In order to improve the service life of copper alloy propeller, four Ni45 composite coatings with 5%, 10%, 15% and 20% WC particles were prepared on the surface of copper alloy propeller by laser cladding technology. The microstructure and properties have been investigated by XRD, SEM, EDS and friction and wear tester. The results indicate that the coatings primarily consist of γ-(Fe, Ni) solid solution, Cr0.09Fe0.7Ni0.21, Ni3B2, Ni14W4 and carbides (M23C6, M7C3 and WC). The microstructure mainly consists of cellular grains, dendritic grains and hard-phase particles, which increase along with the increase in WC particles. The average values of four coatings’ microhardness are 782, 875, 1091 and 986 HV0.5, respectively. When the WC content is 15%, the average microhardness has a maximum value of 1091 HV0.5. The wear rates of four coatings are 4.9 × 10–5, 4.2 × 10–5, 3.9 × 10–5 and 8.9 × 10–5 mm3·N−1·min−1, respectively. The coating of 15% WC has a minimum wear rate. When the WC content was 20%, its corrosion current density is the minimum (3.865 × 10–6 A·cm−2) and corrosion potential is the maximum (− 0.127 V), which has a good corrosion resistance. Therefore, when the WC content is maintained within 15–20%, the wear and corrosion resistance of the coating are synergistically enhanced. © The Indian Institute of Metals - IIM 2025.

The Cr-Zr-Cu copper alloy is widely used to manufacture mold for continuous casting. The proper coating can avoid the mold's failure under the condition of a high-temperature and friction environment. Three kinds of Inconel 718/WC-12Co coatings (micro-, nano-, and micro-nano-WC particles) were prepared on the surface of the copper alloy by laser. The phases, microstructure, and elemental distribution of L1-L3 coatings were observed and analyzed by x-ray diffractometer, scanning electron microscope, and energy dispersive spectrometer. The properties of L1-L3 coatings were tested by a Vickers hardness tester and friction and wear testing machine. The results show that the main phases are γ-Ni, M3W3C, MC, W0.15Ni0.85, and W2C in the L1-L3 coatings. In the L1 coating, there is an obvious phenomenon of WC agglomeration. In the L2 coating, there are many columnar, dendritic compounds, and "fish-bone" crystals with small size due to the addition of nanoparticles. In the L3 coating, the structure is scattered due to the uneven distribution of compounds. The average values of L1-L3 coatings' microhardness are 709.6, 851.9, and 600.1 HV0.5, respectively. The L2 coating has the maximum average microhardness. When the experimental temperature is 400 °C during the friction and wear test, the wear rates of L1-L3 coatings are 3.29, 1.89, and 2.83 × 10−4 mm3 N−1 mm−1, respectively. The L2 coating has the minimum wear rate due to the smaller grain size, denier microstructure, and "fish-bone" structure. © 2025 Author(s).

Longitudinal cracks are a common defect on the surface of continuous casting slabs, and cause increases in additional processing costs or long-time interruptions. The accurate identification of surface longitudinal cracks is helpful to ensure the casting process is adjusted in time, which significantly improves the quality of slabs. In this research, the typical temperature characteristics of thermocouples at the position of longitudinal cracks and their adjacent locations were extracted. The principal component analysis (PCA) method was used to reduce the dimensions of these characteristics to remove the redundant information. The particle swarm optimization (PSO) method was introduced to optimize the parameter. On this basis, a recognition model of surface longitudinal cracks was established, based on a particle swarm optimization-eXtreme gradient boosting (XGBOOST) model. Finally, this model was trained and tested using longitudinal crack and non-longitudinal crack samples and compared with the decision tree, the gradient boosting decision tree (GBDT) and XGBOOST models. The test results showed that PSO-XGBOOST had the best identification performance in all evaluation indexes. The accuracy, F1 score and alarm rate results were 95.8%, 92.3% and 100%, respectively, and the false alarm rate was as low as 5.5%. The research results provide a theoretical basis and a reliable model for surface longitudinal crack identification.

The parameters of laser cladding have a major impact on the quality of coating. The suitable parameters are helpful to improve the coating's morphology and properties. In this paper, a multi-objective optimization method is proposed to obtain the optimal parameters of laser cladding based on response surface methodology (RSM) and experiments. The laser power, scanning speed and preheating temperature are used as input factors, while coating's height, depth and hardness are used as target responses. According to ANOVA, the second-order model between the target response and input factors is established to analyze the influence of input factors on height, depth and hardness. Then a multi-objective optimization model is built up to obtain the optimal process parameters of laser cladding. Finally, a coating is successfully prepared with those parameters. The height, depth and hardness of coating are analyzed. The experimental results show that the laser power and preheating temperature have more influence on copper alloy coating. The optimal process parameters are laser power 1400 W, scanning speed 120 mm/min and preheating temperature 200 °C. The corresponding height, depth and average hardness of coating are 0.48 mm, 0.12 mm and 941.6 HV0.5, respectively. © 2023 Elsevier Ltd

The longitudinal crack is a common and serious defect on the surface of wide and heavy slab. The mould heat transfer and friction characteristics of 28 surface longitudinal cracks are collected and investigated in order to reveal the rule of the surface longitudinal cracks. The results show that the decrease amplitude of temperature in the presence of longitudinal crack is between -4.0 and -22.6 degrees C, and the increase amplitude of temperature is between 3.4 and 28.2 degrees C. The decrease of temperature velocity is between -0.4 and -1.5 degrees C.s(-1), while the increase of temperature velocity is between 0.32 degrees C.s(-1) and 1.64 degrees C.s(-1). When longitudinal cracks occur in mould, the heat flux of 21 cases has a decrease more than -0.02 MW center dot m(-2). There are 18 abnormal fluctuations of mould's transient friction during occurrence of the surface longitudinal crack, which is more than the stable casting. And there are 85.7% longitudinal cracks, which has an upward trend of friction tension or a downward trend of friction pressure.

