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Very High Cycle Fatigue Behaviour of the 316L Weldment Fabricated By Laser Butt-Welding
摘要： In nuclear industry, 316L weldments are widely used in components fabricating, which usually suffer from very-high-cycle fatigue. Therefore, the very high cycle fatigue (VHCF) behaviour of 316L weldment fabricated by laser butt-welding joint were studied using an ultrasonic fatigue testing system. The microscopic examination indicated that an evident pore is observed in the weld seam and the fine columnar-dendrite structure is formed in the central part of the weld seam. Near the weld interface in the weld seam, the weld microstructure shows larger columnar-dendrite. The hardness distribution of the weldment is to coincide with the characteristic of the microstructure. In the central part of the weld seam, the hardness is the highest, and is the lowest in the base metal. Fatigue failure still occurred in the VHCF regime. The fatigue crack initiated from the internal pores caused by laser butt-welding. Although the fatigue strength of weld seam might be decreased due to the pore, the fatigue strength of the weldment was the same as the base metal in this research. That is, the defect with a certain size in the weld seam does not affect the strength of the weldment.
更新于2025-11-28 14:24:20
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Precipitates evolution in the heat affected zone of Mg-Gd-Y-Zr alloy in T6 condition during laser welding
摘要： The precipitates evolution in the heat affected zone of laser-welded Mg-Gd-Y-Zr alloy in T6 condition was investigated based on the TEM observation. Some oval and long-rod shape precipitates along [2110]α were observed, which were not involved in precipitation sequence. Compared with isothermal aged precipitates, the overaged β′ phase presented same morphology and size, while size of needle-shape β became much smaller. The width of complete dissolution zone of the β′ is smaller than that of partial dissolution and transformation zone.
关键词： Precipitates evolution,Heat affected zone,Mg-Gd-Y-Zr alloys,Laser welding
更新于2025-11-28 14:24:20
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A comparison of microstructure and mechanical properties of laser cladding and laser-induction hybrid cladding coatings on full-scale rail
摘要： With the rapid development of high-speed and heavy-haul trains, the surface damages of rails are becoming more and more severe, and how to promote the surface strength of the rail and prolong its service life with high efficiency are becoming extremely important. Laser cladding (LC), with small heat affected zone (HAZ) and low dilution, is a promising novel way to hardface and repair the rail. However, there are two great barriers for the traditional LC to apply on full-scale rails: one is how to prevent the coating from cracking under the rapid heating and cooling cycle; the other is how to eliminate the martensite structure in HAZ, which may threaten the safety of railway transportation due to its high hardness and low fracture toughness and usually be forbidden in almost all the Railway Standards over the world. In this paper, laser-induction hybrid cladding (LIHC) was innovatively proposed to deposit Ni-based coatings on a full-scale rail. The cracking behaviors, microstructures and mechanical properties of the coatings and HAZs by LC, LIHC with induction pre-heating (pre-LIHC) and LIHC with induction post-heating (post-LIHC) were studied systemically. The results indicate that the cracking and martensite transformation occurred in the HAZ can only be prevented by post-LIHC, where fine pearlite with smaller pearlite block size and lower interlamellar spacing formed instead. Therefore, the abrupt change of microstructure and mechanical properties in the HAZ could be avoided by post-LIHC, and the hardness, strength and toughness of the rails can be improved significantly. The post-LIHC technology shows the potentiality to hardface and repair the full-scale rail.
关键词： Martensite,Microhardness distribution,Toughness,Laser-induction hybrid cladding (LIHC),Full-scale rail,Strength
更新于2025-11-28 14:24:20
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Microstructure and properties of WC reinforced Ni-based composite coatings with Y <sub/>2</sub> O <sub/>3</sub> addition on titanium alloy by laser cladding
摘要： In this study, WC reinforced Ni-based composite coatings with Y2O3 addition were deposited on Ti-6Al-4V titanium substrate by laser cladding. The phases, microstructure, microhardness and wear resistance of the composite coatings were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, microhardness tester and wear tester. The results showed that good metallurgical bonding was achieved between the composite coatings and substrate. The phases mainly were γ -Ni, TiC, TiB2, Ni3B, M23C6 and WC. Most of the WC was dissolved in small pieces of WC during the laser cladding process. The microhardness of the composite coatings was about 3 times that of the titanium substrate and the wear resistance of the composite coatings had a significant increase.
关键词： titanium alloy,microstructure,Laser cladding,Y2O3,WC,Ni-based composite coatings
更新于2025-11-28 14:24:20
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Laser in-situ synthesis of high aspect ratio TiB fiber bundle reinforced titanium matrix composite coating
摘要： In this study, coatings are fabricated with laser cladding technique on titanium alloy substrate using TiB2 powder (0.5 μm, 5 μm and 50 μm) as the cladding materials. The effects of different TiB2 particle sizes and different laser powers on the microstructure of laser cladding layer are investigated. The results reveal that the cladding layer of high aspect ratio TiB fiber bundle is formed when using 0.5 μm TiB2 as the cladding material under the condition of high laser power (2.5 kW) of TiB fiber bundle are formed when using 5 μm and 50 μm TiB2 as the cladding materials under the condition of different laser powers. Combined with the evolution of microstructure in the cladding layers, the formation mechanism of high aspect ratio TiB fiber bundle is discussed. Meanwhile, the cladding layer of high aspect ratio TiB fiber bundle exhibits the advantages of high hardness and high wear resistance, and the predominant wear mechanisms of TiB fiber bundle are cutting and fracture.
