Ceramic Coatings in Pump Manufacturing
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ANDREAS KOHL*', HEIUT RIEGGER*, KEITH T. SCOTT**, A. McCABE**, PH. MAURIN-PERRIER "KSB AG Frankenthal, Johann-Klein-Strafe 9, D-67227 Frankenthal, Germany :**EA Harwell Laboratory, Oxfordshire OXI 1, ORA, U KCedex, France HEF,Technology, Z.I. SUD, Rue Benoit Fourneyron, 42166Andr6zieux-Butheon INTRODUCTION
The pump-producing industry uses solid SiC combinations for tribological components. Thanks to their outstanding corrosion resistance, hardness, thermal stability and other qualities, such pairings have gained widespread acceptance, particularly for mating and sliding surfaces. For structural reasons, the brittleness and low tenacity of solid SiC limit its range of applications. The ideal solution, of course, would be to find a coating with identical desirable properties. The application of ceramic coatings is a typical procedure in mechanical engineering. Oxide ceramic coatings like chromium oxide, aluminium oxide or zirconium oxide are used for highly wear and corrosion resistant coatings in the chemical, textile and printing industry. Nonoxide ceramics like carbides or nitrides are used for cermets or for similar coatings in contact with a suitable metal binder. Typical applications are wear loaded machine components'. The favoured spray techniques are plasma or flame spraying. Especially important are vacuum plasma spraying (VPS) or air plasma spraying (APS) and the detonation gun spraying process. The choice of the best process depends on factors like adhesion, density, temperature of the coating powder and the base material. The VPS technique is producing very dense coatings made of reactive materials without the danger of oxidation', 2. It is determined to know about the real load. In pumps and valves they are mainly corrosion, abrasion, cavitation and tribological factors, especially sliding wear. Another very important factor for successful use of coatings is the special design. The user of a coating technique should keep inmind a coating design from the early beginning of the work. In pump industries there are a lot of examples for using of coatings. Mainly these coatings are found in high tech technologies like energy power stations, off shore industry or biotechnology.
Typical components are sealings with chromium oxide, shaft sleeves with chromium carbide or
bearing sleeves made of aluminium/titanium oxide. The present paper was partially sponsored by the EC BRITE EURAM, project number BE 4329 - 90. PROCESSING TECHNIQUE
The coatings for the present paper has been produced by vacuum or air plasma spraying. A typical VPS chamber is seen infig. 1.
'lot
POWDER PRODUCTION
The powder production isvery
important step for a successful development of a new coating. Simi-
lar to common powders like
:
k
IA
-
|f
WC/Ni or Cr3C2/NiCr it should be possible to produce a powder Fig. I Vacuum Plasma Spraying Chamber based on SiC. Unfortunately, SiC I__ 551 Mat. Res. Soc. Symp. Proc. Vol. 355 01995 Materials Research Society
sublimes and dissociates at high temperature (>2000°C) and thus cannot be plas
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