Tribological study of microbearings for MEMS applications

Document Type

Article

Publication Date

7-1-2005

Abstract

Microsleeve bearings intended for microrotational machinery were fabricated by X-ray lithography and Ni electroplating. Coated to the working surfaces of the bearings was a 900 nm thick uniform tungsten hydrocarbon (W-C:H) coating using an inductively coupled plasma (ICP) assisted, hybrid chemical vapor deposition (CVD)/physical vapor deposition (PVD) tool. Tribological characteristics and mechanical properties of aselectrodeposited Ni microbearings, annealed Ni microbearings at 800°C, and W-C:H coated microbearings were investigated. Potential applications of the microbearings may involve very light contact pressure (5-30 MPa) and high sliding speed, such as micromotors and microturbines. Conventional pin-on disk test methods on top flat surfaces, (001) planes, cannot effectively predict tribological characteristics because these microbearings use the sidewall (110 plane) as a working surface. A special micro wear tester and friction tester were developed. Surface morphologies of new and worn bearing surfaces were studied using SEM. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterized the W-C:H coated microbearings. Test results of the W-C:H coated microbearings (wear characteristics and friction) are also presented. W-C:H coated microbearings had much lower wear rate than uncoated bearings. During the wear test, a transfer layer formed on the counter steel shaft even under very small contact pressure, leading to low steady state friction and high wear resistance. Copyright © 2005 by ASME.

Publication Source (Journal or Book title)

Journal of Tribology

First Page

537

Last Page

547

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