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Progressive surfacing of metals

The main goal of the project is to improve and optimise surface properties of advanced metallic materials through the physical and chemical deposition of thin and hard layers and combinations thereof.

Wear and corrosion of materials are the most limiting problems in the industry, since they result in high financial losses. Therefore the efforts leading to the protection of metallic surfaces with various surface treatments are logical. Over the last three decades, PVD (Physical Vapour Deposition) coatings have undergone a large development and many variations of the overlays were introduced into industrial applications. The current status of the coating technology is the use of duplex and multilayered coatings, nano-scale coatings and functionally graded materials consisting of many parallel layers differing from each other mainly by the physical properties. Most of the experimental works were focused on the ferrous-alloys and tool steels. Nevertheless, the structural steels also became the subject of interest during the last decade, mainly from the aspect of improving contact fatigue lifetime and wear properties. At the same time, the protection of non-ferrous and lightweight alloys against corrosion became the interest of the industry. Decorative coatings in bijouterie have also become very important. New linear or stepping micro-motors for automotive and rapid prototyping applications consist of parts that are exposed to severe wear and corrosive environments. This calls for the development of new corrosion and wear-resistant materials or the protection of traditional materials with the complex multi-layered hard and corrosion-resistant coatings. In this context the usability of a pulsed-plasma ion-nitriding process and PVD/CVD (Physical Vapour Deposition/Chemical Vapour Deposition) coating will be investigated for the protection of very small complex motor parts (axles, threads or pulleys, screws, gears, etc.) made of stainless and tool steels, as well as Al- and Ti-based alloys. The cold-work tool steels undergo many types of loading that may result in failure after a very short service time. The heat treatment itself cannot always meet the demands of the end users so the surfacing of the metals and components is then needed. The current status of surface techniques is the duplex - coating, where the PVD -layering is combined with diffusion processes. In this way, many important characteristics of ledeburitic tool steels made by powder metallurgy as well as those produced via ingot large casting can be improved - wear resistance, fatigue - life time, etc. The investigations now tend to achieve a good reproducibility of the processing and to develop the techniques for the materials that are newly introduced into the market. The hot work steels were substantially improved even through the metallurgical preparation. For instance, the total impurity content (P+S) was reduced many times. In the lightweight alloys casting or hot forming, the thermal fatigue and reactivity with the worked material also has to be taken into consideration. Investigations are thus carried out to find out how to improve them, but without the loss of fracture toughness. One of the most promising methods is plasma nitriding which forms compressive stresses in the surface region and improves the fatigue strength. The second possibility is solid-state boronising with subsequent quenching and tempering - given that the process is carried out at a high temperature, the properties of the compound layer remain stable at the operating temperatures normally used for aluminium alloy casting procedures. Titanium and its alloys are prospective materials due to their low weight, high strength and excellent corrosion resistance. To improve the surface properties of titanium alloys, nitriding is widely used. Developed TiN layers lower the friction coefficient and improve wear resistance. However, for the high temperature application combined with extensive loading (valves, turbine blades, moulds), the nitriding cannot ensure the lifetime of the material to a sufficiently high level. For these purposes, the inter-metallic layers consist of silicides and/or aluminides more than in the case of commonly used nitrided layers. Keywords: advanced metallic materials, heat treatment, coating.
Acronym: 
PROSURFMET
Project ID: 
3 437
Start date: 
01-01-2005
Project Duration: 
36months
Project costs: 
550 000.00€
Technological Area: 
Surface treatment (painting, galvano, polishing, CVD, PVD)
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.