Oxidation behavior of Mo–9Si–18B alloy pack-cemented in a Si-base pack mixture

Ito, Kazuhiro; Murakami, Takashi; Adachi, Kohsuke; Yamaguchi, M.

doi:10.1016/s0966-9795(03)00074-8

Cited by 38 publications

(32 citation statements)

References 17 publications

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“…Details about the HAPC method are described elsewhere. [10] Successful coating as an oxidation protective layer was checked by a preliminary oxidation at 1300 °C in air for 12 hours so as to confirm there were no obvious cracks, and no appreciable weight gain or loss occurred. After this check, isothermal oxidation was conducted at 1300 °C and 1500 °C in both flowing dry air (1 L/h) for 50 hours using a SETARAM TG96 hightemperature thermogravimeter and also in static air for 12 to 100 hours using an ADVANTEC KB1701 high-temperature electric furnace.…”

Section: A Sample Preparations and High-temperature Oxidation/annealingmentioning

confidence: 99%

“…[10] The results of these tests are shown in Figure 2. A steady-state weight gain was observed at 1300 °C and 1500 °C and the steady-state constants were obtained by fitting the mass change curve to the parabolic law.…”

Section: A Isothermal Oxidation Behavior Of Pack-cemented Mo-9si-18bmentioning

confidence: 99%

“…As a strategy of coating Mo-9Si-18B alloys with a MoSi 2 layer, we have chosen a halide-activated pack cementation (HAPC) method. [10] Halideactivated pack cementation is a well established chemical vapor deposition technique, which has been widely used for producing high-temperature protective diffusion coatings on superalloys and TiAl alloys. [11,12] The schematic Mo-Si-B phase diagram (based on Sakidja et al [13] ) ( Figure 1) suggests that silicon deposition onto Mo-9Si-18B is the simplest way for the successive formation of MoSi 2 and B-doped T 1 phase layers on the matrix.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation protective silicide coating on Mo-Si-B alloys

Ito

Numakura

Hayashi

et al. 2005

Metall Mater Trans A

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A MoSi 2 coating was successfully formed on a Mo-9Si-18B alloy, consisting of Mo 5 SiB 2 (T 2 ) and Mo solid solution (Mo ss ) phases, using pack cementation with Si. Isothermal and cyclic oxidation tests of pack-cemented Mo-9Si-18B alloys were performed at 1300 °C and 1500 °C. Steady-state oxidation rates at both temperatures are almost equal to those of pure MoSi 2 . The MoSi 2 layer is completely transformed into Mo 5 Si 3 (T 1 ) containing B after oxidation at 1500 °C for 24 hours. Thermal expansion of the T 1 phase is anisotropic, but a [001] texture in the growth direction for the columnar grains in the T 1 layer reduces thermal stresses generated around the phases. Evolution of T 1 layers during oxidation between 1300 °C and 1500 °C was investigated; their growth rate constants and the interdiffusion coefficient of Mo and Si in the Mo-Si-B system have been evaluated and compared with those in the binary Mo-Si system. Furthermore, we have studied phase transformations in a simpler system MoSi 2 vs T 2 using MoSi 2 /T 2 diffusion couples. Layers of T 1 and MoB ϩ T 1 were formed in the diffusion zone during oxidation at temperatures between 1400 °C and 1600 °C. This behavior is different from that of the pack-cemented Mo-9Si-18B alloy. Pack-cemented T 2 single crystals show a diffusion structure similar to that of MoSi 2 /T 2 diffusion couples, but the ratio of layer thickness is different. Based on these diffusion results, a method for extending the lifetime of the MoSi 2 layer is proposed.

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Section: A Sample Preparations and High-temperature Oxidation/annealingmentioning

confidence: 99%

Section: A Isothermal Oxidation Behavior Of Pack-cemented Mo-9si-18bmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxidation protective silicide coating on Mo-Si-B alloys

Ito

Numakura

Hayashi

et al. 2005

Metall Mater Trans A

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“…[1][2][3][4][5][6][7][8][9][10] These studies were usually performed in air or pure oxygen and showed that the boron and silicon in such alloys can produce a passivating borosilicate layer under high-temperature oxidation conditions. The properties of such borosilicate layers depend upon the amounts of silicon and boron in these layers.…”

Section: Introductionmentioning

confidence: 99%

The development of protective borosilicate layers on a Mo-3Si-1B (weight percent) alloy

Helmick¹,

Meier

Pettit

2005

Metall Mater Trans A

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Molybdenum-based alloys with the addition of small amounts of silicon (2 to 4.5 wt pct) and boron (ϳ1 wt pct) can form a passivating layer that protects the alloy from further rapid oxidation. When such molybdenum-based alloys are exposed to oxidizing environments at high temperatures, a borosilicate glass layer can form that will reduce the transport of oxygen to the alloy to limit further oxidation. Oxidation is then controlled by diffusion through the borosilicate glass layer. The focus of this research was to study the development of the borosilicate layer on a Mo-3Si-1B (wt pct) alloy. The oxidation of this alloy was studied in a variety of gas environments over a range of temperatures in order to elucidate the critical factors that allow it to develop a protective borosilicate glass layer. The borosilicate glass layer is protective when no continuous channels exist in the layer extending from the gas interface to the alloy interface. The borosilicate layer is believed to contain channels in the early stages of development, and the elimination of the channels is obtained by appropriate control of the temperature and gas-flow conditions, whereby MoO 3 is removed via vaporization while the borosilicate viscosity is not increased due to loss of B 2 O 3 . Once the borosilicate layer is continuous and free of channels, subsequent oxidation occurs by inward diffusion of oxygen and outward diffusion of molybdenum through this layer, with vaporization of MoO 3 occurring at the gas/borosilicate-layer interface and MoO 2 and additional borosilicate forming at the alloy/MoO 2 interface.

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“…Owing to low cost, simplicity and practicability, pack cementation process has been extensively studied and widely used to form different diffusion coatings. [5][6][7][8][9][13][14][15][16][17][18] In the present paper NbSi 2 coatings were formed on pure niobium by halide-activated pack cementation process. Emphasis was placed on the effect of copper addition in pack mixture on the growth rate, morphology, microstructure and phase composition of the coating.…”

Section: Introductionmentioning

confidence: 99%

Effect of Copper Addition on the Niobium Disilicide Coatings by Pack Cementation

Song

et al. 2004

Mater. Trans.

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NbSi 2 coatings were deposited on pure niobium by halide-activated pack cementation method. The effect of copper addition in pack mixture on the siliconizing process was investigated. After siliconizing on niobium at 1050 C for 2 h using a pack mixture composed of Si, NaF and SiC, a single phase of hexagonal NbSi 2 coating was formed. The addition of copper in pack mixture not only increased the growth rate of the coatings, but also led to form a very thin interlayer between the NbSi 2 coating and the niobium substrate.

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Oxidation behavior of Mo–9Si–18B alloy pack-cemented in a Si-base pack mixture

Cited by 38 publications

References 17 publications

Oxidation protective silicide coating on Mo-Si-B alloys

Oxidation protective silicide coating on Mo-Si-B alloys

The development of protective borosilicate layers on a Mo-3Si-1B (weight percent) alloy

Effect of Copper Addition on the Niobium Disilicide Coatings by Pack Cementation

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