Abstract
Polymer matrix composites are becoming more extensively used for a wide range of engineering applications. Wear of dies and tools has, however, become a significant problem, since the fillers and fibres used to achieve the design properties are often abrasive. Effective means of reducing wear in this type of equipment are therefore becoming increasingly important. Materials currently used for manufacture of tools, dies, screws and barrels, etc. include low alloy non-distortion through hardening steels and steels modified by hard chromium plating, hardfacing with Stellite, particularly for refurbishing worn components, and nitriding. In the present paper wear mechanisms occurring in the processing of polymers are reviewed. The advantages of the currently used processes for extending the life of tools and dies are discussed and this is extended to a discussion of the advantages of nitrogen ion implantation. A tribological test is described which processes a filled polymer through an extrusion system in which a slit die is used; this is made in two parts so that one half can be treated while the other half remains untreated to enable direct comparison. Surface topography and scanning electron microscopy are used to evaluate the extent of wear and the wear mechanism(s) involved. Ion implantation with nitrogen is shown to be effective in extending die life.
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