The Preparation And Brazing Technology Of High Binding Capacity Ceramic Film

Alumina ceramic coating has good thermal insulation,corrosion resistance, oxidation resistance,wear resistance and good electrical insulation,Therefore It has been widely used in mechanical electronics,medicine and chemical industry.But the physical properties ,thermal expansion coefficient and crystal structure of the ceramic coating is very different from the metal,so the adhesion strength is relatively weak.In this paper,vapor deposition soldering by PVD and active brazing are used to improving the adhesion between the ceramic coating and metal substrate.In this way the value and scope of alumina ceramic coating are significantly increasing.It is also a new way to improve the ceramic coating and metal adhesion strength.This present study,the solder deposition target is prepared by the ratio of Ag:Cu : Ti = 23 : 66 : 11 . After deposited the solder composition is close to (Ag₇₂Cu₂₈)₉₇Ti₃.It has a good wetting of ceramic coating and the substrate. When the brazing temperature is 930℃and insulation 30 min,through scarification can be seen,after brazing adhesion strength has been greatly improved.When Scratch testing specimen before welding ,the film was almost completely stripped the matrix, and cracking from each other composite film,showing double membrane structure.The scratch test specimens after welding,the film is still attached to the substrate,and only mild damage.By scanning electron microscopy and lines can be seen that the composite coating after welding changes from a double membrane structure into a single layer structure.elements in solder layer diffused dramatic.in the substrate and the ceramic coating pervaded a large number of solder elements and the solder layer disappeared.In order to ensure the performance of ceramic coating preventing the dramatic spread of solder layer elements is necessary.Brazing process therefore adjusted to 800℃,heat 10min.Adjusted specimen brazing adhesion strength is still much higher than before brazing,but slightly lower than the specimen whose brazing temperature is 930℃,holding 30min.By scanning electron microscopy and lines,you can still see layer of solder.the diffusion of the solder layer elements has been restricted fare,the basic properties of the ceramic coating had no effect.So,we can come to that the brazing temperature 800℃,holding 10min is the ideal brazing process.Through this experiment can be seen,the brazing between films is very different from normal brazing.First by PVD vapor deposition technology is the solder and the ceramic coating film closely,saving the ordinary brazing wetting step.Second the composite film thickness is extremely small and the proliferation of solder elements is intensely,so the brazing between films should be reduced brazing temperature and holding time.