Search Results (783)

With superior manufacturing freedom capability, Selective Laser Melting (SLM) technology is capable of fabricating high-strength Ti-6Al-2Zr-1Mo-1V (TA15) complex titanium alloy parts, thereby finding extensive applications in the aerospace sector. This paper primarily investigates the influence of process parameters on the relative density, microstructure, and mechanical properties of SLMed TA15 under conditions of similar laser linear energy density. The results indicate that the laser linear energy density significantly affects the single-track morphology of SLMed TA15; excessive energy density leads to keyhole defects, while insufficient energy density causes balling phenomena, resulting in discontinuous clad tracks. When the laser linear energy density is appropriate, the scanning spacing affects the forming density of the parts, with both excessively large and small spacings having adverse effects. With a fixed scanning spacing of 100 μm, high-density samples can be produced within a suitable range of linear energy density. However, when the laser linear energy density is comparable, a lower scanning speed leads to heat accumulation, causing in situ decomposition of the α’ martensite and the formation of coarser α + β phases, which reduces strength and hardness but improves plasticity. At a laser power of 90 W, a scanning speed of 400 mm/s, and a scanning spacing of 100 μm, the specimen exhibits a tensile strength of 1233 MPa and an elongation of 8.4%, achieving relatively excellent comprehensive properties. Full article

AlCrCoFeNi high-entropy alloys (HEAs) have been successfully synthesized by laser cladding. The AlCrFeCoNi HEA coatings were composed of planar crystal, columnar grain, and equiaxed grain from bottom to top. Face-centered cubic (FCC) was the major phase in coatings, and its content decreased when increasing laser power or reducing scanning speed. The precipitation in the HEA coatings were Al-Ni enriched B2 phase and FeAl₃ intermetallic compounds. The interface zone had higher microhardness than the cladding zone due to the addition of Fe from the dilution role. The C2 (3 kW, 4 mm/s) and C9 (3.5 kW, 6 mm/s) coatings displayed the best corrosion resistance when taking the E_corr (−0.327 V, −0.335 V), I_corr (0.236 μA·cm⁻², 0.475 μA·cm⁻²), and R_ct (224.2 kΩ/cm², 121.1 kΩ/cm²) into consideration. Pitting dominated the corrosion process of the AlCrFeCoNi HEA coatings. Large grain boundary areas generated by the fine grain in the C2 and C9 coatings enhanced difficulty of ion transport along the grain boundary. Then, multiple corrosion sites on the surface promoted uniform corrosion and formed a protective oxide film, inhibiting serious pitting. This work provided an approach of laser cladding AlCrCoFeNi HEAs with different laser powers and scanning speeds, and insights into the correlation of anti-corrosion properties with the microstructure of AlCrCoFeNi coatings. Full article

Wear-resistant coatings applied to the surface of copper and copper alloys through diverse advanced technologies can substantially enhance their wear resistance and broaden their application spectrum. This paper provides a comprehensive review of the development and current research status of wear-resistant coatings fabricated on copper and its alloys. It presents the research findings on the preparation of wear-resistant coatings using both one-step methods (such as laser cladding, electroplating, thermal spraying, cold spraying, electro-spark deposition, etc.) and two-step methods (chemical plating and heat treatment, electrodeposition and laser cladding, laser cladding and in situ synthesis, etc.). This paper provides an in-depth examination of the characteristics, operating principles, and effects of various coating techniques on enhancing the wear resistance of copper and copper alloys. The advantages and disadvantages of different coating preparation methods are compared and analyzed; meanwhile, a prospective outlook on the future development trends is also offered. Full article

In order to achieve precise shaping control of FeCoNi + 1%Y₂O₃ laser-directed energy deposition (LDED) coatings and to reveal the influence of LDED process parameters on coating morphology, the response surface methodology (RSM) is employed in this study. The process parameters, including laser power, scanning speed, and powder feeding rate, are comprehensively considered, with the dilution rate, width-to-height ratio, and cladding area as evaluation criteria. A regression model is established to analyze both the individual and interactive effects of process parameters on forming quality. The findings indicate that the ideal process parameters are a laser power of 706.8 W, scanning speed of 646.2 mm/min, and powder feeding rate of 12 g/min. Experimental validation shows that the mean actual errors compared to the predicted values for dilution rate, width-to-height ratio, and cladding area are 7.36%, 10.03%, and 3.50%, respectively, proving the reliability of the model. The findings provide a theoretical basis for the prediction and control of the morphology of high-entropy alloy deposited layers with the addition of Y₂O₃. Full article

