MoSi2 coating on Mo substrate for short-term oxidation protection in air

Alam, Md. Zafir; Venkataraman, B.; Sarma, Bijoy; Das, Dipak K.

doi:10.1016/j.jallcom.2009.07.141

Cited by 77 publications

(36 citation statements)

References 17 publications

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“…Most refractory metallics show good temperature resistance only up to 1,200°C, although the tantalum alloys have service temperatures past 1,500°C. Environmental barrier coatings extend the serviceable temperature range of some refractory metallics [45], [46]. ________________________________________________________________________…”

Section: (B) Hot Structure Conceptsmentioning

confidence: 99%

Thermal Management at Hypersonic Leading Edges

Kasen

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The intense heat flux incident upon the leading edges of hypersonic vehicles traveling through the low earth atmosphere at speeds of Mach 5 and above requires creative thermal management strategies to prevent damage to leading edge components. Conventional thermal protection systems (TPSs) include the ablative coatings of NASA's Mercury, Gemini, and Apollo vehicles and the reusable reinforced carbon-carbon (RCC) system of the Space Shuttle Orbiter. The ablative approach absorbs heat by endothermic transformation (phase and/or chemical change to the polymeric coating). The heat is dissipated from the vehicle as the single-use coating eventually vaporizes. The RCC approach manages the intense heat by operating at high temperatures and radiating heat to its surroundings. The effectiveness of both approaches is predicated on keeping the heat flux that impinges upon the susceptible aluminum airframe below a critical level.ii ________________________________________________________________________ This dissertation has explored an alternative metallic TPS concept which seeks to redistribute the heat from the leading edge, thereby eliminating local hot spots. It makes use of high thermal conductance heat pipes coupled to the leading edge so that the thermal load may be redistributed from a high heat flux location (at the stagnation point) to regions where it can be effectively radiated from the vehicle. The sealed system concept is based upon the evaporation of a fluid near the heat source that sets up a region of elevated vapor pressure inside the pipe. The latent heat is transported down the resulting pressure gradient by the vapor stream where it condenses at cooler regions, releasing the heat for removal.Replenishment of the condensed working fluid to the evaporator region is accomplished through the capillary pumping action of a porous wick which lines the interior surface of the pipe.A design methodology for a wedge-shaped heat pipe is presented which uses a coupled flow-wall temperature model to construct design maps which relate design parameters of the leading edge system (overall length, wall thickness, and alloy) to its operating conditions (isothermal temperature, maximum temperature, maximum thermal stress). Potential bounds on heat transport due to physical phenomena linked to the sound speed within a chamber (sonic limit), capillarity, and boiling nucleation are considered by extending models developed for tube designs to the wedge geometry. A new heat flux limit is proposed which, should it be exceeded, subjects the leading edge to thermally-induced plastic deformation of the TPS. iii ________________________________________________________________________To investigate the validity of the design approach and thermal spreading effectiveness of the proposed concept, a low temperature wedge-shaped leading edge was designed and constructed using stainless steel as the case material and water as the working fluid. Under localized tip heating, the maximum temperatures were significantly reduced compa...

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Section: (B) Hot Structure Conceptsmentioning

confidence: 99%

Thermal Management at Hypersonic Leading Edges

Kasen

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“…Meanwhile, the unreacted SiO 2 was spontaneously converted into CaSiO 3 and Ca 3 Si 2 O 7 due to reaction (4) and (5). When the sample was electrolyzed at 3.1 V for 1 h, the products consisted of It was noted that there was no Si detected in the products during the entire electro-deoxidation process.…”

Section: Influence Of Electro-deoxidation Timementioning

confidence: 99%

“…Up to now, several techniques, such as pack cementation, plasma spraying, chemical vapor deposition, magnetron sputtering and molten salt method, have been adopted for preparing MoSi 2 coating [5][6][7]. Among them, the molten salt methods including electrochemical and diffusional synthesis (non-current transfer) are of some advantages due to the relatively lower operable temperatures ( o 1000 1C) [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

In-situ synthesis of MoSi2 coating on molybdenum substrate by electro-deoxidation of a SiO2 layer in molten salt

Dai

Zhou

et al. 2015

Ceramics International

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“…MoSi 2 is also capable of forming a protective SiO 2 scale at high temperatures at its surface [2]. MoSi 2 coatings are often used in high temperature structural applications owing to its outstanding high-temperature oxidation resistance [3]. Moreover, MoSi 2 is a good wear resistant material and well known for its applications in hightemperature corrosive and oxidative environments because of its high hardness and elastic modulus [4,5].…”

Section: Introductionmentioning

confidence: 99%