Study On Laser Cladding Technology Of Hot Extrusion Die For Automobile Stamping Parts

The mould industry is the basis of the national economy,and the mould production technology is one of the important symbols to measure the manufacturing level of a country's products.The performance of die will directly affect the mold processing efficiency and cost,die premature damage will affect product quality,increase the burden of enterprises,thus losing the market competitiveness.Therefore,it is of great significance to improve the quality of the mold and thus prolong the service life of the mold.8407 steel is widely used in hot extrusion die with poor working conditions,after heating and cooling many times,the surface easy to generate damages,such as collapse Angle,deformation,wear and tear.These damages not only affect the dimension precision of the mould surface,but also seriously reduce the quality of extrusion.Laser cladding technology for die surface strengthening and repair can extend the die life,save the cost for the enterprise.H13 alloy coatings with different content of Y₂O₃ and WC were prepared on the surface of 8407 steel.The phase composition,reinforcing phase morphology of the coatings were investigated by XRD,SEM and EDS,using high temperature vickers hardness tester studied the micro-hardness distribution of the laser cladding layer in high temperature,the results indicated that:The content of Y₂O₃ had little effect on the hardness of the cladding layer.Excessive Y₂O₃ will made the laser cladding process react violently and reduced the quality of the cladding layer.The strengthening mechanism of Y₂O₃ for cladding layer was fine crystal reinforcing and dispersal reinforcing.The hardness of the coating was increased with more WC added.The strengthening mechanism of WC was the second phase reinforcing and fine crystal reinforcing.The decomposition of WC was limited to the vicinity of WC particles,so the hardness of the cladding layer was uneven in different area.The phase composition of coatings with both Y₂O₃ and WC contained M₇C3,WC_1-xand W atoms in addition to the matrix phase.The introduction of Y₂O₃ increased the types of carbides in the cladding layer.The optimal mixing ratio of the two strengthening phases was H13+1%Y₂O₃+10%WC,at which point the unmelted WC particles in the cladding layer were the least and the hardness was 820.7HV.The addition of Y₂O₃ promoted the decomposition of WC particles,C and alloy elements such as Fe,Cr can form M₇C₃strengthening phase,W atoms and unmelted Y₂O₃ particles on cladding layer were fine crystal reinforcing and dispersal reinforcing,a variety of reinforcement mechanism makes the function of cladding layer highly increased.The generation of cracks in the cladding layer ascribed to the content and distribution of M₇C₃ composite strengthening phase.The content of M₇C₃ composite strengthening phase was the key to obtain high performance coatings.The main reason for the stable performance of the cladding layer at high temperature was the carbides distributed between the crystals of the cladding layer.After W and Si atoms were dissolved,the melting point was increased and the high-temperature performance was stable.At 600? or higher temperature,with the extension of the holding time,the performance of the cladding layer was decreased,which was caused by the decomposition of carbides in the cladding layer.