The rectangular spot laser cladding system, due to its large spot size and high efficiency, has been widely applied in laser cladding equipment, significantly improving cladding’s efficiency. However, while enhancing cladding efficiency, the rectangular spot laser cladding system may also affect the stability of the melt pool, thereby impacting the cladding’s quality. To accurately predict the melt pool morphology and size during wide beam laser cladding, this study developed a melt pool monitoring system. Through real-time monitoring of the melt pool morphology, image processing techniques were employed to extract features such as the melt pool width and area. The study used laser power, scanning speed, and the powder feed rate as input variables, and established a prediction model for the melt pool width and area based on Support Vector Regression (SVR). Additionally, an Ant Colony Optimization (ACO) algorithm was applied to optimize the SVR model, resulting in an ACO-SVR-based prediction model for the melt pool. The results show that the relative error in predicting the melt pool width using the ACO-SVR model is less than 2.2%, and the relative error in predicting the melt pool area is less than 9.13%, achieving accurate predictions of the melt pool width and area during rectangular spot laser cladding. Full article

This study presents a novel approach in the laser cladding optimization field by integrating economic analysis with performance optimization. Despite extensive research on laser cladding technical performance, its economic evaluation—particularly when merged with productivity assessment—has scarcely received attention. This work addresses this gap by integrating an economic and productivity analysis with a standard performance evaluation through the employment of a multi-criteria optimization approach to balance technical and economic performances. To achieve this objective, a multi-parametric optimization via response surface methodology (RSM) and desirability function analysis has been developed. Results indicate that the employment of desirability analysis after RSM modeling is a valuable approach for laser cladding analysis, allowing the particular weighting of each result and providing the possibility of selecting processing parameters depending on the specific objective at any given time. Full article

Laser cladding faces several challenges, including cracking, fracture, deformation, and interlayer delamination, which hinder its widespread application in part repair. Residual stress within the workpiece is a key factor contributing to these issues. To enhance the quality of laser cladding gear tooth repairs, the study integrates numerical modeling and experimental approaches to examine how varying annealing temperatures influence the residual stress and microstructural changes in Ni60A cladding layers. A theoretical model was established to simulate the laser cladding process and the subsequent annealing treatment utilized in gear repairs. The model was used to study the variations in temperature and stress fields at different annealing temperatures, analyze the effect of temperature gradient on residual stress, and examine the distribution of residual stress. Cladding experiments were then performed under various annealing conditions, with hardness and residual stress measurements taken from the fifth cladding layer. The results demonstrated that residual stress in the samples significantly decreased after annealing, from 781.63 MPa (RT) to 572.24 MPa (400 °C), 494.42 MPa (600 °C), and 393.83 MPa (800 °C). This indicates that the annealing process effectively reduces the residual stress in the workpiece. The residual stress values obtained from experiments showed a deviation of less than 7% from the simulation results, confirming the accuracy of the model. The highest average microhardness of 764.39 HV_0.5 was observed at 600 °C. Microstructural analysis of the cladding layer revealed significant grain refinement after annealing, with previously aggregated phases transforming into a uniformly dispersed structure. Energy Dispersive Spectroscopy (EDS) analysis confirmed the presence of boron (B) in the annealed samples, which contributes to grain refinement and enhances the annealing effect. Full article

Laser-directed energy deposition technology (LDED), a method for repairing worn agricultural machinery parts, is valued for its flexibility, efficiency, and economy. To improve the comprehensive quality of the parts repair layer and reduce the processing energy consumption and time, it is necessary to explore the influence law of process parameters and multi-objective optimization experiments. We used L₉ (3³) orthogonal experiments to evaluate the effects of laser power, scanning speed, and powder feed rate on repair quality. Variance analysis assessed factor level impacts and a multi-objective optimization model was constructed and optimized using a genetic algorithm (GA). Then, a preferred algorithm is proposed to optimize and obtain the optimal process level. The results show that the cladding efficiency increases at first and then decreases with the increase in laser power, decreases with the increase in scanning speed, and increases with the increase in powder feed rate. The dilution rate decreases at first and then increases with the increase in laser power, increases with the increase in scanning speed, and decreases with the increase in powder feed rate. In addition, it is also affected by the interaction between scanning speed and powder feed rate. Taking the maximum cladding efficiency and the minimum dilution rate as the optimization objectives, the verification test was carried out with the process parameters of laser power 1684.7370 W, scanning speed 3.0175 mm s⁻¹, and powder feed rate 1.5901 r min⁻¹. The error rates of cladding efficiency and dilution rate were 3.98% and 4.89%, respectively, which confirmed the method’s effectiveness. The research results can provide a reference for the repair of worn parts of agricultural machinery, which is not only cost-effective but saves time, as well. The free formability of the LDED process also allows it to add special functions to simple damaged castings and forging parts during the repair process to improve their performance. Full article

