The Study Of Erosion Resistance Of Nanostructured WC-Co Coatings

In our country, the high sand-contend in rivers has resulted the severe erosion of hydraulic turbines, shorten their service life, increased their maintaining cost and affects both operating reliability and economy of generators. So the research on both erosion mechanism and preventing coatings for the hydraulic turbines has the important academic significance and actual application values.The composite coatings of micron WC-Co and nanostructured WC-Co are prepared by HVOF, and the coatings of NiWC35, Ni60, Ni46 and Ni67 by thermal spraying. The hardness and erosion resistance of the coatings are tested, the coating surface is inspected with the techniques of metallographic analysis, Scanning Electron Microscope (SEM), Electron Probe Micro-Analysis (EPMA) and X-Ray Diffraction (XRD), and the anti-erosion performance of several kinds of coatings above are compared in order to explore their erosion mechanisms.This text has six chapters:Chapter 1 is a prolegomenon that introduces the overview domestic and international about the theories of nanostructured materials and spray technics, elaborates the research purpose, significance and main research contents of this text.Chapter 2 introduces the research on erosion mechanism both here and abroad, erosion phenomenon, influence factors, and the development process of the preventing coatings for hydraulic turbines. Chapter 3 introduces WC, Co, HVOF, the characteristics of the micron and nanostructured WC-Co materials, optimization of craft parameters and coating preparation.Chapter 4 chooses three kinds of coating, including. NiWC35, Ni46, Ni67, to carry on the anti-erosion experiments under eight kinds of different working conditions to make sure the working conditions to be used in chapter 5.Chapter 5 compares the anti-erosion ability of several coatings, such as Ni45, Ni60, conventional WC-Co and nanostructured WC-Co to appraise their performance under the working conditions selected in Chapter 4...