Microstructures And Properties Of Cavitation-erosion-resistance Coatings For The Fluid Machinery

With the aim to obtain higher cavitation-erosion-resistance coatings for the surface safeguard of fluid machinery, six kinds of coatings are studied in this paper, including the WC-12Co coating prepared by plasma spraying and high velocity oxy-fuel spraying (HVOF), the Ni25 and Ni60 coatings prepared by flame plating, the WC-Cr-Co and Cr₃C₂-NiCr coatings prepared by HVOF.The microstructures and the performances of the coatings are investigated respectively and compared with ZG06Crl3Ni5Mo, which is used actual in water conservancy. The phase compositions are studied by X-ray diffraction technologies and the hardness are examined by the Vickers hardness tester at a load of 200g. In order to analyze the microstructures, the coatings are eroded by different corrosives and then observed by optical microscope and the scanning electron microscope (SEM).The cavitation erosion experiment is actualized according to the Chinese standard GB 6383-86, and disfeatures of different coatings are observed with the help of SEM. In addition, the erosion mechanisms of different coatings are studied also in this paper.The results indicate that the WC-12Co coating prepared by plasma spray and the Ni25 coating have the lowest Vickers hardness, while the WC-12Co coating prepared by HVOF has much higher hardness and more compact structure, but the cavitation erosion resistances of these three coatings are much worse than ZG06Crl3Ni5Mo.Resistances of the rest three coatings (Ni60,WC-Cr-Co and Cr₃C₂-NiCr) are all better than ZG06Crl3Ni5Mo though they have different compositions and different microstructures, and the WC-Cr-Co coating is the best one due to its finer structure. Obviously, the finer structure can strengthen the cavitation erosion resistance of materials.