New Design of Copper–Inconel 601 Ground Electrode Spark Plug Based on a Thermo-Mechanical Model

Abstract

Inconel 601 is one material of choice for intermediate- to high-temperature protective coatings for spark plugs’ ground electrodes. Production of ground electrodes of spark plugs implies the following operations: the tamping of the copper core in an Inconel 601 cup, cold-forming of the assembly, annealing, welding, and bending of the final spark plug. On the production line, the use of Inconel 601 as a protective coating for ground electrodes leads to possible cracking in the welded area after bending. In the present paper, possible causes of cracking are analyzed. It is clearly shown that a combination of Copper –Inconel interface oxidation, Inconel yielding during the heat treatment, and micro-movements during bending lead to cracks in the welded area of the ground electrode. First, the detrimental effect of gaps, between Copper and Inconel 601, is shown experimentally. Second, a thermo-mechanical analysis combined with SEM (Scanning Electron Microscopy) observations identified the annealing treatment and interface oxidation as the main cause of gaps. Third, bending simulations show the relation between these gaps and cracking. Finally, a new ground electrode design, preventing cracks, is suggested.

Analysis of the Influence of the Spark Plug on Exhaust Gas Composition

“…It is one of the smallest and cheapest operating elements of the internal combustion engine and performs one of the most important tasks, which is the initiation of fuel ignition in the cylinder. Using a worn or damaged spark plug, which operates at elevated temperatures in the combustion chamber, may cause uneven engine operation, a decrease in its power or increased fuel consumption [13,14]. The main tasks of the spark plug include the performance of a spark electric discharge of the required nature inside the combustion chamber while ensuring the repeatable operation of the engine in minimum isobaric and isothermal load conditions [15][16][17].…”