Investigation of the microstructure, mechanical properties and cutting performance of multi-layer Fe-based ultrafine-grained laser cladding layers

To enhance the performance of high-speed steel (HSS) cutting tools, 1–3 layers of in situ VC-reinforced Fe-based ultrafine-grained laser cladding layers were applied to their surfaces. The effect of the number of cladding layers on the macrostructure, phase composition, microstructure, mechanical properties, and cutting performance of the cladding layers were investigated. The results indicated that the single-layer cladding layers consisted of α-Fe, γ, VC, Cr₇C₃, Cr₂₃C₆, WC and Mo2C phases, while the two-layer and three-layer claddings exhibited the presence of the Fe₃C phase. As the number of cladding layers increased, the VC particles in the cladding layers transitioned from a petal-like to a dendritic morphology. The cladding layer grains became finer, with the average grain size of the three-layer cladding layer reaching 0.91 μm, corresponding to the submicron ultrafine-grained scale. The third layer exhibited the highest average microhardness of 1055 HV0.2. When the three-layer cladding layer was applied, the wear scar width, depth, and wear volume of the three-layer cladding layers reached their minimum values, measuring approximately 0.5 mm, 1.11 μm, and 0.184 × 107 μm³, respectively. Cutting experiments demonstrated that, compared with the M2 HSS tool, the main cutting force of the three-layer cladding layer tool was reduced by 8.6 %, while the cutting distance was increased by 73 %. The workpiece surface roughness reached a minimum of 2.5 Ra, and the tool wear mode was adhesive wear.