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

Abstract

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.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 87 (2023) 269–278.

Fig. 5 Line analysis of carbon and low magnification SEM images showing microstructures of 10-cycle vacuum carburized samples.