Study on the Structure and Properties of M2 Coating Prepared by Ultrahigh-Speed Laser Cladding Technology

As a new type of surface engineering technology， ultrahigh-speed laser cladding technology has the advantages of rapid processing，precision control， and low thermal influence， which is applicable to the preparation of coatings on a variety of materials.In order to study the effect of cladding speed on the microstructure and properties of M2 coatings， M2 coatings were prepared on the surface of Q235 steel using ultrahigh-speed laser cladding technology.The influence of cladding speed on the microstructure and properties of the coatings was studied.The microstructure， phase composition， hardness， wear resistance， and corrosion resistance of the coatings were tested using scanning electron microscopy (SEM)， X-ray diffraction (XRD)， a hardness tester， a tribometer， and an electrochemical workstation， respectively.Results showed that at a cladding speed of 1.2 m/min， the coating was seamlessly bonded to the substrate， with a microhardness of 757.1 HV， a friction coefficient of 0.448， and a corrosion current density Jcorr of 1.98 × 10-6 A/cm2.As the cladding speed increased， gaps appeared at the coating-substrate interface， grain size decreased， dilution rate decreased， hardness increased， and friction coefficient decreased.At a cladding speed of 40.0 m/min， larger cracks formed at the coating-substrate interface， with an equivalent average grain diameter of 1.76 μm， a dilution rate of 6.8%， an average microhardness of 828.1 HV， an average friction coefficient of 0.345， and a corrosion current density Jcorr of 1.26 ×10-7 A/cm2.The cladding speed had a significant impact on the macroscopic morphology and performance of the ultra-high-speed laser cladding coatings.With increasing cladding speed，cracks appeared in the coating region，while the equivalent diameter of the grains decreased and the hardness， wear resistance， and corrosion resistance improved.The phase composition of all coatings consisted of martensite， retained austenite， and carbides.This work provides a theoretical basis for the preparation and parameter optimization of M2 high-speed steel materials.