Research On Spray Granulation Process Of Co/Al₂O₃ Composite Powder For APS

The backscattering of aircraft engine tail nozzles can significantly hinder the realization of omnidirectional low detectability technology,while the preparation and application of conventional electro-absorption materials and magnetic absorption materials are greatly restricted due to the extreme high temperature at this location.In this application,Atmospheric plasma spraying(APS)technology is proposed and a ferromagnetic ceramic composite absorbing coating is designed,aiming to address the technical problem of high temperature and low detectability,and achieve the effect of reducing the radar cross section.Considering the special requirements of the particle size distribution and microscopic morphology of the sprayed powder when the coating is prepared by the APS process,in this paper,the spray granulation technology is employed to prepare composite particles,the response surface method is used to systematically study the relevant process parameters.The parameters are fitted through mathematics to obtain the model formula,the finally obtained parameters are applied to granulate and prepares the coating followed by related tests,the subject index of powder preparation is realized basically.The main conclusions obtained are as follows:1.During the spray granulated precursor slurry,many factors exhibit a great influence on the particle size,fluidity and sphericity of the powder.Through experimental exploration,the optimized process parameters are:the solid content is50%,the inorganic thickener content is 4.372%,and the content of the grinding ball is500%.According to the formula prediction and fitting,the D10 is 41.219μm,the D50is 58.066μm,the D90 is 80.582μm,the outflow time is 119.155 s/50g and the eccentricity is 1.055;2.The process parameters during the spray granulation also have an important impact on the particle size,fluidity and sphericity of the powder.The optimized process parameters are:the inlet air temperature 276.0℃,the wind air temperature 100.0℃,the nozzle frequency 26.1Hz,the binder content is 2.49%,the dispersant content is 0.09%.The fitting results are:the D10 is 18.79μm,the D50 is 42.65μm,the D90 is 75.28μm,the outflow time is 100.0 s/50g and the eccentricity is 0.017;3.The above parameters are used to granulate the powder for examination,the error between the experimental results and the theoretical fitting calculation is about15%,the model possesses certain accuracy and reference value.Then the granulated composite powder was used to prepare a ferromagnetic ceramic high-temperature absorbing coating through APS process.The density of the coating is about 4960 kg/m~3,and the bonding strength is about 8MPa under the thickness of 200μm.In summary,spray granulation technology is used in this paper to prepare ferromagnetic ceramic composite powders for further in-depth investigation and exploration,a more ideal process parameter fitting formula is achieved.The prepared powder can basically meet the needs of the APS process.The research results exhibit certain engineering significance and reference results.