Abstract
High temperature oxidation causes degradation of materials in aircraft, marine, industrial and land base gas turbines. To obviate this problem, oxidation behavior of Ni and Co based superalloys viz superni 600 and superco 605 (Midhani grade) has been studied in air at 900oC. Both superalloys go through cyclic oxidation which consists of 1 hr heating in silicon carbide tube furnace followed by 20 min cooling in ambient air. Weight change was taken by a digital electronic weighing balance having accuracy of 1 mg after each cycle. Exposed alloys were characterized by XRD, FESEM and EDS. Result shows that the Co base superalloy superco 605 shows less weight gain as compare to superni 600. The oxide layer mainly contains oxides of Cr2O3, NiO and spinel NiCr2O4.
Highlights
INTRODUCTIONSuperalloys find wide application in aeronautics, space, nuclear, chemical, and petrochemical, power generation and furnace industries, where extreme temperatures, mechanical stresses and
Superalloys find wide application in aeronautics, space, nuclear, chemical, and petrochemical, power generation and furnace industries, where extreme temperatures, mechanical stresses andDeepa Mudgal, Surendra SinghVol.11, No.3 corrosive environments are encountered
The development of oxidation resistance is based on addition of an elements namely chromium, aluminum, nickel and silicon which will oxidize selectively and produce protective oxide [2]
Summary
Superalloys find wide application in aeronautics, space, nuclear, chemical, and petrochemical, power generation and furnace industries, where extreme temperatures, mechanical stresses and. Carbon is used to improve grain boundary properties while Al and Cr are added to develop oxidation resistance These alloys possess improved mechanical properties, such as stress rupture [4] and [5] ,[6] and fatigue resistance [7] and [8] .Superalloys provide high creep strength, low thermal expansion, high thermal conductivity, good weld ability and resistance against high temperature oxidation corrosion [9,10]. Liu [14] shows isothermal behavior of Co based superalloys that it can grow protective oxide scale at 900oCand 1000oC He observed that the scale was well adherent and found to consist mainly of CoO and some Cr2O3. The present study focuses on high temperature oxidation behavior of Co and Ni based superalloys in air at 900°C under cyclic condition
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