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Mechanism of laser welding on dissimilar metals between stainless steel and W-Cu alloy

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Chinese Optics Letters 2006年第5期4卷 294-296页

作者：陈铠王智勇肖荣诗左铁钏 College of Laser Engineering Beijing University of TechnologyNational Center of Laser TechnologyBeijing 100022

CO2 laser is employed to join a piece of powder metallurgical material （PMM） to a stainless steel in butt joint welding mode. The powder Ni35, as a filler powder, is used. The weld metal comes from three parts of stainless steel, powder Ni35, and Cu in W-Cu PMM. It is indicated that some parts of the W-Cu base metal are heated by laser and the metal Cu at the width of 0.06--0.12 mm from the edge is melted into the melting pool in the laser welding process. The formation of firm weld joint is just because that the melting liquid metal could fill the position occupied by metal Cu and surround the metal W granules fully. The analysis results indicate that the mechanism of the laser welding for stainless steel and W-Cu alloy is a special mode of fusion-brazing welding.

关键词： carbon dioxide lasers Copper alloys Mechanisms Microstructure Molybdenum alloys Nickel alloys Powder metallurgy Soldered joints Stainless steel

Design of LICVD equipment for preparation of nano powder and study on laser threshold

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Chinese Optics Letters 2004年第11期2卷 643-646页

作者：刘英才尹衍升李静王贵 Institute of Material Science and Engineering Ocean University of China Qingdao 266003 Institute of Material Science and Engineering Ocean University of China Qingdao 266003 Key Lab for Liquid Structure and Heredity of Ministry of Education Engineering Ceramics Key Lab of Shandong Province Shandong University Ji'nan250061 Key Lab for Liquid Structure and Heredity of Ministry of Education Engineering Ceramics Key Lab of Shandong Province Shandong University Ji'nan 250061

A laser-induced chemical vapor deposition (LICVD) nanometer equipment is designed and fabricated. The design conception of key parts is expatiated. The energy threshold of SiH4 decomposing is studied. In the condition of same reactive gas flux, the laser energy threshold decreases with the increase of SiH4 concentration. In the condition of same SiH4 concentration, with the increase of reactive gas flux, the laser energy threshold which induces SiH4 decomposition increases linearly at the beginning, and when the flux is more than 100 ml/min, it turns to increase slowly. The factors which influence the laser threshold are analyzed.

关键词： carbon dioxide lasers Laser applications Nanotechnology Silicon compounds

Study of technique and performance of laser beam welding for W18Cr4V and 65Mn

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Chinese Optics Letters 2004年第1期2卷 39-42页

作者：姚建华方志民张伟 College of Mechanical Engineering Zhejiang University of Technology Hangzhou 310014

In this experiment, we used 7-kW continuous wave (CW) CO2 low order mode laser and YAG impulse laser to deeply weld high-speed steel (W18Cr4V) and spring steel (65Mn). To welded joint, we analyzed its microstructure, micro hardness and fracture appearance for different welding technology by metallography microscope, scanning electron microscopy and bending strength test, discussed its action of fracture and the relation between its structural transformation and strength. At last, we offered an optimum welding technology having no welding defect by the comparison and analysis of processing property.

关键词： carbon dioxide lasers Microhardness Microstructure Steel

Experimental investigation of the effects of laser parameters on laser propulsion

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Chinese Optics Letters 2004年第9期2卷 538-540页

作者：龚平谭荣清唐志平郑义军蔡建柯常军胡晓军万重怡于延宁刘世明吴谨周锦文吕岩郑光 KeyLabforMechanicalBehaviorandDesignofMaterials ChineseAcademyofSciences DepartmentofModernMechanics UniversityofScienceandTechnologyofChinaHefei230026 DepartmentofHighPowerlasers ElectronicsResearchInstituteChineseAcademyofSciencesBeijing100080

The effects of main laser parameters, such as pulse energy, pulse duration, frequency, and work time on laser propulsion of 'air-breathing mode', are investigated experimentally with a high power and high repetition frequency TEA-CO_2 pulsed laser. The results show that the momentum coupling coefficient C_m decreases with increasing the pulse energy for single pulse tests and pulse duration of about 1 μs. Either higher or lower frequency will reduce C_m in multi-pulse tests, which suggests an optimal frequency for the maximum C_m. As to the work time, the longer the work time is, the less the C_m will be.

关键词： carbon dioxide lasers Laser beams

Twist characteristics of the ultraviolet-written long-period fiber gratings

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Chinese Optics Letters 2004年第10期2卷 565-567页

作者：张自嘉施文康高侃方祖捷 Department of Information Measurement Technology and Instrument Shanghai Jiaotong University Shanghai 200030 Lab of Information Optics Shanghai Institute of Optics and Fine Mechanics China Academy of Sciences Shanghai 201800 Lab of Information Optics Shanghai Institute of Optics and Fine Mechanics China Academy of Sciences Shanghai 201800wist characteristics of the ultraviolet-written long period fiber gratings (UV-LPFGs) are investigated in this paper. It was found experimentally that the resonance wavelength of the UV-LPFG shifts to short side proportional to square of the torsion rate when it is twisted in both directions of clockwise and counter-clockwise which is different from that of LPFGs written by CO_2 lasers but similar with that of the corrugated LPFGs. The phenomena can be explained by mechanisms of static compression in twisting and index change caused by photo-elastic effect.

