Wear of nanostructured coated cutting tools during mixed scale machining

Grant Mark Robinson, Purdue University

Abstract

Nanotechnology is creating new forms of manufacture where mass production is not possible at the nano scale, but is possible at the micro scale. Micro scale devices are limited by the materials from which they are made and are usually silicon-based. High-speed machining has the potential to successfully machine engineering materials at the micro scale. The significant problem to overcome is tool wear since this leads to a loss of tolerance and component geometry. Tool wear is caused by various wear mechanisms including chemical wear, triggered by high machining temperatures. Therefore, tools are coated with a thin solid film in order to reduce the cutting temperature and to provide a diffusion barrier against chemical wear during machining. However, cutting temperature and tool wear mechanisms are not very well understood at the micro scale. The purpose of this study was to understand the nature of wear of nanostructured coatings applied to cutting tools at the micro scale and to compare them to wear of cutting tools at the macro scale. It was found that tool coatings applied at the macro scale significantly improves tool life but that the same coatings applied to micro scale tools had no effect on tool life. It was also found that the cutting temperature at the micro scale was approximately 35°C, which is not high enough to cause chemical wear by diffusion. Therefore, tool wear mechanisms that coatings are designed to resist at the macro scale, do not exist at the micro scale. Furthermore, it was discovered that the cutting edge of a micro scale tool is not strong enough to resist abrasive wear. It is concluded that the geometry of a micro scale tool should be fundamentally re-designed and that special coatings must be specifically developed for use at the micro scale especially to resist abrasive wear. Wear mechanisms for coatings deposited to micro scale tools were proposed based on the nature of contact between workpiece material and cutting tool.

Degree

Ph.D.

Advisors

Jackson, Purdue University.

Subject Area

Mechanical engineering

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