Abstract: A model of diffusing growth based on DICTRA software is employed to simulate the precipitating behavior of grain boundary carbide and the evolution of Cr-depletion region in alloy 690 after heat treatment at different temperatures for various times. It is concluded that the simulated Cr distribution in Cr-depletion region is in good agreement with the measured one, which verifies the reliability of the model of diffusing growth. The simulation results also indicates that there is a critical time, when the isothermal treatment time exceeds this time the Cr depleted degree will not change obviously; at last, according to the relation between carbide size and alloy corrosion resistant ability, a mathematic formula is founded to calculate the optimal isothermal treatment processing parameters.

Key words: Alloy 690, Heat treatment, Process optimization, Simulation, Deterministic Model, Rough Surface Contact, Wavelet Filter, Multi-scale