The principle of the FAST/SPS sinter presses | Dr. Fritsch
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The Principle of FAST/SPS-Sintering 

 

  • During FAST/SPS-sintering, current flows directly through the sintering mould and even through the sinter material if it is electrically conductive
  • The electrical resistance of the mould and the sinter material leads to a quick heating. This is also referred to as Joule´s Heating 
  • Temperature is consequently generated only where it is needed
  • The sinter cycles are very short since the atmosphere in the sinter chamber does not need to be heated up
  • The short cycles result in reduced grain growth, higher densities and better microstructure of the materials
  • Since grain growth is reduced to a minimum, nano materials stay nano after sintering
  • Use of a sintering mould made out of graphite, steel or TZM is basically possible
  • Sintering is possible with loose powder or cold pre-pressed green parts
  • Compared to traditional furnaces, the productivity is often increased drastically, while the sinter costs per piece are reduced 
  • FAST sintering allows new material combinations since a soft phase can be created between material layers which creates a connection 
    This allows to create FGMs (Functionally Grated Materials) or to bond a material onto a carrier plate
  • During the sinter cycle, a vacuum is created and the sinter chamber is floated with inert gas
  • Dr. Fritsch FAST/SPS sinter presses are always equipped with a vacuum of 20mbar. As an option, a fine vaccum of 0,05mbar is available 
  • Temperature measurement is done contactless by pyrometer or, in the lower temperature range, by thermocouples
  • In order to prevent over-heating, Dr. Fritsch FAST/SPS sinter presses can take the highest temperature out of three measurements as the reference for the machine control 

The "International Powder Metallurgy Directory" (01/2012) published an article written by Prof. Kieback, at that time Director of the Fraunhofer IFAM (Dresden). Pulsed and unpulsed sintering methods were compared with each other. The article reveals, that there is no substantial difference between pulsed and unpulsed systems . Only the steep heating rates, short sinter cycles and lower sintering temperatures are relevant for the sintering result. 

For us at Dr. Fritsch, it was again proof and confirmation to avoid the unnecessary and ineffective pulsing of the current.