Abstract: A wear-resistant electrode tip for a spark plug, and a spark plug which incorporates the wear-resistant tip. The wear-resistant tip includes an alloy of platinum, iridium, and tungsten. Surprisingly, by addition of a small amount of tungsten to platinum-iridium alloy, the wear-resistance of a resultant spark plug is greatly improved. The spark plug electrode tip according to the invention is either spherical or rivet-shaped. During manufacture, the spark plug electrode tip is annealed in an annealing furnace. The annealing furnace is preferably either charged with an inert gas such as argon or nitrogen, or is subjected to a vacuum. The electrode tip is, optionally, further externally coated with platinum or a compatible bonding metal alloy before attachment to the electrode. Subsequent to annealing and, where used, to external coating, the spark plug electrode tip is placed in a welding fixture. The tip is then aligned with a spark plug electrode and is resistance welded thereto.

Abstract: A spark plug and method of making same, wherein the spark plug includes a platinum alloy tip portion which takes the form of a rivet or a sphere. The tip portion is annealed in an annealing furnace at a temperature between about 700.degree.-1400.degree. C. for a time between about 5-30 minutes. The annealed tip portion is then resistance welded to an electrode of the spark plug. The annealing provides the tip portion with added resistance to corrosion and attack by lead. Preferred embodiments of the spark plug tip material comprise 80% platinum--20% rhodium; 80% platinum--20% iridium; 96% platinum--4% tungsten; and Pt (bal)-Ir(a)%-W(b)%, where "a" ranges from about 15 to 19 percent by weight, "b" ranges from about 1 to 4 percent by weight, and the balance is comprised of platinum and incident impurities, and wherein the sum of iridium and tungsten present ranges from about 16 to 19.

Abstract: A spark plug and method of making same, wherein the spark plug includes an iridium alloy tip portion which may take the form of a rivet or a sphere. The tip portion is coated with platinum, annealed and then resistance welded to a nickel-based electrode of the spark plug. The platinum coating helps to prevent cracks at the welding joint which might otherwise occur due to the differing coefficients of thermal expansion of the iridium-based alloy tip portion and the nickel-based alloy electrode. The iridium alloy tip portion is further not susceptible to attack by lead or combustive gases and therefore increases the life of the spark plug significantly.

Abstract: A spark plug electrode wire composed of an iridium-rhodium alloy exhibits improved erosion resistance and enhanced durability in leaded and unleaded fuel environments. The alloy is formed into a wire having high thermal conductivity, low electrical resistivity, good oxidation resistance, good corrosion resistance, good wear resistance. It exhibits desirable work function in pure metals and alloys such as iridium and iridium-rhodium. The wire is inserted into the center electrode of the spark plug and brazed to an Inconel base metal and copper core thereof using a silver-based brazing alloy. After electrical engine dynamometer testing for 200 hours, an improvement in erosion resistance as high as eight fold was observed with an 60% iridium-40% rhodium alloy, when compared to a conventional 90% platinum-10% nickel alloy. The iridium-rhodium spark plug electrode wire can be used to minimize erosion and wear resistance in leaded and unleaded fuel environments.