Microstructure and growth kinetics of the Mo5Si3 and Mo3Si layers in MoSi2/Mo diffusion couple

Yoon, Jin‐Kook; Lee, Jong‐Kwon; Lee, Kyunghwan; Byun, Ji Young; Kim, Gyeung-Ho; Hong, Kwangjoon

doi:10.1016/s0966-9795(03)00068-2

Cited by 53 publications

(33 citation statements)

References 17 publications

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“…The growth kinetics of the Mo 5 Si 3 layer in the ternary Mo-Si-B system appears to be slower than in the binary Mo-Si system. The activation energy for the growth is calculated as about 310 kJ/mol, which is similar to the values (297-360 kJ/mol) reported for the binary Mo-Si system [5][6][7][8][9][10], while is higher than the value of 220 kJ/mol for MoSi 2 /Mo-9Si-18B [3]. Fig.…”

Section: Growth Rate Of Mo 5 Si 3 and Mobcmo 5 Si 3 Two-phase Layerssupporting

confidence: 85%

Reaction diffusion of MoSi2 and Mo5SiB2

2005

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Section: Growth Rate Of Mo 5 Si 3 and Mobcmo 5 Si 3 Two-phase Layerssupporting

confidence: 85%

Reaction diffusion of MoSi2 and Mo5SiB2

2005

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“…Then, interface 2 shifts to the two-phase side. When 1 mol of MoSi 2 decomposes, the thickness increment of both the T 1 and MoB ϩ T 1 layers is found to be 6.6 ϫ 10 Ϫ5 m. [20] Note that the increase in thickness of the layer of unit area is given by aV T 1 /(1 m 2 ), where a is the number of mols of T 1 and V T 1 is the molar volume of T 1 . For the reaction diffusion between MoSi 2 and Mo-9Si-18B(T 2 ϩ Mo ss ), the reaction at interface 1Ј is identical to the reaction at interface 1 of the MoSi 2 /T 2 system.…”

Section: E Quantitative Modeling Of the Reaction Diffusion Processmentioning

confidence: 96%

“…The growth rate constant of T 1 is found to be about 0.43, 1.4, and 2.9 ϫ 10 Ϫ14 m 2 /s at 1300 °C, 1400 °C, and 1500 °C, respectively. [15] Figure 6 shows their Arrhenius plots, together with the results of earlier studies in the binary Mo-Si system [17][18][19][20][21][22] for comparison. The values of the present study fall at the lower bound of the data for the binary Mo-Si system reported by Tortorici.…”

Section: Reaction Diffusion Of Mosi 2 /(Mo 5 Sib 2 ϩ Mo Ss )mentioning

confidence: 99%

“…The activation energy for the growth is calculated as about 220 kJ/mol, which is lower than the values (297 to 360 kJ/mol) reported in the earlier studies. [17][18][19][20][21][22] However, this result may be affected by insufficient data over a narrow temperature range. Figure 7(a) shows a sample current image of a vertical cross section of a specimen pack cemented for 48 hours and oxidized at 1500 °C in air for 12 hours and (b) EPMA concentration profiles in the diffusion direction.…”

Section: Reaction Diffusion Of Mosi 2 /(Mo 5 Sib 2 ϩ Mo Ss )mentioning

confidence: 99%

“…[13] Experimental diffusion paths for the MoSi 2 /Mo 5 SiB 2 (T 2 ) and MoSi 2 /Mo-9Si-18B systems annealed at high temperatures around 1500 °C, as indicated by solid and broken lines, respectively. [20] D. Reaction Diffusion of MoSi 2 /Mo 5 SiB 2 In order to understand the microstructural evolution described more quantitatively, we have studied phase transformations in a simpler system MoSi 2 vs T 2 than the system MoSi 2 vs T 2 ϩ Mo ss , using diffusion couples made of bulk materials. [26] Figure 9(a) shows a backscattered electron (BSE) image of a vertical cross section of a MoSi 2 /T 2 diffusion couple after annealing at 1500 °C for 12 hours.…”

Section: Reaction Diffusion Of Mosi 2 /(Mo 5 Sib 2 ϩ Mo Ss )mentioning

confidence: 99%

See 2 more Smart Citations

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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Magnetron Sputtered Silicon Coatings as Oxidation Protection for Mo‐Based Alloys

et al. 2020

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Mo‐based alloys with solidus temperatures around and above 2000 °C are attractive high‐temperature structural materials for future applications in the hot section of gas turbines. However, their oxidation behavior is poor due to pesting starting at 600 °C and nonprotective oxide growth at temperatures above 1000 °C. To ensure a sufficient oxidation resistance over a wide temperature range, protective coatings become inevitable. Herein, silicon coatings have been applied by magnetron sputtering on Mo‐9Si‐8B and on titan–zirconium–molybdenum alloy (TZM). The coating architecture is designed to minimize the intercolumnar gaps and porosity, thereby increasing the density. Specimens are tested at 800 and 1200 °C in air isothermally for up to 300 h. The focus is put on the chemical reactions at the coating–substrate interface, the phase formation, and the evolution of the thermally grown oxide. An initially globular SiO2 evolves into a uniform SiO2 layer providing excellent oxidation protection. The investigations reveal a rather slow interdiffusion between the coating and the alloys when tested in air. At the coating–substrate interface exclusively, the Mo3Si phase develops. Finally, the phase formation at the coating–substrate interface is studied in detail for various heat treatments in air and vacuum.

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Microstructure and growth kinetics of the Mo5Si3 and Mo3Si layers in MoSi2/Mo diffusion couple

Cited by 53 publications

References 17 publications

Reaction diffusion of MoSi2 and Mo5SiB2

Reaction diffusion of MoSi2 and Mo5SiB2

Oxidation protective silicide coating on Mo-Si-B alloys

Magnetron Sputtered Silicon Coatings as Oxidation Protection for Mo‐Based Alloys

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