Study On The Microstructure And Properties Of Laser Cladding Ni-Based Wear-Resistant Coatings

In the automobile production process,the widespread use of high-strength steel plates is conducive to lightweight vehicles,but at the same time it will cause severe wear of automobile stamping dies and reduce its service life.The wear of the stamping die will cause the precision of the parts to decrease and even produce defects such as dents and burrs,which will bring economic losses to the enterprise.Laser cladding Ni-Cr-B-Si-C alloy can improve the wear resistance,corrosion resistance and hardness of the mold.Therefore,in this research,a laser cladding method was used to prepare a Ni-based alloy wear-resistant coating on the surface of Cr12Mo V mold steel.The hardness and wear resistance of the coating were improved by changing the composition of the coating to form different hard phases.The microstructure of the laser cladding Ni-based alloy wear-resistant coating is systematically characterized,and it is expected to provide guidance for the micro-theory of improving the wear resistance of automotive molds.The main findings are as follows:Firstly,the effects of laser process parameters on the surface quality,dilution rate and hardness of Ni45 alloy coatings were studied.Considering the coatings quality,the final laser process parameters selected were:laser power(P)of 2200 W,scanning speed(V_s)of 5 mm/s,and powder feed rate(V_p)of 15 g/min.Based on the determination of laser cladding process parameters,a Ni-based coating with Cr12Mo V die steel as the substrate was prepared,and the molar ratio of Cr₃C₂:Ti:Nb added to Ni45 powder was optimized.The experiment shows that with the increase of Cr₃C₂addition,the coating hardness increases.When(Cr₃C₂:Ti:Nb)_mol=4:1:1,the average microhardness of the cladding layer is the highest,reaching 564.8 HV_0.2.The layer phase is mainly?-Ni,Cr₇C₃,(Ti,Nb)C,Cr₂₃C₆,Ni₃B,Cr B and a very small amount of undecomposed Cr₃C₂.At this time,(Ti,Nb)C reinforced phase particles are fine and uniformly distributed.It is the optimal molar ratio of adding Cr₃C₂:Ti:Nb.On the basis of the above studies,the effects of(Ti,Nb)C composite microstructures on the microstructure and properties of Ni45 coatings were further studied in the(Cr₃C₂:Ti:Nb)_mol=4:1:1 coating.In this study,the electron backscatter diffraction(EBSD)and transmission electron microscope(TEM)techniques were used to analyze the microstructure and phase composition of(Ti,Nb)C/Ni45 coatings;the wear resistance of the coatings was tested using a wear tester.The results show that the phase composition of the(Ti,Nb)C/Ni45 coating includes?-Ni matrix,orthorhombic Ni₃B,orthorhombic Cr B,orthogonal(Cr,Fe)₇(C,B)₃Cubic Cr₂₃C₆and cubic(Ti,Nb)C particles;Cr₂₃C₆is mainly distributed near the phase interface between(Ti,Nb)C and?-Ni matrix.The appearance of(Ti,Nb)C reinforcing phase particles and the increase of carbide phase((Cr,Fe)₇(C,B)₃and Cr₂₃C₆)increase the wear resistance of(Ti,Nb)C/Ni45 coating About 3.6 times.