The effect of oxide coatings on fatigue properties of 7475-T6 aluminium alloy

Lonyuk, B. P.; Apachitei, I.; Duszczyk, J.

doi:10.1016/j.surfcoat.2006.02.002

Cited by 129 publications

(95 citation statements)

References 10 publications

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“…The appearance of anodising-induced cracks is more likely for higher differences in temperature (as they occur for hard-anodising processes where lower bath temperatures are used) and for a higher thickness of the coating layer [17,18,23]. Accordingly, thermo-shock-induced cracks have only been observed on the hard-anodised coating EAO2, however, only for the CG T6 substrate.…”

Section: Discussionmentioning

confidence: 99%

“…Due to the mismatch in thermal expansion coefficients of the aluminium alloy and the oxide layer, internal tensile stresses arise in the coating [17,18,23]. This can lead to the for- mation of radial cracks in the oxide layer, as it can be observed for the hard-anodised coating EAO2 on the CG T6 substrate.…”

Section: Characterisation Of Substrate and Coatingsmentioning

confidence: 99%

“…This is mainly due to the brittle and porous nature of the coating and the presence of tensile residual stresses. Under these conditions, cracks can easily form in the coating [15][16][17]19]. Assisted by the good adherence, they will more likely propagate into the substrate than along the interface [16,20] and thus lead to a fast progress of the fatigue damage.…”

Section: Introductionmentioning

confidence: 99%

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The effect of anodic oxide coating on the fatigue behaviour of AA6082 with an ultrafine‐grained microstructure

Hockauf¹,

Köhler²,

Händel³

et al. 2011

Materialwissenschaft Werkst

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In this work, the high-cycle fatigue behaviour of the precipitation hardening aluminium wrought alloy AA6082 was investigated for a conventionally-grained and an ultrafine-grained substrate condition, with each a hard and a soft electrolytic anodic oxide (EAO) coating. The investigations were focused on the susceptibility of the coatings to anodising-and fatigueinduced cracking of the coatings and its impact on the fatigue life. For both substrate materials, the fatigue strength of the coated specimens was significantly reduced compared to the uncoated materials. Considering the resistance to crack initiation in the coating, the soft-anodised coatings were found to be superior compared to the hard-anodised ones. Moreover, the coatings on the ultrafine-grained substrate showed an enhanced resistance to anodisinginduced as well as fatigue-induced cracking. However, it is supposed that the lower resistance to crack transition from the coating into the substrate is one of the most important factors which strongly limits the fatigue life of the EAO-coated specimens. This might be the reason why the fatigue strength of the ultrafine-grained substrates is relatively low, despite their higher resistance to crack initiation.Keywords: equal-channel angular pressing (ECAP) / electrolytic anodic oxidation (EAO) / high-cycle fatigue (HCF) / ultrafine-grained / Al-Mg-Si alloy / In dieser Arbeit wird die Ermüdungsfestigkeit der ausscheidungshärtbaren Aluminiumknetlegierung AA6082 an einen normalkörnigen sowie einem ultrafeinkörnigen Zustand mit jeweils einer hart-und einer weichanodisierten Schicht (electrolytic anodic oxiddation, EAO) untersucht. Die Untersuchungen sind darauf ausgerichtet, die Anfälligkeit der Schichten für Rissbildung, sowohl beim Anodisierprozess als auch bei der Ermüdungsbelastung, zu untersuchen und Verbindungen zur Ermüdungsfestigkeit herzustellen. Für beide Substratmaterialien ergibt sich für die beschichteten Zustände eine deutliche Verschlechterung der Ermüdungsfestigkeit. Dabei zeigen sich die hartanodisierten Schichten generell als deutlich rissanfälliger im Vergleich zu den weichanodisierten Schichten. Darüber hinaus kann im Vergleich der Substratzustände festgestellt werden, dass beide Schichttypen auf dem ultrafeinkörnigen Substrat einen erhöhten Widerstand gegen eine anodisierprozessbedingte oder ermüdungsbedingte Anrissbildung besitzen. Die Untersuchungen zeigen jedoch auch, dass vor allem der Widerstand gegen einen Übergang des Risses von der Schicht ins Substrat die Lebensdauer bestimmt. Für die beschichteten ultrafeinkörnigen Substrate könnte hier der Grund für deren relativ niedrige Ermüdungsfestigkeit liegen, die sich trotz des erhöhten Widerstandes gegen Anrissbildung ergibt.Schlüsselwörter: equal-channel angular pressing (ECAP) / elektrolytisch anodische Oxidation (EAO) / ultrafeinkörnig / Ermüdungsfestigkeit / Al-Mg-Si-Legierung /

