Hot Corrosion Behaviour of Yttria-Stabilised Zirconia as Plasma Sprayed Coated Boiler Steel in Air and Salt at 900°C under Cyclic Condition
- 1 HEEP, Bharat Heavy Electricals Ltd. (Government of India Undertaking) Haridwar, India.
- 2 Metallurgical & Materials Engineering Department, Indian Institute of Technology Roorkee,India
- 3 Metallurgical & Materials Engineering Department, Indian Institute of Technology Roorkee,India
Abstract
Yttria-Stabilised Zirconia (YSZ) coatings were deposited on a T-22 boiler steel. NiCrAlY was used as bond coat and YSZ as top coat. Hot corrosion studies were conducted on uncoated as well as plasma spray coated specimens in air as well as salt (75 wt.% Na 2 SO 4 + 25 wt.% NaCl) at 900°C under cyclic conditions. The thermogravimetric technique was used to establish kinetics of corrosion. X-ray diffraction (XRD) and scanning electron microscopy/energy-dispersive x-ray analysis (SEM/EDAX) techniques were used to analyse the corrosion products. This YSZ overlay coatings enhance resistance to corrosion significantly which can be attributed to formation of zirconium oxides (ZrO 2 ) and yttrium oxide (Y 2 O 3 ). This coating was more effective in salt environment and there is an extra phase of ZrS.
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