Effect On Microstructure And Properties Of Laser Cladding 316L Cladding Layer By Rare Earth Oxide

With the continuous development of China's economy,the rapid exploitation of marine resources has put forward higher requirements for the performance of marine industrial equipment.Faced with the complex ion environment,high humidity and high salt climate in the sea,higher requirements are placed on the corrosion resistance and mechanical properties of marine steel.In this paper,laser cladding technology was applied to study the rare earth oxide modified 316 L coating,The microstructure,surface hardness and corrosion resistance,and wear resistance of the cladding layer were tested by Axioskop2 optical microscope,HVS-1000 digital microhardness tester,electrochemical workstation,salt spray experimental box,reciprocating friction and wear respectively.The SEM and electrochemical workstation results show that the addition of rare earth oxides can refine the grains and significantly improve the corrosion resistance and hardness of the coating by comparing whether rare earth oxides CeO₂ and La₂O₃ is added in 316 L coatings.The grain refinement degree reaches the peak,the hardness is the highest and the corrosion resistance is optimal when the addition amount is 2 %.The results of the reciprocating friction and wear experiments showed that the coating has little effect on the wear resistance of the substrate,and the wear resistance of the substrate is not significantly improved.Finally,the pitting corrosion resistance of the coating was verified by the salt spray test and obvious pitting corrosion phenomenon on 316 L was found.But the size and number of pitting pits are reduced after the addition of rare earth oxides.The number of corrosion pits is the smallest and the area is the smallest when CeO₂ or La₂O₃ content is 2 %,respectively,and CeO₂ is better than La₂O₃,which is consistent with the results obtained by polarization curves and impedance spectra.By comparing the optimal addition of the two rare earth oxides,it can be found that the cladding layer modified with 2 % CeO₂ is superior to the 2 % La₂O₃ modified cladding layer in terms of hardness and corrosion resistance.Since the density and porosity of the 316 L powder coating are highly dependent on the laser cladding power,the effect of power on the 2 % CeO₂ modified cladding layer is further discussed.The experimental results show that the grain size of the cladding layer decreases first and then increases with the increase of power.Meanwhile,the corrosion resistance and hardness of the cladding layer increase first and then decrease,but the wear resistance of the cladding layer is not obviously affected by power.When the laser power is 3000 W,the overall performance of the cladding layer is optimal.Finally,the salt spray test verified the pitting corrosion resistance at three powers,and it can be seen that the pitting resistance is optimal when the laser power is 3000 W.In summary,under the condition of laser cladding power of 3000 W,CeO₂ is added in an amount of 2 %,the overall performance of the cladding layer is optimal.