In this study, Ni60/60%WC composite coatings were fabricated on 45 steel by laser cladding. The optimum process was selected through high throughput optimization experiments which had a laser power of 2400 W, scanning speed of 8 mm/s, and powder feeding rate of 20 g/min. The single-layer multilayer coatings were prepared without any cracks and pores, and the thickness of the coatings was 1.52 mm. The coating and the substrate were found to have an effective metallurgical connection. WC was distributed relatively uniformly throughout the coating, which involved the γ-(Fe, Ni), WC, W₂C, Cr₂₃C₆, and Fe_3.57W_9.43C_3.54 phases. The average microhardness of the coating was 1416.14 HV_0.2, approximately 5.47 times that of the substrate, and the average coefficient of friction of the coating was 0.5144, which was 43.5% lower than that of the substrate. The wear rate was reduced by 79.13%. Full article

The present study effectively produced a high-entropy alloy (HEA) coating of AlCrFeMnNi on AISI 304L steel using resonant ultrasonic vibration-assisted laser cladding (R-UVALC). An investigation was conducted to examine the impact of dilution rate on the phase composition, microstructure, and mechanical and tribological properties of AlCrFeMnNi coatings. The coating, which was created utilizing the appropriate dilution rate, was thoroughly characterized using EDS mapping and TEM investigation. The results suggest that a higher dilution rate causes a change in the AlCrFeMnNi coating, transforming it from a single solid solution phase (BCC) into a two-phase solid solution containing both FCC and BCC phases. The analysis conducted using transmission electron microscopy (TEM) reveals that the AlCrFeMnNi coating, when diluted at an optimal rate of around 37%, is predominantly composed of a disordered body-centered cubic (BCC) phase and an ordered BCC (B2) phase featuring a spinodal decomposition structure. The AlCrFeMnNi coating has an average microhardness of approximately 540 HV, which is over 2.5 times higher than the microhardness of the substrate. Additionally, it was also established that the dilution rate has an impact on the occurrence of phases, which subsequently affects the mechanical and antifrictional properties of the coating. The integration of ultrasonic vibration in laser cladding enhances quality and improves mechanical and tribological properties, thereby reducing material costs and promoting an environmentally friendly process when compared to conventional cladding. Full article

In this study, Inconel 625 coatings were deposited onto the surface of 2Cr13 stainless steel via laser cladding technology to ensure their corrosion resistance and mechanical properties. The microstructure and characteristics of coatings were adjusted by varying laser power (1200, 1500, and 1800 W), scanning speed (10, 15, and 25 mm/s), and overlap rate (40%, 50%, and 70%). The results showed that the impact resistance of blades was improved by 23% to 30% compared to the substrate, whereas the self-corrosion current density was reduced by 94%–98%, which indicated the outstanding resistance of specimens to damage and corrosion. At the same time, the appropriate processing parameters enabled the surface hardness of the 2Cr13 substrate to be improved. This study provides practical technical guidance for the repair of 2Cr13 blades and a comprehensive enhancement of their corrosion resistance and mechanical properties through parameter optimization. Full article

Among many methods to enhance the crack resistance of laser cladding coatings, adjusting the composition of laser cladding material is the most simple, feasible, and effective method. To improve the plastic toughness and crack resistance of A100 laser cladding coating, Ni and Ti powders of an equal molar ratio were added to A100 powder as laser cladding powder. Laser cladding technology prepared A100-(Ni-Ti) coatings without crack defects. The cladding coatings’ phase composition and microstructure were analyzed using XRD and SEM, respectively. A ring-block friction and wear tester tested the wear resistance of the A100-(Ni-Ti) cladding coatings. A100-(Ni-Ti) cladding coatings mainly contain martensite and austenite. The elements Ni and Ti are distributed primarily in the austenitic phase region. The results show that adding Ni and Ti elements can reduce the microhardness of A100 cladding coatings. The average microhardness of the A100-0%(Ni-Ti) cladding coating is 532.50 HV, and the average microhardness of the A100-10%(Ni-Ti) cladding coating is 430.99 HV, while the average microhardness of the A100-30%(Ni-Ti) cladding coating is only 307.49 HV. The wear surface of the A100-10%(Ni-Ti) cladding mainly shows pits and a small amount of adhesive wear. The A100-20%(Ni-Ti) and A100-30%(Ni-Ti) cladding coatings show severe adhesive wear. The A100-10%(Ni-Ti) cladding with high microhardness and good run-in performance exhibits the best wear resistance. Full article

