Carburization of 310 stainless steel exposed at 800-1100 deg C in 2%CH4/H2 gas mixture

Carburization of 310 stainless steel has been investigated after cyclic exposures at high temperatures 800-1100 deg C in a 2%CH4/H2 carburizing gas mixture for 500 h duration. A thermodynamic analysis indicates that 1000 deg C is an approximate boundary temperature, below which the environment should result in mixed oxidizing/carburizing behavior, while above this temperature reducing/carburizing behavior should occur. The experimental results agree well with the thermodynamic analysis. Below 1000 deg C, 310SS suffered external carburization, oxidation, and internal carburization. In excess of 1000 deg C, extensive external carburization occurred and internal Cr-carbides disappeared. Cr segregation is proposed to interpret the effect of temperature on the continuity of an external scale layer and carburization behavior