Within the investigations of the project various hard coatings and five different preprocessing methods for the machining of fine blanking tools were examined. The judgement of the performance of the various hard coatings and the premachining methods was based on the examination of the surface roughness of the blanked parts as well as SEM images and cross-section of the tools.
It was seen that the hard coatings TiCN and TiAlN are suitable for blanking sheet materials causing a mainly abrasive wear on the tools, whereas TiAlN performed best in blanking a sheet material causing a mainly frictional wear on the tools.
Based on the investigations of hard coatings and preprocessing methods it was shown that TiAlNbN coated fine blanking tools performed the best. They result in a very low surface roughness of the fine blanked parts of Ra=2um even after 10.000 strokes.
To summarize one can say that the premachining of the tools has a significant influence on the performance of the subsequent coating. With coating materials suitable for the tribological system of fine blanking it is possible to obtain blanked parts witha smooth sheared surface and low burr formation.
Compared with TiN, the new coatings are characterized by greater hardness, greater toughness, more favourable friction properties, better smoothness and greater resistance to oxidation.
As a result of the greater number of load cycles on the basis of increased tool life quantities, failure of the tools due to fatigue is possible under certain circumstances. The surface engineering is therefore aimed at reaching a favourable residual stress condition of coating, interface substrate with regard to increased resistance to material fatigue.
In particular, the improvement of tool surface is accompanied by an improvement in workpiece quality, especially higher surface quality of the sheared edges and higher accuracy-to-shape-and-size.
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