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Industrial Processes

More than skin deep

   
 
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New generation plasma surface engineered sewing machine parts.
A network of contacts built up over 30 years between eastern and western Europe led to three highly successful steel surface-treatment projects under the Copernicus programme. Key players Plasmaterm and the University of Birmingham worked together with universities and research organisations in Hungary, Poland and Romania as well as Germany and the UK to develop new test methods and novel solutions for improving surface wear and corrosion resistance. The resulting technologies are already being applied extensively to make machine parts for the automotive, chemicals and precision engineering industries.

 

Romanian surface-treatment specialist Plasmaterm is a survivor of the complete shutdown of its local textile industry which employed 10,000 people in Tîrgu Mures, Transylvania - about midway between Budapest and Bucharest. Originally a state-funded research institution, it provided R&D support for precision-engineered textile machinery used in spinning, weaving, sewing and knitting.

Founded in the mid-1960s, to meet a burgeoning need for new technology in Romania, it established an international reputation in surface treatment, with several patents in low-temperature nitrocarburising. However, the political turmoils of the early 1990s paralysed operations and funding dried up. So its director, Dr Zoltán Kolozsváry, proposed a workers' buyout of the unit from the state - a gamble which has paid off.

EU RTD support through the Copernicus programme played a crucial role in the company's rebirth. "The programme should not be used to replace vanished state subsidies for research," says Dr Kolozsváry, now managing director of Plasmaterm. "But what it can do is allow valuable laboratories to survive the transition into viable business-oriented units. Taking part in the Copernicus programme was the turning point for us."

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Plasmaterm inherited a unique expertise in surface treatment, along with a wonderful array of measuring and testing equipment, much of it home-made.

Unique expertise
The company had a valuable inheritance. Sewing machines run at very high speeds - up to 10,000 cycles per minute - and intermittently, so parts must be extremely resistant to wear. Plasmaterm had therefore developed unique expertise in surface treatment and testing. It has used this to build up a business in contract materials testing and analysis, failure analysis, and of course surface treatment, especially plasma nitrocarburising. This high-tech surface technology causes nitrogen and carbon molecules to diffuse into the surface of the steel, creating a hard layer composed largely of iron carbonitride. Traditionally, this has been achieved by immersing the steel in a cyanide bath or an equivalent gaseous medium. However, the toxicity of these media can result in undesirable side effects.

Plasma nitrocarburising offers a more environmentally sound approach. It involves applying an electric charge to the objects to be hardened while they are immersed in an atmosphere containing nitrogen, hydrogen and carbon. The gases' atoms become excited and react with the surface of the charged engineering components.

Treatment is normally carried out by hanging parts from a stainless steel cathode in the centre of a cylindrical stainless steel chamber at around 750 volts and 590°C. Depending on customer requirements, each batch may be treated for up to 12 hours, resulting in a carbonitride diffusion layer up to half a millimetre deep. A hardness of up to 1000 Vickers units can be obtained on stainless steels, coupled with a reduced friction coefficient.

From steel to polymers
The company is now embarking on its third European collaborative project within the Copernicus programme. All of them have been led by Professor Tom Bell of the University of Birmingham, and have involved partners in Hungary, Poland and Romania as well as Germany and the UK.

From Professor Bell's perspective, the collaboration is natural: "I've known Zoltán Kolozsváry for 30 years, and we are both world experts in surface treatment. He is the current president of the International Federation of Heat Treatment and Surface Engineering (IFHT); I was president 15 years ago and will be the 'millennium' president. Through my involvement with the IFHT, I have an extensive network of contacts in both eastern and western Europe. So when Copernicus came along, it was possible to take quick action for three projects. The results have been very beneficial, considering the very small amounts of money that have been invested, and the economic potential is tremendous."

The first project ran from 1994 to 1996. It investigated how to increase the wear and fatigue resistance of machine parts by optimising process parameters for plasma nitrocarburising. The work covered plain carbon and low-alloy steels as well as special nitriding steels. Results included a new test method for improving the ductility of surfaces and led to an improved industrial process. The latter has since been applied in Romania, where three plasma units now work almost round the clock to carry out nitriding and nitrocarburising.

Improved corrosion resistance for chromium steels - keeping stainless steel stainless - was the objective of the second project, which started in 1995 and finished in 1998. Two approaches were examined, and both were successful. Professor Flis at the Institute of Physical Chemistry of the Polish Academy of Sciences investigated surface passivation techniques, while Dr Bell at the University of Birmingham carried out innovative studies on phase structure. Both processes are now in use in Romania for components applied in the chemical industry and for food machinery.

The third project is in its start-up phase and runs until early 2000. It applies an ion-beam technique to improve the friction and wear properties of polymers, and will have practical application in improving orthopaedic implants such as hip- and finger-joints. Fundamental in-situ studies are being carried out in Hungary using advanced analytical techniques, while tribological properties are being investigated in Germany. Nano-scale surface properties after treatment are being measured in the UK by the SME partner Micro-Materials, and Plasmaterm is building a small robot for testing prostheses.

 

 

Project Title:  
Optimisation of the plasma nitrocarburising process

Programmes:
PECO/COPERNICUS

Contract Reference: CIPA-CT-93-0254

Project Title:  
Improvement of corrosion resistance of nitrided chromium-alloy steels

Programmes:
PECO/COPERNICUS

Contract Reference: CIPA-CT-94-0151

 

Project Title:  
Ion beam surface modification of polymers for improved friction and wear propertiess

Programmes:
INCO

Contract Reference: ERBIC 15CT960705

 

CORDIS databaseFor more information on this project,
go to the Cordis database Record 1-2-3

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