• Nowak, Wojciech J.

Abstract

<jats:p>In the present work, a performance of ASTM A439 Austenitic Ductile Iron typeD5S at high temperature in the oxidizing environment was investigated. Theobtained results revealed that exposure at temperatures 800?C, 850?C and900?C resulted in relatively high mass gain and an extensive oxide scalespallation from the samples? surfaces during cooling. On the contrary, thematerial exposed at 950?C revealed a better oxidation resistance and nooxide scale spallation. The material exposed at 1000?C showed the bestoxidation resistance among the studied samples. The surfaces andcross-sectional investigation revealed that the material exposed at 950?Cformed mostly Ni/Cr/Mn-mixed protective oxide scale and local formation ofFe-rich nodules. In comparison with the sample exposed at 1000?C, a smalleramount of Fe-rich nodules per area unit was observed and most of the surfacewas covered by Ni/Cr/Mn-mixed protective scale. The latter was explained bythe change in the calculated diffusion coefficients in the alloy for Ni andFe, namely up to 900?C the diffusion coefficient for Fe was much higher thanfor Ni, while above 900?C the diffusion coefficient for Ni becomes higherthan for Fe. This phenomenon was correlated with a phase transformation from?-Fe into ?-Fe resulting in the diffusion coefficient change.</jats:p>

Topics

• surface
• phase
• iron
• durability