Made in China Fuel Injection Pump Plunger 1 418 325 005 1418325005 Pump Elements Engine Accessories

Plungers are critical precision components in fuel injection and hydraulic systems, where they operate under high contact pressure, repeated sliding motion, and insufficient lubrication conditions. Surface wear of plungers directly affects sealing performance, volumetric efficiency, and service life. Surface nitriding has been widely adopted as an effective strengthening method to improve surface hardness and wear resistance. However, the relationship between nitriding process parameters and the resulting wear performance of plunger surfaces requires systematic investigation.

In this study, the influence of key nitriding process parameters—including nitriding temperature, treatment duration, nitrogen potential, and cooling conditions—on the wear resistance of plunger surfaces was analyzed. Gas nitriding was applied to alloy steel plungers under different process settings, followed by microstructural characterization and tribological testing. Surface hardness profiles were measured using microhardness testing, while wear behavior was evaluated through reciprocating sliding tests under simulated operating loads.

The experimental results showed that nitriding temperature has a dominant influence on the formation of the nitrided layer. At moderate temperatures, a dense compound layer combined with a well-developed diffusion zone was formed, resulting in a gradual hardness gradient from the surface to the substrate. This structure effectively reduced stress concentration and improved resistance to adhesive and abrasive wear. Excessively high nitriding temperatures, however, led to the formation of brittle nitride phases and increased surface roughness, which negatively affected wear performance.

Nitriding duration was found to strongly affect the thickness of the diffusion layer. Longer treatment times enhanced nitrogen diffusion depth and load-bearing capacity, improving wear resistance under high contact stress. Nevertheless, overly prolonged nitriding resulted in excessive compound layer growth, increasing the risk of surface cracking and spalling during sliding contact. Therefore, an optimal balance between compound layer thickness and diffusion depth is essential.

Nitrogen potential played a crucial role in controlling phase composition within the compound layer. A stable nitrogen potential promoted uniform nitride formation and improved surface hardness consistency. Wear tests indicated that plungers treated under optimized nitrogen potential exhibited lower friction coefficients and reduced wear rates compared to untreated specimens.

In conclusion, the wear resistance of plunger surfaces is closely related to nitriding process parameters. Optimized nitriding temperature, duration, and nitrogen potential can significantly enhance surface hardness, improve microstructural stability, and reduce wear damage. The findings of this study provide practical guidance for the surface treatment optimization of plungers used in high-load and high-precision mechanical systems.