Currently funded project

Development of a coating of short fibres using the fluidised bed coating process (3D-FRG)

Motivation

Fluid bed coating plant for ceramic short fibres
© Fraunhofer-Centre HTL
Fluid bed coating plant for coating ceramic short fibres

The overall objective of the project is the additive production of fibre-reinforced SiC/SiC and C/SiC components with significant property and environmental advantages over conventionally processed ceramics. The first step is the development of fibre-filled granulates for the additive production of short fibre reinforced preforms, which are further processed by reactive infiltration with molten silicon to form complex Ceramic Matrix Composites (CMC) structures. Short fibre or particle-reinforced CMC with isotropic properties are particularly suitable for the manufacture of geometrically complex but compact components which are subjected to high loads in different load combinations and load directions and additionally to very high temperatures. Examples are fittings of all kinds as well as nozzles, combustion chambers, turbine parts, brake discs, high-temperature fans or structural parts for optics.

Objective

Fluid bed coating process Pyrolysis ceramic coatings
© Glatt Ingenieurkeramik GmbH, Process Technology, Food, Feed & Fine chemicals
Principle of the fluid bed coating process including pyrolysis for burn-in of ceramic coatings

Within the scope of the individual project of the Fraunhofer Centre HTL, a coating of ceramic short fibres using a fluidised coating process is to be developed. Ideally, the short fibres should be completely covered with a boron nitride coating so that the end faces are also coated. The coating is intended to adjust the bonding of the fibres to the matrix in such a way that an improvement of the mechanical characteristics of the additive produced short fibre reinforced CMC is achieved. The coated short fibres are processed by the project partners into CMC by means of additive manufacturing processes.

Approach

BN/Si<sub>3</sub>N<sub>4</sub>-coating SiC continuous fibre dip coating process
© Fraunhofer-Centre HTL
SEM image of a BN/Si3N4 coating on a SiC continuous fibre produced by a dip coating process
  • Synthesis of air-stable precursor for boron nitride coatings
  • Adaption of the rheological properties and the wetting
  • Process development for coating of short fibres using fluid bed and dip coating processes
  • Drying of the applied coating with avoidance of agglomerate formation
  • Development of the pyrolysis process for burn-in of the coatings with the aim of achieving stoichiometric crystalline boron nitride coatings as far as possible

Project Data

Project Duration 01.04.2019 - 31.03.2022
Sponsor Bavarian State Ministry of Economic Affairs, Regional Development and Energy
Funding Amount 50,000 Euro
Project Partners Fraunhofer-Centre HTL
Fraunhofer ISC
Bavarian State Ministry of Economic Affairs, Regional Development and Energy
Project Coordination Joint project
Project Management at the HTL Dr. Andreas Nöth