Degradation of Silicon Nitride Glow Plugs in Various Environments. Part 2: Gas Burner Rig

In the development of advanced natural gas and hydrogen direct injection combustion engines, a challenge is providing reliable hot-surface (glow plug, GP) ignition systems; most promising are GPs with silicon nitride-based heaters. This paper presents experimental results of accelerated degradation tests of the GPs on natural gas-burning rig, continuing previously published results on GP degradation in air. Degradation, ultimately leading to GP failure, occurs through the synergistic effects of electric field and chemical reactions in the combustion environment. The resulting microstructural modifications of the ceramic heater, studied by SEM/EDS, are a combination of sintering additive ions migration and surface oxidation.