Investigation Of The Formation Mechanism,Microstructure And Properties Evoltuion Of The FeCoCrNiAl High-entropy Laser Cladding Layers

In this paper,FeCoCrNiAl+Ti C composite high-entropy laser cladding layers were used to improve the wear resistance,corrosion resistance and high-temperature oxidation resistance of Cr12MoV cold die steel.Systematically explored the formation mechanism and strengthening mechanism of the multi-phase high-entropy cladding layers.High-temperature stabilities of the microstructure and properties of the high-entropy cladding layers were studied in detail.The influence of hysteresis diffusion in the high-entropy cladding layers on the microstructure of ceramic particles was analyzed.The research results have important theoretical significance and guiding effect on the practical production and application.Based on the generating conditions and influencing factors of the FeCoCrNi high-entropy cladding layers,the influence of the dilution rate on the microstructure and properties of FeCoCrNi high-entropy cladding layer was studied.The results showed that the wettability between the alloying elements and the matrix metal in the cladding layer had more influence on the dilution rate than the laser parameters.When the content of the Fe element in the original alloy powder was 0 mol,the substrate could translate enough Fe elements to the cladding layer by the dilution effect.So that the atomic percentage of the four alloy elements,including Fe,Co,Cr and Ni in the cladding layer,was about 1:1:1:1,and the standard high-entropy alloy cladding layer was obtained.The strengthening mechanism of the multiphase FeCoCrNiAl high-entropy cladding layers was studied.The results showed that the strengthening effect of the high-entropy cladding layers was formed under the action of four strengthening mechanisms.Rapid condensation produced fine crystal strengthening.The slip system and dislocation type between the FCC and BCC phases were different.Multi-elements produced the severe lattice distortion.The interaction produced by different degree of lattice distortion in various phases.The lattice distortion effect was quantitatively verified by calculating the information of diffraction spots with different crystal band axes.The influence of high-temperature environment on the high-temperature oxidation resistance,phases and microstructures transformation of the FeCoCrNiAl_xhigh-entropy cladding layers was studied.The results showed that the compact oxide film was easily formed by Al element at the high temperature.The air medium was preventd from further encroaching the high-entropy cladding layer and improved the high-temperature oxidation resistance of the cladding layer.The high-temperature effect caused a full transformation of the FCC and BCC phases,and improved the wear resistance and corrosion resistance of the cladding layers.Based on the special phenomenon of atom diffusion difficulty in the high-entropy cladding layer,the microscopic morphologies of TiC ceramic particles in the FeCoCrNiAl high-entropy cladding layer was studied.The results showed that the hysteresis diffusion effect determined that the micro-morphology of ceramic particles in the FeCoCrNiAl high-entropy alloy cladding layer was simpler than that in the Co-based alloy cladding layer.The FeCoCrNiAl+15%(Ti C)composite high-entropy alloy coating could effectively improve the wear resistance,corrosion resistance and high-temperature oxidation resistance of the Cr12MoV cold die steel.