Study On Microstructure And Corrosion Resistance Of High Entropy Alloy Coating

The surface alloying is one of the most important methods to improve corrosion resistance of metals. With the diversification and complication of material implication, the requirements for protective surface alloying coating are varied. However, most of the surface alloying coating is hard to provide the high hardness, high heat resistance, high corrosion resistance, high wear resistance and good oxidation resistance synchronously.As a new alloy system, high entropy alloy(HEA) contains at least five principal elements,each of which ranges from 5 at% to 35 at%. This high mixing effect entitles HEA extraordinary comprehensive performance, such that corrosion resistance can be prior to 304 stainless steel. So it is implication attractive to lead HEA into surface alloying for protective use.In this paper, plasma five-target magnetron sputtering technique was used to prepare corrosion resistant Al Ti Cr Ni Ta high entropy alloy coating on X80 steel substrate. The phase,morphology, composition and adhesion of the coating were investigated using XRD, SEM, AFM,ED and automatic scratch. The effects of bias voltages(0V,-100 V,-120 V,-160V) and sputtering pressure(0.2Pa, 0.4Pa, 0.6Pa, 0.8Pa) on deposition rate, roughness, density, adhesion of the coating. Besides, the corrosion resistance of Al Ti Cr Ni Ta high entropy alloy coatings, which were prepared under different processing parameters(bias voltages, sputtering pressure, annealed temperature) were valued by electrochemical method in 0.5 mol/L H2SO4 solution. Furthermore,corrosion behavior of the coating and X80 substrate both in 3.5wt% Na Cl solution and 0.5 mol/L H2SO4 solution were analyzed respectively by comparison.The results show that: the sample treated at 0.4Pa and-100 V possesses a Al Ti Cr Ni Ta high entropy alloy coating which has a BCC fine-nanocrystalline structure and behaves higher density,lower roughness and stronger critical load. The electrochemical test investigates that the Clcorrosion resistance and passive performance of X80 substrate were highly improved after sputtered Al Ti Cr Ni Ta coating. However, the coating prepared at 0.4Pa and-100 V performs negative passive current density in 0.5 mol/L H2SO4 solution. Under natural corrosion condition,Cl-accelerate the corrosion degree overall the coating. And annealing process is advantageous toimprove the localized corrosion resistance of the coating by releasing partial internal stress.