Microstructure formation and corrosion behaviour in HVOF-sprayed Inconel 625 coatings

Zhang, D; Harris, S.J.; McCartney, D.G.

doi:10.1016/s0921-5093(02)00420-3

Cited by 125 publications

(59 citation statements)

References 15 publications

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“…On impact molten material spreads out and resolidifies whereas nonmolten material deforms and adheres mainly by mechanical interlocking. The coating microstructure shown in Figure 3b is typical of HVOF metallic coatings and has been discussed in detail in previous work [4]. Individual particles, or splats, can be seen, it is also clear that the coating consists of two distinct types of material: deformed non-melted material and areas of resolidified material.…”

Section: Microstructurementioning

confidence: 62%

“…The resolidified regions are depleted in oxide forming elements due to formation of oxides during coating deposition [4,6]. Previous work by the present authors has shown that formation of galvanic cells between these different regions decreases the corrosion resistance of the coating, resulting in the observed performance gap [6].…”

Section: Introductionmentioning

confidence: 66%

“…However, previous work [4,6] has shown that partial oxidation during coating formation results in localised regions of the coating that are Ni-rich and Cr-depleted. Such areas have previously been identified as the cause of the lower corrosion resistance of the sprayed coating compared to the wrought material [6].…”

Section: Discussionmentioning

confidence: 96%

“…Such coatings do usefully improve corrosion resistance, however, there is a well established performance gap between the coating and the equivalent bulk material [2][3][4][5]. This is attributed to the characteristic microstructure of the thermally sprayed coating.…”

Section: Introductionmentioning

confidence: 99%

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X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

Bakare

Voisey

Roe

et al. 2010

Applied Surface Science

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There is a well known performance gap in corrosion resistance between thermally sprayed corrosion resistant coatings and the equivalent bulk materials. Interconnected porosity has an important and well known effect, however there are additional relevant microstructural effects. Previous work has shown that a compositional difference exists between the regions of resolidified and non-melted material that exist in the as-sprayed coatings. The resolidified regions are depleted in oxide forming elements due to formation of oxides during coating deposition. Formation of galvanic cells between these different regions is believed to decrease the corrosion resistance of the coating. In order to increase understanding of the details of this effect, this work uses X-ray photoelectron spectroscopy (XPS) to study the passive films formed on thermally sprayed coatings (HVOF) and bulk Inconel 625, a commercially available corrosion resistant Ni-Cr-Mo-Nb alloy. Passive films produced by potentiodynamic scanning to 400mV in 0.5M sulphuric acid were compared with air formed films. The poorer corrosion performance of the thermally sprayed coatings was attributed to Ni(OH) 2 , which forms a loose, non-adherent and therefore non-protective film. The good corrosion resistance of wrought Inconel 625 is due to formation of Cr, Mo and Nb oxides.

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Section: Microstructurementioning

confidence: 62%

Section: Introductionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

Bakare

Voisey

Roe

et al. 2010

Applied Surface Science

View full text Add to dashboard Cite

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“…Due to its excellent corrosion resistance 6,7 , Inconel 625 often appears as an option for coating steels for operation in aggressive environments, such as sea water with CO 2 and H 2 S, especially in conditions where wear and erosion are not major issues 8 . For the aforementioned reasons, HVOFspraying is an attractive way of applying such coatings 9,10 .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Influence of Surface Finishing on the Corrosion Resistance of HVOF Applied Inconel 625 Coatings on Steel

et al. 2017

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In this work, the corrosion resistance of Inconel 625 coatings applied to AISI 4140 steel plates was evaluated. Coatings were produced by High Velocity Oxygen Fuel (HVOF) by use of two different equipment which use either kerosene (liquid) or propane (gas) as fuel. The resulting coatings were evaluated in two conditions: as-deposited and after a surface finishing process by grinding. Residual stress distributions in the coatings were characterized by X-ray diffraction and their morphology was verified through metallography and roughness measurements. Potentiodynamic polarization corrosion testing complemented their analysis. The results show a strong influence of the surface finishing process on the corrosion performance of the coatings.

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Microstructure Characterization of Alloy 625 Deposited on Nickel Foam using Air Plasma Spraying

et al. 2008

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Sandwich constructions offer many advantages over traditional stiffened shapes including light weight, high strength to weight ratio, and high stability. The basic concept of sandwich structures consists of two thin skins (faces) and a lightweight thicker core. The skin materials may be metallic, wood, or composite laminates, while cores can be made from a variety of materials including metallic and nonmetallic honeycombs, cellular metallic or polymeric foams. [1,2] Foam structures are attractive due to their outstanding mechanical and physical properties such as relatively low specific weight, high specific strength, high stiffness and gas permeability. [3,4] Due to their excellent performance, they are finding widespread use in aerospace, marine and offshore industries, and civil structures. A variety of new applications would become possible if foam core sandwich structures capable of operating at high temperatures and in corrosive environments were available. Ni foams have been available for several years [5,6] and more recently foams of high temperature alloys have been developed. [7] Ni-based superalloys are well known for their good combination of creep strength, yield strength, tensile strength and high service temperature, and so would be attractive candidates for the skin material. However, the bonding of thin sheets of such alloys to the foam core, and the fabrication of complex shapes are challenging manufacturing issues.In recent years there has been a growing worldwide interest in the use of thermal spray processes such as air plasma spraying (APS) to deposit protective superalloy coatings onto the surfaces of engineering components to improve their performance under severe conditions. APS is a well developed industrial process capable of depositing dense coatings of up to a few millimeters in thickness on complex shaped substrates. APS coatings are built up from splats, consisting of columnar and cellular grains, which result from the impact, flattening, and solidification of completely or partially melted powder particles on the substrate. The cooling rate during solidification of the splats is very high (∼ 10 4 -10 8°C /sec) [8] which may lead to formation of unusual amorphous or other metastable phases not found in conventionally manufactured materials. Individual splats are connected to each other by mechanical and chemical bonding, forming a lamellae structure exhibiting anisotropic behavior, with mechanical properties parallel to the substrate (longitudinal) different than those through the coating thickness (transverse). Microstructural features also include defects such as pores and microcracks. Due to the entrainment of the surrounding air into the plasma jet, the existence of oxide phases in APS metal coatings is not unexpected and a number of studies have addressed the existence of an oxide phase in the final microstructure. [8,9] Due to high velocity and temperature gradients in the plasma plume, changes in process parameters can result in significant changes in the characteristics of t...

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Microstructure formation and corrosion behaviour in HVOF-sprayed Inconel 625 coatings

Cited by 125 publications

References 15 publications

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

Evaluation of the Influence of Surface Finishing on the Corrosion Resistance of HVOF Applied Inconel 625 Coatings on Steel

Microstructure Characterization of Alloy 625 Deposited on Nickel Foam using Air Plasma Spraying

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