Structural changes in high-velocity oxy-fuel thermally sprayed WC–Co coatings for improved corrosion resistance

Godoy, Cristina; Lima, Maria Luísa; Castro, M.M.R.; Avelar-Batista, J.C.

doi:10.1016/j.surfcoat.2004.07.123

Cited by 25 publications

(5 citation statements)

References 10 publications

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“…Reduced porosity with increasing levels of Co binder, observed by Saenger et al [5] may be responsible for increased resistance. Significant improvement in the corrosion behaviour of HVOF WC-Co coatings was observed after modifying the coating composition with additions of NiCrAl and / or conducting a post melt treatment [6].…”

Section: Introductionmentioning

confidence: 99%

Corrosion Behaviour of Modified HVOF Sprayed WC Based Cermet Coatings on Stainless Steel

Ward¹,

Hinton²,

Gerrard³

et al. 2011

JMMCE

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WC based cermet coatings have been considered as alternative replacements to the more traditional hard chrome plating for improved surface properties of aircraft landing gear. While these coatings are used in engineering applications requiring superior hardness and improved wear resistance, little is known about the corrosion resistance. In this study, three WC based composite coatings were deposited onto ferritic stainless steel substrates using high velocity oxy fuel (HVOF) technology. Salt spray testing and potentiodynamic scanning studies in a saline environment were conducted on the coatings. Characterisation of the coating structure, composition and morphology, was carried out, prior to and after corrosion testing, using optical microscopy, scanning electron microscopy and EDX elemental analysis. The results showed that poor corrosion performance was exhibited by all three coatings. This was attributed to the high levels of porosity and the presence of micro-cracks within the coatings, resulting in attack of the substrate directly by the saline environment and possible galvanic coupling effects between the substrate and the coating. Dissolution and / or erosion of specific phases within the coating, resulting in the formation of micro-channels and increased number / size of voids may have accelerated corrosion of the system.

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Section: Introductionmentioning

confidence: 99%

Corrosion Behaviour of Modified HVOF Sprayed WC Based Cermet Coatings on Stainless Steel

Ward¹,

Hinton²,

Gerrard³

et al. 2011

JMMCE

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show abstract

“…The corrosion performance of the bilayer coating was found to be dependent on the intermediate layer's microstructure [11]. It was The advantages of the bilayer coatings over the single-layer ones have already been shown in several works [4,10,11,16,18,19]. The intermediate layer was shown to be effective in impeding the penetration paths of the corrosive ions to the metallic substrate [10].…”

Section: Introductionmentioning

confidence: 90%

Electrochemical Behavior of Bilayer Thermal-Spray Coatings in Low-Temperature Corrosion Protection

Sadeghimeresht

Markocsan

2017

Coatings

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Cr 3 C 2 -NiCr coatings are greatly used to protect critical components in corrosive environments and to extend their lifetime and/or improve functional performance. However, the pores formed during spraying restrict the coating's applicability area for many corrosion protection applications. To overcome this technical challenge, bilayer coatings have been developed, in which an additional layer (the so-called "intermediate layer") is deposited on the substrate before spraying the Cr 3 C 2 -NiCr coating (the so-called "top layer"). The corrosion behavior of the bilayer coating depends on the composition and microstructure of each layer. In the present work, different single-layer coatings (i.e., Cr 3 C 2 -NiCr, Fe-and Ni-based coatings) were initially sprayed by a high-velocity air fuel (HVAF) process. Microstructure analysis, as well as electrochemical tests, for example, open-circuit potential (OCP) and polarization tests, were performed. The potential difference (∆E) had a great influence on galvanic corrosion between the top and intermediate layers, and thus, the coatings were ranked based on the OCP values (from high to low) as follows: NiCoCrAlY > NiCr > Cr 3 C 2 -NiCr > NiAl > Fe-based coatings (alloyed with Cr) > pure Ni. The Ni-based coatings were chosen to be further used as intermediate layers with the Cr 3 C 2 -NiCr top layer due to their capabilities to show high OCP. The corrosion resistance (R p ) of the bilayer coatings was ranked (from high to low) as follows: NiCoCrAlY/Cr 3 C 2 -NiCr > NiCr/Cr 3 C 2 -NiCr > NiAl/Cr 3 C 2 -NiCr > Ni/Cr 3 C 2 -NiCr. It was shown that splat boundaries and interconnected pores are detrimental for corrosion resistance, however, a sufficient reservoir of protective scale-forming elements (such as Cr or/and Al) in the intermediate layer can significantly improve the corrosion resistance.

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“…By applying this treatment, one may reduce the coating porosity and possible microcracks or internal oxides [12][13][14]. Moreover, the chemical composition might be improved especially with respect to Cr and Mo-content, the latter one being responsible for a good corrosion resistance in salt water [15][16][17]. The present work concerns …”

Section: Introductionmentioning

confidence: 99%

Microstructure refinement and alloying of WC–CoCr coatings by electron beam treatment

Mărginean

Uţu

2010

Surface and Coatings Technology

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Structural changes in high-velocity oxy-fuel thermally sprayed WC–Co coatings for improved corrosion resistance

Cited by 25 publications

References 10 publications

Corrosion Behaviour of Modified HVOF Sprayed WC Based Cermet Coatings on Stainless Steel

Corrosion Behaviour of Modified HVOF Sprayed WC Based Cermet Coatings on Stainless Steel

Electrochemical Behavior of Bilayer Thermal-Spray Coatings in Low-Temperature Corrosion Protection

Microstructure refinement and alloying of WC–CoCr coatings by electron beam treatment

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