Study on correlation between AlCoCrFeNi_2.1YHf high-entropy alloy coatings on steel surface for downhole tools by plasma cladding and cladding current

In this paper, AlCoCrFeNi_2.1YHf high-entropy alloy coatings are prepared on the 35CrMo steel for downhole tools by plasma cladding at three currents of 130 A, 140 A and 150 A. The effects of current on the microstructure, micro-hardness, and corrosion resistance of the coatings are analyzed by scanning electron microscope（SEM） equipped with energy spectrometer（EDS）, X-ray diffractometer（XRD）, microhardness tester, and electrochemical workstation. The results show that the coatings consists of dendrites and a small number of equiaxed grains, the intracrystalline phase is FCC phase, while the intercrystalline phase is mainly B2 phase. With the increase of current, the content of B2 phase increases, and the microstructure of the coating coarsens and the micro-hardness gradually decreases; the corrosion resistance of the coatings shows a non-linear relationship of increasing and then decreasing with the increase of current, and the coating with the current of 140 A has the best corrosion resistance.