Plasma Spray Coatings of Sol-Gel Ceramic Nanopowders

摘要

The use of a dense ceramic layer on a substrate as a barrier coating is often limited due to poor mechanical strength of the ceramic layer. Moreover, structural changes resulting sintering and phase transformation can contribute to failure of a coating, especially in operation at high temperatures. Nanocrystalline ceramic materials have been recognized to have special mechanical properties. Ceramic nanopowders were synthesized through sol-gel method and deposited on metal substrate by Atmospheric Plasma Spraying (APS). Commercial ceramic coatings were also developed for comparison reasons, as well as nanophased coatings using high-energy ball milled powders. All coatings were fully characterized in terms of porosity, adhesion strength, microhardness and microstructure. Studies were focused on effects of powders' properties and spraying conditions on the crystallinity and mechanical properties of the coatings. Results suggested that thermal spraying of ceramic nanopowders leads to coatings with properties comparable to those of conventional powders (microhardness up to 1146 HV, porosity down to 13 %, adhesion up to 30.6 MPa for a coating thickness of 169 μm )and the reduction of the initial powder grain size to nanoscale favours the development of high crystallinity coatings with improved mechanical properties and thermal stability.