| Remanufacturing engineering is through the use of advanced surface engineering technology and other means to repair and strengthen locally damaged parts to extend the service life of difficult to manufacture,high value parts,which is an important way to achieve the "reduction,reuse,resource recovery" of circular economy.Electron beam wire-feeding deposition technology has become an emerging remanufacturing technology due to its high energy density,high deposition efficiency,low cost wire materials and vacuum processing environment.The electron beam wire-feeding deposited coating has fine grain,good growth orientation,excellent comprehensive performance and good metallurgical bonding surface,which can realize the repair and reinforcement of high precision complex components.It has huge potential and broad application prospects for remanufacturing of high value parts,such as gas turbine and aeroengine turbine blade.Inconel 718 alloy is a precipitation-hardenable nickel-based superalloy with addition of Nb elements.It has excellent wear resistance,corrosion resistance,oxidation resistance,fatigue resistance and good welding performance in the range of-253 ? 650?,making it an excellent remanufacturing and repair material.In this paper,the nickel-based superalloy coating was fabricated by electron beam wire-feeding deposition technology using Inconel 718 wire as the cladding material,and the preparation technology,microshtructure and properties of the deposited coating were studied.Firstly,the effects of processing parameters on the forming quality of the deposited coating were explored by adjusting beam current,wire feeding rate and travelling speed,and the optimal processing parameters for preparing coating were found.Then,the Inconel 718 alloy coating with good surface appearance,no flaws and good combination with matrix was prepared with optimized processing parameters,and the macrostructure,microstructure,precipitated phase,hardness and wear resistance of the deposited coating were studied systematically.Additionally,the influence of different heat input on the microstructure and properties of the deposited coating was revealed.Finally,three different heat treatments were carried out for the deposited coating,and the microstructure evolution,precipitation phase,hardness and wear resistance of the deposited coating after heat treatment were analyzed.Besides,the correlation between different heat treatment and the microstrusture and properties of the deposited coating was discussed.The results showed that:(1)the best process parameters for electron beam wire-feeding deposition of Inconel 718 alloy coating were 10 m A of beam current,350 mm/min of wire feeding rate and 300 mm/min of travelling speed.It was found that the wire feeding rate determines the thickness of the deposited coating,while the beam current and travelling speed mainly affect the dilution rate and shape coefficient of the deposited coating.With the increase of the beam current and the decrease of travelling speed,the dilution rate and shape coefficient of the deposited coating increase,and vice versa.(2)The cross section of the deposited coating can be divided into three regions: clad zone(CZ),fusion zone(FZ)and heat affected zone(HAZ).Equiaxed dendrites and circular Laves phase are formed in the CZ,while columnar dendrites and long-chain Laves phase are formed in the FZ.With the increase of the beam current and the decrease of the travelling speed,both the dendrites and Laves phase in the CZ and FZ are coarsened,and vice versa.The hardness value of the deposited coating decreases with the increase of the distance from the surface and the average hardness of the CZ is higher than that of the FZ.With the increase of the beam current and the decrease of the travelling speed,the hardness and wear resistance of the deposited coating deteriorated.(3)Heat treatment has an important influence on the microstructure and properties of the deposited coating.After the direct dual aging treatment,the microstructure of the deposited coating was not significantly different from that of the sedimentary state coating,indicating that the direct dual aging treatment has little effect on the elimination of Laves phase.After 980? solid solution + aging treatment,the dendrite structure of the deposited coating was obviously refined,part of Laves phase was dissolved and the content of Laves phase decreased.After the standard heat treatment,the Laves phase was almost completely dissolved and a large number of Nb elements were remelted into the ?austenite,indicating that complete recrystallization has occurred in the deposited coating.Heat treatment can improve the hardness and wear resistance of the deposited coating.Among the three heat treatments,the standard heat treatment and 980? solid solution + aging treatment can improve the hardness and wear resistance of the deposited coating significantly. |
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