Arc spraying repair technology of gear pump
1, the principle and characteristics of arc spraying
Arc coating technology in the past 20 years in materials, equipment and applications developed rapidly, its working principle is to be two sprayed wire as a melting electrode，loader multi way valve
2, gear pump arc spraying repair process
Bushing bore, sleeve outer circumference, gear shaft and pump casing uniform wear and scratches in the 0.02-0.20mm, should adopt high hardness, strong combination with the body parts, good wear resistance arc spray repair Process. Arc spraying process: the working surface pretreatment → preheat → spray bonding the bottom → spraying the working layer → cooling → coating processing.
Spraying process, the requirements of the workpiece without oil, no rust, surface roughness, preheating temperature is appropriate, the bottom combined with a solid, smooth working layer, the material particles melt-bonded reliable, good wear resistance and corrosion resistance. Spray coating quality and workpieces surface treatment and spraying process has a great relationship, therefore, choose the appropriate surface treatment and spraying process is very important. In addition, the non-sprayed portions adjacent to the coated surface should be bundled with a thin sheet of metal or copper during spraying and spraying.
⑴ surface pretreatment coating and the basic bonding strength and substrate cleanliness and roughness. Before spraying, the basic surface cleaning, degreasing and surface roughening and other pretreatment is an important process spraying process. The first part of the spray should be sprayed with gasoline, acetone degreasing treatment, with a file, fine sandpaper, whetstone will remove the fatigue layer and the oxide layer, exposing the metal color. Then roughening treatment, roughening treatment can provide surface compressive stress, increase the bonding area and clean the surface of the coating and the substrate, reduce the stress when cooling the coating, ease the internal stress of the coating, it is conducive to the increase of adhesion . Sandblasting is the most commonly used roughening process, sand to sharp, hard as well, the choice of quartz sand, emery and so on. Rough fresh surface easily oxidized or polluted by the environment, it should be timely spraying, if placed more than 4h will be re-roughened.Loader full hydraulic steering gear
⑵ surface preheat treatment The temperature difference between the coating and the substrate surface will produce shrinkage stress coating, causing the coating cracking and peeling. Preheating of the substrate surface can reduce and prevent the above adverse effects. But the preheating temperature should not be too high, so as not to cause the substrate surface oxidation and affect the bonding strength of the coating and the substrate surface. Preheat temperature is generally 80-90 ℃, commonly used to complete the neutral flame.
⑶ spray-bonded primer coating before spraying the work of a thin layer of metal coating for the follow-up to provide a clean, rough surface, thereby enhancing the bond between the coating and the substrate strength and shear strength. Bottom bonding materials generally use ferrochrome nickel alloy. The main principle of choosing the spraying process parameters is to increase the bonding strength between the coating and the substrate. Spray gun and the workpiece during the relative movement speed is greater than the flame moving speed, the speed of the size of the coating thickness, spray wire feeding speed, arc power and other parameters determined jointly. Spray gun and the surface of the workpiece is generally about 150mm. Other specifications for arc spraying are determined by the characteristics of the coating equipment and the coating material.
⑷ spraying working layer. Wire brush should be used to remove the adhesion of the bottom surface of the sediment, and then immediately spray coating. Materials for the carbon steel and low alloy wire, the coating has a higher wear resistance, and lower prices. Spray coating thickness should be based on the amount of wear and tear of the workpiece, machining allowance and other relevant factors (diameter shrinkage, clamping deviation, spray coating diameter uneven amount, etc.) to determine.
⑸ cooling spray temperature after the workpiece is not high, the general can be directly air-cooled.
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