| Plasma Additive Manufacturing?PAM?uses plasma arc as the heat source,modeling 3D components,and manufacturing them layer by layer,which owns broad prospects in various fields.At present,the researches on PAM are mainly focused on low-energy plasma arc using wire material,while the researches on high-energy transfer arc PAM using powder material are relatively scarce.Using transferred arc as heat source makes PAM components more efficient in packing;when using powder materials,the forming accuracy of the sample is also higher than wire,and the composition of powder is convenient to change according to individual environment.In this paper,vibration is introduced to improve the stress deformation and microstructure of PAM.In this paper,the transfer arc plasma welding machine is used,and Fe314 powder is used to feed powder synchronously.The formation process of PAM and vibration-assisted PAM specimen macro forming,residual stress,residual deformation,microstructure and properties and internal mechanism are studied.First,the single-layer forming process experiment was conducted,and the influence of parameters on the single-layer forming was obtained.Then,a quadratic regressive rotation experiment was designed to obtain the numerical relationship between forming dimensions and process parameters for multi-pass single pass forming.The PAM process parameters range was obtained.The welding current I ranges from 30 to 40 A,the powder feeding speed V1 ranges from 4 to 5.6 g?min-1and welding speed V2 ranges from 100150 mm?min-1.Vibration was assisted during PAM process.The results showed that vibration is not conducive to PAM sample formation.When the vibration is applied,the residual stress and residual deformation of the specimen are reduced.The vibration parameter of 4m/s2 showed the best effect on the residual stress,and the vibration parameter of6m/s2 showed the best effect on the residual deformation.When it comes to organization,vibration refines the grain structure of PAM components,and the effect of dendritic refinement is most obvious.The main phase composition of the sample is??Fe,Ni,Cr?phase and??Fe,Cr?phase,which were both solid solution structure.Vibration did not show significant effect on the phase composition of the tissue.The element Cr is enriched in the inter-layer binding region.After vibration assistance was applied,the element distribution was diffused,however,compositional segregation still exists in the inter-layer bonding region.In terms of performance,samples made of Fe314 powder can be applied to marine structures,as a reslut,various performance tests have been performed based on the application background.The researches showed that the vibration makes the microhardness distribution of the PAM specimen uniform,among which the vibration acceleration of 4m/s2 improves the best;the vibration increases the tensile strength of the PAM specimen,and the vibration parametre of 2m/s2 is the most significant.Vibration improves the wear resistance of PAM components.In this experiment,the wear patterns of the samples were oxidation wear,abrasive wear and peeling.The wear resistance performance is best improved at 4m/s2 and 6m/s2.The vibration enhanced the corrosion resistance of PAM samples.Among the parametres,the vibration resistance of 4m/s2 increases the corrosion resistance the most.The addition of vibration in the PAM interferes with the forming accuracy of the sample,but the microstructure of the sample is refined,the properties are improved,the residual deformation and the residual stress are decreased,which proves that the vibration-assisted PAM shows certain application value. |
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