Toward the Achievement of Substrate Melting and Controlled Solidification in Thermal Spraying

Zhang, W.; Wei, Guanghua; Zhang, H.; Zheng, Lili; Welch, D. O.; Sampath, Sanjay

doi:10.1007/s11090-007-9104-0

Cited by 9 publications

(8 citation statements)

References 31 publications

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“…4a and b. Analogous plastic deformation phenomena have already been described in previous observations of single splats sprayed onto soft substrates by the high-velocity oxygen-fuel or air-fuel processes [19,33]. Perhaps, a further contribution to such deformation might also come from localised melting of the substrate material at the impact location, because of the heat input coming both from the gas jet and from the molten particle [34,35], although this phenomenon is more likely to occur during plasma spraying of very high melting point material and has not yet been considered explicitly for the HVOF-spraying process.…”

Section: Discussionsupporting

confidence: 66%

HVOF-sprayed WC–CoCr coatings on Al alloy: Effect of the coating thickness on the tribological properties

Bolelli

Lusvarghi

Barletta

2009

Wear

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a b s t r a c tThe microstructure, the micromechanical properties, the wear behaviour and the impact resistance of WC-CoCr cermet coatings, deposited onto an aluminium alloy substrate by High Velocity Oxygen-Fuel (HVOF) flame-spraying, were examined as a function of the coating thickness, which was varied between 50 m and 150 m by performing different numbers of scans of the HVOF torch in front of the substrate. The coatings became denser and significantly harder as the number of torch scans increased: the analysis of single WC-CoCr splats by combined SEM and Focused Ion Beam (FIB) techniques enabled the interpretation of the mechanisms underlying this phenomenon. In accordance to such densification, the sliding wear resistance increased with the number of torch scans, as abrasive grooving and brittle failure mechanisms were progressively suppressed. The resistance to cyclic impact was also enhanced. In comparison to anodised films, the WC-CoCr coatings appeared much more resistant against wear and cyclic impact; specifically, three torch scans seem enough to produce a coating having suitable characteristics.

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Section: Discussionsupporting

confidence: 66%

HVOF-sprayed WC–CoCr coatings on Al alloy: Effect of the coating thickness on the tribological properties

Bolelli

Lusvarghi

Barletta

2009

Wear

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“…Li et al [4] have recently shown that the substrate melted and interacted with the spreading droplet. These experimental results confirmed that better bonding between the sprayed coating and the substrate could be achieved through the formation of intermetallic compounds as a result of substrate melting during droplet-substrate interaction [1,2,[4][5][6].…”

Section: Introductionsupporting

confidence: 65%

“…A trace of a chromium-rich phase was also found in the centre pore (1). Inter-diffusion between splat and substrate occurs in localised regions (6). In addition, trace of FeO was formed in the enclosed pores (2) and at the periphery of the splat (4).…”

Section: Tem Resultsmentioning

confidence: 99%

Evidence of Substrate Melting of NiCr Particles on Stainless Steel Substrate by Experimental Observation and Simulations

Tran

Brossard

Hyland

et al. 2009

Plasma Chem Plasma Process

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Single NiCr splats were plasma-sprayed onto a polished stainless steel substrate held at room temperature. The splat-substrate interface was characterized by focused ion beam and transmission electron microscopy. The frequent observation of NiO particles, particularly in pores within the splat, and at the periphery of splat, suggests that the principal oxidation process occurs at the substrate surface, where the splats are exposed to a water vapor-rich environment. It was also observed that the splat adhered well in some locations where elemental-diffusion and jetting of the substrate occurred, suggestive of substrate melting. A three-dimensional numerical model was developed to simulate the impact of a splat onto a substrate. The simulation shows that the observation of the central pore in the splat and the phenomenon of substrate melting may occur. Based on these results, the effect of water release on oxide formation and splat morphology can be explained.

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“…Although in RSP, due to the extreme temperature gradient and interfacial velocity of the solidification front, a planar or columnar front growth is often observed (as opposed to dentritic) [11], the specific crystallographic orientation of the splat grains and its relationship with the substrate orientation, if any, is complex to predict. It has been suggested that the establishment of epitaxy in thermally-sprayed materials depends on a combination of substrate crystalline structure, surface temperature and surface melting at droplet impact [12,13]. A number of studies have addressed the grain structure of thermallysprayed single splats, mainly focussing on plasma spray and ceramic materials.…”

Section: Crystallisation and Solidificationmentioning

confidence: 99%

Residual stress and adhesion of thermal spray coatings: Microscopic view by solidification and crystallisation analysis in the epitaxial CoNiCrAlY single splat

et al. 2018

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A new approach is proposed to achieve an in-depth understanding of crystallisation, residual stress and adhesion in epitaxial splats obtained by Combustion Flame Spray. Modelling of the fundamental process mechanisms is achieved with the help of experimental observations providing details with a sub-micrometre spatial resolution. At this scope, High Angular Resolution Electron Backscatter Diffraction and Transmission Electron Microscopy analysis are employed to provide insights into crystallisation and residual stress levels, while FIB-milled microcantilever beam bending is used for fracture strength measurements in the case of single splats. A comparison to fully-developed coatings is achieved by employing the X-ray Diffraction sin 2 ψ technique and pull-off methods for residual stress and fracture strength, respectively. The methodology is applied to metallic CoNiCrAlY material sprayed onto a Ni-based superalloy substrate. The establishment of different crystallisation regions: epitaxial and polycrystalline, is the result of variations in the heat flux direction at the solidification front. Significant dislocation density is also reported, indicating the relevance of impact dynamics and plastic deformation mechanisms. The comparison with fully-developed coatings suggests a reduction in inter-splat bonding at splat overlapping.

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Toward the Achievement of Substrate Melting and Controlled Solidification in Thermal Spraying

Cited by 9 publications

References 31 publications

HVOF-sprayed WC–CoCr coatings on Al alloy: Effect of the coating thickness on the tribological properties

HVOF-sprayed WC–CoCr coatings on Al alloy: Effect of the coating thickness on the tribological properties

Evidence of Substrate Melting of NiCr Particles on Stainless Steel Substrate by Experimental Observation and Simulations

Residual stress and adhesion of thermal spray coatings: Microscopic view by solidification and crystallisation analysis in the epitaxial CoNiCrAlY single splat

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