Evaluation of the Hot Corrosion Behavior of LPG Assisted HVOF NiCr Wire Sprayed Boiler Tube Steels in Molten Salt Environments
Hazoor Singh SIDHU, Buta Singh SIDHU, S. PRAKASH
ISIJ International
Abstract
NiCr coatings were deposited on some boiler tube steels by High Velocity Oxy Fuel spraying process using LPG as fuel gas. Hot corrosion behaviour of uncoated as well as HVOF sprayed specimens was stud- ied in an environment of Na2SO4 60%V2O5 at 900 C under cyclic conditions. The thermogravimetric tech- nique was used to establish the kinetics of corrosion. SEM/EDAX, XRD and EPMA techniques were used to analyse the corrosion products. The NiCr coating found to be very effective in decreasing the corrosion rate of the uncoated steels. The NiCr coated samples showed no cracking or spalling of oxide scale during hot corrosion. The formation of protective oxide scale as observed may be contributing to the development of hot corrosion resistance in the coatings studied, which mainly consists of oxides of NiO, NiCr2O4 and Cr2O3.
Key words: HVOF coatings; Hot corrosion; NiCr; boiler steels.
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