Effect of Heat Treatment Temperature on Carbon Flux Characteristics Using Ultra-Rapid Carburizing above Eutectic Temperature

Carburizing and quenching is known as a surface modification treatment applied to impart mechanical properties to materials. The authors have developed an ultra-rapid carburizing using induction heating above the eutectic temperature, which enables in-line carburizing as a next-generation heat treatment method, in order to coexist in the future carbon-neutral society. Previous studies have reported on carbon penetrating behavior at a constant 1523 K, for carburizing on an alloyed steel SCM420. However, in order to apply it to various steels, it is necessary to elucidate the carburizing mechanism of this treatment, which is different from gas carburizing and vacuum carburizing. In this study, the temperature range was expanded to 1473 K and 1573 K to investigate the carbon penetration characteristics as a detailed mechanism elucidation. As a result, it was shown that the tendency of carbon penetration characteristics was similar to that of 1523 K. Moreover, the rate of carbon penetration varied exponentially with the carburizing temperature. The activation energy of the ultra-rapid carburizing reaction obtained by the Arrhenius plot was equivalent to that of the methane decomposition reaction, which was the raw material gas. Thereby, it was verified that carburizing reaction was rate-controlled by the decomposition reaction of methane.