Hot Corrosion Behaviour of HVOF Sprayed (Cr3C2–35 % NiCr) + 5 % Si Coatings in the Presence of Na2SO4–60 % V2O5 at 700 °C

Abstract

The hot corrosion behavior of high velocity oxyfuel sprayed (Cr 3 C 2 -35 % NiCr) ? 5 % Si coatings on three substrate alloys of SA213-T22, MDN-310 and Superfer 800 H was investigated. The as-sprayed coatings are characterized with respect to microstructure and mechanical properties. Thermocyclic hot corrosion studies were performed in a molten salt environment of Na 2 SO 4 -60 % V 2 O 5 for 50 cycles at 700°C. Thermogravimetric technique was used to establish the kinetics of hot corrosion of uncoated and coated steels. It was observed that the coated steel showed better hot corrosion resistance than the uncoated steels. The coated steels follow the parabolic rate law of oxidation and the parabolic rate constant values are appreciably lower in comparison to the uncoated steels. The coated steels showed slow oxidation kinetics which indicated that the reaction rate is diffusion limited. The oxides of Cr 2 O 3 and SiO 2 formed on the outermost surface of the coatings are found to be passive in the molten NaVO 3 melt.

Hot corrosion behaviour of constant and pulsed current welded Hastelloy X in Na2SO4, V2O5, and NaCl salt mixture at 900 °C

“…At the beginning of the cycle, MS I coated substrate revealed a light greenish color, whereas MS II showed a light yellowish color. The substrate active elements enhance the rate of corrosion rapidly during the initial few cycles, and then it increases gradually until the 50th cycle [22]. In the GTA weldment of C263 and ERNiCr-3 fillers coated with MS I, during the 2nd cycle, the substrate color changes to light grey from light greenish and then to a dark grey color.…”

“…In a nitrogen gas environment, Yan Wang et al [22] studied Ni-Cr-Al-Fe alloy for its oxidation mechanism in the 850 °C to 1000 °C temperature range. The oxidized substrate reveals the presence of NiO, Al 2 O 3 , NiCr 2 O 4 , and Cr 2 O 3 .…”

“…During the initial stages, the gamma prime phase favors the formation of these oxides. Sreenivasulu et al [22,23] investigated the corrosion behavior of Nimonic 80A coated with metallic powder through air plasma and HVOF technique in 40%+60% of Na 2 SO 4 +V 2 O 5 MS environment and air environment for 50 h at 900 °C. The authors concluded that spinel oxides and Cr 2 O 3 enhance corrosion resistance, whereas the MoO 3 decreases the corrosion resistance at the prescribed condition.…”

High-Temperature Corrosion of APS- and HVOF-Coated Nickel-Based Super Alloy under Air Oxidation and Melted Salt Domains

“…Steel base metals exhibited a better OR than uncoated steel. Both coated and uncoated steel followed the parabola curvature rate oxidizing law, and the parabolic rate constant of coated steel was lower than that of uncoated steel [24]. Cr 2 O 3 and SiO 2 oxides developed over the exterior layer were inactive in the melted NaVO 3 salt.…”

Development of protective coating for X8CrNiMoVNb16-13 alloy in high-temperature molten salt environment through high-velocity oxy-fuel sprayed NiCrMoNb and Cr3C2-25NiCr powder coating

“…The better coating characteristics, cost-effective coating, feasibility of performing the coating on the site and its flexibility in HVOF coating make the substrate suitable in automotive, paper, steel, power generation and general engineering applications. 8…”