Effective protection of turbine runner blades in hydropower stations by supersonic flame spraying

       The Qingtongxia Hydropower Plant uses supersonic flame spraying technology to protect the runner blades with all-round surface coating, with a total spraying area of 45m2. The coating material SXH-70 is composed of a mixture of ceramics and metal alloys, which has both good rigidity and toughness. Laboratory simulation tests show that on the base material of 0Cr13Ni4Mo parts, the spray thickness is 0.25mm~0.3mm, the bonding strength is ≥70MPa, the cavitation resistance is 1.55 times that of 0Cr13Ni4Mo, and the resistance to mud and sand wear is 91.5 times. Before the technology was adopted, several power stations in the Yellow River silt and sand basin had carried out coupon tests for more than two years. It was verified that the anti-abrasion effect was ideal.



    The comparison of the abrasion conditions of the runner blades of the 6# machine of the Qingtongxia Hydropower Plant before and after spraying is as follows:

     1) Abrasion of runner blades before spraying

     The 6# machine runner was updated in 1996, and the blade material was 0Cr13Ni4Mo. After 1816 hours of operation, the blade showed an overall thinning trend, and the back of the blade was severely eroded from the water inlet to the water outlet. The area 500mm from the outer edge; Perforations appear at the outer edge and the inlet and outlet angles, the gap between the blade and the runner chamber increases by 15mm~30mm, the cavitation area reaches 9.56m2, the total weight loss is 423.7kg, the maximum cavitation depth is 40mm, and the average depth is 5mm~7mm.

     2) Abrasion of runner blades after spraying

      After 15284 hours of operation, the spray coating of the runner blades was checked on June 18, 2003. The coating on the front of the blade is intact, and the thickness of the coating is not significantly reduced; the outer edge of the blade is basically intact, and the gap between the blade and the runner chamber is not enlarged; the local coating in the strong cavitation area on the back of the blade is cavitated and peeled off, with a total area of 0.408m2 and a total weight loss of 10.7 kg, the average cavitation wear of the base metal is 2mm~4.4mm.

      Judging from the results before and after spraying of the runner blades of the 6# machine and the actual before and after operation, the surface of the axial flow turbine of Qingtongxia Hydropower Plant was sprayed with supersonic flame, and the SXH-70 anti-abrasion coating was used to prevent and obtain obvious effects, which fundamentally relieved the mud and sand. Wear and damage, alleviate the harm of cavitation, prolong the service life of the turbine and the maintenance cycle of the unit.