Evolution Mechanism Of Microstructure And Properties Of The FeCoCrNiMnAl High-Entropy Laser Cladding Layers

As the"mother of industry",mold is widely used for the fabrication of components in the aviation and aerospace and other fields.Its industrial development level has become an important factor to measure the level of development of a nation’s manufacturing industry.In this paper,in order to solve the problems of surface failure caused by the decrease in hardness and poor high temperature resistance of hot working die steel under the condition of long-term high temperature service,FeCoCrNiMnAl_x high-entropy alloy（HEA）cladding layers were produced on the surface of hot working die steel（H13）by laser cladding process.The mechanisms of strengthening,wear resistance and high temperature oxidation resistance of the HEA cladding layers were systematically investigated.A composite HEA material was proposed and produced to solve the problem of toughness reduction caused by the high strength of HEA cladding layer.The results obtained in this study have important theoretical significance and practical guidance for prolonging life of hot working die.Firstly,the strengthening mechanism in the FeCoCrNiMnAl_x HEA cladding layers was studied.The results showed that with increase in Al element content,under the action of grain refinement and solid solution strengthening as the main strengthening mechanisms and dislocation strengthening and lattice distortion strengthening as the secondary strengthening mechanisms,the FeCoCrNiMnAl HEA cladding layer exhibited excellent plastic deformation resistance,but its elastoplastic ability decreased significantly.Secondly,the wear resistance and corresponding wear mechanism of the FeCoCrNiNiAl_x HEA cladding layers were investigated.The results showed that with the increase in Al content,the microhardness and wear resistance of the HEA cladding layers increased gradually.The weight losses of the FeCoCrNiMnAl cladding layer at room temperature and at 600°C were 5.70%and 7.14%of that of the substrate,respectively.The wear mechanism involved a combination of abrasive wear,abrasive wear and oxidation wear.The normal temperature and high temperature wear of the cladding layer was better than that of Fe50,Co50 and Ni60alloy cladding layers.Thirdly,the high temperature oxidation resistance and corresponding mechanism of FeCoCrNiNiAl_x HEA cladding layers were researched.The results showed that with the increase in Al content,the high temperature oxidation resistance of HEA cladding layers increased gradually.The thin and denseα-Al₂O₃ oxide film that was formed on the surface of the FeCoCrNiMnAl cladding layer effectively improved its high temperature oxidation resistance.After heat treatment at 600°C/100 h,the grain size and phase content of the cladding layer did not change significantly,but the microhardness and wear resistance decreased slightly,by 9.7%and 10.5%,respectively.Finally,the FeCoCrNiNiAl_0.5-Fe Co Cr Ni Ni NAl composite HEA cladding layer was produced,and a balanced strength and toughness combination was obtained for the cladding layer.The compressive strength of the composite HEA cladding layer was 504 MPa at 600°C,and there was no crack on the surface of the cladding layer up to 78.3%strain.Overall,the results indicated that the laser cladding technology could be utilized to produce FeCoCrNiMnAl HEA cladding layer with high hardness and strength,high temperature oxidation and wear resistance on the surface of H13 hot working die steel,but the toughness of the cladding layer was relatively poor.On this basis,the FeCoCrNiMnAl_0.5-FeCoCrNiMnAl composite HEA cladding layer solved the problem of imbalance between the strength and toughness of single HEA cladding layer,which can effectively prolong the service life of the die and broaden the application scope of HEAs.