Ni–Al composite coatings: diffusion analysis and coating lifetime estimation

Abstract

The interdiffision of Ni matrix/Al particle composite coatings and nickel substrates was studied using electron probe microanalysis (EPMA) and a one-dimensional diffusion model. The initial coating microstructure was a two-phase mixture of y(Ni) and y'(Ni3Al).The coating/substrate assemblies were aged at 800 to 11OO°C for times up to 2000 hours. It was found that aluminum losses to the substrate are significant at 1000"C and above. The "experimental results for the diffusion of Al into the substrate were compared to model predictions based on a diffusion equation for a finite layer on an infinite substrate. Using combined experimental and model results, the effects of temperature and coating thickness were determined and a rationale was developed for coating lifetime prediction.

Effect of diffusion barrier on the high-temperature oxidation behavior of thermal barrier coatings

“…Maybe the reasons are: the mainly oxide formed on the surface of the bond coat at high temperature is Al 2 O 3 , which results in a large amount of depletion of Al in the bond coat due to outward diffusion of Al. Combined with the result that the diffuse inward of Al from bond coat to substrate is continually confirmed according to the calculated result of the interdiffusion coefficient of Al mentioned by Susan [14]. On the other hand, the ␤-NiAl phase presented in the bond coat participates in the reaction together with oxygen, i.e.…”

Influence of Aluminum and Rhenium on the Isothermal Oxidation Behavior of CoNiCrAlY Alloys

“…Similar study in a Ni-based superalloy CMSX-5 has also shown an influence of Re on the diffusion behavior of alloying elements, particularly that of Al, to the surface [31]. Limited diffusion data demonstrated that at 1000°C the diffusion coefficient of Al in c-Ni with 3 wt% Re was 4.38 9 10 -11 cm -2 s -1 [32], but in Re-free c-Ni was 1.2 9 10 -11 cm -2 s -1 [33]. EDS results obtained in the present work (Tables 6, 7) revealed that Al-rich oxides in the Re-containing alloys prevailed over that found on Re-free alloys, which strongly indicate that the addition of Re favored a higher flux of Al to the oxidizing surface, resulting in an accelerated formation of a complete, purer Al 2 O 3 layer with less Co, Ni containing spinels, like NiAl 2 O 4 .…”

Potentiostatic Electrochemical Preparation and Characterisation of Aluminium Containing Nickel Selenide

“…For data acquisition transistor based power supply unit Model 613 (systronics electronics limited) and multimeters were used for the measurement of current and potential during electrochemical codeposition. Three different solutions were prepared by taking NiSO 4 3 and SeO 2 was prepared. All these solutions were prepared in deionised water.…”

“…Moreover, transition metal aluminides have sufficient aluminium content to form an adherent alumina layer on the surface when exposed to air or oxygen atmospheres 3 compounds. Although the electrodeposition of Al metal in aqueous solutions is rather difficult because of the high electropositivity of Al, some authors were successful in fabricating Ni-Al composite coatings on various substrates through electrodeposition under proper conditions [4][5][6][7][8] . Properties of electrolytic nickel coatings are well known.…”