Precipitation development simulation of high-temperature carburization along the process chain

The specific addition of microalloying elements allows realization of carburization annealing at high temperatures. These microalloying additions are used for precipitation hardening and for the increase of fine grain stability by particle pinning during high-temperature carburization. In this work the precipitation evolution along an exemplary process chain for the microalloyed steel 25MoCr4 for transmission components is analyzed using STEM and EFTEM and modeled using the software MatCalc. The process chain consists of a FP-annealing, a cold forming, an additional FP-annealing followed by the carburizing process at a temperature of 1050 degrees C. By comparing the experimental and numerical simulation results the simulation chain can be validated and the influence of different microalloyed precipitates on the Zener force can be quantified. Based on this validated model, simulations are carried out for different process chains and the influence on the Zener force and therefore on the fine grain stability is calculated. Thus, optimization hints have been formulated for the process chain.