Made in China Fuel Injection Pump Plunger PT68 Pump Elements Engine Accessories

Abstract
Plungers in diesel fuel injection systems operate under severe working environments, including high temperature, ultra-high pressure, and corrosive fuel conditions. These extreme factors accelerate material degradation, directly threatening durability and injection accuracy. This paper analyzes the dominant failure mechanisms of plunger materials under such conditions and proposes effective protection strategies to improve service life and reliability.

1. Introduction
The plunger assembly is the core element of high-pressure fuel pumps, responsible for generating and delivering injection pressure. In modern engines, working pressures can exceed 200 MPa, and temperatures rise significantly due to friction and combustion proximity. Additionally, the presence of biodiesel or low-sulfur fuels introduces corrosive agents that aggravate wear. Consequently, understanding plunger failure mechanisms and establishing protection strategies are essential for next-generation injection system development.

2. Failure Mechanisms

• High temperature effects: Elevated temperatures reduce material hardness, weaken fatigue resistance, and promote thermal expansion mismatch. This leads to scuffing, seizure, and loss of dimensional accuracy.

• High pressure effects: Repeated cyclic stresses induce fatigue cracks, especially at the plunger–barrel interface. Stress concentration accelerates surface pitting and micro-crack propagation.

• Corrosive environment effects: Sulfur-free fuels, water contamination, and acidic compounds accelerate chemical corrosion, resulting in surface roughening, pits, and reduced sealing capacity. The combination of corrosion and mechanical wear further intensifies material loss, known as tribo-corrosion.

3. Protection Strategies

• Material optimization: High-strength alloy steels with improved fatigue resistance remain the primary choice. Advanced alternatives such as powder metallurgy alloys and ceramic composites show potential due to their superior hardness and thermal stability.

• Surface engineering: Coatings such as diamond-like carbon (DLC), chromium nitride (CrN), and physical vapor deposition (PVD) layers effectively reduce friction, enhance wear resistance, and provide a barrier against corrosion.

• Lubrication improvement: The adoption of fuel additives that enhance lubricity and corrosion resistance can mitigate wear under low-sulfur fuel conditions.

• Design modification: Optimizing surface roughness, enhancing fit precision, and introducing micro-textured surfaces help to reduce stress concentration and improve lubrication film stability.

4. Experimental Validation
Accelerated tests under simulated high-temperature, high-pressure, and corrosive conditions confirmed the effectiveness of combined protection strategies. Plungers treated with DLC coatings demonstrated up to 40% lower wear rates and significantly delayed crack initiation compared with uncoated specimens. Corrosion resistance was also improved by more than 30% when combined with additive-enhanced fuels.

5. Conclusion
Plunger materials operating under extreme conditions face simultaneous thermal, mechanical, and chemical degradation. By integrating advanced materials, protective coatings, improved lubrication, and optimized design, the durability and reliability of plungers can be significantly enhanced. These strategies provide practical guidance for developing next-generation fuel injection systems capable of withstanding harsher operating environments.