Tungsten and iridium multilayered structure by DGP as ablation-resistance coatings for graphite

Wu, Wangping; Chen, Zhaofeng; Cheng, Han; Wang, Liangbing; Zhang, Ying

doi:10.1016/j.apsusc.2011.03.108

Cited by 31 publications

(10 citation statements)

References 32 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: 94%

“…The interlayer material should be compatible with both Ir and C/C chemically and physically. Wu et al [13] selected tungsten (W) as the interlayer between Ir and graphite to enhance the adhesion of Ir coating on carbonaceous material, and compared the ablation resistance between W/Ir multilayer coating and Ir single-layer coating on the graphite substrates at 2000°C. The ablation test results showed an improved ablation resistance of the W/Ir multilayer coating compared with that of the Ir single layer.…”

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: 94%

Section: Introductionmentioning

confidence: 99%

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

Zhang

Zhu

2015

Rare Met.

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“…In previous publications, thermal stability and oxidation resistance of the Ir coating by a double glow plasma process on refractory materials were studied. After high‐temperature treatment at 1400 °C under an inert atmosphere, micropores and microbubbles appeared on the surface of the coating.…”

Section: Introductionmentioning

confidence: 99%

“…After high‐temperature treatment at 1400 °C under an inert atmosphere, micropores and microbubbles appeared on the surface of the coating. After high‐temperature treatment at 2000 °C under an oxyacetylene flame, micropores were still formed on the surface of Ir coating, which could provide pathways for oxygen to attack the substrates. To date, Reed et al have claimed that CVD is the only established process for the fabrication of Ir‐coated Re combustion chambers.…”

Section: Introductionmentioning

confidence: 99%

Micropore formation mechanism in iridium coating after high‐temperature treatment

Chen

2016

Surface & Interface Analysis

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Noble metal iridium is of great interest for high-temperature applications and extreme environments. A high (110)-oriented iridium coating was prepared by a double glow plasma process on the surface of niobium substrate. The morphology and composition of the coating were determined by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, respectively. The phase of the coating was identified by X-ray diffraction analysis. The misorientation angle distributions of grains on the surface and cross section of the coating were characterized by electron backscatter diffraction system. The uniform and pure iridium coating consisted of the submicrometer-sized columnar grains with high-angle boundary. The mean misorientation angles on the surface and cross section of the coating were 38.6°and 45.6°, respectively. After hightemperature treatment, the coating was composed of equiaxed grains with distinct grain boundaries. Micropores appeared on the fracture surface of the coating. The micropore formation mechanism in Ir coating after high-temperature treatment was investigated.

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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.…”

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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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Tungsten and iridium multilayered structure by DGP as ablation-resistance coatings for graphite

Cited by 31 publications

References 32 publications

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

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

Micropore formation mechanism in iridium coating after high‐temperature treatment

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

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