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Oxidation resistance comparison of MoSi 2 and B‐modified MoSi 2 coatings on pure Mo prepared through pack cementation
Author(s) -
Tian X. D.,
Guo X. P.,
Sun Z. P.,
Qu J. L.,
Wang L. J.
Publication year - 2015
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201407631
Subject(s) - cementation (geology) , coating , materials science , layer (electronics) , isothermal process , substrate (aquarium) , diffusion , chemical engineering , metallurgy , composite material , cement , oceanography , physics , engineering , thermodynamics , geology
A MoSi 2 coating and a B‐modified MoSi 2 coating were prepared on pure Mo by halide activated pack cementation (HAPC) method. The B‐modified MoSi 2 coating consisted of a thick MoSi 2 outer layer with MoB precipitates distributed in its inner part, a Mo 5 Si 3 second layer, a MoB third layer, and a Mo 2 B inner layer. Both coatings were oxidized isothermally at 873, 1523, and 1773 K. It was found that pest oxidation did not occur in both coatings at 873 K for full cover scales could form on their surfaces after 100 h oxidation. During oxidation, B atoms in the B‐modified MoSi 2 coating diffused outward to the coating surface and oxidized to low viscose B 2 O 3 , which promoted the formation of full cover scale and significantly reduced the volatilization of MoO 3 at 1523 K, while that effect was negligible at 1773 K for silica had good fluidity at such a high temperature. It was also found that the MoB layer of the B‐modified MoSi 2 coating retarded the inward diffusion of Si from MoSi 2 to the substrate, which could increase the coating oxidation‐resistant lifetime.