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SUMMARY:Plasma Spray and Plasma Electrolytic Oxidation Coatings - Professo
 r Bill Clyne\, Dept of Materials Science &amp\; Metallurgy\, Uni of Cambri
 dge
DTSTART:20180426T103000Z
DTEND:20180426T113000Z
UID:TALK104098@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:A brief introduction will first be given to the plasma spray p
 rocess\, which is in extensive industrial use for the creation of (relativ
 ely thick) surface coatings.  In order to illustrate some of the character
 istics\, a particular application will be covered   -  the production of (
 zirconia-based) thermal barrier coatings (TBCs) on gas turbine components.
   This technology is at the forefront of attempts to improve the efficienc
 y of (aero-engine and power production) turbines by achieving further incr
 eases in the turbine entry temperature (TET).  An overview will be given o
 f how such coatings tend to degrade under service conditions\, particularl
 y in terms of sintering effects and consequent stiffening\, which can prom
 ote spallation.  This can be accelerated by the presence of impurities\, w
 hich can promote grain boundary diffusion and may even lead to liquid phas
 e sintering.  In this context\, there is a concern about the effect of ing
 ested volcanic ash (VA) within gas turbine aero-engines.  Some of the fact
 ors involved will be briefly described\, including those affecting the lik
 elihood of ingested particulate adhering to surfaces inside the turbine.\n
 \nA brief overview will then be given of the plasma electrolytic oxidation
  (PEO) process\, which evolved from anodization and can be used to create 
 thick\, adherent and durable coatings on certain metals\, via repeated loc
 al dielectric breakdown (sparking) within an electrolytic bath.  These con
 vert surface layers of the substrate to oxide.  While the process is very 
 different from plasma spraying\, the resultant coatings do have certain fe
 atures in common. Although it is in quite extensive industrial use\, disch
 arge characteristics are affected by a number of processing variables and 
 understanding of the process is incomplete.  However\, the inter-relations
 hips between electrical conditions\, electrolyte composition\, coating mic
 rostructure and rates of growth\, which are linked via the characteristics
  of the discharges\, have become a little clearer over recent years and an
  outline will be provided of current scientific and technical developments
 .\n
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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