Matrix Metal Component Design And Preparation For Carbide Ceramic Composite Coatings

Molten metal corrosion is one of the most common forms of material failure.Especially,molten zinc and aluminum have strong corrosiveness.They can react with most metals or alloys and form compounds of iron-zinc and iron-aluminum alloy,these compounds continuously consume iron in metal,resulting in failure of metal materials.Therefore,there are many methods that people have developed to prevent metal corrosion.Hot-dipping is one of the earliest,the most economical and effective methods.It is a way to improve the life of Hot-dip galvanizing components that using metal,ceramic and composite coatings prepared by thermal spraying.There are many reports on its application at home and abroad,but most of them involve application effect and process method while failure mechanism is less.The metal binding phase in the protective layer is a weak link,and the main reason for the failure of the protective coating is the diffusion corrosion between Zn and metal binding phase in the coating.The four metals,Co,Ni,Mo and Cr,were selected as the basic test materials.The main reason is that these four metals are often used as metal binding phases.First,these four metals and zinc were made into a diffusion couple,and they were at different heat treatment temperatures and different heat preservation times.After analysed the microstructure and morphology of the diffusion layer that formed in the diffusion couple.The diffusion behavior of the diffusion layer was analyzed,and the main factors affecting the thickness of the diffusion layer were discussed.Combined with the above analysis,the corrosion resistance test of WC-12Co ceramic composite coating and WC-10Co-4Cr ceramic composite coating were carried out.The reasons of the failure are mainly due to the diffusion corrosion of the metal bonding phase.The metal binding phase Co and the brittle phase of zinc gradually exfoliate and disconnect,and the metal Co and zinc liquids first generate a?(Co₅Zn₂₁)phase.At this time,the concentration of zinc liquid in the interface decreases,the concentration of Co increases,and the concentration balance is broken.With the increase of corrosion time,zinc atoms in the zinc liquid constantly diffuse to the Co-Zn interface and eventually turn into the?₂(CoZn₁₃)phase,While the?₂(CoZn₁₃)phase phase is a brittle phase,which produces transverse cracks under the action of thermal stress,and eventually leads to the failure of the whole coating.The zinc corrosion resistance of the WC-10Co-4Cr ceramic composite coating is better than the WC-12Co ceramic composite coating,mainly because of the addition of the Cr element,because Cr almost does not react with Zn,so it effectively obstructs the invasion of the zinc liquid.