Study On Performance Control And Post-treatment Of Rare Earth Doped WC@Ni/Ni60 Laser Cladding Coating

With the popularization of the concept of green remanufacturing and the continuous improvement of the manufacturing level,people have put forward new requirements for the manufacturing,repairing and remanufacturing of die-cutting tools.Traditional one-piece die-cutting tools have high manufacturing costs and large machining allowances,and the cutting edges are prone to failures such as chipping,deforming,cracking and wearing.The performance of the insert clamping carbide cutting edges has greatly increased,but the machining accuracy is limited.The traditional repair method is to adjust the center distance of the cutter roll after grinding the cutting edge.The processing volume is large,the energy consumption is high,the time consuming is long,and the economic benefit is poor.Laser cladding technology uses additive manufacturing to manufacture,strengthen or repair the cutter roll,which greatly reduces the cost and is the best choice to solve the full life cycle of die-cutting tools.In this paper,the main conclusions are as follows from the optimization of powder formulation and laser process parameters,the optimal addition ratio of rare earth oxides,and the exploration of appropriate heat treatment methods:Using a preset laser cladding scheme,stable focus distance(10mm),through orthogonal experiments,select four key factors of WC@Ni powder type,WC@Ni/Ni60 ratio,laser power and scanning speed for testing.Through intuitive and variance analysis,the best process parameter group is obtained:WN25(25%WC@Ni),WC@Ni 40%,laser power1600W,scanning speed 5mm/s,and use the best group of process parameters to verify.In the test,the prepared coating has good morphology,reasonable dilution rate(9%),high hardness(62.4HRC),and good wear resistance(wear volume is13.49×10⁶?m³).Follow-up tests are carried out with this group of parameters.Two series of single factor experiments are used to explore the influence of the addition ratio of two rare earth oxides(Y₂O₃and La₂O₃)on the performance of laser cladding coatings.The study found that the addition of Y₂O₃and La₂O₃can significantly refine the grains,but excessive rare earth oxides will weaken the performance of the cladding layer.The dilution rate of the sample with 3%La₂O₃is 2.4%and the wear volume is26.5×10⁶?m³;the dilution rate of the sample with 3%Y₂O₃is 45.6%and the wear volume is25.1×10⁶?m³.After a comprehensive comparison,the coatings of 1%La₂O₃(microhardness 66.1HRC,wear volume9.87×10⁶?m³,Coefficient of friction 0.45)and 0.5%Y2O3(microhardness72.7HRC,wear volume10.66×10⁶?m³,Coefficient of friction 0.46)in the two tests have high microhardness,good wear resistance,fine structure and excellent performance.These two ratios are selected for the following tests.In order to further improve the microstructure and optimize the stress distribution of the coating,a heat treatment study is carried out on the basis of the aforementioned experiments.The results show that annealing heat treatment at 700°C can reduce the residual stress of the cladding layer(the maximum residual stress of 1%La₂O₃sample is reduced from 291 MPa to151 MPa,and the residual stress of 0.5%Y₂O₃sample is reduced from 410 MPa to 199 MPa),under the premise that the microhardness is basically unchanged,but the heat treatment can improve the wear resistance of the coating,the friction coefficient of the 1%La₂O₃sample after 700?heat treatment is 0.41,and the friction coefficient of the 0.5%Y₂O₃sample after700?heat treatment is 0.45.