Preparation And Application Of High Performance Metal Silicide Coatings（Fe₃Si And MoSi₂）via Molten Salt Infiltration

Fe-Si and Mo-Si intermetallic compounds containing covalent and ionic bonds have high strength,high hardness,excellent corrosion resistance and wear resistance,and high temperature oxidation resistance,but such materials exist when they a re used as structural materials,the brittleness and the oxidation resistance need to be improved.From the perspective of widening the wide application of Fe-Si and Mo-Si materials,when considered as a film layer material,it can protect the substrate and at the same time can effectively reduce the problem of large brittleness of the silicide,from the perspective of ease of engineering application,Proposed a new idea of using electroplating（including composite electroplating）combined with molten salt non-electrolytic treatment to prepare high-performance Fe-Si and Mo-Si metal silicide,and comparatively studied the surface alloyed Fe-Si and Mo-Si composite infiltration layer The effect of preparation on the surface corrosion resistance,wear resistance and high temperature oxidation resistance of 2Cr13 steel and molybdenum alloy.This research developed the molten salt non-electrolytic infiltration technology,and obtained composite plating combined with molten salt non-electrolytic treatment to prepare high-performance Fe-New technology approach of Si and Mo-Si metal silicide compound infiltration layer.Important results of the research is as follows:（1）The surface is first electroplated with a N i layer of 30μm,and then the composite molten salt infiltrated silicon is kept at 800℃for different lengths to prepare composite silicide infiltrated layers with different thicknesses.N i₃Si,Ni₂Si and Fe₅Si₃,and finally the evolution process of Fe₅Si₃ and N i₂Si composite silicide,the formed composite infiltration layer can increase the surface hardness to varying degrees,improve the wear resistance and play a protective role.Although the corrosion resistance of the molten salt infiltrated silicon layer is not as good as the corrosion resistance of the surface electroplated N i layer,they all have certain passivation characteristics to varying degrees,and are more resistant to corrosion in sulfuric acid solution.The corrosion resistance is the best,which is attributed to the better passivation and passivation effect of Fe₅Si₃ in sulfuric acid,so that the corrosion resistance of the Fe₅Si₃ and N i₂Si infiltration layer is better than that of the pure N i₂Si infiltration layer.（2）A dense N i alloyed Fe₃Si composite infiltrated layer can be prepared by first electroplating a 3～5μm nickel layer and then molten silicon infiltrating at 800℃for 4h.Compare the four kinds of Fe₃Si prepared the corrosion resistance and wear resistance of the infiltrated layer were found to be higher than those of the Fe₃Si infiltrated layer prepared by direct silico nizing:Fe₃Si<（N i）-Fe₃Si<（N i-CeO₂）-Fe₃Si<（Ni-SiC）-Fe₃Si,this rule shows that the alloyed Fe₃Si infiltrated layer has different structures due to the effects of different alloying element types Thereby showing different hardness,toughness and electrochemical corrosion performance.This composite technology has the advantages of easy operation,outstanding economic benefits,and strong engineering applicability.（3）MoSi₂ metal compounds containing alloying elements（N i）-,（Ni-SiC）-and（Ni-CeO₂）-were prepared on the surface of the molybdenum alloy TZM by electroplating and neutral molten salt infiltration composite treat ment techniques.The infiltration layer obtained after TZM direct silicon infiltration can effectively improve the high temperature oxidation resistance of TZM.Moreover,the nickel alloy MoSi₂/CeO₂ infiltration layer prepared by N i-CeO₂ composite plating and molten salt infiltration has the strongest"pest"suppression ability.However,the high temperature oxidation resistance of the alloyed MoSi₂ infiltration layer obtained by electroplating the Ni layer to provide alloying elements is not as good as the oxidation resistance of the MoSi₂ infiltration layer obtained by direct silicon infiltration.