Abstract: In this paper the reason of chromium coating seepage on piston rods is analyzed. The results show that the chromium coating seepage is mainly caused by the net structure of micro-cracks produced in electroplating process. According to this special structure of chromium coating, experiments are made to study the feasibility that the chromium coating is burnished by using the ultrasonic elliptical vibration burnishing (UEVB) process to prevent seepage. The results of study demonstrate that the UEVB process make the micro-cracks on the surface of chromium coating closed or eliminated because the UEVB process could make the chromium coating plastic-forming. Thereby airtightness of piston rods is increased and seepage is prevented approximately. Compressive stress within the material of chromium coating will produce so that the micro-cracks propagation would be restrained and the life of parts is extended.

An Ultrasonic Elliptical Vibration Burnishing Process for Reducing Surface Roughness

Authors: Wei Qin, De Yuan Zhang

Abstract: It is widely recognized that the chipless finishing process — the burnishing process can be used efficaciously to reduce the surface roughness of components. But most of previous works published concentrated on the conventional burnishing process and experimental researches in the last few years. There are some limitations on the conventional burnishing process in reducing surface roughness. Ultrasonic elliptical vibration burnishing (UEVB) process is proposed. Theoretical model is established to analyze theoretical surface roughness. Steel 45 was selected as material for making the specimens in the experiments and a new device developed by us was used for the burnishing process. The comparison shows that the surface roughness in describing the burnishing process is better than the conventional burnishing process obviously.

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