Influence Of B,Ti,Nb Content On The Performance Of Laser-remelted FeCoCrNiAl High Entropy Alloy Coatings

High entropy alloy is a new concept of alloy design which is proposed in recent years.There are 5 or more than 5 kinds of elements in one alloy system and the system entropy are enhanced by controlling each element in 5%-35% content.High entropy alloy has wide applications in the preparation of coatings because of its excellent mechanical properties.However,the coating preparation process,the effect of element content for the alloy system and the experimental data are imperfect since the system of high entropy alloy is too large and wide.The research time of it is short,therefore more studies are needed to be done.This paper focus on the effect of B,Ti and Nb content on the structure of FeCo Cr NiAl high entropy alloy coating and compared the effect of laser cladding and laser re-melting treatment on the coatings.The formation mechanic of high entropy structure and the process of phase evolution were systematically studied.The mechanical properties of the coating were tested and the influence factors were then discussed.The results shows that the molten pool deposited by laser re-melting is shallow compared with the molten pool by laser cladding directly.However,the phase composition and the mechanical property are similar.B,Ti and Nb play an important role in the grain refinement of FeCo Cr NiAl high entropy alloy coatings.With the increase of B content,the amount of FCC phase decreases and the amount of BCC phase increases.The FCC phase disappears after the addition of Ti and the BCC2 phase appears.The FCC2 phase forms after adding Nb.The FeCoCrNiAlB0.75 coating,FeCo CrNiAlTi coating and Fe Co CrNiAlNb0.5 coating has shown the highest hardness which are 726 Hv,966Hv,773 Hv respectively.Simultaneously,the wear resistance of the coatings reaches to the maximum value.The research has shown that both B and Ti are BCC stabilizer while Nb are FCC stabilizer.The impact mechanism of B and Ti on the structure and properties of FeCo Cr NiAl high entropy alloy are similar.The mechanical property of coatings are enhanced with the persistently addition of B and Ti.When the Nb element is added in the alloy,the hardness reaches to the maximum value while the alloy is composed of FeCo Cr NiAlNb0.5.With the continuous addition of Nb,it presents a downward trend.