|
1556 |
|
Tuesday, June 03, 2008, Room 04 11:50 AM Corrosion Protection 2 Corrosion protection through thermal sprayed coatings including cathodic and high temperature corrosion, coating of large areas for offshore facilities and comparable applications |
|
Degradation behavior of HVOF sprayed Ni-based coatings on superalloy in 40%Na2SO4-60%V2O5 environment at 900°C |
|
R A Mahesh* / Indian Institute of Technology Roorkee, India Subhash Kamal / Indian Institute of Technology Roorkee, India Ankur Modi/ Metallizing Equipments Company Pvt Ltd , India R Jayaganthan/ Indian Institute of Technology Roorkee, India Satya Prakash/ Indian Institute of Technology Roorkee, India |
|
High velocity oxy fuel thermal spray (HVOF) processing is one of the proven thermal spray technologies to develop high temperature oxidation and corrosion resistant coatings for various high temperature applications such as thermal power plants, aero turbines, and energy conversion systems. The superalloy coatings, using HVOF technique, have been successfully developed on various superalloy grades to combat corrosion problems in the aggressive high temperature environments as known in the literature. In the present investigation Nickel based coatings, viz. Ni-5Al, NiCrAl, and NiCrAlY-0.4wt%CeO2 were sprayed on Fe based superalloy (Superfer 800) by High Velocity Oxy fuel (HVOF) spray process as the chosen superalloy finds extensive use steam boilers, furnace equipment, heat exchangers and piping in chemical industry The degradation behaviour of the coated superalloy was studied in the aggressive environment of 40%Na2SO4-60%V2O5 at 900oC, using thermogravimetric technique, to understand the protective nature of the coatings under cyclic conditions. The coatings were found to be effective in increasing the resistance to the degradation in the given environment. Among the coatings investigated, NiCrAlY-0.4wt%CeO2 coating was found to be more protective on the superalloy in the given aggressive environment. The corrosion mechanisms were elucidated through the microstructural characterization techniques such as FE-SEM/EDAX and X-Ray mapping, and X-Ray mapping analysis of the corroded products formed at high temperature. |