Masters Theses

Date of Award

6-1987

Degree Type

Thesis

Degree Name

Master of Science

Major

Engineering Science

Major Professor

Carl J. McHargue

Committee Members

Jack F. Wasseman, Raymond A. Buchanan

Abstract

Several thin film adhesion tests have been examined to determine which provides the most reliable method for the measurement of the adhesion of thin metallic films to ceramic substrates. An attempt was made to use the testing techniques described to measure adhesion changes caused by ion beam mixing for a variety of metal/ceramic systems.

The testing techniques analyzed were the scratch test, the acoustic emission test, and the pull test. The major variables of the scratch test include film thickness, substrate hardness, and stylus radius but it is not known precisely what effects changes in these have on the measurement of adhesion. The scratch analyses methods discussed in the literature, each describing a load or stress on the system that is presumed to cause de-adhesion, do not always hold because none of the analyses account for both plastic and elastic deformation or incorporate many of the important parameters. The scratch test was much more likely to reveal a critical value for de-adhesion for relatively brittle films such as chromium than for ductile films such as nickel.

The acoustic emission test did not work for the scratch testing equipment used in this research. Whatever specimen emissions might have occurred were overshadowed by those of the drive motor, which could not be adequately isolated from the system.

An adaptation of the pull test, utilizing a thin gold layer under a portion of the test film, was developed because the adhesion of the test films was greater than the strength of the epoxy used in the standard test. Since this non-adherent layer served as a reproducible crack, the analysis was analogous to that used in fracture toughness testing. Comparison of film adherence was based on the calculation of the stress Intensity factor necessary to cause film de-adhesion. The results of this modified pull test were very promising and involved fewer parameters than the scratch test.

Scratch test data for most of the systems exhibiting critical values for de-adhesion revealed that Ion beam mixing significantly Improved the adhesion of the films to their substrates. Ion beam mixed films also withstood a greater applied tensile stress and a greater stress Intensity factor without de-adhesion than unmixed films with similar flaws.

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