Thermal Conductivity Analysis of Compacted Graphite Cast Iron After a Creep Test

The thermal conductivity of compacted graphite cast iron (CGI) after creep test (temperature ranging from 350 °C to 550 °C; stress ranging from 40 to 150 MPa) was measured at different testing temperatures (200 °C to 550 °C) in an argon atmosphere. The thermal conductivity increased slightly when the creep temperature increased from 350 °C to 500 °C under 150 MPa and then decreased dramatically when the creep temperature surpassed 500 °C. When the creep temperature was 550 °C, the thermal conductivity initially decreased slightly, and then decreased dramatically when the stress surpassed 100 MPa. Crack propagation was the main cause of the decrease in the thermal conductivity, which was related to interphase debonding between the graphite and matrix, and grain boundary sliding. Interphase debonding was related to the creep temperature and stress. Compared to the creep stress, the creep temperature played an important role in the interphase debonding between the graphite and matrix.