Ogre mp Production and characterisation of composites made of metal foams with 
{ n 
ho thermally sprayed coatings 
Ur 
alt sich 
Unit). Matthias Maurer, Dieter Koch, Erich Lugscheider, Materials Science Institute, RWTH Aachen 
Wird der 
nk Eisen. 
Abstract 
108r den 
WN 7 . . . . . . 
NA Metal foams do not possess a high strength; to increase their mechanical properties and to improve 
Site the surface finish, electric arc sprayed coatings can be applied. The quality of the coating depends 
et on the coating material, the chosen process, the preparation of the surface, spraying parameters and 
Werden, . . ; . . 
on the adhesion of the coating. The main focus of this paper is to reveal the necessary requirements to 
a realise a sound composite made of a thermally sprayed coating onto aluminium foam. Basic 
el: investigations are carried out using metallographic analysis. 
1 Introduction and goal 
In general, the mechanical strength of metal foams is not sufficient for constructive applications. 
Stiff composites at low weight however can be produced using metal foams as core. Common 
techniques for joining the metal shell include welding, brazing and gluing onto foams. Yet, these 
techniques are limited to composites of regular, simple shapes. Applying thermal spraying 
nn techniques, even composites of complex shapes can be produced. Further advantages of this method 
+ Forum lie in higher possible operation temperatures (compared to glue-bonded composites), easy recycling 
of used composites and a good surface finish. 
The current research activities aim at the development of stiff, lightweight composites made of 
metal foam cores with a thermally sprayed shell. Questions to be solved are: selection of the coating 
material, coating process and spraying parameters, the appropriate preparation of the metal foam 
before coating as well as the development of a potential post treatment. The main focus of this paper 
is to reveal the necessary requirements to realise a sound composite made of a thermally sprayed 
coating onto aluminium foam. Basic investigations are carried out using mainly metallographic 
analysis. During a later stage of the project parameters are to be identified which allow to describe 
the properties of the new composite material. 
2 Thermally sprayed coatings and their mechanical properties 
Thermal spraying is a coating process in which a coating material (in form of a wire or powder) is 
heated and (partially) molten by a source of energy and then accelerated by a transport gas towards 
the substrate. The source of energy may be an electrical arc, a plasma or the combustion of a gas. 
Common coating materials comprise metals, ceramics and some selected polymers. Depending on 
the chosen process particle speeds between 150-600 m/s and particle surface temperatures up to 
4000 K can be reached. In electric arc spraying an electric arc melts the tips of two wires of the 
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