关键词： TiB fiber bundle,Microstructure,Wear,Laser cladding,Hardness
更新于2025-11-28 14:24:20
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Quasi-continuous-wave laser surface melting of aluminium alloy: Precipitate morphology, solute segregation and corrosion resistance
摘要： A quasi-continuous wave laser surface melting is performed on 2219 aluminium alloy to improve the corrosion resistance. The fast cooling rate and the multi-directional solidification behavior of the process transform large and long-chained constituent particles into fine and isolated circular precipitates with alleviated solute segregation. The improved corrosion resistance is due to formation of low-flaw-density passive film, reduction of the driving force for corrosion and improvement of the re-passivation capability of the modified surface. The large and long-chained constituent particles are the preferred sites for corrosion initiation and propagation.
关键词： C: Segregation,B: Polarization,C: Pitting corrosion,A: Aluminium,B: EPMA
更新于2025-11-28 14:24:20
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Computational and Experimental Investigation of Micro-Hardness and Wear Resistance of Ni-Based Alloy and TiC Composite Coating Obtained by Laser Cladding
摘要： The influence of processing parameters on the micro-hardness and wear resistance of a Ni-based alloy and titanium carbide (TiC) composite cladding layer was studied. Mathematical models were developed to predict the micro-hardness and wear resistance of the cladding layer by controlling the laser cladding processing parameters. Key processing parameters were the laser power, scanning speed, gas flow, and TiC powder ratio. The models were validated by analysis of variance and parameter optimization. Results show that the micro-hardness is positively correlated with laser power and TiC powder ratio, where the TiC powder ratio shows the most significant impact. The wear volume decreased with an increasing TiC powder ratio. The targets for the processing parameter optimization were set to 62 HRC for micro-hardness and a minimal volume wear. The difference between the model prediction value and experimental validation result for micro-hardness and wear volume were 1.87% and 6.33%, respectively. These models provide guidance to optimize the processing parameters to achieve a desired micro-hardness and maximize wear resistance in a composite cladding layer.
关键词： Ni35A + TiC composite,laser cladding,central composite design,wear resistance,micro-hardness
更新于2025-11-28 14:24:20
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Microstructural evolution and wear performance of the high-entropy FeMnCoCr alloy/TiC/CaF2 self-lubricating composite coatings on copper prepared by laser cladding for continuous casting mold
摘要： The FeMnCoCr high-entropy alloy/TiC/CaF2 self-lubricating coatings were successfully prepared on a Cu–Zr–Cr alloy for continuous casting mold by laser cladding for wear-resistance. The intriguing ?nding was that the laser-cladded FeMnCoCr is mainly composed of face-centered cubic and hexagonal close-packed solid solution phases. During the cladding process, the FeMnCoCr/TiC or the FeMnCoCr/TiC/CaF2 mixed suf?ciently with Cu matrix, while FeMnCoCr exhibited a spherical shape owing to being insoluble in Cu. The average hardness of the FeMnCoCr/TiC/CaF2 self-lubricating high-entropy alloy (HEA) coatings was twice that of the pure FeMnCoCr HEA coating. By addition of TiC, the friction coef?cient and wear rate were decreased from 0.35 and 3.68 × 10?15 mm3/m to 0.27 and 3.06 × 10?15 mm3/m, respectively. When CaF2 was added, the friction coef?cients and wear rate were decreased to 0.16 and 2.16 × 10?15 mm3/m, respectively, which was 54% lower than the pure FeMnCoCr HEA coating. The main wear mechanism of the FeMnCoCr coating is abrasive wear while that of the FeMnCoCr/TiC coating is abrasive and adhesion wear. But adhesion wear is dominant for the FeMnCoCr/TiC/CaF2 coating.
更新于2025-11-28 14:24:20
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A facile method to fabricate a novel 3D porous silicon/gold architecture for surface enhanced Raman scattering
摘要： Si-based surface enhanced Raman scattering (SERS) sensing technology is a powerful tool for the detection of various chemical and biological species. Further improvement of the simplicity, stability, sensitivity, and low cost of Si-based SERS platforms is still in great demand for real applications. In this study, the facile fabrication of three-dimensional (3D) porous Si/Au SERS platform with attractive SERS performances was reported. The developed method relied on laser-induced dendrite-like microstructure on the surface of Al-Si cast alloy followed by dealloying Al from the laser treated surface, leaving a 3D dendrite-like porous Si substrate. By sputtering, the substrate was coated with Au film to form 3D porous Si/Au SERS platform. Such 3D porous Si/Au SERS platform had high SERS sensitivity that enabled ultralow concentration detection of R6G molecules down to 10-15 M with enhancement factor in the range of 1011 to 1012. The relative standard deviation of 6.2% was obtained from 15 random SERS spectrum, indicating superior reproducibility of the as-fabricated 3D porous Si/Au SERS platform.
关键词： laser,porous Si/Au,SERS,dealloying
更新于2025-11-28 14:24:20
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High temperature wear performance of laser cladding Co06 coating on high-speed train brake disc
摘要： Abnormal wear sometimes occurs on the high speed train brake disc surface in winter time. In this paper, Co-based alloy powders were deposited by laser cladding technology to improve the wear resistance of train brake discs. Sliding wear at room temperature, 200℃, 400℃ and 600℃ were conducted to investigate the wear behavior. Microstructure, hardness, and phase composition of Co06 cladding layers were also studied. The results showed that Co06 cladding layer exhibited better wear resistance than the substrate, with different wear mechanisms at high temperatures. Co06 cladding layers also exhibited better high temperature oxidation resistance than the substrate. Cr23C6 played a significant role in anti-friction.
关键词： high temperature wear behavior,laser cladding,high speed train,brake disc
更新于2025-11-28 14:24:20