Papers by Keyword: High Power Diode Laser

Abstract: A simple model is presented for the propagation of macroscopic defects within the quantum well (QW) plane of broad-area high power diode lasers. The catastrophic optical damage (COD) effect is considered the mechanism for creating an initial damage site and further development of defect pattern. The relations between the parameters used in the model and the actual physical properties of the semiconductor materials are discussed. Experimentally observed damage patterns are well described.

Abstract: As diode laser is simple in structure, small size, longer life expectancy and easy modulation and the advantages of low prices, widely used in the industry processing, such as heat treating, welding, hardening, cladding and so on. Respectively, diode laser could make it possible to establish the practical application because of rectangular beam patterns which are suitable to make fine bead with less power. Therefore diode laser cladding will open a new field of repairing for the damaged machinery parts which must contribute to recycling of the used machines and saving of cost. in order to output high power, in this paper, we utilized polarization coupling technology to couple two 808nm laser diode stack together, and designed the optical system to expand and focus the beam, through the experiment, we realized the overall efficiency more than 60%, focusing the beam size of 2×2mm2.

Abstract: The goal of this paper is to present the structure and properties of the magnesium cast alloys in as-cast state and after heat treatment. Moreover the purpose of this paper is to extend a complex evaluation of magnesium alloys after laser surface treatment and the new methodology to determine thermal characteristics of magnesium alloy using the novel Universal Metallurgical Simulator and Analyzer Platform (UMSA). The presented results concern X-ray qualitative and quantitative microanalysis as well as qualitative X-ray diffraction method, light and scanning microscope.

Abstract: The laser surface remelting (LSR) process was successfully applied to restore localized corrosion resistance in sensitized stainless steel and also as a useful method to improve passivity of some martensitic stainless steels. The LSR process can be successfully applied to repair cracks and defects at the surface of highly thermo-mechanically loaded parts of stainless steel. The purpose of presented study was to evaluate the microstructure and properties of laser remelted surface of stainless steels. The wrought austenitic stainless steel and sintered in vacuum 316L type were studied. The laser treatment was performed with the use of high power diode laser (HPDL) and the influence of beam power of 0.7-2.1kW on the properties of the surface layer was evaluated. The geometrical characteristics and x-ray analysis of weld bead were studied as well as microhardness, surface roughness and corrosion resistance were measured. The increase of laser beam power of LSR resulted in the increase of hardness of sintered stainless steel due to the reduction of porosity and formation of fine dendritic and cellular-dendritic microstructure. The corrosion resistance of remelted surface increased for sintered materials, when remelted at 2.1kW. The wrought stainless steel revealed impairment of pitting corrosion when remelted at lower beam power rate.

Abstract: Stainless steel sheet metals were laser bent by means of a high power diode laser at different values of power and scan velocity. The laser power ranged from 100 to 300 W (with an increment of 50 W); two scan speeds were used, 4 and 8 mm/s, and the number of passes was 2, 4 or 6. In the experimentation, the values of bending angle, microstructure and residual stresses of the laser bended sheet metals were analyzed with regard to the input variables. In particular, residual stresses were evaluated by means of X-ray analysis in terms of first and second order stress. Measurements were performed on the convex surface of the sample in the laser beam action zone. The bending process was numerically simulated by means of a thermo-mechanical finite element model, implemented to predict the sheet metal bending angle as a function of the laser power and scan velocity. The residual stress distribution was extracted from the numerical simulations and its agreement with the experimental observations was discussed. As a general conclusion, the effect of multiple scans is hardly simulated by thermo-mechanical models which do not take into account the material annealing during forming.

Abstract: A process innovation is proposed by the authors to weld aluminum alloy tubes by means of a high power diode laser. In order to make the temperature profile uniform along the entire welding line, multiple passes of the laser source along the welding path can be performed at very high scan speeds. In the current study, this effect is achieved by focusing the standstill laser spot on the external surface of the aluminum alloy tubes which were put in rotation at high speed. The tubes were clamped together by using a threaded rod passing inside the tubes. Experimental tests were performed by changing the aluminum alloy heat treatment (6060 T1 and 6060 T5), the length of the samples to weld (80 and 100 mm), and the laser power (ranging from 800 to 950 W). The outer diameter of the tube was 10 mm, the thickness was 1 mm, and the rotational speed was kept constant at 1000 rpm. The welding time was monitored during the tests and ranged from 30 to 100 s in dependence on the material and process parameters. Specimens were extracted from the joints to perform tensile tests so as to measure the tensile strength. In the best condition, a high tensile strength was obtained (about 140 MPa).

Abstract: High power lasers, including CO2 laser, Nd:YAG laser, Excimer laser, Diode laser, LD pumped YAG laser, LD pumped Disk laser, LD pumped Fiber laser and Femto second laser, are now used as a modern tool for industries as well as a computer alike in the 4th wave of modernization. Lasers are currently used for welding, cutting, drilling, cladding, direct fabrication, marking, cleaning, micro-machining peening and forming of materials in modernized factories. The joining speed (= product of welding speed and penetration depth) of 45,000mm2/min for steel sheet can be obtained by a 10kW Yb: fiber laser and is that of 50kW electron beam welding, which require the vacuum chamber. As a result of large numbers of research and developments the Advanced Laser Integrated Manufacturing System (ALIMS) using high power diode lasers has been developed and used for modernization in many industrialized countries. The laser materials processing is now penetrated as a machining tool into many industries. In the present paper, an advanced laser integrated manufacturing systems and its applications to industries such as automotive, electronics, ship building and steel making industry are introduced. In addition, development of an advanced laser integrated manufacturing system using a 2kW fiber laser for welding a car panel and “Laser Roll Welding” system for dissimilar metal joints such as mild steel/high strength steel to aluminium alloys, titanium to aluminium and steel to titanium, is described for modernization of industries. It will be a magnificent for the industries. And the 4th wave of modernization and opto-mechatronics will be promoted more by laser/photon technology in the future.

Abstract: Due to manifold variants of joining processes feasible by laser, new possibilities have opened up in product design. An economic application of laser technology is usually connected to a laser adapted modification of the part design and a laser system technology, which meets the requirements of the chosen process in an optimum manner. For this contribution, three applications have been chosen in order to demonstrate the versatility of the laser joining technology.

Abstract: The objective of the present work was to study the modification of the microstructure of hot-work tool steels X40CrMoV5-1 and X38CrMoV5-3 during the surface modifying by means of laser technology. This treatment aims to harden and alloy the steel surface which had been previously coated with tungsten carbide (WC) and were introduced using the rotor conveyer to improve the properties of the surface layer. The fine grained, dendritic structure occurs in the remelted and alloyed zone with the crystallization direction connected with the dynamical heat abstraction from the laser beam influenced zone. The fine grained martensite structure is responsible for the hardness increase of the alloyed layer.