PROTECTION OF MOLYBDENUM FROM OXIDATION BY MOLYBDENUM DISILICIDE BASED COATINGS
Vapor-deposited molybdenum disilicide coatings on molybdenum prevented oxidation for 200 hr at 1450 deg C and similar ones were still protective after six months at 1000 deg C. This protection was reduced to three hours under thermal cycling between 1000 and 20 deg C. By adding either iron or chromium to the silicide the cyclic life was trebled, with no effect on the above resistance at 1000 deg C, though at 1450 deg C it was reduced to 20--80 hr. Failure in the thermal cycling test was due to cracks propagating through the coating, whereas failure under stable conditions occorred when the disilicide was replaced by the less oxidation-resistant silicides Mo/sub 3/Si and Mo/sub 5/Si/sub 3/. Maximum cycling resistance was obtained with silicide coatings approximately 30 mu thick, though for static conditions the thicker the coating the longer the life. The cycling resistance was unaffected either by the preparation of the molybdenum surface prior to the coating or by the coating structure, but lowering the preparation temperature improved it. (auth)
- Research Organization:
- Royal Armament Research and Development Establishment, Fort Halstead, Eng.
- NSA Number:
- NSA-18-012586
- OSTI ID:
- 4113657
- Journal Information:
- J. Less-Common Metals, Vol. Vol: 6; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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