Fabrication and evaluation of plasma sprayed nanostructured alumina-titania coatings with superior properties

Reconstituted nanostructured powders were plasma sprayed using various proc essing conditions to produce nanostructured alumina-titania coatings. Prope rties of the nanostructured coatings were related to processing conditions through a critical plasma spray parameter (CPSP) that in turn, can be relat ed to the amount of unmelted powder incorporated into the final coating. Th ose coatings that retain a significant amount of unmelted powder show optim um microstructure and properties. Selected physical and mechanical properti es were evaluated by X-ray diffraction (XRD), optical and electron microsco py. quantitative image analysis and mechanical testing. Constituent phases and the microstructure of the reconstituted particles and plasma sprayed co atings were examined with the aid of quantitative image analysis as a funct ion of processing conditions. Mechanical properties including hardness, ind entation crack growth resistance, adhesion strength, spallation resistance during bend- and cup-tests, abrasive wear resistance and sliding wear resis tance were also evaluated. These properties were compared with a commercial plasma sprayed alumina-titania coating with similar composition. Superior properties were demonstrated for nanostructured alumina-titania coatings pl asma sprayed at optimum processing conditions. (C) 2001 Elsevier Science B. V. All rights reserved.