Changes in Carburized Microstructures and Creep Properties of Nb-Added SCH13A Heat-Resistant Cast Steel due to Different Pouring Temperatures

The relationship between pouring temperature and carburized microstructure of 1%Nb-added SCH13A heat-resistant cast steel manufactured by the self-hardening mold casting process at pouring temperatures of 1753 K, 1823 K and 1883 K was investigated. The creep properties of these materials subjected to repeated carburizing and quenching treatment were also examined. As a result, with increasing pouring temperature, the carburized depth decreases and the carbon concentration distribution in the carburized layer increases. A relative comparison of the creep properties revealed that the volume of primary carbides and the number of voids and micro-cracks in carbides generated due to repeated vacuum carburizing quenching treatment affects the creep rupture time. Creep rupture time of the carburized samples is shorter than that of the as-cast samples. Additionally, pouring at 1823 K exhibits the longest rupture time among the samples poured at the three different temperatures.