Modeling and Simulation of Vacuum Low Pressure Carburizing Process in Gear Steel

Abstract

A combination of simulation and experimental approaches to optimize the vacuum carburizing process is necessary to replace the costly experimental trial-and-error method in time and resources. In order to accurately predict the microstructure evolution and mechanical properties of the vacuum carburizing process, a multi-field multi-scale coupled model considering the interaction of temperature, diffusion, phase transformation, and stress was established. Meanwhile, the improved model is combined with the heat treatment software COSMAP to realize the simulation of the low-pressure vacuum carburizing process. The low-pressure vacuum carburizing process of 20CrMo gear steel was simulated by COSMAP and compared with the experimental results to verify the model. The results indicated that the model could quantitatively obtain the carbon concentration distribution, Fe-C phase fraction, and hardness distribution. It can be found that the carbon content gradually decreased from the surface to the center. The surface carbon concentration is relatively high only after the carburizing stage. With the increase in diffusion time, the surface carbon concentration decreases, and the carburized layer depth increases. The simulated surface carbon concentration results and experimental results are in good agreement. However, there is an error between calculations and observations for the depth of the carburized layer. The error between simulation and experiment of the depth of carburized layer is less than 6%. The simulated surface hardness is 34 HV lower than the experimental surface hardness. The error of surface hardness is less than 5%, which indicates that the simulation results are reliable. Furthermore, vacuum carburizing processes with different diffusion times were simulated to achieve the carburizing target under specific requirements. The results demonstrated that the optimum process parameters are a carburizing time of 42 min and a diffusion time of 105 min. This provides reference and guidance for the development and optimization of the vacuum carburizing process.

Optimisation of hardness profiles in high-speed train axlebox bearings

“…The lower diffusion temperature could enhance the carbon concentration in the surface region, within 2 mm, but reduce the carbon concentration in the core. It suggests that the higher temperature boosted the diffusion of carbon atoms from surface to the core, consistent with the finding of Guo [39]. In Figure 10(b), the retained austenite content was below 5% when the depth exceeds 2 mm.…”

Modulation of Thermal Insulation and Mechanical Property of Silica Aerogel Thermal Insulation Coatings

“…While the zirconium containing ceramic fibers can effectively reduce the crystallization process at high temperatures and delay the sintering effect at fiber interleaving contact pinto. Therefore, it is ensured that the coating still has good mechanical strength [16,31,32].…”

Heat Treatment Consideration in Structural Simulations of Machine Elements: Analysis of a Starter Clutch Barrel

“…In the study of Song et al [16], the carbon content distribution during the carburising process of the gear ring was followed by performing a finite element analysis and then based on the results, the quenching process was simulated; the distributions of the microstructure, temperature and stress fields versus time and space were analysed. Another study by Guo et al [17] simulated the low-pressure vacuum carburising process of a round sample by the heat treatment software COSMAP and compared it against the experimental results to find a good agreement between the simulated surface carbon concentration and experimental values. Similarly, Ferguson et al [18] simulated the heat treatment using finite element based tool DANTE to compare two quench hardening processes to improve the tooth bending fatigue strength of carburised steel gears used in helicopter transmissions.…”