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Role of CaO inhibitor in enhancing high‐temperature corrosion resistance of some Ni‐based superalloys
Author(s) -
Bala N.,
Singh H.,
Prakash S.
Publication year - 2015
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201307534
Subject(s) - superalloy , materials science , corrosion , metallurgy , alloy , scanning electron microscope , carbide , electron microprobe , high temperature corrosion , oxide , coating , silicon carbide , weight change , tube furnace , composite material , chemical engineering , engineering , medicine , weight loss , obesity
High‐temperature corrosion of metals and alloys can be controlled by the use of inhibitors and fuel additives. In this work, the role of a superficially applied CaO coating to combat high‐temperature corrosion of some Ni base superalloys viz Superni 75 (alloy A), Superni 718 (alloy B), and Superni 601 (alloy C) has been investigated. Accelerated corrosion testing of the coated as well as bare superalloys was done in a molten salt environment (Na 2 SO 4 –60% V 2 O 5 ) at 900 °C for 50 cycles. Each cycle consisted of 1 h heating in a silicon carbide tube furnace followed by 20 min cooling in ambient air. Weight change measurements after each cycle were taken by an electronic balance having an accuracy of 0.01 mg. X‐ray diffraction (XRD), scanning electron microscope (SEM), and electron probe micro analysis (EPMA) analyses of the exposed specimens were carried out to characterize the oxide scales. The bare superalloys showed more overall weight gains, in general, in comparison with their CaO‐coated counterparts. It was concluded that CaO was most effective in reducing corrosion rate in alloy A.