Microstructure and evolution of iridium coating on the C/C composites ablated by oxyacetylene torch

Chen, Zhaofeng; Wu, Wangping; Cheng, Han; Liu, Yong; Wang, Shiming; Xue, Ruijuan

doi:10.1016/j.actaastro.2009.08.008

Cited by 38 publications

(12 citation statements)

References 22 publications

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“…However, since Ir exceeds its ductile/brittle transition temperature (760°C [35]), it will become plastic and deform under the compressive stress, resulting in a rumpled Ir coating [ Fig. 7bB], which was reported by other researchers [10,13]. The stress relaxation of the Ir coating may occur at 1800°C following Path B-C in Fig.…”

Section: Characterizationmentioning

confidence: 93%

“…6d, e, located mainly along the grain boundaries and at the grain boundary junctions. The formation of the voids could be owing to the migration and aggregation of the inner microvoids in Ir coating at high temperatures [10].…”

Section: Characterizationmentioning

confidence: 99%

“…Various methods were used for preparing Ir coatings on C/C composites, including magnetron sputtering (MS) [4], electrodeposition (ED) in molten salt [8,9], laser-induced chemical decomposition (LICD) [2], double glow plasma (DGP) [10], and metal organic chemical vapor deposition (MOCVD) [11]. However, the protection capability of the Ir coatings produced directly on the C/C composites seems not satisfactory.…”

Section: Introductionmentioning

confidence: 99%

“…The Ir coating prepared by direct current (DC) MS turns into interconnected islands of Ir after heat treatment at 1727°C for 20 min, due to poor wettability of Ir on C/C substrate [12]. Cracking and rumpling occur in the Ir coating deposited by DGP after oxyacetylene torch ablation at 2000°C for 40 s, resulting from the huge thermal mismatch stress between Ir and C/C [10]. Besides, the poor adhesion of Ir coating on C/C composites, which was proved to be van der Waals forces [11], usually leads to the delamination and spalling of the coating during use.…”

Section: Introductionmentioning

confidence: 99%

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Ablation-resistant Ir/Re coating on C/C composites at ultra-high temperatures

Zhang

Zhu

2015

Rare Met.

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An iridium/rhenium (Ir/Re) double-layer coating was prepared on carbon/carbon (C/C) composites by chemical vapor deposition (CVD) and electrodeposition. The morphologies and bond strengths of the coatings on the C/C substrate were examined. The ablation resistance of the Ir/Re coating was studied at 1800°C in an oxyacetylene torch flame for 300 s. The results show that Re interlayer increases the bond strength between Ir coating and C/C substrate by over 100 %. During entire hightemperature ablation process, Ir/Re coating keeps intact without any signs of ablation damage. Ir coating gets smoother and the grain size becomes larger after ablation, with the preferred orientation changing from 311 h i to 220 h i: Although some voids are observed along the grain boundaries of the as-ablated Ir coating, Ir/Re coating keeps intact on C/C composites. The study indicates that Ir/Re coating can provide good ablation resistance up to 1800°C for C/C composites, especially for the continuous ablation applications.

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Section: Characterizationmentioning

confidence: 93%

Section: Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ablation-resistant Ir/Re coating on C/C composites at ultra-high temperatures

Zhang

Zhu

2015

Rare Met.

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“…It is thus one of the most promising candidates for protective coating of either structural carbons or Re-based components for extreme environments. 2,17,18 Iridium-coated Re nozzles are used in aerospace applications for small chemical rockets and resistojet thrusters. 19 A combustion chamber composed of Re substrate and Ir coating has been demonstrated to be stable for extended lifetimes at temperatures as high as 2,200 • C. 20,21 NASA has reported the development of Ircoated Re rocket chamber technology, allowing an increase in satellite life from 12 to 15 years, and gaining 30-60 M$ in the added revenue per satellite.…”

mentioning

confidence: 99%

The Effects of pH and Temperature on Electrodeposition of Re-Ir-Ni Coatings from Aqueous Solutions

Eliaz

Gileadi

2014

J. Electrochem. Soc.

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The Re-Ir system is of great interest for high-temperature applications and extreme environments. Here, Re-Ir-Ni alloy coatings were electroplated from aqueous solutions. The effects of pH and temperature on the faradaic efficiency (FE), chemical composition, surface morphology and crystallographic structure of the coatings were studied. The results show that the pH and temperature of electrolytes have a significant effect on the electrodeposition of Re-Ir-Ni. As the pH was increased from 2.0 to 8.0, the FE, partial current densities for deposition of the three metals, and deposition rate increased. The highest Re-content (82 at%) was obtained at pH = 2.5. At pH = 2.0, the coating consisted of an amorphous phase, and no cracking was observed. When raising the pH to 4.0 and above, crystalline phases (including hydrides) formed, and both columnar crystals and micro-cracks were observed. The bath temperature affected the surface crack density and the size of the grains that form the mesoscopic colonies. At the two lowest temperatures studied herein (50 and 60 • C), no codeposition of Ir was observed. The phase composition of the coating changed from amorphous Re-Ni at 50 • C; to amorphous Re-Ni, hcp-Ni and hexagonal Pure rhenium (Re) has high melting point (3,186• C), excellent wear resistance, and superior strength and ductility at elevated temperatures. In addition, it does not suffer from ductile-to-brittle transition, and it does not form carbides while having good mutual wettability with carbon. 1,2At present, the main manufacturing processes of Re and its alloys are powder metallurgy and chemical vapor deposition (CVD). 1-3In recent years, we have studied electroplating 4-12 and electroless plating 13,14 as alternative processes. Electrodeposition of pure Re was found to have a low faradaic efficiency (FE) and poor quality.4 Addition of iron-group metal salts to the plating bath results in the formation of Re-Me alloys (Me = Ni, Co or Fe) with high Re-content and at high FE, thus showing a catalytic effect of the iron-group metals on the electrodeposition of Re. 5,7 Rhenium and its alloys with iron-group metals tend to oxidize readily in moist air at temperatures above 600• C. 1,2 In order to protect them from high-temperature oxidation, a top coating such as rhodium (Rh) or iridium (Ir) is often applied. Iridium has high melting point (2,446• C) and excellent corrosion resistance. 15,16 Re and Ir show extensive mutual solubility and no intermetallic compounds in their binary phase diagram. Iridium can also act as an effective diffusion barrier for inward-diffusing oxygen and outward-diffusing carbon. It is thus one of the most promising candidates for protective coating of either structural carbons or Re-based components for extreme environments.2,17,18 Iridium-coated Re nozzles are used in aerospace applications for small chemical rockets and resistojet thrusters.19 A combustion chamber composed of Re substrate and Ir coating has been demonstrated to be stable for extended lifetimes at temperatures as high ...

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