Study Of Al-FeCoNiCrAl High Entropy Alloying Composite Coatings On SUS 304 And TC4 Using MA

High entropy alloy is an emerging alloy that was being widely studied.304 stainless steel has good cold working properties and good corrosion resistance,but has low hardness.Ti-6Al-4V(TC4)alloy has a small density and high specific strength,but easy to fail in high temperature environment.These problems severely affect the widespread application of SUS 304 stainless steel and TC4.In this paper,Al-Fe Co Ni Cr Al composite coating was prepared on the surface of SUS 304 stainless steel and TC4by mechanical alloying(MA)method.This paper study from three aspects,the preparation and study of the Al-Fe Co Ni Cr Al coating on SUS 304 stainless steel,the preparation and study of the Al-Fe Co Ni Cr Al coating on TC4 and the effect of annealing on the phase and properties of the coating.In the first part,the effects of different powder ratios and ball milling time on the preparation,phase,micro-morphology and hardness of the304 stainless steel surface coating were studied.The hardness of the outer surface of the coating was much higher than that of the substrate.In the second part,the effect of milling time and Al content on the phase and micro-morphology of Al-Fe Co Ni Cr Al coatings on TC4 surface were studied.As the milling time increased,the coating thickness increased and then decreased.The coating prepared on the surface of TC4 was thinner and has higher hardness compared with SUS 304.The Al-Fe Co Ni Cr Al coating was BCC phase.As the milling time increases,the intensity of all diffraction peaks decreased and the peak shape became broader.The Al-Fe Co Ni Cr Al coating fabricated on the TC4 surface after 4 h MA exhibited excellent high-temperature oxidation resistance.Because the coating was uniform and dense.Al₂O₃formed on the coating surface during cyclic oxidation,which could effectively protect the TC4 substrate.In the third part,the effects of annealing at different temperature on the phase,micro-structure and properties of Al-Fe Co Ni Cr Al coatings were studied.DSC-TG analysis showed that phase transition of Al-Fe Co Ni Cr Al particle occurred at 387.8?,629.0?and 926.6?.The L1₂phase,?phase and(Ni,Co)₃Al₄were formed in the coating after annealing at 387.8?.The L1₂phase disappeared after annealing at 629.0?,and ordered BCC was formed at the same time.Only BCC and ordered BCC were present after annealing at 926.6?.After annealing at 550?,750?and 1050?,the high-temperature oxidation resistance of the coating decreases,which was due to the holes in the coating.The hardness of the coating after annealing at 550?and 750?is higher than that of the coating before annealing.Because the high hardness?phase generated in the coating,and amplitude modulation decomposition occurred during annealing.