Cermet composites, process for producing them and arc tube incorporating them
AssigneeNorth American Philips Lighting Corporation
InventorsDeborah P. Partlow, Shih-Ming Ho
Life of this patent
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Abstract
Composite cermets having a central core of a first cermet composition and one or more surrounding layers of different cermet compositions are formed by a multi-step pressing operation, followed by sintering. A tungsten/alumina or molybdenum/alumina composite cermet is useful as an end closure for alumina arc tubes of metal halide discharge lamps.
Claims12
A composite sintered cermet body comprising a core portion of a first cermet composition having a central axis, and one or more layers of other cermet compositions surrounding the core and substantially coaxial therewith, the top and bottom surfaces being substantially planar and normal to the axis.
A composite sintered cermet body having a central axis, planar top and bottom surfaces normal to the axis, and an annular outer wall surrounding the axis, characterized in that the composition of the cermet changes substantially continuously, radially outward from the central axis to the outer wall.
A process for producing a composite cermet body, comprising the steps of:
- (1) pressing a first cermet powder composition to form a powder compact having a central cavity opening into the top and bottom surfaces of the compact;
- (2) filling the cavity with a second cermet powder composition;
- (3) pressing the powder filled compact to form a green composite;
- and
- (4) sintering the composite to form an integral cermet body.
Dependencies are inferred from the claim text.