Research On Laser Cladding Strengthening Of Aluminum Alloy Die Casting Mold Surface

The crucible,die casting mold,etc.,which are directly in contact with the aluminum liquid,can be corroded by aluminum liquid because the molten aluminum liquid have an affinity with almost all metals during the molding process of aluminum alloy,which resulting in erosion pits,falling off or even invalid,etc.in the contact surface,meanwhile,it will also cause problems such as pollution,quality decline in aluminum products.Surface strengthening technology has a good prospect in improving the mold surface resistance to liquid aluminum corrosion,one of these technologies is laser cladding,which heats the material by high energy laser beam,makes the material melt and cool quickly,and forms a good metallurgical bond with the matrix,has the advantages of simple process,wide application range,good cladding layer performance,etc.This paper mainly studies the surface laser cladding process,and the Co base alloy and WC enhancement Ni-based alloy melting layer are prepared in the surface of the H13steel.The microstructure,surface hardness,corrosion resistance and high temperature wear resistance of the cladding layer were analyzed by various common test methods.The corrosion resistance of H13 steel,Co-based alloy cladding layer and WC-reinforced Ni-based alloy cladding layer were investigated.The experimental results show that both the Co base alloy cladding layer and the WC reinforced Ni base alloy cladding layer bonded well with the H13 steel matrix,and the cross section can be divided into three parts according to the microstructure:the cladding layer,the heat affected zone and the matrix zone.The microstructure of Co based alloy cladding layer is uniform without obvious defects,which is mainly composed of dendrite and intergranular structure.The main strengthening mechanisms are solution strengthening and dispersion strengthening;The WC-reinforced Ni-based alloy cladding layer is mainly composed of?-(Fe,Ni)and unmelted spherical WC particles which deposited at the bottom of the cladding layer,the microstructure has crack defects,and the main strengthening mechanism is precipitation strengthening and diffusion strengthening.In the test of the mechanical properties of the cladding layer,the average hardness value is obtained:WC reinforced Ni base alloy cladding layer>Co base alloy cladding layer>H13 steel matrix,the unmelted WC particles are the main reinforced hard phase in the WC reinforced Ni base alloy cladding layer.Through electrochemical corrosion test,the corrosion resistance is obtained:Co base alloy cladding layer>WC reinforced Ni base alloy cladding layer>H13 steel matrix;Through the high temperature wear resistance test,the wear resistance is obtained:WC reinforced Ni base alloy cladding layer>Co base alloy cladding layer>H13 steel matrix.The results of mechanical properties test show that the hardness,wear resistance and corrosion resistance of the two cladding layers are greatly improved compared with H13 steel matrix.Compared with H13 steel substrate,the corrosion rate of Co based alloy and WC reinforced Ni based alloy cladding layer decreases after 24 h high temperature aluminum corrosion,the Si,Cr and other elements in the Co based alloy cladding layer can improve the surface corrosion resistance of molten aluminum,and the main corrosion products are(Co,Fe,Cr)₂Al₉,(Si,Cr)₄Al₁₃and(Co,Fe,Cr)₂Al₅;The WC reinforced phase in the cladding layer of Ni-based alloy has strong corrosion resistance of liquid aluminum and can remain in liquid aluminum for a long time without being dissolved by liquid aluminum.The dendritic structure in the cladding layer hinders the diffusion of Al element and improves the corrosion resistance of the cladding layer.