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To improve the wear resistance of Fe-based cladding, NbC particles with different morphology are generated in situ by adding Nb, Cr 3 C 2 and C with different content. The composition of samples and the morphology of NbC particles generated in situ are revealed by XRD, SEM and EDS. The wear resistance is studied by a reciprocating friction and wear testing machine. The wear mode and the wear mechanism of each sample are investigated. The results show that although NbC particles are generated in situ in samples with different Nb, Cr 3 C 2 and C content, the morphology of NbC particles is varied. The wear resistance of samples containing cross-shaped NbC particles is more outstanding than that of samples containing only rectangular NbC particles. In addition, changing Nb, Cr 3 C 2 and C content does not result in a change in wear mode, but leads to the formation of continuous lattice structure of Cr 0.19 Fe 0.7 Ni 0.11 and Cr 23 C 6 compounds at grain boundaries and a change in the wear resistance. When the additions of Nb, Cr 3 C 2 and C are 11.2 wt%, 8.6 wt% and 0.2 wt% respectively, the coefficient of friction of the sample is the lowest, and the wear resistance is the most outstanding. [ABSTRACT FROM AUTHOR]

The cladding layer formed by laser cladding is formed by solidification of the molten pool. The quality of the cladding layer is directly determined by the evolution of the molten pool. The numerical simulation of the evolution of the molten pool is carried out, revealing the relationship between different powers and the evolution of the molten pool. The results show that the volume of the molten pool exhibits a nonlinear expansion of "expansion-shrinkage-re-expansion" before reaching the steady state, and the volume and expansion rate of the molten pool are determined by the laser power. In addition, the degree of shrinkage of the molten pool and the speed of convection can also be controlled by the laser power. When the laser power reaches a certain level, evaporation occurs on the surface of the molten pool. The convection pattern of the molten pool can be changed by evaporation. However, due to the impact of shielding gas and Marangoni movement, the effect of evaporation on the geometry of the cladding layer is limited. [ABSTRACT FROM AUTHOR]

Because the convection pattern inside the laser cladding transient molten pool is difficult to measure by experimental means, the numerical analysis model of the inside of the laser cladding molten pool was constructed, and the forming mechanism of the cladding layer was simultaneously analyzed. The internal convection pattern of the single-track, multi-track and multi-layer laser cladding molten pool was analyzed. The results show that the convection inside the laser cladding molten pool in different types is mainly annular convection. The fluid at the bottom of the molten pool flows to the surface of the molten pool, and the fluid on the surface of the molten pool flows along the sides to the bottom of the molten pool. Therefore, the cladding layer is mainly solidified by the fluid flowing from the bottom of the molten pool to the surface of the molten pool. [ABSTRACT FROM AUTHOR]

• A numerical model of laser cladding for V-grooves was constructed. • The volumetric evolution of the oscillatory expansion of the melt pool, different from that in the planar, V-shaped trough, was revealed. • The heat transfer characteristics of the melt pool with different angles of the V-groove were revealed with Marangoni convection patterns at different viewing angles. • The mechanism of cavitation generation in V-grooves with small pinch angles and its avoidance measures were predicted. In comparison to planar-oriented laser cladding, non-planar laser cladding also deserves to be discussed. A numerical model of non-planar laser cladding was constructed for V-grooves with different tension angles. The simulation results show that the melt pool generated at the bottom of the V-groove undergoes an oscillatory expansion phase similar to that of planar laser cladding and ends up in a periodic steady state. As the tension angle θ of the V-groove decreases, the absorption of laser energy by the bevels on both sides becomes more and more, and the melt pool volume starts to decrease. However, after θ is reduced to a certain threshold, the melt pool volume starts to become larger instead, and this change brings about a complex melt pool convection pattern. Finally, the mechanism of cavitation generation at the bottom of the V-groove when θ is less than 60° and the possible avoidance measures are also analyzed. [ABSTRACT FROM AUTHOR]