课程思政是新时代高等教育的机遇和挑战，混合式教学是高等教育实施的新途径，二者有机结合为高等教育课程思政提供了新方法。文章以微信公众号为学习平台，采用混合式教学模式，将课程思政元素与专业课程有机结合，统计分析推送消息的阅读、点赞及分享次数。实践表明，采用微信公众平台的混合式教学方法，可以更好地将课程思政融入专业课程学习中，有助于促进专业知识的学习，二者之间存在相互依存、相互促进的作用，混合式教学为高等教育课程思政提供了新方法和新思路，为课程思政建设提供了参考。

In order to improve the wear resistance and service life of die steel, Ni-based alloy coatings with different amount of WC–TiC ceramic particles were fabricated on the substrate of Cr12MoV die steel by laser. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to analyze the microstructures and phases of four coatings. The results show that four coatings have a good metallurgical bonding with the substrate and no crack and porosity on the surface. The reinforced phases were mainly γ~(Fe, Ni), Cr23C6, WC and Cr2Ti. The microstructure was mainly columnar dendrite, cellular dendrite and equiaxed crystal. When the mass fraction of WC particles was 40%, equiaxed crystal appeared in the coating. The WC and TiC particles were evenly distributed among γ~(Fe, Ni) and Cr23C6 phases. With the increase of WC mass fraction, the values of microhardness increased significantly, which were 680.5, 704.3, 752.6 and 806.4 HV0.5, respectively. The coating of 40% WC particles had the maximum microhardness (806.4 HV0.5). The wear volumes of four coatings were 0.47, 0.44, 0.26 and 0.40 mm3, respectively. With the increase of WC content, the wear resistance increased firstly and then decreased. When the mass fraction of WC particles was 30%, the coating had the minimum wear volume (0.26 mm3) and obtained the best wear resistance. It can be seen that the proper amount of WC and TiC ceramic particles enhanced the wear resistance of laser cladding coating. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

The copper alloy is widely used to prepare pipes in ocean engineering. The surface is washed and corroded by seawater for a long time, which gradually shortens the service life of the condenser tube. In order to improve the wear and corrosion resistance of copper alloy, a Ni60-WC coating was fabricated on a preheated copper alloy by laser cladding. Experiments on the Ni60-WC coatings were carried out by SEM, XRD, Vickers-microhardness meter, wear tester and electrochemical workstation. The microstructure, phases, hardness, wear and corrosion resistance were investigated. The results show that from the top to bottom, the microstructures were columnar dendrites, dendritic crystals and grains, respectively. The wear rate of the Ni60-WC coating was only 4.9 x 10(-5) mm(3)center dot N-1 center dot m(-1), which was only 1.14% of copper substrate. In addition, the corrosion current density was 2.34 x 10(-7) mA center dot mm(-2), which was much lower than that of copper alloy substrate (1.14 x 10(-6) mA center dot mm(-2)). The experimental results show that this Ni60-WC coating has a good metallurgical bonding and hardness, and it also has good wear and corrosion resistance, which is helpful to improve the service life of the condenser tube.

The coating on copper plate is difficult to be fabricated by laser. In order to obtain the optimal parameters of laser cladding coating, the temperature fields at different laser power and scanning speed were investigated and analyzed. The optimal parameters were selected with the depth and width of molten pool and compared with the experimental results. Then, the cooling rate, temperature gradient and solidification rate were calculated and analyzed with the coating's microstructure. The results show that the optimal process parameters are 1500 W and 2 mm/s. And at these parameters, the temperature field is consistent with the morphology of cladding coating. From bottom to top of the coating, the corresponding cooling rates are 1056.7, 936.5 and 762.6 degrees C/s, and the microstructure are elongated disordered dendrites, columnar dendrites and planar crystals, respectively.

The casting parameters and behaviour of 61 sticker breakouts were analysed during the continuous casting of the conventional slab. The difference of sticker breakouts between the conventional slabs and wide and heavy slabs was also studied. The results show that the high casting speed or change of casting speed is the main reason. The mould level of the conventional slab is small and not the reason for sticker breakouts, which is different from the causes of wide and heavy slab. In terms of propagation behaviour, there are 14 cases out of 61 sticker breakouts occurred only around one column of thermocouples. The vertical velocity is in the range of 0.3 similar to 2.4 m center dot min(-1), and the horizontal velocity is in the range of 1.0 similar to 9.0 m center dot min(-1). The vertical velocities of the three sticker breakouts are higher than their casting speeds, which is different from the wide and heavy slab.