In the framework of studies on the control rods lifetime for Sodium Fast Reactor, three commercial steels were exposed to B4C powder in liquid sodium at 600°C for durations up to 3000 h. Analyses by optical and secondary electron microscopy, electron microprobe and glow discharge optical emission spectrometry revealed the formation of borides layers at the surface of the steels and slight carburization underneath. The growth of the boride layers followed parabolic kinetics. The nature of the formed boride layers was in good agreement with thermodynamic equilibrium predicted by Thermo-Calc software. The carburization depths were much lower than the ones obtained in pure carburizing sodium at 600°C. Finally, the carbon penetration depth did not grow with time revealing possible protective character of the boride layers against carbon penetration.

Subject
Carburization, Steel surfaces, Carbides, Hydrogen concentration, Substrates, Solubility, Boron, Liquids, Kinetics, Sodium, Powders, Steel, Carbon
Keywords:
Carburization, Boriding, Steels, Sodium
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2018
Association for Materials Protection and Performance (AMPP)
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