Hot Corrosion Behavior of Arc-Sprayed NiCrB and NiCrTi Coatings with Different Oxide Contents

Abstract

In this study, newly developed NiCrB and conventional NiCrTi coatings were produced by arc spraying using compressed air and nitrogen as atomization gases. In this way, four coatings with different oxide contents were produced. The coatings were investigated in terms of their phase compositions, oxygen contents, and microstructures. The results showed that the oxygen contents in coatings were pronouncedly reduced by nitrogen-atomized compared to air-atomized. The oxygen contents in the nitrogen-atomized coatings were about one-fourth of those in the corresponding air-atomized coatings, respectively. No significant oxide phases were observed in the XRD patterns of the nitrogen-atomized coatings. Moreover, the corrosion behavior of the coatings was studied using a hot corrosion test in molten Na2SO4-10 wt.% NaCl salt at T = 800 °C. All coatings were significantly corroded under this test condition. However, NiCrB coatings exhibited higher corrosion resistance than NiCrTi coatings. The NiCrB and NiCrTi coatings prepared by nitrogen atomization corroded more severely in the initial stage than the corresponding coatings prepared by air atomization. The NiCrB coating with air-atomized showed the best corrosion resistance due to the low chromium content and the addition of boron.

Hot Corrosion Behavior of TWAS and HVOF NiCr-Based Coatings in Molten Salt

“…Figure 6 displays the EDX elemental mappings of the NiCrTi coating. Detected XRD phases are consistent with those reported by Wang [ 57 ] for the TWAS spray NiCrTi coating in a molten salt environment of 90% Na 2 SO 4 -10% NaCl. The results are found to be also similar to those reported by Guo [ 58 ] for the TWAS sprayed NiCrTi in a molten salt environment of 70% Na 2 SO 4 -30% K 2 SO 4 .…”

Review of Thermal Spray Coatings Perform in Protecting Boiler Steels Against Corrosion at High Temperatures

“…In a study, Singh et al, 38 revealed that TiO 2 functions as a protective barrier against corroding agents by occupying any gaps or fractures in the coating's microstructure. Wang et al, 39 found that NiCrB coatings have greater corrosion resistance in comparison to NiCrTi coatings as a result of boron's inclination towards producing small oxide particles, ultimately augmenting the safeguarding of oxide layers. Abuwarada et al, 40 showed that the presence of a stable Al 2 O 3 oxide scale on the CoNiCrAlY coating reduced chloride penetration and prevented the degradation of the protective oxide scale through the formation of chromates.…”