Additive Manufacturing of Platinum Alloys

Additive manufacturing of jewellery alloys has been actively investigated during the last 10 years. Several, but limited studies have been conducted on gold and platinum jewellery alloys. Platinum is of increased interest due to the technological challenges in investment casting. In the present paper, typical platinum jewellery alloys have been tested by laser track experiments on sheet materials. The effect of alloy composition on width and depth of the laser tracks was studied by metallography. Optimum parameters of the LPBF process were determined for a typical 950Pt jewellery alloy by the preparation of dedicated test samples. Densities of >99.8% were reached for a wide range of processing parameters. However, in case of real jewellery parts the resulting density was found to depend significantly on the part geometry and on the chosen support structure. The supports have to take into account the geometrical orientation of the part relative to the laser build direction and the orientation on the build plate. Local overheating gives rise to porosity in these areas. Therefore, the supports play an important role in the thermal management and have to be optimized for each part. The design of suitable supports was successfully demonstrated for a typical jewellery ring sample.