Polished diamond coatings for dry tapering of aluminum

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Lubricants are used in forming technologies to lower friction and prevent adhesive wear. The use of lubricants combined with the chemical purification of the work pieces, which is necessary for subsequent processing, leads to a significant environmental impact.Preliminary investigations showed a low coefficient of friction of a polished diamond coating in a dry oscillating ball-on-plate tribometer test with an aluminum ball as counter body. Neither on the diamond coating nor on the alumina ball adhesion could be detected. The diamond coating did not show any wear after a test duration of 5.5 hours. The alumina ball showed an increase of the amount of oxide in the contact area, which might be explained by the occurring rise in temperature.The aim of the project is the realization of lubricant free tapering of aluminum with diamond coated tools. The hypothesis, which is supported by the tribometer tests, is, that sufficiently well polished diamond coatings enable dry forming of aluminum alloys. The production of polished polycrystalline CVD diamond coatings on reduction dies for economic prices represents a hurdle. The solution approach is that the coating deposition will be carried out with the CVD process which exists at BIAS. The polishing of the diamond coating should be realized for low costs in a two-stage process. Initially the roughness peaks are ablated using a picosecond laser and afterwards the final surface roughness will be achieved by commissioned mechanical polishing.Within the scope of the project reduction dies out of tungsten carbide will be coated with polycrystalline CVD diamond coatings. The aim is to achieve a homogenous coating thickness on the inner wall of the die. Furthermore it will be examined which surface roughness can be obtained by the use of a picosecond laser. The procedure of laser ablation has to be transferred onto the geometry of the reduction die. Throughout the project duration forming tests of the tapering of aluminum alloys will be examined dry as well as lubricated.