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Section: Discussionmentioning

confidence: 99%

Section: Characterisation Of Substrate and Coatingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The effect of anodic oxide coating on the fatigue behaviour of AA6082 with an ultrafine‐grained microstructure

Hockauf¹,

Köhler²,

Händel³

et al. 2011

Materialwissenschaft Werkst

View full text Add to dashboard Cite

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“…Both inner diffusion of elements toward the metallic substrate (i.e., saturation) and diffusion toward the surface take place. The surface saturation is possible during both anodic and cathodic processes [62][63][64][65]. Depending on the nature of electrolyte, a composite saturation with nonmetals such as O, C, N, and B (and their combinations) or carbide forming transition metals such as W, Mo, V, etc, is possible.…”

Section: Diffusion and Plasma Chemical Reactions Cataphoretic Effectsmentioning

confidence: 99%

Electrolytic plasma processing for plating coatings and treating metals and alloys

Pogrebnyak

Kaverina

Кылышканов

2014

Prot Met Phys Chem Surf

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Abstract-A review of the methods of electrochemical treatment classified as plasma electrolysis is given. Special attention is paid to the physicochemical processes that proceed in electrolytes and the techniques of surface modification and application of protective coatings. The results of investigation of such coatings and surfaces upon electrolytic plasma processing illustrate the efficiency and effectiveness of the method. Being an efficient technique of the surface treatment, which involves both the surface cleaning and plating the coat ing, the plasma electrolytic method is being rapidly developed and adapted for commercial use at present.

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“…Therefore, this porous anodic film is sealed by different methods like boiling water, nickel acetate and dichromate solutions [3][4] to further improve the corrosion resistance. Despite the benefits obtained in terms of enhanced corrosion properties, the anodic film has a detrimental effect on the fatigue performance of the base material [5][6][7][8] in particular by promoting crack initiation. The anodization produces a brittle and hard oxide layer as compared to aluminum substrate, with inherent pores, and it easily cracks under cyclic stress.…”

Section: Introductionmentioning

confidence: 99%

Effect of sealed anodic film on fatigue performance of 2214-T6 aluminum alloy

Shahzad

Chaussumier

Chieragatti

et al. 2012

Surface and Coatings Technology

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The aim of present study is to investigate the influence of anodic film, grown by sulfuric acid anodizing and sealed in nickel-acetate solution, on fatigue strength of aluminum alloy 2214-T6 by conducting axial fatigue tests at stress ratio 'R' of 0.1 and − 1. The influence of sealed anodic film is to degrade the stress-life (S-N) fatigue performance of the base material at all stress levels. Effects of pre-treatments like degreasing and pickling employed prior to anodizing were also studied and no influence of these pre-treatments was observed on fatigue life. The surface and cross-section observations of anodic film were made by scanning electron microscope (SEM) before and after fatigue tests. The surface observations have revealed cavities which resulted from dissolution of coarse Al 2 Cu particles during anodization and network of micro-cracks on anodic film surface which were initiated as a result of sealing process. Some of these micro-cracks were found to penetrate up-to substrate and have detrimental effect on subsequent fatigue strength. The decrease in fatigue life for anodized-sealed specimens as compared to bare condition has been attributed to decrease in initiation period and multi-site crack initiations. Multi-site crack initiation has resulted in rougher fractured surfaces for the anodized specimens as compared to bare specimens tested at same stress levels.

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The effect of oxide coatings on fatigue properties of 7475-T6 aluminium alloy

Cited by 129 publications

References 10 publications

The effect of anodic oxide coating on the fatigue behaviour of AA6082 with an ultrafine‐grained microstructure

The effect of anodic oxide coating on the fatigue behaviour of AA6082 with an ultrafine‐grained microstructure

Electrolytic plasma processing for plating coatings and treating metals and alloys

Effect of sealed anodic film on fatigue performance of 2214-T6 aluminum alloy

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