Microstructure and morphology of high temperature oxidation in superalloys

Khalid, Fazal Ahmad; Hussain, Nazar; Shahid, K. A.

doi:10.1016/s0921-5093(98)01181-2

Cited by 49 publications

(25 citation statements)

References 11 publications

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“…5c. The formation of voids was thought to accelerate spallation of oxide scale due to the decrease in adherence of scale/substrate interface [9,10]. Figure 6 shows the cross-sectional micrograph and the corresponding element distribution maps of T-800 after exposure at 1,000°C for 20 h, which presents a relative simple structure compared to the case at 800°C.…”

Section: Isothermal Oxidation Kineticsmentioning

confidence: 99%

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

et al. 2008

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The oxidation behavior of Co-based Tribaloy T-800 alloy has been studied isothermally in air at 800 and 1,000°C, respectively. The results showed that the oxidation mechanism was dependent on the exposure temperature. The oxidation of the alloy followed subparabolic oxidation kinetics at 800°C. The oxide scale at this temperature exhibited a multi-layered structure including an outer layer of Co oxide, a layer composed of complex oxide and spinel, a nonuniform Mo-rich oxide layer, an intermediate mixed oxides layer and an internal attacked layer with different protrusions into Laves phase. During 1,000°C exposure, it followed linear kinetics. The oxidation rendered a relatively uniform external Cr-rich oxide layer coupled with a thin layer of spinel on the top surface and voids at local scale/alloy interface and intergranular region together with internal Si oxide at 1,000°C.

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Section: Isothermal Oxidation Kineticsmentioning

confidence: 99%

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

et al. 2008

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“…Khalid et al 15 reported in their studies on high temperature oxidation behaviour of Incoloy 800H and Incoloy 825 alloys at 1000 and 1200 o C and observed that the former exhibited a compact, dense and adherent oxide layer, whereas in the latter the oxide layer has broken. They attributed the comparatively less oxidation resistance of the Incoloy 825 to the presence of coarse Ti-rich inclusions, which shows the less dissolution of Ti in the alloy.…”

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confidence: 99%

Oxidation behaviour of selected Ni- and Fe- based superalloys in air at 900°C under cyclic conditions

Mahesh

Jayaganthan

Prakash

2008

Trans Indian Inst Met

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alloy. Khalid et al 15 reported in their studies on high temperature oxidation behaviour of Incoloy 800H and Incoloy 825 alloys at 1000 and 1200 o C and observed that the former exhibited a compact, dense and adherent oxide layer, whereas in the latter the oxide layer has broken. They attributed the comparatively less oxidation resistance of the Incoloy 825 to the presence of coarse Ti-rich inclusions, which shows the less dissolution of Ti in the alloy. Sadique et al.,16 showed that aluminium addition has a marked effect on the oxidation characteristics of Fe-10Cr at all temperatures. They observed a reduction in rate of oxidation in terms of specific weight gain with increasing aluminium content. The amount of spallation of the oxide scale was also found to be decreasing with increasing Al content. Al content was shown to help in enhancing the adhesion of Cr 2 O 3 . It was concluded that a minimum level of aluminium exists for the formation of a complete protective scale on the alloy surface depending upon the temperature. High temperature oxidation involves the oxidation of reactive elements, formation of oxide scales, and internal oxidation 17 . The knowledge of reaction kinetics and the nature of the surface scales formed during higher temperature oxidation are essential for evaluating the alloys for their use in high-temperature applications. The high temperature oxidation behavior of complex alloys is not well understood in the literature and therefore requires thorough investigation for high temperature applications 18 . In the present investigation, the oxidation behaviour of Ni-and Febased superalloys has been studied at 900 o C under cyclic conditions. The cyclic condition has been chosen to test the alloys in the rigorous conditions which are similar to actual service conditions. EXPERIMENTAL SETUP Substrate MaterialsThree types of superalloys, i.e., Superni 76, Superni 750 and Superfer 800 were obtained from M/S Mishra Dhatu Nigam Limited, Hyderabad, India, in the form of rolled sheet. The chemical compositions of the substrate superalloys are given in the Table 1. The samples measuring approximately 20 mm x 15 mm x 5 mm were cut from the rolled sheet and polished with SiC paper down to 180 grit and then subjected to cloth polishing with 3 ìm diamond suspensions followed by a final step of 0.05 ìm alumina suspension. ABSTRACTOxidation behavior of Ni-and Fe-based superalloys has been studied in air at 900 o C under cyclic conditions. The mass change measurement with time was used to establish the oxidation kinetics. The oxide scales formed on the surface of the superalloys were characterised by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX) analyses. The oxide scales formed on the superalloys contained NiO, Cr 2 O 3 and Fe 2 O 3. The scales were adherent and only microspalling was observed. Superfer 800 has provided best resistance to oxidation among the alloys studied.

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“…Besides, a SiO 2 film is formed during growth of oxides due to a lower solubility of Si and the variation in the activities of the elements in the solution [23,16].…”

Section: Oxidation Behavior Of the Ebs 740 Superalloymentioning

confidence: 99%