Twist characteristics of the ultraviolet-written long-period fiber gratings (UV-LPFGs) are investigated. It was found experimentally that the resonance wavelength of the UV-LPFG shifts to short side proportional to square of the torsion rate, when it is twisted in both directions of clockwise and counter-clockwise, which is different from that of LPFGs written by CO2 lasers, but similar with that of the corrugated LPFGs. The phenomena can be explained by mechanisms of static compression in twisting and index change caused by photoelastic effect.

关键词： carbon dioxide lasers Optical fibers Refractive index Strain Stresses Technical writing Ultraviolet devices

Wear resistance of laser cladding and plasma spray welding layer on stainless steel surface

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Chinese Optics Letters 2004年第3期2卷 151-153页

作者：王新林石世宏郑启光 Department of Electrical Engineering Nanhua University Hengyang 421001 State Key Laboratory of Laser Technology Huazhong University of Science and Technology Wuhan 430074

The effect of coatings, which are formed with laser cladding and plasma spray welding on lCrl8Ni9Ti base metal, on wear resistance is studied, A 5-kW transverse flowing CO2 laser is used for cladding Co base alloy powder pre-placed on the substrate. Comparing with the plasma spray coatings, the spoiled rate of products with laser clad layers was lower and the rate of finished products was higher. Their microstructure is extremely fine. They have close texture and small size grain. Their dilution resulting from the compositions of the base metal and thermal effect on base metal are less. The hardness, toughness, and strength of the laser cladding layers are higher. Wear tests show that the laser layers have higher properties of anti-friction, anti-scour and high-temperature sliding strike. The wear resistance of laser clad layers are about one time higher than that of plasma spray welding layer.

关键词： carbon dioxide lasers Laser applications Microstructure Stainless steel Wear resistance

Microstructure and properties of plastic deformed martensite induced by laser shock processing

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Chinese Optics Letters 2004年第12期2卷 715-717页

作者：杨继昌花银群陈瑞芳蔡兰张永康颜红 School of Mechanical Engineering Jiangsu University Zhenjiang 212013 Guangdong Md Comsumer Electric Manufacturing Co. Ltd. Shunde 528311

Firstly, 45# steel was quenched by the NEL-2500A rapidly axial flow CO2 laser. The experimental parameters were the laser power of 750 W, the laser beam diameter of 4 mm, the scanning velocity of 7 mm/s. The thickness of coating layer was 0.1 mm and the width was 8 mm. Secondly, the martensite induced by laser quench was shocked by Nd:YAG laser. The parameters of laser shock processing were the wavelength of 1.06 μm, the pulse duration of 23 ns, and the output energy of 16-20 J. The laser was focused on a spot of φ7 mm. K9 optical glass was used as confinement. The sample was coated with black paint 86-1 (the thickness is about 0.025 mm). By testing and analysis of samples which were treated by laser quench and laser quench+shock with transmission electron microscope (TEM), it was discovered that the surface layer of martensite was deformed plastically by laser shock processing. In the secondary hardened zones, there were a lot of slender secondary twin crystal martensites, dislocation tangles, and cellular dislocations. Compared with that of the hardened zones through laser quench only, the residual stress and mechanical properties of the secondary hardened zones were improved and increased through laser compound method.

关键词： carbon dioxide lasers Martensite Mechanical properties Metallographic microstructure Neodymium lasers Plastic deformation Quenching Residual stresses Steel metallography Transmission electron microscopy

Periodical rocking long period gratings in PANDA fibers for high temperature and refractive index sensing

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Optoelectronics Letters 2017年第5期13卷 354-357页

作者：金娃毕卫红付兴虎付广伟 Key Laboratory for Special Fiber and Fiber Sensor of Heibei Province School of Information Science and EngineeringYanshan University

We report periodical rocking long period gratings(PR-LPGs) in PANDA fibers fabricated with CO_2 laser. The PR-LPGs achieve very high coupling efficiency of 19 dB with 12 periods and a 3.5° twist angle in just one scanning cycle, which is much more effective than the conventional CO_2 laser fabrication technique. This type of LPGs exhibits polarization-selective resonance dips which demonstrate different sensitivities to environmental parameters. The high temperature and external refractive index sensitivities are measured simultaneously, so it can be used as a wavelength-selective polarization filter and sensor.

关键词： carbon dioxide carbon dioxide lasers Fiber optic sensors Polarization Polarization maintaining fiber

Theoretic model of myocardial revascularization by far Infrared laser and experimental validation

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Optoelectronics Letters 2009年第2期5卷 158-160页

作者：罗乐陈兴张霆宗仁鹤邓善熙 Department of Applied Physics Hefei University of TechnologyHefei 230009 China

A theoretic model of myocardial revascularization by a far infrared laser has been established and a quantificational rela- tionship between the aperture of laser channel and parameters of laser has been concluded according to thermodynamics and the law of interaction of far infrared laser and myocardium. The experiment of a carbon dioxide laser revascularization in porcine myocardium has been done for different laser powers and irradiation time. The relative errors between experi- mental result and theoret...

关键词： carbon dioxide carbon dioxide lasers Errors lasers Optically pumped lasers