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.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to a high performance electrode made from a dilute nickel alloy containing alloying additions of zirconium and boron that is temperature, oxidation, sulfidation and fracture resistant and, more particularly, toward an electrode for an ignition device, such as a spark plug for an internal combustion engine, furnace, or the like.[0003]2. Related Art[0004]A spark plug is a spark ignition device that extends into the combustion chamber of an internal combustion engine and produces a spark to ignite a mixture of air and fuel. Recent developments in engine technology are resulting in higher operating temperatures to achieve improved engine efficiency. These higher operating temperatures, however, are pushing the spark plug electrodes to the very limits of their material capabilities. Presently, Ni-based nickel-iron-chromium alloys specified under UNS N06600, such as those sold under the trade names Incon...

AI Technical Summary

Benefits of technology

[0007]In one aspect, the present invention includes an electrode for an ignition device having improved resistance to high temperature oxidation, sulfidation and related corrosive wear, as well as improved high temperature tensile, creep rupture and fatigue strength and resistance to cracking and fracture which is formed from a dilute nickel alloy which 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 aluminum, silicon, chromium, titanium and manganese as diluent alloy elements may be added in any combination and relative amounts, including all six elements. The addition of zirconium and boron has been observed to have a synergistic effect on the improvement in properties noted in these alloys as compared to the improvements resulting from the addition of either of these elements separately. The zirconium and boron will generally be present in a weight ratio of Zr / B of about 5 to 150, and more particularly about 50 to 100, and most particularly about 70 to 80. While zirconium and boron may be present in any amounts consistent with the requirements of the electrode alloy, it is believed that zirconium in an amount of about 2.74% by weight or less and boron in an amount of about 3.50% by weight or less are generally believed to be the preferred upper limits for these constituents. It is also believed to be preferred that the amount of zirconium be greater than the amount of boron. In dilute nickel alloys which include as diluent elements a combination of aluminum and silicon; aluminum, silicon and yttrium; and chromium, silicon, manganese and titanium, the use of zirconium in the range of 0.005-0.5% by weight of the alloy and boron in the range of 0.001-0.01% by weight of the alloy is particularly useful.

Problems solved by technology

These higher operating temperatures, however, are pushing the spark plug electrodes to the very limits of their material capabilities.

Since combustion environments are highly oxidizing, corrosive wear including deformation and fracture caused by high temperature oxidation and sulfidation can result and is particularly exacerbated at the highest operating temperatures.

), tensile, creep rupture and fatigue strength also have been observed to decrease significantly which can result in deformation, cracking and fracture of the electrodes.

Depending on the electrode design, specific operating conditions and other factors, these high temperature phenomena may contribute individually and collectively to undesirable growth of the spark plug gap and diminished performance of the ignition device and associated engine.

In extreme cases, failure of the electrode, ignition device and associated engine can result from electrode deformation and fracture resulting from these high temperature phenomena.

These failure modes and effects can be particularly problematic in competitive applications, such as racing engines.

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