In-situ synthesis and rapid consolidation of fully dense MoSi[sub 2]

Journal Article · Fri Jan 01 04:00:00 EST 1993 · JOM (Journal of the Minerals, Metals and Materials Society); (United States)

DOI:https://doi.org/10.1007/BF03223368· OSTI ID:6859687

Raman, R V; Rele, S V; Paskowitz, M J ^[1]

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1. Ceradon Inc. (United States)

Molybdenum disilicide (MoSi[sub 2]) is emerging as a high-temperature material of significant technical interest because of its unique combination of high-temperature oxidation resistance, outstanding corrosion resistance, and high melting point. Its outstanding oxidation resistance is due to the formation of a glassy silica phase on the surface that acts as a protective layer at higher temperatures. However, a number of issues impede the use of MoSi[sub 2] in structural applications. Above the brittle-to-ductile transition temperature, MoSi[sub 2] behaves as a metal but loses strength and undergoes creep and plastic deformation. Synthesis of MoSi[sub 2] is an expensive and lengthy process involving sintering or hot pressing in high-temperature furnaces. Such processing unavoidably results in the formation of a grain-boundary silica phase that degrades the mechanical properties at both ambient and elevated temperatures. Conventional processing techniques, such as hot pressing and hot isostatic pressing (HIPing), require expensive dies, canning materials, long cycle times, and are not cost-effective or energy efficient. Extended high-temperature exposure during processing results in a less-than-optimum microstructure. MoSi[sub 2] also pests, disintegrating rapidly during oxidation at temperatures around 500[degrees]C. However, pesting does not occur in materials with a density greater than 98% of the theoretical. To overcome some of the drawbacks of high processing costs and long processing times, the use of self-propagating, high-temperature synthesis (SHS) to fabricate MoSi[sub 2] from elemental molybdenum and silicon powders has been explored. An advantage of the SHS process is that higher phase purities compared to conventional synthesis are achieved. However, porosity values of up to 50% persist in SHS-processed samples.

• OSTI ID: 6859687
• Journal Information: JOM (Journal of the Minerals, Metals and Materials Society); (United States), Journal Name: JOM (Journal of the Minerals, Metals and Materials Society); (United States) Vol. 45:1; ISSN JOMMER
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
360103 -- Metals & Alloys-- Mechanical Properties
CREEP
FABRICATION
FURNACES
HOT PRESSING
MATERIALS WORKING
MECHANICAL PROPERTIES
MOLYBDENUM COMPOUNDS
MOLYBDENUM SILICIDES
PRESSING
REFRACTORY METAL COMPOUNDS
SILICIDES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS