Journal of Mechanical Science and Technology

, Volume 20, Issue 3, pp 358–365 | Cite as

Improvement of the low-speed friction characteristics of a hydraulic piston pump by PVD-coating of TiN

  • Yeh-Sun Hong
  • Sang-Yul Lee
  • Sung-Hun Kim
  • Hyun-Sik Lim


The hydraulic pump of an Electro-hydrostatic Actuator should be able to quickly feed large ume of oil into hydraulic cylinder in order to reduce the response time. On the other hand, it should be also able to precisely dispense small amount of oil through low-speed operation so t the steady state position control error of the actuator can be accurately compensated. Within the scope of axial piston type hydraulic pumps, this paper is focused on the investigation how the surface treatment of their cylinder barrel with TiN plasma coating can contribute to the reduction of the friction and wear rate of valve plate in the low-speed range with mixed rication. The results showed that the friction torque of the valve plate mated with a TiN-coated cylinder barrel could be reduced to 22% of that with an uncoated original one when load pressure was 300 bar and rotational speed 100 rpm. It means that the torque efficiency of the test p was expected to increase more than 1.3% under the same working condition. At the same time, the wear rate of the valve plate could be reduced to 40–50%.

Key Words

Low-Speed Friction Characteristics raulic Piston Pump Plasma Coating TiN-Layer inder Barrel 



Effective area of cylinder barrel (mm2)


Cross-sectional area of piston (mm2)


Balance coefficient


Normal force acting on valve plate (N)


riction coefficient of valve plate


ssure of each cylinder chamber (bar)


Moment arm of normal force on valve plate w.r.t. pump shaft (mm)


Rotation angle of pump shaft (°)


Friction torque on shaft bearings (Nm)


Friction torque acting on cylinder barrel


Ideal input torque of pump (Nm)


ational speed of pump shaft (rpm)


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  1. Bebber, D. and Murrenhoff, H., 2002, “Metal/Carbon Layers (ZrCg and HfCg) to Reduce Wear and Friction in raulic Components,”Proc. 3 rd Int. Fluid Power Conference, Aachen/Germany, Vol. 2, pp. 443–455.Google Scholar
  2. Hong, Y. S. and Doh, Y. H., 2004, “Analysis on the Friction Loss of a Bent-Axis Type Hydraulic Piston p,”KSME Int. J., Vol. 18, No. 9, pp. 1668–1679.Google Scholar
  3. Lee, S. Y., Kim, S. D. and Hong, Y. S., 2005, “Application of the Duplex TiN Coatings to Improve the Tribologocal Properties of Electro Hydrostatic Actuator Pump Parts,”Surface & Coatings Technology, Vols. 193, pp. 266–271.CrossRefGoogle Scholar
  4. Nevoigt, A., 2000, “Untersuchung der Tribologischen Eigenshaften Beschichteter Bauteile in Hydraulik- Zylindern und ilkolbenmaschinen,” Dissertation, RWTH Aachen, Germany.Google Scholar

Copyright information

© The Korean Society of Mechanical Engineers (KSME) 2003

Authors and Affiliations

  • Yeh-Sun Hong
    • 1
  • Sang-Yul Lee
    • 2
  • Sung-Hun Kim
    • 4
  • Hyun-Sik Lim
    • 3
  1. 1.Faculty of A eronautical & Mechanical EngineeringHankuk A viation UniversityGoyangKorea
  2. 2.Faculty of Materials ScienceHankuk A viation UniversityGoyangKorea
  3. 3.School of Aeronautical & Mechanical EngineeringHankuk A viation UniversityGyeonggi-doKorea
  4. 4.Faculty of A eronautical & Mechanical EngineeringHankuk A viation UniversityGoyangKorea

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