Objective
The experimental research work basically consisted in alloy development and required a well-defined frame, which based on literature data and data/experience available from the partners. In a first experimental phase, a screening testing programme was carried out on very small test pieces. This was aimed at a first overview on the most significant properties of the alloys, i.e. regarding colour, deformability, hardness and microstructure in various states. In the following phase which proceeded until the end of the first project year, more detailed investigations into the material/manufacturing properties of some selected alloys have been carried out at the laboratories of the R&D performers using larger quantities of material and larger sample sizes. From these investigations, the alloys with the most promising properties were recommended for application testing by the industrial partners, namely Mn- and Cr-based alloys (Pd-free and alloys with reduced Pd-content), as well as conventional Pd-based alloys containing grain refiners.
During industrial testing the different steps/methods of jewellery production were followed at the SMEs using the new materials: production of semi-finished products, investment casting, mechanical fabrication of rings/chains, joining and refining/recycling. Grain refinement by Ir-additions proved to be highly beneficial for improving ductility, polishing and surface properties of jewellery products. Most important, however, it turned out that the newly developed Cr-alloy systems despite of several problems related with reactivity of the alloys with air and graphite, is highly interesting and would mean a lot of advantages in comparison with the developed Mn-alloys or other existing alternatives. In particular, the Cr-alloys possess excellent colour and corrosion properties not reached by far by any other available alternative.
Further development of manufacturing procedures and improvements of equipment (melting, casting, annealing) are necessary, however, to reduce oxidation of the Cr-alloys to an acceptable level. The further major remaining problems are: accuracy of assaying, better solder/flux systems, removal of oxides from surfaces after casting/annealing/soldering and replacement of graphite components (crucible etc.) in casting/melting equipment which means largest difficulties especially for continuous casting (chain manufactory).
White gold alloys have been developed since the 1920s, initially as alternatives to platinum in certain types of jewellery. The world wide usage of white gold alloys in jewellery manufactory is steadily increasing. Currently the amount has reached approximately one third of the world gold demand in jewellery, which is about 2800 tons, and therefore equals about 1000 tons or 10.000 million ECU. However, the manufacturers of jewellery and watches, which to a large share are SMEs, actually have to face a serious problem: Nickel, being the main constituent of commercial white gold alloys in the past, has been commonly recognised to cause severe allergic reactions when it is in contact with the human skin. Due to this it is expected that National and European legislation will in near future strictly prohibit the use of nickel, even as a minor alloying component, in all materials used for jewellery, watches, spectacles and other products in contact with the skin. For this reason there is strong industrial need for white gold alloys which are essentially free of nicke/ The Ni free white gold alloys which are currently available consist of a high content of palladium. But due to an enormous and ever increasing prize of palladium ( 7500 ECU/kg) e.g. compared to nicke/ ( 7 ECU/kg) these Pd based white gold alloys obviously are not a commercially viable solution. This holds especially for mass manufacturing products. But furthermore, Pd based white gold alloys have other detrimental properties which restrict their application even for individual 'one off items. The industrial objectives of the project therefore are: - to develop Ni free white gold alloys (14ct and 18ct) of which the production/material costs are significantly reduced compared to the conventional Pd based alloys (10 15% for 18ct alloys, >20% for 14ct alloys); - to adjust the property spectrum of Ni free white gold alloys especially regarding colour, ductility, strength, corrosion and wear resistance in such a way, that they are equal or even better than the former Ni containing white gold alloys; - to adjust the properties of these alloys to the different types of industrial jewellery production These improvements will be achieved by addressing the restrictions of Ni free white gold alloys by substantial alloy modifications (partial substitution of palladium, addition of grain refiners etc. ), elaborate process development (heat treatments etc.) and substantial application testing. The project consortium structure Consists of two refiners/manufacturers of semifinished products, two jewellery casters, two mechanical manufacturers of jewellery items and three research institutions and therefore is especially complementary regarding the industrial SME partners: all main and different steps/types of jewellery fabrication are represented. Two firms with comparable product spectrum but from different European countries have been chosen per type/step in order to guarantee a most objective property evaluation of the developed alloys during industrial production. The innovative aspects of the present project are given by: - Development of commercially viable and marketable Ni free white gold alloys especially suitable for mass production which meet all basic requirements of jewellery manufactory; - Development of highest quality Ni free white gold alloys for individual jewellery items with high but justifed prize level; - Collaborative work driven by both, scientific background and industrial experience, in an industrial branch formerly baring systematic material/process development due to the dominance of SMEs without adequate facilities. This project has been launched under a stimulation action supported by the European Commission and performed in the Jewels sector. The proposal addresses the research area '2.1. Materials Engineering' according to the work program 'Industrial and Materials Technologies'.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- engineering and technology environmental engineering waste management waste treatment processes recycling
- engineering and technology materials engineering colors
- agricultural sciences agriculture, forestry, and fisheries agriculture grains and oilseeds
- natural sciences chemical sciences electrochemistry electrolysis
- natural sciences chemical sciences inorganic chemistry transition metals
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Coordinator
75173 PFORZHEIM
Germany
The total costs incurred by this organisation to participate in the project, including direct and indirect costs. This amount is a subset of the overall project budget.