Method of fabricating an interconnect for a fuel cell stack
Methods for fabricating an interconnect for a fuel cell stack that include providing a protective layer over at least one surface of an interconnect formed by powder pressing pre-alloyed particles containing two or more metal elements and annealing the interconnect and the protective layer at elevated temperature to bond the protective layer to the at least one surface of the interconnect.
1. A method of fabricating an interconnect for a fuel cell stack, comprising:
providing a first metal powder comprising at least one first metal material in a die cavity of a powder press apparatus;
providing a second metal powder comprising at least one second metal material in the die cavity of the powder press apparatus, wherein the at least one second metal material is different than the at least one first metal material;
compressing the first metal powder and the second metal powder in the powder press apparatus to form a pressed powder interconnect having a layer of the second metal material over a layer of the first metal material; and
subjecting the pressed powder interconnect to an oxygen-containing environment at an elevated temperature to oxidize at least a portion of the at least one second metal material and form a metal oxide protective layer over a surface of the pressed powder interconnect.
2. The method of claim 1 , wherein the first metal material of the first metal powder comprises at least about 90 wt % of chromium.
3. The method of claim 2 , wherein the first metal material of the first metal powder comprises greater than 0 wt % and less than about 10 wt % of iron.
4. The method of claim 3 , wherein the first metal material of the first metal powder comprises at least one of:
(a) a mixture of elemental chromium powders and elemental iron powders; and
(b) pre-alloyed particles comprising chromium and iron.
5. The method of claim 2 , wherein the second metal powder is comprised of the second metal material comprising manganese and cobalt, and the second metal material is oxidized to form a manganese cobalt oxide protective layer over a surface of the pressed powder interconnect.
6. The method of claim 5 , wherein the second metal material of the second metal powder comprises at least one of:
(a) a mixture of elemental manganese powders and elemental cobalt powders; and
(b) pre-alloyed powders comprising manganese and cobalt.
7. The method of claim 5 , wherein the second metal material is substantially completely oxidized to form the manganese cobalt oxide protective layer over a layer of the first metal material.
8. The method of claim 7 , wherein subjecting the pressed powder interconnect to the oxygen-containing environment at the elevated temperature oxidizes at least a portion of an interior volume of the layer of first metal material to reduce a porosity of the interconnect.
9. The method of claim 5 , wherein the second metal material is partially oxidized such that a layer of the second metal material comprising manganese and cobalt is located between the manganese cobalt oxide protective layer and a layer of the first metal material.
10. The method of claim 1 , wherein subjecting the pressed powder interconnect to an oxygen-containing environment comprises:
incorporating the pressed powder interconnect into a fuel cell stack; and
annealing the interconnect at the elevated temperature in the oxygen containing environment in the fuel cell stack to form the protective layer.
11. The method of claim 10 , wherein:
the pressed powder interconnect is incorporated into a fuel cell stack without first sintering the pressed powder interconnect; and
the pressed powder interconnect has a cathode side comprising ribs and gas flow channels and an opposing anode side comprising ribs and gas flow channels.
12. The method of claim 1 , wherein the first metal powder and the second metal powder are compressed using high velocity compaction.
13. The method of claim 12 , wherein the pressed powder interconnect formed by high velocity compaction is incorporated into a fuel cell stack without first sintering the pressed powder interconnect.