Effect of high-frequency beam oscillation on microstructures and cracks in laser cladding of Al-Cu-Mg alloys

Laser cladding, a novel surface treatment technology, utilizes a high-energy laser beam to melt diverse alloy compositions and form a specialized alloy-cladding layer on the surface of the substrate to enhance its property. However, it can generate substantial residual stresses during the rapid cooling and heating stages, due to inadequate selection of cladding process parameters and disparities in thermophysical properties between the clad layer and substrate material, leading to the formation of various types of cracks. These cracks can significantly impact the quality and performance of the coating. This paper presents a comprehensive review of crack types and their causes in laser cladding coatings, and identifies that three primary sources of residual stresses, thermal stress, organizational stress, and restraint stress, are the fundamental causes of crack formation. The study proposes several strategies to control coating cracks, including optimizing the coating layer material, refining the coating process parameters, incorporating heat treatment, applying auxiliary fields, and utilizing numerical simulations to predict crack initiation and propagation. Additionally, the paper summarizes crack control methods for emerging structural materials and novel preparation processes. Lastly, the paper analyzes the prospects, technical approaches, and key research directions for effectively controlling cracks in laser cladding coatings.

Section: Other Methodsmentioning

confidence: 99%

Crack Formation Mechanisms and Control Methods of Laser Cladding Coatings: A Review

Li¹,

Huang²,

Yi³

2023

“…During cooling, the temperature drops rapidly; the difference in shrinkage between the materials then leads to a concentration of thermal stresses, especially at the bonding interface, and contributes to the formation of cracks [29]. The rapid cooling process of laser cladding leads to temperature variations between the coating and substrate, resulting in different shrinkage rates and tensile or shear stresses that tend to produce cracks near the bonding region between the coating and substrate [30]. Furthermore, pores are found at the edges of the coating near the surface of the substrate, as shown in Figure 10b,e.…”

Section: Microstructural Characteristicmentioning

confidence: 99%

Microstructure, Hardness and Corrosion Resistance of Al-TiC MMC Prepared by Laser Cladding on AZ31B Magnesium Alloy

Pi,

Zhi,

Chen

et al. 2024

Magnesium alloy is extensively used in aircraft, automobiles, and electronic industries due to its low density, high specific strength, and enhanced machinability. However, low hardness and poor corrosion resistance limit its application. In this work, an Al-TiC metal matrix composite (MMC) was prepared on AZ31B magnesium alloy via laser cladding. The effects of laser power and TiC content on the microstructure, hardness, and corrosion resistance of the MMC were investigated. The results showed that the MMC with 10% TiC had a hardness of 184 HV0.1, which was 3.5 times higher than 52 HV0.1 of the substrate. The current density of MMC with 10% TiC was 3.90 × 10−7 A/cm2, which was three orders of magnitude lower than 5.45 × 10−4 A/cm2 of the substrate. Due to more intermetallic compounds (IMCs) and TiC particles, the MMC with 30% TiC had higher hardness. The increased laser power would not change the phase composition, but it contributed to the formation of a concave crescent shape, promoted the diffusion of Mg, and induced the formation of a thicker Al3Mg2 transition layer. Modifications in the TiC concentration markedly influenced the coating’s microstructural characteristics.

“…The objective of the multi-objective optimization of the process carried out in this study was to obtain the best combination of magnetic-thermal-assisted cladding processes to prepare self-lubricating coatings with good formability. The requirement of good formability of the coating is to ensure the minimum dilution rate, minimum porosity, and maximum microhardness within the specified constraints; the optimization model, i.e., the fitness function of MOPSO is shown in Equation ( 14), Equation (15), and Equation ( 16), respectively, and the constraints of the model are shown in Equation (21).…”

Section: Multi-objective Process Optimizationmentioning

confidence: 99%

“…Among these preparation techniques, laser cladding technology provides an effective solution to realize the preparation of functional coatings owing to its advantages such as fast cooling rate, high efficiency, and high automation [17][18][19]. However, the cladding process is affected by the coupling of light, gas, and solid phases, and the solidification conditions of the molten pool are complicated, which is prone to the formation of metallurgical defects such as cracks, porosity, or uneven distribution of the lubrication phase [20][21][22], which seriously hinders the industrial application of laser cladding of nickel-based self-lubricating coatings. As modern technology progresses, the introduction of external physical fieldassisted cladding to improve the coating quality has become a focus of research at home and abroad.…”

Section: Introductionmentioning

confidence: 99%

Co-Optimization of the Preparation Process of Ni-Based Self-Lubricating Coatings by Magneto-Thermal-Assisted Laser Cladding

Gong,

Shu,

Zhang

et al. 2023

To reduce the metallurgical defects that are prone to occur in the preparation of nickel-based self-lubricating coatings, a method of process co-optimization for magneto-thermal-assisted laser cladding of nickel-based self-lubricating coatings is proposed in this paper. The laser energy density, preheating temperature, and electromagnetic intensity are selected as input factors; the prediction models of coating dilution rate, porosity and microhardness are established by the CCD test method; the interactive effects of the magnetic-thermal-assisted cladding process on the coating response are analyzed, and the optimal process parameter combinations are obtained by using the optimization method of MOPSO-AE-TOPSIS. Finally, the coatings under the parameters are successfully prepared. The results show that the optimal process parameter combinations obtained are laser energy density of 56.8 J/mm2, preheating temperature of 350 °C, electromagnetic intensity of 49.1 mT, and the error of the experimental results with this parameter is less than 3% from the algorithm optimization results. When the microstructure of unassisted and magneto-thermal-assisted fields are analyzed by comparison, it is found that the tissues are more homogeneous and finer, and the distribution of graphite is more homogeneous, which proves the effectiveness of the optimization method.