Appeal No. 2002-0895
Application No. 09/402,552
reduction of surface oxides. By the same mechanism, some
oxide powders tend to reduce when sprayed in an inert
atmosphere.
Mills further states that the optimum spray conditions will vary
with the chemistry and the particle size of each spray material.
See page 364, column 3. Consistent with Mills’ and Boxall’s
teachings, Gruenr also teaches forming a 100% titanium diboride
coating or intermediate layer having the claimed thickness by
plasma spraying a spray powder having an optimum particle size of
25 micrometer maximum. See column 3, lines 41-60 and column 4,
lines 13-27. Specifically, Gruenr teaches (column 3, lines 53-
60) that:
The grade of sprayed powder is advantageously 25
:m maximum, which ensures that all spray powder
particles form the spray layer as molten drops not only
during the spraying of the coating layer of the
adherence layer but also particularly during the
spraying of the intermediate layer. In this way and
including the effect of the high mechanical impact
energy, the compactness of the spray layer is ensured.
Given the above circumstances, we concur with the examiner
that one of ordinary skill in the art would have been led to
plasma spray titanium diboride powder having the claimed
characteristics, including the optimum particle size, such as
that claimed, in an inert atmosphere chamber virtually free of
oxygen to form a spray powder coating of titanium diboride having
the claimed thickness, motivated by a reasonable expectation of
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