Secondary phase thermal stability and strengthening are strongly influenced by the interface structure between the secondary phase and the matrix. The influence of hydrogen on the interfacial structure of (Fe,Cr)23C6 carbides in ferritic matrix at high temperatures is systematically studied. The incoherent interface between (Fe,Cr)23C6 and ferrite matrix acts as a hydrogen trap region at high temperatures. Moreover, the hydrogen at high temperatures does not change the morphological features of (Fe,Cr)23C6 in the ferritic matrix. (Fe,Cr)23C6 obeys the Kurdjumov-Sachs orientation relationship with the ferritic matrix. Hydrogen at high temperatures decreases the mismatch between (Fe,Cr)23C6 and ferrite matrix interface from 7.65 % to 4.63 %. Furthermore, the (Fe,Cr)23C6 interface induced by hydrogen at high temperatures acts as a dislocation emission source. The decrease in interfacial misfit caused by hydrogen at high temperatures is the reason for (Fe,Cr)23C6 to maintain thermal stability and act as a dislocation emission source under a high-temperature hydrogen atmosphere.
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