rings.
The volume fractions of the carbides in the inner and outer rings were 6.7% and 7.5%, respectively. The volume fractions of the retained austenite in the inner rings of the three groups were calculated as 1.869%, 1.268%, and 0.943%, and the average value was taken to be 1.36% as shown in Fig. 17a. The volume fractions of the retained austenite in the outer rings of the three groups were calculated as 0.877%, 0.427%, and 2.684%, and the average value was taken to be 1.32% as shown in Fig. 17b. The retained austenite content of inner and outer rings obtained from simulation is 0.83% with less error from experimental results.
Experimental and simulated values of retained austenite content in the rings: (a) inner ring, (b) outer ring.
Three pieces each of inner and outer ring after the heat treatment process were selected to measure the surface hardness of the rings by Rockwell hardness tester, and the results are shown in Fig. 18. The experimental results are compared with the simulated results, it is found that the hardness simulation results are reliable.
Experimental and simulated values of hardness of bearing rings, (a) inner ring, (b) outer ring.
The ACBBs (7008C) rings for the spindles of the high-end CNC machine tools are selected as the object in this study. The microstructure evolution mechanism of the inner and outer ring during the heat treatment process was studied, the variation of the microstructure evolution and the mechanical properties were revealed. Besides the accuracy of the simulation results was also verified. The main conclusion could be drawn:
During the cooling process, the temperature is reduced firstly at the end face of both sides of the inner and outer rings, and the transformation from the austenite to the martensite occurs first. In the center of the bearing ring raceway, the decrease rate of the temperature is slow. There is a lag phenomenon in the transformation of martensite, resulting in a large difference in hardness between the end face on both sides and the center of the bearing rings.
After the quenching and tempering process, the retained austenite content of the inner ring and outer ring is measured to be 1.36% and 1.32%, and the hardness is measured to be 62.5 HRC and 62.7 HRC. The error between experimental and simulated residual austenite content is within 38%, and the error between experimental and simulated values of hardness is within 0.8%.
The main microstructure of the inner and outer ring after the quenching and tempering process is cryptocrystalline martensite. The average sizes of the spherical carbides precipitated at the grain boundaries are 0.39 μm and 0.38 μm. The variance of the carbide sizes is 0.27 and 0.34, respectively, which indicates that the carbides are fine and uniform, and the service life of the rings is effectively improved.
All data generated or analyzed during this study are included in this published article.
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This work was financially supported by a grant from the Ministry of Industry and Information Technology Special Projects (TC220H05V-W03), Henan Provincial Department of Science and Technology (231111221000) and Longmen Laboratory Project (LMQYTSKT036).
School of Mechatronics Engineering, Henan University of Science and Technology, Luoyang, 471003, China
Ruijie Gu, Yi Tong, Qiang Wang, Liaoyuan Chen & Ziyang Shang
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Ruijie Gu: Conceptualization, Funding acquisition, Project administration, Resources, Supervision, Writing-review and editing. Yi Tong: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Software, Validation, Visualization, Writing-original draft. Qiang Wang: Conceptualization, Data curation, Project administration, supervision, Visualization, Writing-review and editing. Liaoyuan Chen: Formal analysis, Visualization, Writing-review and editing. Ziyang Shang: Formal analysis, Project administration, Visualization, Writing-review and editing. All authors reviewed the manuscript.
The authors declare no competing interests.
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Gu, R., Tong, Y., Wang, Q. et al. Study on the microstructural evolution mechanism of the angular contact ball bearing rings during the quenching and tempering process. Sci Rep 15, 1171 (2025). https://doi.org/10.1038/s41598-024-84570-2
DOI: https://doi.org/10.1038/s41598-024-84570-2
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