Spark plug with volume-stable electrode material
View Patent ↗A spark plug having one or more electrodes at least partially fabricated from an aluminum-containing Ni-based alloy. The alloy is a volume-stable alloy that includes a Ni 3 Al precipitate in a γ′-phase distributed in a Ni matrix γ-phase. The precipitate is formed in the alloy prior to the alloy being used to fabricate electrodes and thus prevents additional Ni 3 Al precipitate from being formed in the alloy once in service in a high-temperature environment. This, in turn, prevents a volume decrease of the alloy that may lead to an increased spark gap and spark plug malfunction. The volume-stable alloy may be made by solution treatment, quenching, and heat aging of a Ni—Cr—Al—Fe alloy.
1. A spark plug, comprising:
a metallic shell having an axial bore;
an insulator having an axial bore and being at least partially disposed within the axial bore of the metallic shell;
a center electrode being at least partially disposed within the axial bore of the insulator; and
a ground electrode being attached to a free end of the metallic shell;
wherein the center electrode, the ground electrode or both includes a nickel-based volume-stable alloy including nickel (Ni), aluminum (Al), and a pre-formed Ni 3 Al phase in an amount that does not substantially change when the volume-stable alloy is subsequently exposed to a high temperature environment of an internal combustion engine.
2. The spark plug of claim 1 , wherein nickel (Ni) is present in the volume-stable alloy in an amount of at least about 65.0 wt %.
3. The spark plug of claim 1 , wherein aluminum (Al) is present in the volume-stable alloy from about 4.0 wt % to about 8.0 wt %.
4. The spark plug of claim 1 , wherein the volume-stable alloy further comprises chromium (Cr) from about 12.0 wt % to about 20.0 wt %.
5. The spark plug of claim 1 , wherein the volume-stable alloy further comprises iron (Fe) from about 1.5 wt % to about 15.0 wt %.
6. The spark plug of claim 1 , wherein the volume-stable alloy further comprises cobalt (Co) up to about 20 wt %.
7. The spark plug of claim 6 , wherein the combined amount of cobalt (Co) and nickel (Ni) that is present in the volume-stable alloy is at least about 65.0 wt %.
8. The spark plug of claim 1 , wherein the pre-formed Ni 3 Al phase is present in the volume-stable alloy from about 20% to about 70% of the overall volume of the alloy.
9. The spark plug of claim 1 , wherein the pre-formed Ni 3 Al phase includes a Ni 3 Al precipitate as a γ′-phase that is dispersed within a Ni-based matrix and includes particles ranging in size from about 0.2 to about 4 μm.
10. The spark plug of claim 1 , wherein the volume-stable alloy includes at least 65.0 wt % Nickel (Ni), 4.0-8.0 wt % aluminum (Al), 12-20 wt % chromium (Cr), and 1.5-15.0 wt % iron (Fe).
11. The spark plug of claim 10 , wherein the volume-stable alloy further comprises at least one element selected from the group consisting of: yttrium (Y), lanthanum (La) or hafnium (Hf) up to about 1.0 wt %.
12. The spark plug of claim 10 , wherein the volume-stable alloy further comprises yttrium (Y) in an amount up to about 0.01 wt %.
13. The spark plug of claim 10 , wherein the volume-stable alloy further comprises at least one element selected from the group consisting of: manganese (Mn) in an amount less than about 1.0 wt %, silicon (Si) in an amount less than about 1.0 wt %, carbon (C) in an amount less than about 0.1 wt %, boron (B) in an amount less than about 0.03 wt %, or zirconium (Zr) in an amount less than about 0.5 wt %.
14. The spark plug of claim 1 , wherein an electrode that includes the volume-stable alloy does not undergo any substantial decrease in volume when the electrode is exposed to a high temperature environment of a combustion chamber in an internal combustion engine.
15. The spark plug of claim 1 , wherein the total amount of Ni 3 Al in the volume-stable alloy does not substantially increase over the amount of Ni 3 Al in the pre-formed Ni 3 Al phase when the electrode that includes the volume-stable alloy is exposed to a high temperature environment of a combustion chamber in an internal combustion engine.
16. The spark plug of claim 1 , wherein the center electrode, the ground electrode or both includes an attached firing tip that is made from the volume-stable alloy.
17. The spark plug of claim 1 , wherein the center electrode, the ground electrode or both is integrally formed from the volume-stable alloy such that the entire electrode is made of the volume-stable alloy.
18. A spark plug, comprising:
a metallic shell having an axial bore;
an insulator having an axial bore and being at least partially disposed within the axial bore of the metallic shell;
a center electrode being at least partially disposed within the axial bore of the insulator; and
a ground electrode being attached to a free end of the metallic shell;
wherein the center electrode, the ground electrode or both includes a nickel-based volume-stable alloy including a Ni-based matrix phase and a pre-formed Ni 3 Al precipitate phase dispersed within the Ni-based matrix phase.