Microstructure And Properties Of Fe25 Based On MPAW Additive Manufacturing

In recent years,plasma cladding rapid prototyping technology,as a branch of rapid prototyping technology,show a rapid development.Plasma arc is similar to the laser and electron beam in high arc temperature and high precision,and overcome the disadvantage of expensive equipment and high running cost.But current research about plasma additive manufacturing still exist many problems,such as rarely build process parameter model to control dimension precision.At the same time,the cladding materials always choose carbide reinforced iron-based alloy or nickel base and cobalt base alloy.Nickel base and cobalt base alloy are with high cost,which reduce the economic benefits,carbide show a poor formability and easily cause grain boundary embrittlement.This paper aims to build additive manufacturing platformbased on micro-plasma cladding technology.Experiment was carried out around process parameters including welding current,scanning velocity,powder feeding rate.Relationship between quality of cladding layer and process parameters was reflected through Matlab statistical model to obtain high quality layer with good dimensional stability.Influence on Fe25 iron base alloy powder of Ti,Al is studied.Phase transition of alloy powder is simulated through JMat-Pro to provide guidance for design of powder composition.Then,using the micro-plasma cladding additive manufacturing platform complete alloy powder cladding.elements transition,organization,microhardness,wear resistance,tempering performance of layer are studied to provide theoretical basis and practical reference for precision parts surface repair.The results show that in single layer cladding,the different aspect ratio can be obtained under different process parameters,and target fusion width and depth can be realized through the establishment of parameters statistical model.When cladding the second layer,layer width increase about 25%under the same process parameters,aspect ratio decrease.The study of Fe25 type alloy cladding with different alloy adding show that 0⁶ wt%Al addition lead to a transformation of crystallization type in coatings.With the increasing of Al contents,the preliminary phase changes from austenite to ferrite,with?-Fe core,carbide and boride skeletons forming gradually,while the final coating is comprised of ferrite and granular bainite.Microhardness of cladding layer increases at first and then decrease with the increment of Al contents,reaching to a peak microhardness value(about 618 HV_0.2)in 4wt%Al,increasing 285HV_0.2.2 more than Fe25 coating,friction coefficient reduce about 45.32%.While the high temperature oxidation resistance of coatings show a continuous improvement because of Al in solid solution and the formation of Fe₂AlCr and Fe₃Al.2wt%Ti coating reaches the highest microhardness,According to XRD and electronic probe test,TiB,TiC and Fe₂Ti are formed in grain boundary,some Ti is soluble in primary phase result in solid solution strengthening.After tempering,2wt%Ti temper soften,4wt%Ti coating reaches the highest hardness because of intermetallic and carbide precipitation.In 6wt%Ti coating,excessive Ti capture C atoms,which restrain the precipitation of Cr₂₃C₆,so the average microhardness is slightly reduced.