Wear of soft tool materials in sliding contact with zinc-coated steel sheet

In order to reduce costs of tooling for press operations, efforts are made to use alternative tool materials like wood or plastic. Friction and wear characteristics in sliding contact with zinc-coated steel sheet could, however, limit the applicability of these tool materials for automotive applications. In this work the wear resistance of alternative tooling materials is studied by a combination of forming tests at a high speed stamping line and model wear tests using the TNO slider-on-sheet tribometer. With this tribometer, volume loss of alternative tooling materials can be determined as a function of the sliding distance, using sheet materials from automotive practise. Results show that the wear rate of a soft tool material can change two orders of magnitude as a result of the zinc layer type used. Furthermore, it is shown that the relative performance of alternative tool materials is strongly related to the hardness of the (tooling and sheet) materials. Industrial forming tests with a selection of alternative tooling materials confirmed the model wear test results. The same ranking of the tooling materials with respect to volume loss is obtained per sheet material.