Electrode for an Ignition Device

Abstract

An electrode for an ignition device is made from a dilute nickel alloy which has improved resistance to high temperature oxidation, sulfidation, corrosive wear, deformation and fracture and includes at least 90% by weight of nickel; zirconium; boron and at least one element from the group consisting of aluminum, magnesium, silicon, chromium, titanium and manganese. The weight ratio of Zr/B may range from about 0.5 to 150, and may include amounts of, by weight of the alloy, 0.05-0.5% zirconium and 0.001-0.01% boron. The oxidation resistance of the alloy may also be improved by the addition of hafnium to the alloy in an amount that is comparable to the amount of zirconium, which may include an amount of, by weight of the alloy, 0.005-0.2% hafnium. Electrodes of dilute nickel alloys which include aluminum and silicon, as well as those which include chromium, silicon, manganese and titanium, are particularly useful as spark plug electrodes. These electrode alloys of the may also include at least one of cobalt, niobium, vanadium, molybdenum, tungsten, copper, iron, carbon, calcium, phosphorus or sulfur as trace elements, generally with specified maximum amounts. The ignition device may be a spark plug which includes a ceramic insulator, a conductive shell, center electrode and ground electrode. The center electrode, ground electrode, or both, may be made from the dilute nickel alloy of the invention. These electrodes may also include a core with thermal conductivity greater than that of the dilute nickel alloy, such as copper or silver or their alloys.

1 . An electrode for an ignition device, said electrode formed from an alloy comprising: at least 90% by weight of nickel; zirconium; boron and at least one element from the group consisting of aluminum, silicon, chromium, titanium and manganese. 
     
     
         2 . The electrode of  claim 1 , further comprising hafnium. 
     
     
         3 . The electrode of  claim 1 , wherein said at least one element is selected to include silicon and aluminum. 
     
     
         4 . The electrode of  claim 3 , comprising, by weight of said alloy: 1.0-1.5% aluminum; 1.0-1.5% silicon; 0.005-0.5% zirconium; 0.001-0.01% boron and the balance substantially Ni. 
     
     
         5 . The electrode of  claim 3 , further comprising at least one rare earth element from the group consisting of yttrium, hafnium, lanthanum, cerium and neodymium. 
     
     
         6 . The electrode of  claim 5 , comprising, by weight of said alloy: 1.0-1.5% aluminum; 1.0-1.5% silicon; 0.005-0.5% zirconium; 0.001-0.01% boron; 0.1-0.2% yttrium and the balance Ni and trace elements. 
     
     
         7 . The electrode of  claim 5 , wherein said at least one rare earth element is selected to include yttrium and hafnium. 
     
     
         8 . The electrode of  claim 7 , comprising, by weight of said alloy: 1.0-1.5% aluminum; 1.0-1.5% silicon; 0.005-0.5% zirconium; 0.001-0.01% boron; 0.1-0.2% yttrium, 0.005-0.2% hafnium and the balance Ni and trace elements. 
     
     
         9 . The electrode of  claim 6 , wherein said trace elements comprise at least one of cobalt, niobium, vanadium, molybdenum, tungsten, copper, iron, carbon, calcium, phosphorus or sulfur. 
     
     
         10 . The electrode of  claim 8 , wherein said trace elements comprise at least one of cobalt, niobium, vanadium, molybdenum, tungsten, copper, iron, carbon, calcium, phosphorus or sulfur. 
     
     
         11 . The electrode of  claim 1 , wherein said at least one element is selected to include chromium, silicon, manganese and titanium. 
     
     
         12 . The electrode of  claim 11 , comprising, by weight of said alloy: 1.65-1.90% chromium; 0.35-0.55% silicon; 1.80-2.10% manganese, 0.20-0.40% titanium, 0.005-0.5% zirconium; 0.001-0.01% boron and the balance substantially Ni. 
     
     
         13 . The electrode of  claim 11 , further comprising hafnium. 
     
     
         14 . The electrode of  claim 13 , comprising, by weight of said alloy: 1.65-1.90% chromium; 0.35-0.55% silicon; 1.80-2.10% manganese, 0.20-0.40% titanium, 0.005-0.5% zirconium; 0.001-0.01% boron, 0.005-0.2 hafnium and the balance Ni and trace elements. 
     
     
         15 . The electrode of  claim 12 , wherein said trace elements comprise at least one of cobalt, niobium, vanadium, molybdenum, tungsten, copper, iron, carbon, calcium, phosphorus or sulfur. 
     
     
         16 . The electrode of  claim 14 , wherein said trace elements comprise at least one of cobalt, niobium, vanadium, molybdenum, tungsten, copper, iron, carbon, calcium, phosphorus or sulfur. 
     
     
         17 . The electrode of  claim 1 , wherein said ignition device is a spark plug further comprising:
 a generally annular ceramic insulator;   a conductive shell surrounding at least a portion of said ceramic insulator;   a center electrode disposed in said ceramic insulator having a terminal end and a sparking end with a center electrode sparking surface; and   a ground electrode operatively attached to said shell having a ground electrode sparking surface located proximate said center electrode sparking surface, said center electrode sparking surface and said ground electrode sparking surface defining a spark gap therebetween; wherein at least one of said center electrode or said ground electrode is said electrode.   
     
     
         18 . The electrode of  claim 17 , wherein said center electrode is operable with one of a positive polarity or a negative polarity and the ground electrode is operable at a ground potential. 
     
     
         19 . The electrode of  claim 17 , further comprising a sparking tip attached to at least one of said center electrode or said ground electrode, wherein said sparking tip comprises one of gold, a gold alloy, a platinum group metal or a tungsten alloy. 
     
     
         20 . The electrode of  claim 19 , wherein said platinum group metal comprises at least one element selected from the group consisting of platinum, iridium, rhodium, palladium, ruthenium and rhenium. 
     
     
         21 . The electrode of  claim 20 , wherein said platinum group metal further comprises at least one element from the group consisting of nickel, chromium, iron, manganese, copper, aluminum, cobalt, yttrium, tungsten, zirconium, hafnium, lanthanum, cerium and neodymium.