Application Of CoCrFeNi Multi-component Alloy Cladding In Strengthening Of Compacted Graphite Iron

High entropy alloys（HEAs）have attracted increasing attention for their unique multi-elements solution and excellent strength.Compacted graphite iron（CGI）is often used in manufactury of heavy engine parts,such as cylinder heads,for to its comprehensive mechanical properties.The valve seats of cylinder heads,will suffer severe wear over long periods at high temperatures,further inhibiting the effective operation of the engine.CoCrFeNiMn high-entropy alloy claddings were prepared on the surface of compacted graphite iron by plasma transfer arc melting to improve its wear resistance.This is an important guide to promote the realisation of the application of high entropy alloy materials for surface strengthening of cast iron components in remanufacturing to improve its wear resistance.In this work,the CoCrFeNi alloy was used as the basis,and the powder composition was optimised by adding different contents of Mn element to it.The coatings were prepared by plasma transfer arc claddings to investigate the effect of Mn content on the microstructure and mechanical properties of the CoCrFeNi alloy.Optimization of Mn content in the composition of CoCrFeNiMn_x,the effect of plasma arc current and heat treatment on the microstructure and mechanical properties of CoCrFeNiMn_x high-entropy alloy claddings were investigate,final study of the effect at heat treatment on the structure and mechanical properties of the cladding layers of CoCrFeNiMn high entropy alloys.Results show that the CoCrFeNiMn_x high entropy alloy claddings had a single FCC phase and were composed of equiaxed grains.When the Mn element content was 1.0 at%,the overall mechanical properties of the CoCrFeNiMn_x high-entropy alloy claddings were optimal,with microhardness,tensile strength,elongation and wear mass for 406.2 HV_0.2,835 MPa,1.5%and0.96 mg.There were mainly martensite and ledeburite in the bonding zone of the high-entropy alloy claddings.Columnar grains and equiaxed grains in the middle of the claddings,and equiaxed grains in the top of the claddings.The claddings had a single FCC phase.The overall mechanical properties of the CoCrFeNiMn high-entropy alloy claddings were best when the plasma arc current is 65 A.The microhardness,tensile strength,elongation and wear mass were 394±21.6HV_0.2,786 MPa,10.67%and 0.96 mg.The CoCrFeNiMn high-entropy alloy claddings had better mechanical properties than compacted graphite cast iron.Heat treatment temperature at 660°C,780°C,860°C and 1000°C with a holding time of90 min,the CoCrFeNiMn high-entropy alloy claddings retained the FCC phase.The grain size of the claddings became fine and dense.When the heat treatment temperature was below 1000°C,the microhardness and wear resistance of the CoCrFeNiMn high-entropy alloy claddings were greatly improved.The claddings heat treatment at 660℃had the lowest friction coefficient and the lowest wear mass,and had the best wear resistance.At the heat treatment temperature of780℃,both the tensile strength and elongation after break down of the claddings were the highest.When the heat treatment temperature was below 1000°C,the overall mechanical properties of the claddings were improved as compared to the untreated owes.The high entropy alloy claddings were subjected to adhesive wear,abrasive wear and oxidative wear,and the tensile fracture of the claddings were characterised by tough dimple,all of which were ductile fracture.