Al-Co-Cr-Fe-Ni high-entropy coatings produced by non-vacuum electron beam cladding: Understanding the effect of Al by in-situ synchrotron X-ray diffraction

Abstract

This study investigates the structure and properties of Al-Co-Cr-Fe-Ni high-entropy alloy (HEA) based coatings on steel substrates produced by non-vacuum electron beam cladding. Powder mixtures with Al molar ratios of 0.5, 1, and 1.5 were used for cladding, resulting in coatings with fcc, bcc + fcc, and bcc structures, respectively. The Fe content, which entered the coating from the substrate during cladding, increased from 9.9 up to 48.1 at. %. with the decrease of the Al molar fraction from 1.5 to 0.5. In-situ synchrotron X-ray diffraction analysis showed that this effect can be attributed to the higher solidus temperatures of the compositions with higher Al content. Electron backscatter diffraction showed that differences in grain morphology and crystallographic texture were related to the crystallization temperatures in different zones of the coatings. The bcc coating with an Al molar ratio of 1.5 demonstrated superior hardness and wear resistance. Fcc coating, which received more Fe from the substrate, had lower hardness and was prone to plastic flow. However, the specific wear rate of the fcc coating was close to that of the bcc + fcc one due to the hardening of the fcc phase during sliding wear.