Laser Cladding Of High Entropy Alloy Coating Resistant To Strong Acid Erosio

To prolong the service life of agitator blade,a series of[Cr-Fe₄Co₄Ni₄]Cr_2.6-xTi_xMo_0.4（x=0,0.3,0.6,0.9）and[Cr-Fe₄Co₄Ni₄]Cr_2.6-xAl_xMo_0.4（x=1,1.25,1.5,1.75,2）high entropy alloys（HEA）were designed based on the cluster-plus-glue-atom model.HEA coatings were prepared on the surface of 904L stainless steel by laser cladding.Firstly,in order to realize the controllable preparation of the coating,the process parameters are optimized.Secondly,under the optimal process parameters,the effects of Ti and Al additions on the microstructure and properties of high-entropy alloy coatings in the Co Fe Cr Ni-M 3d transition family system were explored to obtain the optimal high-entropy alloy composition.Finally,the acid erosion resistance behavior of the coating was studied,and the mechanism of acid erosion resistance was revealed.The relevant research results will provide new ideas for the development of high wear and corrosion resistant materials and coating preparation technology under extreme conditions.The main contents and conclusions are as follows:（1）The high entropy alloy coating was prepared by fiber laser.The results show that the coating under different process parameters only has FCC solid solution phase.Equiaxed crystals,dendrites and columnar crystals appear in the coating.The optimal process parameters:P=2.9 k W,v=5 mm/s.（2）The phase structure of[Cr-Fe₄Co₄Ni₄]Cr_2.6-xTi_xMo_0.4（x=0,0.3,0.6,0.9）coatings is FCC solid solution phase.From the bottom to the top of the coating,the microstructure changes from cellular crystal to columnar crystal and then to cellular crystal.With the increase of Ti content,the microhardness,wear resistance,corrosion resistance and strong acid erosion resistance of the coating gradually increase.When x=0.9,the performance of the coating is better than that of 904L stainless steel.Therefore,the high-entropy alloy coating has a wide application prospect in agitator blade in extreme environments.（3）The phase structure of the[Cr-Fe₄Co₄Ni₄]Cr_2.6-xAl_xMo_0.4（x=1,1.25,1.5,1.75,2）coating is composed of a single FCC phase.The microstructure is a typical dendritic structure,and there are some Al₂O₃ oxidation particles.With the increase of Al content,the microhardness,wear resistance,corrosion resistance and strong acid erosion resistance of the coating first increase and then decrease.When x=1.5,the coating has excellent acid erosion resistance.（4）The erosion mechanism of the coating is the synergistic effect of passivation film and work hardening.By analyzing the strong acid erosion resistance of the coating,it is found that the protective effect of the passivation film is stronger at a slower erosion rate.At medium erosion rate,the protective effect of passivation film and work hardening is not much different.At higher erosion rates,the protective effect of work hardening is stronger.