High-Temperature Corrosion Studies of HVOF-Sprayed Cr3C2-NiCr Coating on SAE-347H Boiler Steel

Abstract

Cr 3 C 2 -NiCr coating was deposited on SAE-347H boiler steel by high velocity oxy fuel (HVOF) spray process. Subsequently, high-temperature corrosion behavior of the bare and coated boiler steel was investigated at 700°C for 50 cycles in Na 2 SO 4 -82Fe 2 (SO 4 ) 3 molten salt, as well as air environments. Weight-change measurements after each cycle were made to establish the kinetics of corrosion. X-ray diffraction, field emission-scanning electron microscopy/energy dispersive spectroscopy, and x-ray mapping analyses were performed on the exposed samples to analyze the oxidation products. The bare 347H steel suffered accelerated oxidation during exposure at 700°C in the air as well as the molten salt environment in comparison with its respective coated counterparts. The HVOF-spray Cr 3 C 2 -NiCr coating was found to be successful in maintaining its adherence in both the environments. The surface oxide scales were also found to be intact. The formation of chromium rich oxide scale might have contributed for the better hot corrosion/oxidation resistance in the coated steel.

Influence of Process Parameters on High Velocity Oxy-Fuel Sprayed Cr3C2-25%NiCr Coatings

“…Chromium carbide-based materials are generally employed to produce hard coatings for high temperature wear applications including sliding, fretting, abrasion, and erosion in powder generation industry, aerospace industry, oil-refining industry, heat-treatment rolls, and coal burning boiler tubes [1,2]. The chromium carbides-nickel chromium (Cr 3 C 2 -NiCr) cermet coatings have been widely practiced in industry, caused by the advantageous combination of Cr 3 C 2 ceramic phase with good wear-resistance and NiCr metal phase which provides high oxidation resistance to high temperature [3,4].…”

High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

“…The FE-SEM analysis (Figure 3(a)) from the surface also validates the presence of Fe and O on the surface of the sample, which is further confirmed by EDS analysis from the cross-section in Figure 4(a), which shows Fe in very high percentage at points 3, 4, 5, 6 and 7 of the oxide scale layer along with a sufficient amount of O, indicating the formation of iron oxide. Formation of such types of oxide has also been analyzed by Sidhu et al, [3] Prakash et al, [23] Srikanth et al, [24] Singh, [25] Bala, [26] Kaushal et al, [27] and Kaur et al [28] . The presence of Fe 2 O 3 is further confirmed by EPMA analysis (Figure 5).…”

Characterization and Evaluation of Cyclic Hot Corrosion Resistance of Detonation-Gun Sprayed Ni-5Al Coatings on Inconel-718

“…The cyclic hot corrosion studies create the severest conditions for testing, which simulate the conditions prevailing in actual service environment of the superalloy components, where breakdown/shutdown occurs frequently. The hot corrosion test procedure used in this study is similar to the one reported by many researchers ( Ref 1,[30][31][32]. The thermo-gravimetric technique was used to establish kinetics of corrosion.…”