Electrode material for a spark plug

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;
• the center electrode, the ground electrode or both includes an electrode material having a refractory metal and a precious metal, wherein the refractory metal is the single largest constituent of the electrode material on a wt % basis, and the electrode material includes a protective surface layer where the refractory metal has volatized or evaporated and the precious metal has formed a stable oxide.

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;
• the center electrode, the ground electrode or both includes an electrode material having a refractory metal and a precious metal, wherein the refractory metal is the single largest constituent of the electrode material on a wt % basis, and the electrode material includes tungsten (W) from about 50 wt % to about 99 wt %, inclusive, and rhodium (Rh) from about 1 wt % to about 50 wt %.

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;
• the center electrode, the ground electrode or both includes an electrode material having a refractory metal and a precious metal, wherein the refractory metal is the single largest constituent of the electrode material on a wt % basis, and the electrode material includes ruthenium (Ru) from about 50 wt % to about 99 wt %, inclusive, and rhodium (Rh) from about 1 wt % to about 50 wt %.

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;
• the center electrode, the ground electrode or both includes an electrode material having a refractory metal and a precious metal, wherein the refractory metal is the single largest constituent of the electrode material on a wt % basis, and the electrode material further includes at least one grain stabilizer selected from the group consisting of:
• yttrium (Y), niobium (Nb), tantalum (Ta) or hafnium (Hf).

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;
• the center electrode, the ground electrode or both includes an attached firing tip that is at least partially made from an electrode material having a refractory metal and a precious metal, wherein the refractory metal is the single largest constituent of the electrode material on a wt % basis, and the firing tip is a multi-piece rivet that includes a second component attached to the center electrode or the ground electrode, and a first component that is attached to the second component and is at least partially made from the electrode material.