Microstructure And Wear Resistance Of Plasma Surfacing Coatings On Orchard Mower Blades

With the development of modern orchards and the continuous improvement of fruit quality requirements,orchard mechanical grass control methods have been widely used.Timely cutting weeds have significant functional inhibiting weed growth and making soil more fertility.However,due to frequent impacts and frictions in the field by grass stems,soil and sandstone,mower blades are susceptible to passivation,deformation,and fracture,resulting in poor smashing and increased power consumption.At present,mower blades have the problems of short service life,poor reliability,time-consuming and laborious replacement mower blades,and inability to operate efficiently for a long time.For this situation,the study has modified the structure of the existing mower blades,designed trapezoidal grooves,and used plasma surfacing technology to prepare a Fe-based metal coating at the location of the trapezoidal grooves aimed to form a bimetal layer structure.Finally,microwave heat treatment is used to further improve the performance of mower blades.With Fe19 powder as the main material,Fe-Cr alloy coating and microwave heat treatment process were fabricated on the trapezoidal groove of 65Mn mowing blade by plasma surfacing technology.With wear resistance as the evaluation index,the process parameters of plasma surfacing were determined by orthogonal experiments:operating current 55A,powder feeding amount 22 g·min^-1,surfacing welding speed 16cm·min^-1.After optimization of microwave heat treatment process parameters,the quenching temperature was 870°C,the holding time was 5 minutes,and quenching cooling method was oil-cooled.Remove the oil on the surface of the mowing blade and temper it.The tempering temperature is 350°C and the holding time is 30 minutes.The cooling mode is air cooling.The SEM image analysis,EDS spectrum analysis,and XRD diffraction analysis were performed on the coating prepared with the optimal process parameters.The hardness and performance of the coating were tested using a micro-hardness tester and a reciprocating friction and wear tester.The test results showed that the coating and the matrix exhibited a good metallurgical combination,there was no obvious cracks and holes on the surface of the coating,the main phases found in the coating are:?-Fe,Cr₇C₃,[Cr,Fe]₇C₃,Fe-Cr and Mo₂C.After heat treatment,the average hardness of the Fe19 coating is 58HRC,the hardness of the 65Mn matrix is 42HRC,the friction coefficient is about 0.25,and the wear loss is about 1/3 of the 65Mn steel.The results show that the indicators of the Fe19 surfacing layer are significantly higher than commonly used 65Mn steel.Field comparison tests were carried out on blades with Fe19 coating and conventional 65Mn mowing blades.Tests showed that the wear rate of the mower blade with the coating was 1/3 that of the ordinary mower blade,and the service life was improved.3 times,it shows better wear resistance.