This study is to investigate the oxidation phenomenon and the thermal-fatigue property of compacted graphite cast iron(CGI) at high temperature. The effects of matrix (ferrite, pearlite and austenite) and various alloying elements (C, Si, Cr, Ni, Cu and Mo) on the oxidation resistance and thermal-fatigue resistance for CGI at different temperatures (673K, 873K and 1073K) have been evaluated. The dimensions of specimens examined are 20mm{sup}φ×30mm{sup}H for the oxidation test and 110mm{sup}L×20mm{sup}W×6mm{sup}H for the thermal-fatigue test. In addition, use of the optical microscope, SEM+EDS and XRD identifies the compositions of the oxidation layers and observes microstructure changes caused by high temperature. The results indicate that additions of Si(3%, 4.5% or 6%), Cr(0.5%) or Cr(3%)+Ni(14%)+Cu(6%) respectively had no significantly improved the oxidation resistance of sample at 673K. But, adding the above elements would increase the oxidation-resistant capacity at 873K. As at 1073K, the specimens added only with Si (3%, 4.5% or 6%) or only with Cr(0.5%) would increase the oxidation-resistant capacity. In addition, the result of adding Cr into higher Si content specimens showed a better oxidation resistance than the lower Si content specimens added with Cr at 873K, but at 1073K, the result was inverted. The matrix changed from pearlite to ferrite through annealing heat treatment would have better oxidation resistance at any temperature. The inner oxidation layer contained FeO and SiO{sub}2, and the outer oxidation layer contained Fe{sub}2O{sub}3. It was found that there was graphite burned and lost in the inner oxidation layer, but no graphite burned and lost at the outer oxidation layer. The thickness of oxidation layer would be furthermore increased with the increase of time and temperature. Comparing the effects of adding different alloying elements on the thermal-fatigue resistance of specimens at 1073K, those added with Ni, Cr and Cu showed the superior resistance. Next followed in order are those added with Mo, Cu and Sn, those added only with Mo, and then those added no alloying element..
Compacted graphite cast iron Oxidation resistance Thermal-fatigue resistance