engleski

Comparison of Cast Irons for Automotive Engine Thermo-mechanical Loaded Parts

The influence of elevated temperatures (550 °C and 850 °C) on microstructure and resistance to oxidation of gray iron quality EN-GJL-250 and ductile irons qualities: EN-GJS-400-18, EN-GJS- 500-7, EN-GJS-SiMo4-1 and EN-GJS-AXNiCr20-2 were analyzed in this paper. The highest resistance to oxidation and microstructure changes at 550 °C and 850 °C shows austenitic ductile iron quality EN-GJS-AXNiCr20-2, followed by ferritic ductile iron quality EN-GJS-SiMo4-1. During oxidation of those cast irons at elevated temperatures two oxide layers over the surface of samples were occurred. Outward layer is easy detachable and consists of iron oxide. Inward layer is tightly connected with metal matrix and prevents progression of oxidation to the samples inside. This oxide layer consists of Fe2SiO4 (fayalite) or complex oxides (Fe, Cr, Ni, Si, and O). Due to favorable high-temperatures properties, those materials are suitable for construction of thermo-mechanical loaded parts of automotive engine, such as turbocharger housings and exhaust manifolds. Ferritic ductile iron quality EN-GJS-400-18, pearlitic ductile iron quality EN-GJS-500-7 and pearlitic gray iron quality EN-GJL-250 did not show an adequate resistance to oxidation and microstructure changes at 550 °C and 850 °C.

cast irons ; elevated temperatures ; microstructure

ISSN 1318-9123