ICMCTF2007 Session TS1P: TS2 Poster Session
Thursday, April 26, 2007 5:00 PM in Room Tiki Pavilion
TS1P-1 Studies on Tribological Behaviors of Cr-X-N (X=Si, Zr) Coatings Deposited on Hydraulic Pump Part
S.Y. Lee, E.Y. Kim, J.T. Kim (HanKuk Aviation University, Korea)
The hydraulic pump for an Electro-hydrostatic Actuator should not only be able to quickly feed large volume of oil into hydraulic cylinder in order to reduce the response time, but it should also be also able to precisely dispense small amount of oil by low-speed operation so that the steady state position control error of the actuator can be accurately compensated. In this paper, the effects of duplex treatment consisting of plasma nitriding and PVD hard coating on the surface properties of hydraulic pump parts were investigated. Two different coatings (CrSiN coating and CrZrN coating) were deposited on AISI 4340 steel using reactive unbalanced magnetron sputtering method. A high-speed disk-to-disk type wear tests under a mineral oil environment with various loading were performed and the results from the pump parts with PVD coatings were compared with those from a conventional plasma-nitrided pump part pump parts. Much improved tribological behaviors could be observed from pump parts with PVD coatings, compared with pump part with a plasma nitriding treatment. CrZrN coating showed excellent tribological behaviors especially at low speed range in that friction coefficient dropped quite rapidly below 0.01 even before 200rpm. Pump part with CrSiN coating showed similar friction coefficients to CrZrN coating at high speed range but much higher friction coefficients at low speed range, especially below 200 rpm was observed. Based on the results form this work, CrZrN coating is considered to be applied successfully for improvement of friction characteristics of hydraulic pump parts, especially for improvement of the torque efficiency, Detailed experimental results will be presented.