FRACTAL CHARACTERISTIC OF MICROSTRUCTURE OF WC, ZrO₂, Cr₂O₃AND Al₂O₃ CERAMIC PARTICLES/ NICKEL ALLOY COMPOSITE COATINGS

Four kinds of WC, ZrO₂, Cr₂O₃ and Al₂O₃ ceramic particles/ nickel alloy composite coatings were prepared with the plasma spraying method. The X-ray diff raction analysis was used to investigate the phase constituentof ceramic particles in composite coatings. The hardness of the ceramic particles/ nickel alloy composite coating wasmeasured by the Leeb hardness tester. The properties of bend breaking of composite coatings were measured usingCSS-1110 elect ric all-purpose test meter. The micro-st ructures of composite coatings were t reated as a binarizationaf ter morphological processing. The f ractal dimensions of the ceramic particles/ nickel alloy composite coatings withdifferent volume f ractions of particles were obtained by means of the Sandbox method. Experimental result s indicatethat the dist ributions of ceramic particles in metal mat rix have a f ractal characteristic. The f ractal dimensions increase with the increase of particle volume f ractions. The dimensions are irrelative with the kinds of ceramic particles. The hardness and dimension of composite coatings increase with the decrease of diameter of ceramic particles.The bending f racture angles decrease with the increase of dimensions of ceramic particles/ nickel alloy compositecoatings.