Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings

Sadeghimeresht, Esmaeil; Reddy, Liam; Hussain, Tanvir; Huhtakangas, Matti; Markocsan, Nicolaie; Joshi, Shrikant V.

doi:10.1016/j.matdes.2018.03.048

Cited by 51 publications

(27 citation statements)

References 57 publications

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“…The annealed 50-75C possesses lower porosity, thereby having higher hardness. In general, high porosity definitely results in poor corrosion resistance for many porous materials [56,68]. Therefore, the outcomes of electrochemical tests seem to be contrary to the traditional consideration.…”

Section: Electrochemical Resultsmentioning

confidence: 98%

Particle Size-Dependent Microstructure, Hardness and Electrochemical Corrosion Behavior of Atmospheric Plasma Sprayed NiCrBSi Coatings

Sang

Chen

Zhao

et al. 2019

Metals

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Particle size is a critical consideration for many powder coating-related industries since it significantly influences the properties of the produced materials. However, the effect of particle size on the characteristics of plasma sprayed NiCrBSi coatings is not well understood. This work investigates the microstructures, hardness and electrochemical corrosion behavior of plasma sprayed NiCrBSi coatings synthesized using different-sized powders. All coatings mainly consist of Ni, N 3 B, CrB, Cr 7 C 3 and Cr 3 C 2 phases. The coatings produced by small particles (50-75 µm) exhibit lower porosity (2.0 ± 0.8%). Such coatings show a higher fraction (15.5 vol.%) of the amorphous phase and lower hardness (700 HV 0.5 ) than the counterparts (8.7 vol.% and 760 HV 0.5 , respectively) produced by large particles (75-100 µm) with higher porosity (3.0 ± 1.6%). Meanwhile, the coatings produced from smaller particles possess a larger number of non-bonded boundaries, leading to the easier penetration of corrosive medium, as well as a higher corrosion current density (0.254 ± 0.062 µA/cm 2 ) and a lower charge transfer resistance (0.37 ± 0.07 MΩ cm 2 ). These distinctions are attributed to particle size-induced different melting degrees and stackings of in-flight particles during deposition. studied the effects of particle size and structure on the preferential Ce evaporation for La 2 Ce 2 O 7 particles during plasma spraying and indicated that the evaporation loss of Ce is significantly influenced by particle size, thereby affecting the properties of the as-sprayed La 2 Ce 2 O 7 coatings. Sun et al. [16] used different-sized WC powders to sinter three sets of WC-8Co cemented carbides and found that the transgranular fractures of the prepared cemented carbides are more evident with increasing WC particle size. From all this one can conclude that powder appearance potentially influences the properties and therefore the end applications of the produced products.NiCrBSi alloy coatings are also commonly prepared by metallic powder-related techniques including spraying [17,18] and laser cladding [19,20], with the aim to produce barriers to protect substrates from wear and/or corrosion. Amongst these techniques, atmospheric plasma spraying (APS) is frequently used due to its high synthesis speed and few limitations on equipment [21]. APS adopts a plasma gun as a heat source to melt the feedstock powder sprayed from the nozzle and impinges these powder particles on the substrates in a layer by layer method [22]. As a result, this processing method results in a typical lamellar microstructure in APS-prepared NiCrBSi coatings associated with a large number of pores and non-bonded boundaries (including lamellar boundaries and particle boundaries). Pores generally decrease the cohesion of the as-sprayed NiCrBSi coatings, thereby reducing their hardness and wear resistance [22]. In the meantime, non-bonded boundaries in as-sprayed NiCrBSi coatings provide diffusion paths for the ingress of corrosive species in a corrosive environment [22]. ...

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Section: Electrochemical Resultsmentioning

confidence: 98%

Particle Size-Dependent Microstructure, Hardness and Electrochemical Corrosion Behavior of Atmospheric Plasma Sprayed NiCrBSi Coatings

Sang

Chen

Zhao

et al. 2019

Metals

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“…In all alloy systems Mn, Fe as well as Cr were preferentially attacked while Mo and Ni enriched as leftovers on the surface of the alloys. Thermodynamically, Ni and Mo are rather similar concerning their chlorination reaction [28]. However, the activation energy of the dissociative adsorption of chlorine on the metal surface is also much higher for Mo than for Ni [51].…”

Section: Structure and Surface Morphology Of Corrosion Productsmentioning

confidence: 95%

“…Both flat surfaces of the buttons were then HVAF sprayed, so that the specimens were fully coated (on all sides). More details about the substrate preparation can be found in a previous work [28].…”

Section: Hvaf Sprayingmentioning

confidence: 99%

Effect of SiO2 Dispersion on Chlorine-Induced High-Temperature Corrosion of High-Velocity Air-Fuel Sprayed NiCrMo Coating

et al. 2018

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NiCrMo coatings with and without dispersed SiO2 were deposited using high velocity air-fuel (HVAF) technique. Thermogravimetric experiments were conducted in 5% O2+500 vppm HCl+N2 with and without a KCl deposit at 600 °C for up to 168 h. The SiO2-containing coating showed lower weight change due to formation of a protective and adherent Cr-rich oxide scale. SiO2 decelerated short-circuit diffusion of Cr 3+ through scale's defects, e.g., vacancies, and promoted the selective oxidation of Cr to form the protective Cr-rich oxide scale. Furthermore, the presence of SiO2 led to less subsurface depletion of Cr in the coating, and accordingly less corrosion of the substrate. The formed corrosion product on the SiO2-free coating was highly porous, non-adherent, and thick.

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“…Instead, the cross sections are prepared using broad ion beam milling (BIB) which results in a very smooth surface and facilitates more accurate analysis by making features in the coatings more distinguishable. The difference between mechanically polished surface [32] and a surface prepared by broad ion beam milling can be seen in Fig. 11.…”

Section: Comparison With Other Spraying Techniquesmentioning

confidence: 99%

High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications

et al. 2019

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The present study investigates the initial corrosion behaviour of HVAF-sprayed NiCr, NiAl and NiCrAlY coatings in two different environments, O 2 + H 2 O and O 2 + H 2 O + KCl at 600 °C for up to 168 h in order to evaluate the possibility of utilizing such coatings in biomass-and waste-fired boilers. SEM/EDX analysis showed that all coatings displayed a protective behaviour in O 2 + H 2 O. Upon addition of KCl (O 2 + H 2 O + KCl), the corrosion behaviour of the NiCr coating drastically changed as it formed a thick oxide layer and displayed major chlorine diffusion down to the substrate. The NiCrAlY coating displayed a significantly better corrosion resistance with only minor oxide formation. The NiAl coating exhibited a protective behaviour similar to when exposed in the absence of KCl indicating that a thin protective oxide has formed on the coating surface. The performance of the NiAl and NiCrAlY coatings is promising for future studies with long-term exposures in more corrosive environments such as in a biomass-and waste-fired boiler.

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Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings

Cited by 51 publications

References 57 publications

Particle Size-Dependent Microstructure, Hardness and Electrochemical Corrosion Behavior of Atmospheric Plasma Sprayed NiCrBSi Coatings

Particle Size-Dependent Microstructure, Hardness and Electrochemical Corrosion Behavior of Atmospheric Plasma Sprayed NiCrBSi Coatings

Effect of SiO2 Dispersion on Chlorine-Induced High-Temperature Corrosion of High-Velocity Air-Fuel Sprayed NiCrMo Coating

High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications

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