Structure, mechanical properties, and oxidation behavior of nanolayered MoSi{sub 2}/SiC coatings
- Technical Research Centre of Finland, Espoo (Finland)
- Helsinki Univ. (Finland). Dept. of Physics
- Los Alamos National Lab., NM (United States)
Structure, hardness, elastic properties, and oxidation of nanolayered MoSi{sub 2}/SiC were examined. DC-magnetron and rf -diode sputtering were used to deposit MoSi{sub 2} and SiC, respectively. Total number of sublayers of each kind was 90. Nominal thickness of MoSi{sub 2} sublayers was 10 and that of SiC 3 nm. As-deposited microstructure was amorphous whereas annealing at 500C for 1 h resulted in transformation of MoSi{sub 2} into C40 type hexagonal structure. However, silicon carbide remained still amorphous. Hardness of 11.6 and 20.8 GPa were obtained for as-deposited and annealed structure; Young moduli were 220 and 290 GPa, which yield 232 and 332 GPa for Young moduli of amorphous and crystalline MoSi{sub 2}. Oxidation tests were carried out in wet conditions at 400 and 500C; degree of oxidation was determined using the reaction {sup 16}O(d,p){sup 17}O at 950 keV. The MoSi{sub 2}/SiC coating gave a good protection against oxidation for unalloyed steel. As compared to a single MoSi{sub 2} coating, a slightly higher degree of oxidation and a significantly different mechanism of oxidation was observed. This was also supported by secondary ion mass spectroscopy. Cracking of the coating caused by a thermal mismatch and transformation stresses was worse in the case of the single MoSi{sub 2} layer than in the case of the composite coating. Thus cracking of the coating can be significantly reduced by using a nanolayered structure.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10121339
- Report Number(s):
- LA-UR-92-4298; CONF-921101-50; ON: DE93005472
- Resource Relation:
- Conference: 16. Materials Research Society (MRS) fall meeting,Boston, MA (United States),30 Nov - 5 Dec 1992; Other Information: PBD: [1992]
- Country of Publication:
- United States
- Language:
- English
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