Study On Microstructure And Properties Of Laser Surface Remelted Fe-based Amorphous Coating

Fe-based amorphous alloy coatings were fabricated by air plasma spraying.The coatings were further treated by laser surface remelted treatment to reduce or eliminate coating porosity and as far as possible to keep the coating of amorphous phase.An orthogonal experimental design method was applied to study the relationship between the laser parameters and the characteristics of the laser-treated coatings.The best parameters were as follows: laser power 800 W,beam focal distance 2 mm,beam scanning speed 4 mm/s,overlapping coefficient 0.4.On the basis of the orthogonal experiment's result and considered the influence of parameters on the remelting quality,this paper choosed three sets of parameters to do fully remelting experiment.The best parameters were as follows: laser power 1800 W,beam focal distance 2 mm,beam scanning speed 8 mm/s.It is detailed studied that the influence law of organizational structure,wear resistance and corrosion resistance by laser remelting.After the process of laser remelted,the original coating experienced the process to melt and solidification contraction in rapid rate of cooling under the high laser power density which eliminated the flat granule joining structure,and formed the compact molten alloy zone.The coating ccurred the crystalline phases after the laser remelted.The surface remelting coating was mosaic the structure of crystalline phases in amorphous structure by TEM analysis,which amorphous content is about 64%.However,the fully remelting coating appeared a large number of clusters crystal phase,which amorphous phase content was decreased to 33%.The microhardness of the coating is greatly improved due to the formation of the nanocrystalline phase and the increase of the coating density.The Micro-hardness of iron-based amorphous coating is 742.8 HV0.1,while the laser surface remelting coating and the laser fully remelting is respectively 1276.8 HV0.1and 1182.6 HV0.1.In the test of wear,the determining coefficient of iron-based amorphous coating was steady about at 0.25,while the surface and the fully remelting coating is respectively about 0.15 and 0.12.Therefore,the performance of wear resistance of laser fully remelting is the most superior,the surface remelting coating was the second superior,iron-based amorphous coating was the worst.The corrosion resistance of the three coatings was studied by polarization curve and surface wetting test.Compared with the plasma spray coating and the laser remelting coating,the corrosion resistance of the laser remelting coating is improved mainly owe to the coating more uniform and dense,which decides the corrosion resistance of the coating,and crystallization phenomenon has less negative influence on the corrosion resistance.The densification of the surface remelting and the fully remelting coating is nearlly identical,but the content of the crystalline phase is quite different.The corrosion resistance of the surface remelting coating is better than the fully remelting coating which shows the cycstalline phase have a great effect on the corrosion resistance.The contact angle of iron-based amorphous coating,surface remelting coaingand fully remelting coating's was 56.3°,82.7 o,71.2°.The corrosion resistance of the three coatings is: the laser surface remelting> the fully remelting coating> the Fe-based amorphous coating.