Abstract
The dangerous process in boiler steel tube is corrosion due to loss of metal by the attack of corrosive agents. In order to prevent this corrosion Cr3C2-25 (Ni-20Cr) and Ni-20Cr coatings were deposited on T91 boiler tube steel by high velocity oxy-fuel (HVOF) process. Hot corrosion studies were conducted on uncoated and HVOF-coated T-91 steel specimens after exposure to a molten salt (Na2SO4-60%V2O5) environment at 900°C under cyclic conditions. Each cycle consisted 1 h of heating in tube furnace followed by 20 min of cooling in air. The weight change measurements were performed after each cycle in order to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDS) were used to analyze the corrosion products. The bare steel experienced higher weight gain due to the formation of unprotective Fe2O3 dominated oxide scales. The Cr3C2-25(Ni-20Cr) coating was found to be more protective than the Ni-20Cr coating.
Highlights
Corrosion mainly occurs due to high temperature oxidation, hot corrosion and erosion
1) Cr3C2-25(Ni-20Cr) and Ni-20Cr coatings have been successfully deposited by high velocity oxy-fuel (HVOF) technique on ASTM-SAE213-T91 boiler steel
2) In case of uncoated T-91 boiler steel Fe2O3, Cr2O3 and Fe3O4 were indicated as main phase by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDS) in salt environment
Summary
Corrosion mainly occurs due to high temperature oxidation, hot corrosion and erosion. Coating is that technique in which material is added or deposited on the surface of same or different material It basically has two main purposes [2].Thermal Spray technique was firstly invented by Dr Schoop by designing a gun, in which O2 & acetylene were used as a source of heating & for projection of molten metal on the substrate compressed air was used. Value of hardness of HVOF technique depends upon porosity, 58 Performance of Cr3C2-25(Ni-20Cr) and Ni-20Cr Coatings on T91 Boiler Tube Steel in Simulated Boiler Environment at 900°C unmelted & semimelted particles, oxidized & inclusions. T. Sidhu et al [7] Developed NiCr-BSi coatings on steel substrates and performed high temperature corrosion studies in the salt environment of Na2SO4-V2O5 at 900°C in cyclic conditions. XRD, SEM and EDS testing are used to characterize the corrosion products formed after the experimentations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
