Technologies And Properties Of High Temperature Microwave Absorbing Coatings By Plasma Spraying Technology

With the rapid development of radar detection technology,the role of radar absorbing materials in improving the survival and penetration capabilities of weapon systems is becoming more and more important.Plasma spraying technology has been studied in the preparation of wear-resistant coatings,thermal barrier coatings and high-temperature wave-absorbing coatings.Therefore,plasma spraying technology is of great research value in the preparation of high temperature wave-absorbing coatings.In this paper,spray voltage,spray current,argon flow rate and spray distance are selected as the factor variables of plasma spray process parameters,and each factor takes three characteristic levels for orthogonal test design.The research content and results of this paper are as follows:(1)Analysis of coating phase composition and surface microscopic 3D morphology and surface structure morphology:The coating is mainly composed of seven phases of MoSi₂,Cu,?-Al₂O₃,Cu₂O,?-Al₂O₃,Mo₅Si₃ and hep-MoSi₂.A phase change occurred during the plasma spraying process.A small amount of Cu powder was oxidized and a new Cu₂O phase appeared in the coating,which could promote the microwave absorption effect.Some?-A1₂O₃ was transformed into?-A1₂O₃.A small amount of Mo₅Si₃ and a new phase of hep-MoSi₂ appear in the coating.Analysis of the coating's microscopic 3D morphology and surface structure morphology revealed that the surface of the coating was uneven and rough,and all 9 groups of coatings had different degrees of pores.(2)Determination and analysis of coating microhardness:The microhardness of the nine groups of tests is above 200 kgf·mm^-2,and the highest reaches 391.5 kgf·mm^-2.Compared with the substrate,the microhardness has a significant increase.Through orthogonal test analysis,the primary and secondary law of the influence of the selected four factors on the coating microhardness is C(argon flow)>A(spray voltage)>D(spraying distance)>B(spray current),and the intensity ratio is about 2.4:1:3.3:1.8.(3)Determination and analysis of coating porosity:The porosity of the nine groups of coatings is between 5.87%and 10.21%,and each group of coatings has different degrees of porosity.Through orthogonal test analysis,the primary and secondary law of the influence of the selected four factors on the coating porosity is C(argon flow)>A(spray voltage)>D(spraying distance)>B(spray current),and the intensity ratio is about 3.5:1:6.75:2.55.(4)Determination and analysis of coating thickness:The thickness of the nine groups of coatings ranges from 27.16?m to 50.17?m,and the thickness of each coating fluctuates within a certain range.Through orthogonal test analysis,the primary and secondary law of the influence of the selected four factors on the coating thickness is D(spraying distance)>B(spray current)>A(spray voltage)>C(argon flow),and the intensity ratio is about1.03:1.3:1:2.5.(5)The waveguide method was used to test the dielectric constant of the absorbing coating at different temperatures,and the high temperature absorbing properties of the nine groups of coatings were analyzed.The test found that the 9 groups of coatings all have certain high temperature wave absorption properties,among them,the 9th group coating has the best high temperature absorbing performance.The thickness of the coating has a positive correlation with the high-temperature absorbing performance.