Growth of intermetallic layers in the iridium-molybdenum system

Growth of intermetallic layers between molybdenum and an iridium alloy (Ir-0.3 wt.%W-0.006 wt.%Th-0.005 wt.%Al) has been evaluated over the temperature range 1473–1748 K, in argon and in vacuum. Two intermetallic layers, with compositions corresponding to IrMo and Ir 3Mo, are formed over the entire...

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Bibliographic Details
Published in:Journal of alloys and compounds 1991-12, Vol.177 (2), p.219-227
Main Authors: Ohriner, E.K., George, E.P.
Format: Article
Language:English
Subjects:
Applied sciences
Chemical interdiffusion
diffusion barriers
Condensed matter: structure, mechanical and thermal properties
Diffusion in solids
Exact sciences and technology
Metals. Metallurgy
Physics
Transport properties of condensed matter (nonelectronic)
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Summary:Growth of intermetallic layers between molybdenum and an iridium alloy (Ir-0.3 wt.%W-0.006 wt.%Th-0.005 wt.%Al) has been evaluated over the temperature range 1473–1748 K, in argon and in vacuum. Two intermetallic layers, with compositions corresponding to IrMo and Ir 3Mo, are formed over the entire temperature range. The two layers have approximately equal thicknesses, and the total layer thickness formed during a 4 h exposure can be expressed as t=1200 exp(- Q/ RT), where t is the total thickness of the intermetallic layers in micrometers, Q=64 kJ mol −1, R is the gas constant, and T is the absolute temperature. Vapor-phase transport of molybdenum (as MoO 3) is suggested as a possible mechanism for the growth of these intermetallic layers in (oxygen-contaminated) argon. There was no indication of molybdenum transport through the iridium alloy grain boundaries in advance of the intermetallic layer interface. The resistance of these intermetallies to attack by several acids and acid mixtures is similar to that of iridium.
ISSN:0925-8388
1873-4669
DOI:10.1016/0925-8388(91)90075-7