Method for the partial re-furbishing of blade surfaces of water turbine, comprises partially smoothing the surface in and around the damaged and/or worn-down area and subsequently treating through sand radiation

摘要

The method comprises partially smoothing blade surfaces of water turbine in and around the damaged and/or worn-down area and subsequently treating by sand radiation. An intermediate layer (3) is electrochemically applied on the surface part sanded through the sand radiation. A new hard material layer (4) is applied from cermet (ceramic-metal-mixture) in a thermal spraying process and subsequently the newly coated surface part is sanded off corresponding to the geometrical condition of the component. The new hard material layer is applied from the cermet in high velocity flame spraying method. The method comprises partially smoothing blade surfaces of water turbine in and around the damaged and/or worn-down area and subsequently treating through sand radiation. An intermediate layer (3) is electrochemically applied on the surface part sanded through the sand radiation. A new hard material layer (4) is applied from cermet (ceramic-metal-mixture) in a thermal spraying process and subsequently the newly coated surface part is sanded off corresponding to the geometrical condition of the component. The new hard material layer is applied from the cermet in a high velocity flame spraying method. Through the sand radiation, the surface of the primary hard material layer (2) partially sanded off in and around the damaged and/or worn-down area is worn out in the damaged area up to a substrate (1) and partially worn out and roughened in an area of 15 mm. The sand radiation of the surface is implemented with aluminum oxide with a pressure of 1-10 bar from a distance of 50-200 mm in such a way that the surface roughness is obtained to 4 mu m. The layer thickness of the radiation is less than 50 mu m. In the expanded area, a surface roughness is obtained to 5 mu m. The intermediate layer provided as nickel layer is applied at 40-50[deg] C with a thickness of 50-70 mu m. The new hard material layer has a thickness of 100-300 mu m and has the same or better characteristics regarding to the wear or corrosion as the original hard material layer subjected on the substrate.