| The emulsion pump station is used as a power equipment for conveying pressure liquid to the hydraulic support of the fully mechanized coal mining face or the single hydraulic prop of the conventional coal mining face.The emulsion pump station system mainly consists of emulsion pump box,crankshaft,connecting rod and slider.The wear and abrasion failure is easy to happen to the crankshaft during the operation of emulsion pump station,which leads to the pressure drop in pumping station.Crankshaft is one of the important and expensive parts of imported emulsion pump station system,which worths about RMB 10W yuan and has high remanufacturing value.It is estimated that about 90%of crankshaft failure is caused by wear.The crankshaft can only be removed and left idle once worn out,which results in considerable waste of resources.Thermal spraying technology is one of the key technologies in remanufacturing engineering.Functional coatings with high properties such as wear resistance and corrosion protection can be prepared,which is superior to the substrate.The surface performance of part can be improved while restoring its size.Therefore,to tackle the wear failure problem of emulsion pump crankshaft,high speed arc spraying is adopted.The wear resistant coating is prepared according to the crankshaft material and the actual working conditions.The main contents of this thesis are as follows.(1)The difficulties of the work is that the material components and heat treatment of the imported S375 emulsion pump are unknown.Chemical compositions of the crankshaft were analyzed.The crankshaft metallographic was observed.The hardness of crankshaft was measured.And the wear failure mechanism was described according the the working conditions and the observed shaft journal wear morphology.The results show that the type of crankshaft material is 42CrMo4.The depth of surface heat treatment layer is about 0.3mm without nitriding.The microstructure is tempered bainite.The average hardness of shaft journal surface is 288 HV0.1.(2)Three kinds of high speed arc spraying coatings were designed and prepared.The microstructure,microhardness,bonding strength,XRD patterns,oxide and porosity content of the coating were analyzed.The results show that the three coatings exhibit typical lamellar structure.The microhardness of the coatings is a little higher than that of the crankshaft substrate.The bonding strength is up to 42.6 MPa.The coating is mainly composed of α-Fe and intermetallic compounds such as FeNi,FeCr,FeCrNi and a small amount of Al2O3.The sum of oxide and porosity contained in the coating is about 10%.(3)Taking the crankshaft substrate and 3Crl3 coating as the reference objects,the abrasion wear resistance properties of the three coatings were compared and analyzed.The wear resistance property of 3Cr13 coating is better than that of the crankshaft substrate and the three coatings under dry friction condition with 2.5N load.Under the lubrication conditions with 25N load and 50N load respectively,the wear resistance properties of the three coatings are better than that of 3Cr13 coating,and the coating with 10%Cr content is better than that of the crankshaft substrate.The property excellence of wear resistance coating is due to a large number of intermetallic compound acted as the skeleton of coatings,and a small amount of Al2O3 distributed in the coating,which improve the ability of anti-adhesion wear and abrasive wear. |
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