Effect of alternating magnetic field on microstructure and mechanical properties of Ni60/La2O3 laser cladding layer

A Ni60 cladding layer containing 1.6 wt% La2O3 was prepared on 35CrMoV steel using an alternating magnetic field-assisted laser cladding technique. The microstructure, phase composition, microhardness, and tribological properties of the composite coatings were characterized. Based on experimental results, the main components of the 1.6 % Ni60 + La2O3 cladding layer are γ-(Fe,Ni), Cr23C6, FeNiSi, Ni3B, Ni4B3 and Cr2B. The EBSD analysis reveals that the increase in intensity of the alternating magnetic field leads to a significant refinement in the average grain size of the cladding layer, thereby greatly enhancing microstructural uniformity. The average grain sizes of the layers with 0–15 mT magnetic field intensity are 28.515 μm, 26.076 μm, 23.878 μm and 18.337 μm, respectively. The TEM bright field images reveal that the enhancement of magnetic field intensity facilitates the precipitation of γ′ within the cladding layer. Friction and wear experiments demonstrated that a Ni60 composite coating containing 1.6 % La2O3 exhibited superior friction and wear performance at a magnetic field intensity of 15 mT due to its highest average hardness (608.97 HV1), lowest friction coefficient (0.394), and excellent wear morphology.