ISSN:
1013-9826
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Thermal spraying consists in a technology aiming at producing coatings whosethicknesses range from 10 μm to a few millimeters onto mechanical components to confer themspecific and unique functional properties, such as wear and corrosion resistances, frictioncoefficient adaptation, thermal and electrical insulation, biocompatibility, repair, etc., among theprincipals. Thermal spraying consists in injecting in a viscous enthalpic jet (animated by amomentum) powder with particles which average size ranges from 0.01 to 100 μm. These particlesare melted and simultaneously accelerated towards the surface of the part to be covered. They form,after impact, spreading and solidification, near-circular lamellae the stacking of which form thecoating. Due to the versatility of the available processes exhibiting a wide range of enthalpic andmomentum contents, virtually any kind of material exhibiting congruent melting behavior can beprocessed, from alloys and ceramics to polymers, ever since its melting temperature differs from itsvaporization or decomposition temperature by at least 300 K and that it can be processed previouslyunder the form of powder particles or wires.Thermal spray techniques offer the unique capability to manufacture a large variety of coatings oncomponents of a large variety and geometry. However, thermal spraying constitutes a specialprocess for which the coating service properties derive mostly from the structure and indirectlyfrom the selection of the operating parameters. Very significant improvements over the past yearspermitted to diagnose the in-flight particle characteristics, mostly in terms of velocity andtemperature. Recently, these new capabilities have made possible the development of on-lineprocess controls. This should participate to a drastic increase in coating reliability.In convetntional thermal spraying processes, a pulverulent feedstock (i.e., powder particles) isinjected within the plasma jet via a carrier gas. This approach does not permit to process smalldiameter particles; i.e., nano-sized particles, which could permit to form finely grained coatings.Replacing gas by liquid to carry particles offer the unique possibility to process nano-sizedparticles. Cold gas spraying may appear as an alternative process to reach the same goal.Indeed, thermal spray processes experienced very significant developments over the past years,opening new doors to manufacture coatings with a high reliability and superior properties.This papepr indend at presenting some of those developments
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/57/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.384.1.pdf
Permalink