Bond layer for silicon containing substrate

Details Bond layer for silicon containing substrate Bond layer for silicon containing substrate

2003-05-22

2004-08-17

McNeil, Jennifer (Department: 1775)

Stock material or miscellaneous articles

Composite

Of silicon containing

C428S446000, C428S701000, C428S702000, C428S325000, C428S697000, C428S699000, C428S293100, C416S24100B

Reexamination Certificate

active

06777093

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is drawn to an environmental barrier coating and, more particularly, an environmental barrier coating applied to a silicon containing substrate.
Silicon based ceramics exhibit accelerated oxidation rates in high temperature, aqueous environments such as for example, the combustor and turbine sections of gas turbine engines. In order to reduce the rate of oxidation on silicon based substrates used as ceramic components in such environments, significant effort has been given to providing environment barrier coating, i.e., barrier layer(s), for the silicon based substrates so as to increase the service life of such component parts.
With reference to
FIGS. 1
a
and
1
b
, prior art environmental barrier coatings form a composite
10
comprising a silicon based substrate
12
, a bond coat or layer
14
which comprises a dense continuous layer of silicon metal, a barrier layer
16
which comprises either an alkaline earth aluminosilicate based on barium and strontium, or a yttrium silicate and a top coat or layer
18
which comprises a refractory oxide and/or silicate or other metal oxide such as, for example, zirconium oxide. In addition, an intermediate layer
20
may be provided between the
14
bond coat and the barrier
16
and/or between the barrier layer
16
and top layer
18
. The intermediate layer comprises, for example, a mixture of the barrier layer material with an additional oxide such as mullite. These prior art environmental barrier systems have proved to be protective with respect to oxidation of the silicon based substrate and, in addition, adherent. However, it has now been found that certain mechanical properties of the silicon substrate suffer as demonstrated by a significant reduction in 4-point bend strength at room temperature. It is believed that the loss of mechanical properties results from the cracking of the bond layer adjoining the silicon containing substrate which causes stress concentrations which initiate cracks in the substrate itself. The cracks in the bond coat or layer arise from many causes including differences in the coefficient of thermal expansion between the substrate and bond layer and stresses introduced as a result of rapid cyclic cooling and heating of the component parts.
Naturally, it would be highly desirable to provide an improved bond coat layer for silicon containing substrates which do not result in significant loss of mechanical properties.
Accordingly, it is a principle object of the present invention to provide an improved bond layer for an environmental barrier coating which overcomes the foregoing prior art problems.
SUMMARY OF THE INVENTION
The foregoing object is achieved by way of the present invention wherein a bond layer for a silicon based substrate comprises a silicon layer having a dispersion of particulate material therein, wherein the particulate material is selected from the group consisting of (1) alumina, (2) yttria, (3) aluminum silicate, (4) compounds of rare earth elements, alkaline earth elements, aluminum, oxygen, yttrium, nitrogen, niobium, tantalum, hafnium, zirconium, carbon, silicon and mixtures thereof.
A particular advantage of the present invention is that the fracture toughness of the bond layer, or any other layer in which the particulates are introduced, is improved. In addition, as a particulate material can be in the form of particles, fibers, whiskers and mixtures thereof, the fibers can be located and oriented within a bond layer and any other layer of an environmental barrier coating based on the end use application.
The particulate material may be applied by any method known in the prior art. Such as, for example, a thermal spray method.
Further objects and advantages will appear hereinbelow.


REFERENCES:
patent: 5110652 (1992-05-01), Allaire et al.
patent: 6254935 (2001-07-01), Eaton et al.
patent: 6284325 (2001-09-01), Eaton, Jr. et al.
patent: 6296942 (2001-10-01), Eaton, Jr. et al.
patent: 6299988 (2001-10-01), Wang et al.
patent: 6312763 (2001-11-01), Eaton, Jr. et al.
patent: 6352790 (2002-03-01), Eaton et al.
patent: 6365288 (2002-04-01), Eaton et al.
patent: 6410148 (2002-06-01), Eaton, Jr. et al.
patent: 6444335 (2002-09-01), Wang et al.
patent: 6541134 (2003-04-01), Strangman et al.
patent: 2002/0025454 (2002-02-01), Wang et al.

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