Effect of Nb components on the microstructure and mech-anical properties of high-entropy alloy coatings
CoCrFeNiTi0.8Nby(y = 0.25,0.5,0.75,1.0)coatings were prepared on the surface of Q235 steel using laser cladding.The phase structure and microstructure of the coat-ings were analyzed by optical microscope(OM),X-ray dif-fractometer(XRD),scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS).The hardness and wear resistance of the coatings were tested by micro-Vickers hard-ness tester and friction wear tester.The results show that the microstructure shows a typical dendritic crystal structure,and the addition of Nb elements decreases the size of the grains;by increasing the content of Nb elements,the crystal structure of the high-entropy alloy coatings consists of BCC phases,a small amount of FCC phases,and Fe2(Ti,Nb)-type Laves phases;the microhardness of the coatings is improved by the combined ef-fect of fine-grained reinforcement,solid solution strengthening,and the strengthening of the second phase;The presence of the intermediate phase can hinder the plough cutting process to a certain extent,which improves the wear resistance of the coat-ing;CoCrFeNiTi0.8Nb0.75 coating has the best hardness and wear resistance,the hardness of 710 HV,about 4 times that of the substrate,and the coating has the smallest amount of abra-sion,and the abrasion marks are relatively flat.
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