Institute Advanced Ceramics

Project title:

MeCeram - Processing of novel metal-ceramic composites with defined functional properties and prototypes for ceramic roller bearings

Objectives:

A novel powder metallurgical process for the fabrication of metal reinforced ceramics was developed at the Institute of Advanced Ceramics. The so called s-MAC process (sintered metal-alumina composites) has recently been shown to be an alternative route for low-cost fabrication of highly dense cermets. Aim of the current project is the investigation of the s-MAC process for commercial production of high-performance ceramic materials with adjustable properties (e.g. electrical conductivity, wear resistance or surface stresses).

Methods:

For fabrication of these cermets precursor powders composed of aluminium oxide, aluminium and metal powders (e.g. Cr, Mo, Fe) are wet milled, dried and subsequently uniaxial and/or cold isostatic pressed. Green bodies are reactively sintered under an inert gas atmosphere as shown in Fig. 1. The addition of aluminium allows pressureless densification as it promotes sintering by reducing the native oxide layer of metals. Because only small amounts of aluminium are present, redox reaction takes place on a very small scale and thereby thermal runaway does not occur. These cermets offer improved mechanical (e.g. fracture toughness, bending strength) and tribological properties (e.g. wear resistance, friction coefficient) when compared to single phase ceramics.

Fig. 1

For industrial production the s-MAC process will be combined with plastic shaping by extrusion or injection molding. In the present project, the focus is on bearings exhibiting increased wear resistance and special sensory functions (Fig. 2).

Fig. 2

Publications:

• R. Janssen, S. Scheppokat and N. Claussen, “Tailor-made ceramic-based components – advantages by reactive processing and advanced shaping techniques”, J Eur Ceram Soc, vol. 28, pp.1369-1379, 2008.
  
  
• M. Leverkoehne, A. Dakskobler, M. Valant, R. Janssen and T. Kosmac, “Cr-Al₂O₃ layered composites with a high electrical anisotropy prepared by repeated deformation processing”, J Eur Ceram Soc, vol. 25, pp. 65-72, 2005.
  
  
• S. Scheppokat, R. Hannink, R. Janssen, G. de Portu and N. Claussen, “Sliding wear of Cr-Al₂O₃-ZrO₂ and Mo-Al₂O₃-ZrO₂”, J Eur Ceram Soc, vol. 25, pp. 837-845, 2005.
  
  
• G. Arslan, R. Janssen and N. Claussen, “Processing and characterisation of three-layer alumina-based composites with enhanced damage tolerance”, J Eur Ceram Soc, vol. 25, pp. 3553-3561, 2005.
  
  
• S. Schicker, T. Erny, D. Garcia, R. Janssen and N. Claussen, “Microstructure and mechanical properties of Al-assisted sintered Fe/Al₂O₃ cermets”, J Eur Ceram Soc, vol. 19, pp. 2455-2463, 1999.