Pump Rotation Parts Failure Mechanism Analysis And Wear-Resisting Ceramic Coating Protection Research Under Hangzhou Bay Seawater Environment

Seawater corrosion of nuclear power plant in Hangzhou bay is much more serious that it in normal seawater condition, due to the special water quality in Qiantang River.After first use of ten to twelve months, duplex stainless steel impeller of main circulating water pump MAS/6001 25/5 was damaged heavily in Qinshan phase II. The failure mechanism analysis and SEM pictures indicated: damage of impeller is typical erosion-corrosion of metal in solid-liquid double phase liquid. Followed by the silt mechanical scouring and wear, there is electrochemical corrosion, the rate of silt mechanical scouring and wear is much more qiucker than seawater erosion. The diameter of grains of sand is tiny, most of them shaped like arris sheets, the main expression of abrasion is micrographic cutting. Interaction between silt scouring and erosion-corrosion enhances the micrographic cutting of silt; Solid phase in seawater promotes nucleation by cavitation which formed cavitation corrosion pit on surface of materials, accelerates erosion-corrosion.The most effective and adoptive method in mesoporphyrin protection is overlaying coating on surface of materials. Wear-resisting ceramic compound coating is made up of five kinds epoxy wear-resisting protection coating of two components, that is bulky grain wear-resisting protective agent, finely ground particle wear-resisting protection agent, ultra metal healant, white brushing ceramic powder and gray brushing ceramic powder. There are vickershardness measurement test, resisting-erosion-corrosion test by using homemade machine, adhesion measurement test by using tension machine and coating moisture pickup test about wear-resisting ceramic compound coating, based on site water power factor, used five kinds of test sample.The result of test research and engineering practice of wear-resisting ceramic coating indicates: different each mechanism performance in different coating proportioning.The weight losed rate of coating and duplex stainless steel is biggest at 45°scouring angle. With increased of fluid velocity and improved of silt contents in seawater, the weight losed rate of coating and duplex stainless steel is multi-times'rise. Due to it contains more high hardness ceramic grains, the coating can obstruct the micrographic cutting to the metal materials by silt of hangzhou bay seawater and make the surface passivation. The hardness and erosion-corrosion resisting performance of coating are obviously excellent than duplex stainless steel, its density is good and water absorbing capacity is lower. Coating has excellent combination property, its wear-resisting and erosion-resisting are far better than duplex stainless steel; Comparing with WC coating thermal sprayed which supplied by Weir Pumps Ltd. the cavitation resisting and erosion-corrosion resisting property of wear-resisting ceramic coating are better. Furthermore, the wear-resisting ceramic coating takes on good economic performance and manufacturability, it obtains the aims that sacrifices coating for protecting the impeller and prolongs using longevity of impeller. The wear-resisting ceramic coating can entirety fulfills twelve months'refueling period of units operation, and it can also attain fourteen months'even eighteen months'refueling period.