Five-axis grinding of wear-resistant, thermally sprayed coatings on free-formed surfaces
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The abrasive wear resistance of tribologically stressed free-formed surfaces can be increased with thermally sprayed tungsten carbide coatings. In order to improve the surface topographies and shape accuracies, the workpieces must be finished prior to industrial application. A suitable machining process is NC grinding on five-axis machining centres using abrasive mounted points. However, the high hardness of the applied coatings and the small diameter of the utilized tools pose a great challenge for the process design. In this paper both, the results of fundamental investigations on the grinding of tungsten carbide coatings as well as a process optimization for the finishing of a coated forming tool are presented. This includes the heat transfer into the coating and the tool wear during the grinding process as well as the wear behaviour of the coating in dependence of the generated surface topography. In order to achieve a smooth surface, elastic-bonded diamond tools were used during polishing in a multi-stage machining process.
KeywordsGrinding Hard material coatings Surface integrity Free-formed surfaces
The investigations and scientific results described in this paper are based on the research project A5, which has been kindly funded by the German Research Foundation (DFG) within the SFB 708 3D-Surface Engineering of Tools for Sheet Metal Forming Manufacturing, Modeling, Machining. The authors thank Peter Hollingsworth and Weifeng Luo from the Chair of Material Engineering (LWT) at Technische Universitortmund, Germany, for preparing the machined coatings.
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