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Research progress on anti - cavitation and wear protection of water pump
Cavitation, abrasion and the joint damage of the pump have always been an important issue in the operation, maintenance and management of the pump. The traditional surface protection materials and processes are far from meeting the requirements of the pump for cavitation and erosion resistance. In order to enhance the ability of anti-cavitation and erosion on the surface of pump over-current components, besides the use of stainless steel or other cemented carbide materials to manufacture blades and impellers, the surface protection technology is continuously tested. This article describes its progress as follows. 1 surface protection technology research 1 1 Introduction to surface protection technology 1 1 1 non-metallic coating research China in the 20th century, 60, 70 began to epoxy resin and its compounds applied to the pump for anti-erosion protection. In the 1980s have also developed a composite nylon coating, polyurethane coating, imitation ceramic coating and rubber coating and other non-metallic coatings. In addition, there are some non-metallic coatings formed using materials such as quick-acting titanium rubber, rubber, enamel, ceramic, glass and the like, which are less used due to complicated processing techniques and the like. The 20th century, 90's, also introduced in the industrial area of ​​the United States Devcon repair agent, ARC composite coatings, synthetic rubber and other polymer materials. These non-metallic coating materials in pumping station harsh environment, often due to the coating and the metal matrix bonding ability and the material itself is not enough hardness, it is difficult to achieve the desired anti-cavitation, anti-erosion effect. 1 1 2 Metal Coatings [2] Metal surface coatings are also widely used in pump anti-abrasion surface protection technologies. The most widely used is electrode surfacing and wire coating. The use of stainless steel electrode surfacing method can guarantee the welding layer and the substrate has a high bonding strength, but the surfacing fade rate, welding thick and uneven processing margin, demanding solderability of the substrate material . The surface of the pump blade treated by the surfacing welding method is generally subjected to new cavitation destruction immediately around the surfacing spot until no cavitation damage occurs at the surfacing zone until the bottom of the surfacing layer. The stainless steel spray particle coating formed by wire spraying is mechanically combined, which is not suitable for the pump impact load and anti-cavitation repair. For some large pump parts, such as large diameter (3m diameter and above) axial pump impeller chamber, the surface can be mounted with a stainless steel plate to increase the anti-erosion ability. However, this method needs to be sent to large-scale pump plant specialized processing, turning, setting, welding, expensive, long cycle, non-ordinary pumping station can be implemented. Alloy powder coating is developed on the basis of wire spraying. Compared with the surfacing method, the molding is smooth, the thickness is easy to control, the fading rate is small, the method is simple, the heat source is easily obtained, and the processing is not limited by the climate and the site. However, since the sprayed layer is formed by regularly stacking alloy powder particles in a semi-molten state sprayed onto the surface of a substrate at a high speed and in a layered structure, the physical properties of the sprayed layer are directional and, in each spraying process, Powder particles appear condensation, shrinkage, deformation and other phenomena in the coating developed into an internal stress, so the alloy powder coating is generally only used for cavitation and erosion less serious surface protection of small and medium-sized pumps. 1 2 surface protection materials and process requirements 1 2 1 surface protection materials technical requirements Anti-wear coatings must have [1] :( 1) high strength and hardness to resist cavitation, abrasion damage; (2) with A certain toughness to absorb the impact energy; (3) has a high bond strength to ensure that the coating in the pump 30 ~ 35m / s under the impact of high-speed flow will not spall; (4) the coating material must be affordable , In order to ensure the large and medium-sized pumping station and a large amount of rural small and medium-sized pump stations in rural areas to promote the use; (5) coating materials should be non-toxic, non-flammable, explosive materials, easy to custody transport, do not pollute the surrounding environment. 1 2 2 processing requirements In order to ensure the promotion and application of surface protection technology, processing technology must be: (1) the process is simple and can be mastered to different levels of operators; (2) the tools used in processing (apparatus) Should be readily available in the market or necessary for general pumping station maintenance work, and at affordable prices, without special and expensive equipment; (3) The process should not be affected by the seasons and the surrounding environment to ensure that the pump station in the winter , The spring maintenance period can be carried out; (4) the coating does not require special insulation curing, after coating can be quickly cured or put into use to shorten the maintenance cycle.