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Laser cladding is a powerful surface treatment technique that can significantly enhance the properties of metal alloys. This study delves into the liquid phase separation behavior of Cu-Fe-Cr alloys under the rapid solidification conditions inherent in laser cladding and evaluates the influence of 4% Mo and 2% B4C additions on the resulting alloy characteristics. The intensive undercooling characteristic of the laser cladding process facilitates the alloy's entry into the liquid-phase immiscibility gap, prompting pronounced phase separation. Our investigation reveals the emergence of Fe-rich regions, exhibiting a variety of shapes, set against a continuous Cu-rich matrix. The incorporation of Mo and B4C was found to modulate the mixing enthalpy and entropy, thereby refining the phase distribution: Mo was observed to prevent the agglomeration of Fe cores, resulting in a dispersion of isolated Fe cores throughout the Cu-rich matrix, while B4C promoted a more uniform compositional distribution. This study further enumerates the enhancements in microhardness, wear resistance, and magnetic properties of the alloys. Notably, the Cu-Fe-Cr-Mo-B4C alloy demonstrated a microhardness exceeding 600 HV, a low coefficient of friction around 0.15, high saturation magnetization, and reduced coercivity. These results underscore the efficacy of laser cladding in tailoring the microstructure and properties of Cu-Fe alloys, providing insights for the controlled manipulation of phase separation to optimize surface characteristics for engineering applications. [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]

As an advanced additive manufacturing technology, laser cladding has become a research hotspot in the fields of rapid manufacturing and surface modification in recent years. The quality of the cladding layer directly depends on the choice of process parameters. In order to obtain high quality cladding layer, the effects of laser power, scanning speed, and powder feeding rate on the quality of JG-3 iron-based powder cladding layer were studied by interaction orthogonal experiments. Three-dimensional measurement laser microscopy (3D MLM) and variance analysis were used to analyze the results. It was found that the interaction between laser power and powder feeding rate directly affects the optimum process parameters. Laser power 750 W, scanning speed 420 mm/min, and powder feeding rate 6.96 g/min were selected as the optimum process parameters. Scanning electron microscope (SEM), X-ray diffraction (XRD), and Thermo-Calc software were used to analyze the microstructure, phase composition, and solidification process of the coating, and compared with the experimental results. The results show that under the optimum process parameters, a dense crack-free and non-porous coating was obtained. The coating can be divided into three areas: coating zone (CZ), bonding zone (BZ), and heat affected zone (HAZ). The CZ is composed of α-Fe, Cr2B, Fe2B, and Cr23C6 phases. The calculated results obtained from the Thermo-Calc software are in good agreement with the experimental data. It is beneficial to the coating design for a desirable microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

Dilution rate is an important factor affecting the properties of laser cladding. However, the exact estimate of dilution rate in direct laser fabrication is still not fully developed. In this study, high-strength and wear-resistant YCF102 alloy powder is used to laser clad on the steel substrate. The area of the cladding layer is replaced by a part of the circle, and the relationship among the deposition angle, the clad width, and the area of the cladding layer is established. The geometry of the fusion zone is replaced by polynomial function of the fourth degree, and the relationship among the thermal tension angle, the clad width, the melting pool depth, and the area of the fusion zone is established. The value of the dilution rate is obtained by the area of the cladding layer and the fusion zone. The correlation coefficient of the area of cladding layer, the area of the fusion zone, and the dilution rate is also obtained. The estimate results coincident with the measurement results very well. The proposed theoretical model offers a basis for estimate of dilution rate in laser cladding. [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]

The aim of this paper is to investigate the effect of laser re-melting on the morphology and mechanical properties of cladding layer under different laser power conditions. In this study, the laser re-melting tests were performed on YCF102 cladding layer with different laser power, and the morphology and microstructure of each cladding layer were researched by optical microscopy. Meanwhile, the microhardness and wear resistance of YCF102 cladding layer after laser re-melting with different laser power were studied. The results show that laser re-melting can not only improve the morphology of cladding layer, but also improve the microhardness and wear resistance of cladding layer. However, the excessive re-melting laser power leads to the increase of the number of defects in the cladding layer and the deterioration of the mircrohardness and wear resistance of cladding layer. When the re-melting laser power is 650 W, the cladding layer not only has a small surface roughness and no defects, but also has good mechanical properties. • Laser re-melting can reduce the number of defects in the cladding layer. • Laser re-melting can improve the surface morphology and mechanical properties. • Excessive re-melting laser power causes degradation of the mechanical properties. • Re-melting laser power is related to surface morphology and mechanical properties. [ABSTRACT FROM AUTHOR]

Due to the complex transient characteristics, it is difficult to directly measure the formation and development of a molten pool formed by laser cladding. Considering the change of thermophysical properties at high temperatures and the coupling between the heat source and the molten pool surface, a new numerical simulation method was proposed and verified. The thermal history and formation of the molten pool, the convective pattern, and the solidification morphology of the cladding have been analyzed. The results show that the molten pool can reach steady-state in a very short time, and both considerable temperature gradient and fast circular convection exist in the molten pool. The bottom of the molten pool mainly showed columnar growth, while the top was equiaxed. Columnar to equiaxed transition occurred at the center of the molten pool. • Established a multiphysics three-dimensional simulation model for laser cladding. • Two annular Marangoni convections were founded inside the molten pool. • Evaporation hardly affects the shape of the cladding. • CET occurs during solidification. [ABSTRACT FROM AUTHOR]

• An improved finite element model is developed for the laser cladding process. • The powder temperature-rise and shielding gas pressure are taken into account. • The average error between experiment and simulation is less than 6.05%. • The dynamic growth and solidification mechanism of the coating are revealed. To accurately predict the three-dimensional (3D) characteristics of the coating and dynamic solidification process during coaxial powder-fed laser cladding, an improved 3D multi-physics finite element model including heat transfer, fluid flow, shielding gas pressure, powder temperature-rise, surface tension, and free surface movement is proposed. The input parameters of the model only depend on the thermophysical properties of the deposited material and the process parameters. Therefore, the model has good universality, and can be flexibly applied in other laser cladding systems or deposited materials. The average width and height error for the experimental and simulated is 6.05% and 4.15%, respectively. The numerical model has good abilities to predict the 3D geometry of the coating. The accuracy of the model can be indeed improved by considering the powder temperature-rise and shielding gas pressure during the modeling process. The dynamic growth process of the coating, spatiotemporal variations of the temperature and temperature gradient were discussed in detail to reveal the solidification mechanism. Finally, the relationship between the crystal characteristic (planar, cellular, columnar, and equiaxed grains) and thermal parameters (the temperature, the temperature gradient, and the solidification rate) was established. The results show that the temperature gradient and undercooling at the solidification interface are significantly responsible for the crystal characteristic, while the grain size is mainly governed by the solidification rate. [ABSTRACT FROM AUTHOR]