|
2609 |
|
Tuesday, September 27, 2011, Saal C2.1 2:25 PM Nanomaterial Coatings 1 |
|
Nanostructured WC-Co coatings manufactured from fine powders (10 + 2 µm) with ultra fine carbides (400 nm) by means of HVOF |
|
Ingor Theodor Baumann / University of Dortmund, Germany Wolfgang Tillmann / Institute of Materials Engineering, Technische Universität Dortmund, Germany Peter Hollingsworth*/ Institute of Materials Engineering, Technische Universität Dortmund, Germany Metin Tolan/ Faculty of Physics/DELTA, Technische Universität Dortmund, Germany Michael Paulus/ Faculty of Physics/DELTA, Technische Universität Dortmund, Germany Florian Wieland/ Faculty of Physics/DELTA, Technische Universität Dortmund, Germany |
|
Thermal sprayed WC-Co coatings are widely used for various industrial applications due to their high wear resistance. It has been reported by many researchers, that the use of agglomerated and sintered powders with submicron or nano-sized carbides can provide the deposition of WC-Co coatings with superior mechanical and tribological characteristics. This can only be achieved, as long as optimized coating conditions adapted to the specific thermo-kinetic behavior of such powders are considered. However, the porosity in the coating morphology represents an inherent problem when using powders with conventional agglomerate size (10 50 µm) and high internal porosity. Consequently, a minimum coating thickness is often necessary to provide suitable wear properties, which reduces the shape or dimensional accuracy when applying such coatings to complex surfaces. In addition, a reduction in surface roughness of the coatings cannot be accomplished by ne carbides since large agglomerates are employed. In this study we used two different ne WC-12Co powders to manufacture nanostructured coatings with high hardness, moderate toughness, low surface roughness and low porosity by means of HVOF. The first powder is a ne agglomerated and sintered powder with particles size of 10 + 2 µm and carbides in the ultra ne range (400 nm). The second powder consists of a loose mixture of ne Co (Fisher grain size FSS = 3.5 µm) with WC (FSS = 3.0 µm). Statistical Design of Experiments (DoE) was utilized to determine optimum spray conditions. Mechanical properties, microstructure and the phase development have been correlated to the thermo-kinetic in-flight particle behavior. Phase analyses were performed by XRD using a conventional x-ray tube. In addition, diffraction experiments using synchrotron radiation were conducted at the synchrotron radiation source DELTA to achieve a deeper penetration in the coatings subsurface and to record more detailed phase information. Finally, the sliding and abrasive wear behavior was analyzed at optimized coatings. |