Study On Technology,properties And Application Of Modified Fe-Co-V Alloy Functional Coatings Prepared By Laser Cladding

Magnetic fluid sealing technology has been widely used in aerospace field due to its advantages of zero leakage and high torque transfer efficiency.In this thesis,based on the service condition of rotating shaft of magnetic fluid sealing device,Fe-Co-V functional coating with wear-resistance and high-permeability was prepared by laser cladding.Firstly,the coating system,in which the Fe49Co2V alloy with high saturation magnetic induction intensity ratio was adopted as main component and Si and B were used as alloying elements to improve the mechanical properties,was determined and the forming performance and mechanical performance of the coatings under different process parameters were studied by means of laser cladding,and the optimal process parameters were also determined.Then,the effects of different doping contents of Si and B on the formability,microstructure,mechanical properties and soft magnetic properties of Fe49Co2V alloy were studied,and the coating composition with excellent comprehensive properties was confirmed.Finally,the functional coating was prepared on the rotating shaft by using the optimal process parameters and coating composition,and the magnetic fluid sealing device was assembled and its application performance was monitored.The main conclusions of this thesis are as follows.1)Coating with good surface quality can be obtained through powder preparation process and coating preparation process.Uniform powder can be obtained by mixing single powder by ball milling and mixed powder with surface alloying can be obtained by high-speed ball milling.Orthogonal experimental analysis shows that laser power is the most important factor to determine the surface quality of coating,followed by scanning speed and defocus quantity.Under the selected process parameters,the heat-affected zone of the coating is moderate,and the dilution rate is 18.17%.Besides,the coating cladding effect is best at 40%overlapping ratio.2)Si and B elements possessing excellent deoxidation slagging ability,form a dense oxide film on the surface of the cladding layer to prevent oxygen in the air from entering the molten pool.Under the process parameters determined in this thesis（laser power of 1350 W,scanning speed of 1.5 mm/s,defocus of-10 mm,overlapping rate 40%）,the surface of the coating is smooth,with clear morphology of fish scale pattern,and no pores and impurities in the coating.Good metallurgical bonding,between the coating and the substrate,and moderate range of heat affected zone are shown.Compared with Fe49Co2V,the hardness of the alloy coating can reach 45 HRC after adding Si element,and 50 HRC after adding B element.With the increase of Si and B content,the hardness value of the coating increases,and the friction performance of the coating becomes better,and the wear rate of the coating is as low as 1×10^-5 mm3/N·m.However,the introduction of Si and B destroys the original domain structure,resulting in the reduction of domain area and the increase of energy required for magnetization and demagnetization.3)Modified Fe-Co-V alloy coating was prepared on the rotating shaft.After heat treatment,the saturation magnetic induction intensity of the coating is 1.5 T～2.0 T,the coercivity is 4×10~3 A/m,and the initial permeability is 100.Through the design and development of typical rotating sample with high performance magnetic fluid seal,the application of the wear-resistant coating with high magnetic conductivity is realized,and the coating surface exhibits no wear under the stable rotating operation for three months.