Phase Investigations Under Steam Oxidation Process at 800 °C for 1000 h of Advanced Steels and Ni-Based Alloys

Abstract

During the test, no spallation of the external oxide scale was observed. The kinetic data showed that only the 263 alloy oxidized according to parabolic behaviour, whereas the other alloys deviated from the parabolic rate law, with time exponents of 0.4-0.6 or 0.3. Finally, cross-sectioned investigations of the exposed samples revealed that Ni-based alloys underwent extended internal oxidation, with the highest extent in HAYNES Ò 282 Ò reaching 25 lm and the lowest in HAYNES

Steam Oxidation Resistance of Advanced Steels and Ni-Based Alloys at 700 °C for 1000 h

“…In addition, due to the formation of a thin oxide scale on Haynes Ò 230 Ò , the XRD pattern shown as well double carbides, g: Co 3 W 3 C and Co 6 W 6 C. In the 617 alloy instead of a MnCr 2 O 4 spinel, an NiCr 2 O 4 phase developed, since the 617 alloy showed no Mn concentration within the metal matrix. In comparison to the study performed at higher temperatures [6] only gamma-prime (c 0 ) strengthened Ni-based alloys showed a difference in phase development due to the lack of formation of TiO 2 and MnTiO 3 compounds. The Ni-based solid solution strengthened alloys developed the same phases as was reported in the work published earlier [6], despite 0.3 wt% Ti in the 617 alloy, no Ti containing phase was observed on XRD pattern.…”

“…In comparison to the study performed at higher temperatures [6] only gamma-prime (c 0 ) strengthened Ni-based alloys showed a difference in phase development due to the lack of formation of TiO 2 and MnTiO 3 compounds. The Ni-based solid solution strengthened alloys developed the same phases as was reported in the work published earlier [6], despite 0.3 wt% Ti in the 617 alloy, no Ti containing phase was observed on XRD pattern. It is suggested that development of Ti containing phases is related strongly to concentration, activity, temperature and perhaps volume.…”

“…Similarly to work performed earlier [6], two solid solution strengthened alloys; Haynes Ò 230 Ò and 617 alloy showed lower weight gain than two gamma-prime (c 0 ) strengthened alloys; 263 alloy and Haynes Ò 282 Ò . Nevertheless, in contrast to previous study [6], there is no strict evidence for the formation of TiO 2 , however mass gain of two gamma-prime (c 0 ) strengthened alloys is higher than that observed for two solid solution strengthened Ni-based alloys, hence it is suggested that the higher mass gain is attributed to a higher degree of internal oxidation found in gamma-prime (c 0 ) strengthened alloys.…”

“…For better traceability of the archived results, Table 3 shows the phases observed under XRD investigations. Furthermore, in comparison with the study performed earlier [6], at 700°C, the following phases were not detected in stainless steels: SiO 2 , Mn 7 SiO 12 , and Cr 3 O 4 . The XRD diffraction patterns for Ni-based alloys exposed at 700°C for 1000 h are shown in Fig.…”

“…In this work, for high-temperature oxidation resistance of Ni-based and Fe-based alloys the same rig was used as shown previously [6]. In general, the rig consisted of a heat resistant furnace, where a reaction chamber made of 8 mm thick 316L stainless steel was used, inside the reaction chamber an Al 2 O 3 5-mm thick ceramic liner was inserted.…”