| Centrifugal compressor, as an important energy conversion mechanical device which is widely used in energy, electric power, petroleum, chemical, natural gas transportation, metallurgy and other industries, plays an important role in the national economic development fields. With the promotion of the sustainable development strategy, remanufacturing research on damaged and retired impeller containing high additional value is getting more and more attention, which is one of the effective ways to make full use of remanufacturing resource and solving the problem of natural resource deficiency. The high performance laser cladding repaired and the high efficiency subsequent machining of damage position of balde are the precondition for compressor remanufacturing.Therefore, the typical compressor impeller material KMN steel was taken as the substrate material. Firstly, the FeCr coating which has excellent properties was preparation through the combination method of finite element simulation and laser cladding test. Secondly, milling characteristics of FeCr coating were studied. And milling parameters of FeCr coating were optimized based on Grey relational analysis. Thirdly, aiming at the drastic vibration problem during laser cladding layer processing, the alloy powder formula which can suppress machining vibration was developed through adding heterogeneous elements in the FeCr alloy powder. And the verification tests were conducted. Fourthly, the effect of milling on the residual stress state of laser cladding layer was investigated. Active control for residual stress of coating was achieved through controlling of milling parameters. Finally, laser cladding repair and subsequent machining of repaired position were conducted on the typical compressor blade.Because of the harsh service environment, high hardness, excellent wear and corrosion resistance is the inevitable requirement for the repaired layer of compressor blade. So, the finite element model of laser cladding, based on ABAQUS software and its user subroutine, was established which used to obtain the optimal combination of process parameters aiming at smaller residual stress and low dilution rate. Then, using the optimal process parameters, the FeCr alloy was deposited on KMN steel by laser cladding. And the main performance of the coating was tested. The results showed that the recovered layer was free of cracks and had a good metallurgical bonding with the substrate. The coating presented a great hardness, excellent wear resistance and corrosion resistance.Laser cladding layer which has high hardness and excellent wear resistance should be machined to meet the function as well as the assembly requirements. So, milling characteristics of FeCr coating, including chip morphology, cutting forces and machining vibration, were obtained and analyzed. Then, milling parameter optimization of FeCr coating based on Grey theory was presented aiming at smaller milling force, better surface quality and larger metal removal rate. And optimized milling parameters for FeCr coating were obtained.Considering the drastic machining vibration, damping alloy formula with great hardness and excellent wear resistance was developed. The effect of heterogeneous elements on the coating properties was investigated. Vibration signal was collected and analysed during side milling of repaired layer. The impact of heterogeneous elements on machining vibration suppressing was studied.Residual stress state has a significant influence on the service life of repairing parts by laser cladding. So, the residual stress states, along the depth direction of laser cladding layer on thin-walled workpiece after side milling, were tested. The influence of axial depth of cut and feed on the residual stress state was analysed. The finite element model of milling was establishment. The influence mechanism of milling on the residual stress state was elucidated based on the effect of cutting parameters on cutting forces, cutting heat which obtained by simulation.In the end, remanufacturing practice of the typical compressor blade which had been preset defect was conducted. Digital model of damage blade was obtained based on reverse engineering, which used to plan the path for laser cladding repaired. The damping alloy formula was used to repair the damage position by laser cladding. After the tool path generation and post processing analysis, CNC milling of repaired blade was conducted. The laser cladding remanufacturing of centrifugal compressor blade was realized. |
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