Diesel Fuel Injection Pump DB4429-6090 Engine Auto Engine Part

Abstract

Oil pumps are critical components in automotive and industrial lubrication systems, responsible for maintaining stable oil pressure and ensuring reliable operation of mechanical assemblies. Under prolonged high-speed and high-load conditions, friction and wear between moving parts such as gears, plungers, and bearings often lead to performance degradation and premature failure. Applying wear-resistant coatings is an effective method to enhance surface durability and extend service life. This study investigates the influence of various wear-resistant coatings—including diamond-like carbon (DLC), chromium nitride (CrN), and titanium nitride (TiN)—on the tribological behavior and longevity of oil pump components. Experimental and simulation analyses demonstrate that appropriate coating selection significantly improves pump efficiency, reduces wear loss, and prolongs operational lifespan.

1. Introduction

The continuous demand for high-efficiency and long-lifetime oil pumps in modern machinery necessitates improvements in material and surface technologies. Conventional steel components suffer from adhesive wear, fatigue spalling, and corrosion when exposed to high-temperature lubricating oil and cyclic pressure fluctuations. Surface engineering technologies such as physical vapor deposition (PVD) coatings offer a promising solution by enhancing hardness, reducing friction, and preventing material transfer during contact. However, the coating’s performance strongly depends on its adhesion strength, thickness, and compatibility with the substrate material. Therefore, understanding the relationship between coating characteristics and pump service life is essential for practical application and optimization.

2. Experimental Methodology

Three types of coatings—DLC, CrN, and TiN—were deposited on steel samples representing gear and plunger surfaces using a PVD process. Coating thickness ranged between 2–4 μm. The samples were evaluated using a reciprocating wear tester under lubrication conditions that simulate oil pump operation, with applied loads of 30–50 N and temperatures up to 120°C. Surface hardness, adhesion strength, and friction coefficient were measured using nanoindentation, scratch testing, and tribometry.
Additionally, the coated and uncoated components were assembled into small gear-type oil pumps and tested on a hydraulic bench for 500 hours of continuous operation. Wear morphology and oil contamination levels were analyzed using scanning electron microscopy (SEM) and spectroscopic oil analysis.

3. Results and Discussion

The results show that the DLC coating exhibited the lowest average friction coefficient (0.08) and superior wear resistance compared to CrN (0.12) and TiN (0.15). The coated pumps demonstrated a significant reduction in gear flank wear—by 65% for DLC and 40% for CrN—relative to uncoated ones. Moreover, DLC-coated components maintained stable volumetric efficiency throughout the 500-hour test, while uncoated samples showed a 10% performance decline due to increased internal leakage.
Finite Element Analysis (FEA) further confirmed that coatings reduced surface contact stress and improved lubrication film stability. Among the tested coatings, DLC achieved the best balance between hardness and toughness, effectively delaying fatigue crack initiation and extending the pump’s predicted lifespan by more than threefold.

4. Conclusions

This study confirms that wear-resistant coatings can greatly enhance the durability and reliability of oil pumps operating under demanding conditions. DLC coatings provided the best performance due to their ultra-low friction, high hardness, and excellent chemical inertness. CrN and TiN also improved wear resistance but were more susceptible to microcracking under cyclic stress. The integration of coating optimization with improved surface finishing and lubrication design can further extend oil pump service life. Future research will focus on multilayer composite coatings and in-situ monitoring of coating degradation to achieve intelligent life prediction and maintenance scheduling.