| 摘要 |
Articles, such as machine components used in for example gas turbine engine combustion liners, shroud, nozzles or blades, heat exchangers and internal combustion engines, for use in high temperature environments containing water vapour have a substrate (20) containing silicon, a bondcoat (30) comprising silicon, an intermediate barrier (40) comprising at least one layer (70) comprising at least one rare earth silicate and being substantially free of mullite and a topcoat (50) comprising a rare-earth monosilicate. The substrate may be silicon nitride, molybdenum disilicide and silicon nitride e.g. silicon carbide matrix reinforced with silicon carbide fibres. The bondcoat may be elemental silicon, silica or a silicide. The rare earth silicate of the layer(s) of the intermediate coat may comprise monosilicate, disilicate, orthosilicate, metasilicate, polysilicate or apatite phase. The intermediate layer may comprise a first layer comprising at least one of lutetium disilicate, ytterbium disilicate and yttrium disilicate and a second layer comprising at least one of lutetium disilicate, ytterbium disilicate and yttrium disilicate and at least one of lutetium monosilicate, ytterbium monosilicate and yttrium monosilicate and the topcoat may comprise at least one of lutetium monosilicate, ytterbium monosilicate and yttrium monosilicate The intermediate layer may comprise a single layer having a compositional gradient, a concentration of the monosilicate increasing as a function of distance in a direction away from the substrate towards the topcoat..
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