In this paper, the effects of different laser powers on the microstructure, microhardness, and wear resistance of Ni65A/WC composite coatings were investigated by using laser cladding technology. The morphology, phase structure, elemental distribution, wear behaviour, and property changes of the fused coatings were systematically characterised and analysed. The mechanism of power parameters on coating properties was summarised. The results show that different laser powers significantly affect the microstructure of the coating and the distribution of the enhanced phase WC. Under the 800 W power condition, the WC particles were not sufficiently dissolved and the organisation was not dense. The hardness and abrasion resistance were low. Under 1200 W power conditions, the enhanced phases were uniformly dispersed. The best microstructure densities and homogeneity were observed. The generated hard phase and matrix toughness achieved a good balance. The hardness of the coating reached 375 HV while also showing optimum wear resistance and stable friction behaviour. Under 1600 W power conditions, although the hard phase was completely dissolved and re-precipitated, some areas of tissue coarsening made the wear resistance slightly inferior to that at 1200 W. The 2000 W power condition resulted in a significant deterioration in the coating properties due to the increase in cracks and pores caused by the overheating of the melt pool. For this reason, 1200 W power conditions proved to be the ideal parameter range for optimising the microstructure and mechanical properties of Ni65A/WC composite coatings. The study in this paper can provide an important reference for the design of high-performance wear-resistant coatings. Full article

A wavelength-swept laser (WSL) demodulation system offers a unique time-domain analysis solution for high-sensitivity optical fiber sensors, providing a high-resolution and high-speed method compared to optical spectrum analysis. However, most traditional WSL-demodulated sensing systems require a synchronous trigger signal or an additional optical dispersion link for sensing analysis and typically use a fiber Bragg grating (FBG) as the sensing unit, which limits displacement sensitivity and increases fabrication costs. We present a novel displacement sensing system that combines a trigger-free WSL demodulation method with a cascaded balloon-like interferometer, featuring a simple structure, high sensitivity, and low temperature cross-sensitivity. The sensor is implemented by bending a short length of single-mode fiber with an optimal radius of around 4 mm to excite cladding modes, which form an interference spectral response with the core mode. Experimental findings reveal that the system achieves a high sensitivity of 397.6 pm/μm for displacement variation, corresponding to 19.88 ms/μm when demodulated using a WSL with a sweeping speed of 20 nm/s. At the same time, the temperature cross-sensitivity is as low as 5 pm/°C or 0.25 ms/°C, making it a strong candidate for displacement sensing in harsh environments with significant temperature interference. Full article

In order to apply laser cladding technology to the complex surface processing of hot-working dies, this study developed a numerical model for curved surface laser cladding along various scanning trajectories under multi-physics coupling considering the dynamics of the molten pool, cladding parameters (scanning speed and laser power), Marangoni effect, and solid–liquid phase transition. Utilizing this model and by altering cladding parameters, the temperature field and the variation in coating thickness along various scanning trajectories were studied as well as the interaction between the two. The following discoveries were made. Variations in scanning trajectories lead to differences in the coating thickness of curved surface laser cladding. Regardless of the combination of cladding parameters, the coating thickness of scanning from top to bottom is always less than that from bottom to top, with a difference of approximately 0.05 mm. The temperature field and coating thickness influence each other. The Marangoni effect induced by the temperature field is the primary cause of coating thickness growth, while the coating thickness affects thermal transfer from the thermal source, ultimately influencing the temperature field. Employing a greater laser power or a slower scanning speed, or a combination of greater laser power and slower scanning speed, can increase the coating thickness and its maximum temperature in curved surface laser cladding. The model, when contrasted with experimental data, exhibits a comprehensive discrepancy of 3.49%, signifying its high precision and practical engineering applicability. Full article